CN114657459B

CN114657459B - Nitrogen-vanadium-titanium-niobium rare earth microalloyed high-strength deep-drawing cold-rolled steel plate and production method thereof

Info

Publication number: CN114657459B
Application number: CN202210155492.6A
Authority: CN
Inventors: 吴光亮; 吴昊天; 肖业明
Original assignee: CHANGSHA DONGXIN ENVIRONMENTAL PROTECTION MATERIAL CO LTD; Central South University
Current assignee: CHANGSHA DONGXIN ENVIRONMENTAL PROTECTION MATERIAL CO LTD; Central South University
Priority date: 2022-02-21
Filing date: 2022-02-21
Publication date: 2022-11-18
Anticipated expiration: 2042-02-21
Also published as: CN114657459A

Abstract

The invention discloses a nitrogen-vanadium-titanium-niobium-rare earth microalloying high-strength deep-drawing cold-rolled steel sheet and a production method thereof, wherein microalloying elements are fully utilized to be combined with residual interstitial carbon and nitrogen in steel and added trace nitrogen atoms to generate carbonitrides of different types, the solid solubility of free interstitial carbon and nitrogen in the steel is reduced to the minimum, a very small amount of solid-solution rare earth elements are ensured, the {111}// ND texture is promoted to be formed, and the r value and the n value of the cold-rolled steel sheet are greatly improved; under the action of factors such as temperature, deformation, cooling rate and the like, the sizes and the distribution of different types of carbonitride precipitates are controlled, the precipitates with larger sizes and micron sizes are beneficial to forming {111}// ND textures, and the dispersed and uniformly distributed nano-scale vanadium carbonitride, titanium carbonitride, niobium carbonitride and rare earth carbonitride block dislocation movement and improve the strength of steel; under the condition of ensuring that the crystal grains are properly coarsened, the formation of cake-shaped crystal grains is promoted, and the deep drawing performance is greatly improved.

Description

Nitrogen-vanadium-titanium-niobium rare earth microalloying high-strength deep-drawing cold-rolled steel plate and production method thereof

Technical Field

The invention relates to a nitrogen-vanadium-titanium-niobium-rare earth microalloyed deep-drawing cold-rolled steel plate and a production method thereof, in particular to a nitrogen-vanadium-titanium-niobium-rare earth microalloyed high-strength deep-drawing steel plate and a production method thereof, belonging to the technical field of cold-rolled steel plate preparation.

Background

Cold-rolled steel sheets for stamping are widely used in the industries of vehicles, ships, household appliances, engineering and construction, etc., and particularly in the automobile industry, the cold-rolled steel sheets for automobile bodies account for about 50% or more of automobile steels. Cold rolled stamped steel sheets have undergone three generations of technology, the first generation being boiling steels such as 08F steel; second generation aluminum killed steels such as 08Al steel; IF steel produced and used in batch at present belongs to a third-generation technical product, and mainly adopts the technological routes of BOF blowing, LF external refining, RH vacuum treatment, continuous casting, hot rolling, acid pickling cold rolling, annealing, leveling and the like, and is mainly characterized in that: the carbon and nitrogen content in the steel is low (the carbon is 0.001-0.004 percent, and the nitrogen content is less than or equal to 0.0040 percent); and adding Ti and Nb elements to reduce the content of solid solution C and N elements in the steel, ensuring that interstitial free atoms C and N exist in ferrite, and obtaining interstitial free steel, namely IF steel. Ensures that the steel has excellent deep drawing performance and can be punched into cold-drawn formed parts with various complicated shapes. IF steel has become a mainstream technical product of punching cold rolled steel sheets nowadays, and is developed toward increasing strength grade of steel sheets while continuously improving punching performance. The method is suitable for the times of 'carbon peak reaching and carbon neutralization' requirements of reduction, low-emission production and light application.

The main characteristic parameters describing the cold forming of the steel for stamping are as follows: work hardening index, value of n; the ratio of the strain in the width direction to the strain in the thickness direction, r value; the in-plane anisotropy index difference delta r value and the plasticity index comprises the following components: a (reduction of area), agt (total elongation), etc., the most important of which are n and r values. The high n value and r value can ensure good expansion deformation capability and deep drawing performance; low Δ r values (especially when Δ r = 0) can mitigate the "earing" phenomenon of the stamping; non-ageing, i.e. not having age-hardening properties, ensures that the steel sheet is easy to transport and store.

The n value is mainly related to the components and the structure of the steel, and no accurate research result is known at present, but the improvement of the purity of the steel is generally considered, namely, the reduction of the contents of carbon and alloy elements and the increase of the grain size of ferrite are beneficial to the improvement of the n value; the r and Δ r values are mainly determined by the crystallographic orientation of the grains (i.e., texture), and the texture is closely related to the composition and processing history of the steel. Texture in steel: when a {111} < 110 > texture, particularly a {111} < 110 > + {111} < 112 > hybrid texture is formed in a ferrite body in steel, the r value is large and Δ r approaches zero. The steel for stamping requires a ratio of texture index {111}/{100}, respectivelyHigh, the larger the r value. Chemical components: c and N dissolved in steel are not favorable for forming {111} texture, and the r value is sharply reduced. C. The high content of N, in particular solid solution N in the steel, will also significantly increase the age hardening tendency of the steel for stamping. Adding Ti and Nb elements into the steel for stamping to combine with C and N to generate carbonitride of Ti or Nb, and removing C and N interstitial atoms dissolved in the steel from ferrite to obtain purer ferrite, which is beneficial to forming {111} texture and increasing r value; ensuring the non-timeliness of the steel for stamping. P is easy to generate segregation phenomenon at grain boundary or subboundary, which is not good for forming and developing {111} texture, and r value is reduced. However, P is an effective ferrite strengthening element, and it is generally possible to increase the strength grade of the steel for press working by adding P. Ferrite grain size: increasing the ferrite grain size, particularly the ferrite size on the {111} plane, increases the r value and decreases the Δ r value. However, excessively large grains may impair other mechanical properties thereof. Second-phase particles: the second phase particles of IF steel are mostly AlN, tiN, tiS, tiC, nb (C, N) and Ti ₄ S ₂ C ₂ Etc., the size and distribution of which have a significant influence on the development of recrystallization and texture. The IF steel having coarse precipitates not only has a strong {111} texture and a high r-value, but also exhibits high grain boundary movement characteristics. Grain size: the IF steel has an annealed structure of equiaxed ferrite, and r and n values are increased as the grain size of the IF steel is increased. However, the excessively coarse grains can cause the surface quality of the stamping part to be poor and damage the strength and the low-temperature toughness of the product; the ferrite grain size should not be higher than ASTM grade 7. The process factors are as follows: the components are key factors for determining the excellent forming performance of the IF steel, but the production process matched with the components is an important measure and means for realizing the texture and the microstructure. The hot rolling process adopts low-temperature heating and rapid rolling with large reduction ratio, and strictly controls the finish rolling temperature and the coiling temperature. The low-temperature heating energy coarsens and precipitates second phase particles such as carbides and sulfides in the hot-rolled steel sheet, which results in a high r-value and good plasticity. The rapid hot rolling with large reduction can accelerate the precipitation of carbon and nitrogen compounds, thereby improving the r value and the plasticity of the steel for cold rolling and annealing stamping. The cold rolling process generally adopts a large reduction ratio, which increases the r value, and the cold rolling reduction ratio is generally recommended to be 70 percent80%, the specific size is determined by the thickness of the steel plate of the final product. The annealing process requires a higher heating temperature and a longer time, and the {111} texture crystal grains will be engulfed by other non- {111} texture crystal grains and grow larger, and the r value is increased accordingly.

In order to meet the requirements of high-strength super deep drawing steel, a proper amount of elements such as A1, ti, nb, cr and V capable of improving the cold formability of the steel are used, the content of elements such as C, N, mn, P and Si in the steel for reducing the cold formability is reduced, the deep drawing performance of a cold-rolled steel plate can be improved, and microalloying elements are required to be used along with the increase of the strength grade of the steel plate, so that the deep drawing performance is poor; in particular, when the deformation is not uniform, cracking is often accompanied, which is related to the yield plateau caused by the pinning and the unpinning of the C and N atoms dissolved in the steel in the ferrite, and is related to the grain size, the texture, the process factors and the like.

With the development of the automobile industry in the direction of weight reduction, energy saving, corrosion prevention and noise reduction, high-strength plates aiming at weight reduction and energy saving, various novel galvanized plates aiming at corrosion prevention, vibration reduction composite plates aiming at noise reduction, mirror plates aiming at making the appearance of cars more beautiful and the like are hot spots for development, and particularly, the development of automobile plates with comprehensive performance such as ultra-deep drawing high-strength plates and ultra-low carbon high-strength BH plates is more attractive.

Currently, deep drawn cold rolled steel sheets can be classified into two categories:

one is a deep drawing steel represented by IF steel, forms a third-generation technical product of the deep drawing steel, is a soft steel with lower strength and better stamping forming performance, and is widely applied to the industries of household appliances, color coating and the like. The main technical characteristics are as follows: (1) The technical scheme of designing components with ultra-low carbon and high cleanliness is adopted. The content of silicon, manganese and other solid solution alloy elements is less; the contents of interstitial elements C and N are extremely low, the content of C is generally less than 0.0020%, the content of nitrogen is less than 0.0040%, and a proper amount of elements such as Ti, nb and the like are added to fix interstitial atoms C and N; the contents of other impurity elements such as oxygen, sulfur, phosphorus, hydrogen and the like in the steel are extremely low; (2) The hot rolling adopts low heating and initial rolling temperature and higher coiling temperature, and the cold rolling adopts large reduction rolling, so as to promote the formation of hot rolling and cold rolling deformation texture {111}// ND; (3) The steel has good and stable formability and non-timeliness, can reduce the punching rejection rate, can improve the geometric precision of a component, reduces the sensitivity to the die and the punching process parameters, and improves the productivity. The steel has obvious defects: (1) However, the steel belongs to clean steel, the preparation process is complex, the technical difficulty is high, the cost is high, the content of alloy elements is very little, the strength of the steel is not high, and the requirement of high-strength parts or equipment is difficult to meet; (2) Because solid-solution carbon and nitrogen are not contained in the grain boundary of the IF steel, the grain boundary strength is low, and the IF steel is easy to break, and particularly the high-strength IF steel containing high P and high Si has strong brittleness after secondary processing. A small amount of B is added, so that the steel can be rapidly segregated at the grain boundary to play a role in strengthening, and the segregation of phosphorus at the grain boundary can be inhibited; in addition, cold working brittleness can be improved by controlling annealing and rolling processes, but B is extremely active, and the evolution law in metallurgy is not easy to control; (3) Ti and Nb in IF steel have the function of cleaning grain boundaries (reducing the content of solid solution C and N in grain boundaries), and the reaction between the grain boundaries and a plating layer (such as a zinc plating layer) is very active, thereby weakening the adhesion of the plating layer. (4) The r value of the deep drawing steel is generally between 2.0 and 2.6, the n value is between 0.20 and 0.30, the elongation is between 50 and 60 percent, the yield strength Rel is generally less than 200MPa, and the application range of the deep drawing steel is limited.

The Steel is mainly characterized in that (1) the Steel adopts micro-alloying component design, and properly improves elements such as Mn, P, cu or Cr and the like as micro-alloying elements, but the content of interstitial atoms C and N is extremely low, especially the content of N is generally less than 0.004 percent, and (2) the Steel has higher strength level, such as multi-Phase ultrahigh-strength Steel, the tensile strength of the Steel can exceed 1500MPa, and the Steel has better deep drawing performance, and can meet the requirement of the high-strength-level deep drawing cold-rolled Steel plate;

the steel has obvious defects that: 1) The bake hardened steel has strength and high formability. Bake-hardened steel is a steel that obtains the strength of the final part by work hardening during machining and aging during paint baking. BH steels have been developed in IF grades, based primarily on the fact that steels contain lower amounts of Nb and Ti than IF grades. So that the BH steel contains a certain amount of interstitial atoms which do not affect the punching performance of the BH steel or have little effect. BH steel is mainly applied to automobile shells, and paint spraying and baking are carried out after stamping. In the baking finish process, the aging reaction of the interstitial atoms is carried out at the baking finish temperature, so that the steel has a solid solution strengthening process in the final process, and the strength is further improved after forming. BH steels have several drawbacks: (1) the effect of baking and hardening is relatively limited, and the tensile strength can only be increased by about 30MPa to 50MPa generally; (2) the most fatal disadvantages are: the aging speed is high due to the existence of a certain amount of solid solution elements C or N in the bake hardening steel. The steel becomes hard and brittle (yield strength and tensile strength are increased, and elongation after fracture is reduced) in a short time after baking (if turnover is not fast, the steel is stored in a warehouse to be used), and obvious defects appear on the surface, so that the material cannot be used and is scrapped; (3) the content of carbon or nitrogen cannot be too low or too high because of ensuring that a proper amount of interstitial atoms C or N exist in the steel. The content of carbon or nitrogen is too low, C or N in the steel is totally precipitated by carbo-nitride of niobium, vanadium and titanium, and the phenomenon of baking hardening can not occur; if the content of carbon or nitrogen is too high, the gap in the steel, especially [ N ], is caused to have adverse effects on metallurgical processes such as continuous casting and rolling processes and product quality, so the content of [ C ] or [ N ] in the steel needs to be controlled in a precise and narrow range, the control parameter range of smelting, hot rolling, cold rolling annealing and flattening processes is small, and if the fluctuation of process parameters is large, the performance fluctuation of the steel is large, and the preparation difficulty is increased. 2) Dual-phase steel: dual-phase steel (DP steel for short), also called dual-phase steel. Steel consisting of a two-phase structure of martensite, austenite or bainite and ferrite matrix. The steel composed of ferrite and austenite phases is generally called duplex stainless steel, which has a significantly different technical background from the high-strength deep-drawing steel to which the present invention relates and will not be discussed here. A steel composed of ferrite and martensite phases is called a dual phase steel. The dual-phase steel is obtained by heat treatment or controlled rolling of low-carbon steel or low-alloy high-strength steel in critical region. Typical dual phase steels have a yield strength Rel of 310MPa and a tensile strength Rm of 655MPa. The dual-phase steel is used for manufacturing complex components formed by cold drawing and deep drawing, is successfully used in the automobile industry, and can also be used as pipeline steel, chains, cold-drawn steel wires, prestressed steel bars and the like. The dual-phase cold-rolled high-strength steel has the characteristics that: the dual-phase steel is a steel mainly composed of a ferrite phase and a martensite phase, and is obtained by subjecting a low-carbon steel or a low-alloy steel to intercritical treatment or controlled rolling. This type of steel has a good combination of high strength and high ductility, and has become a new type of steel for stamping having high strength and good formability. There are related techniques that require further optimization: (1) the dual-phase steel structure is composed of ferrite and martensite, and the steel contains higher manganese, chromium and molybdenum during component control so as to improve the quenching performance of the steel, thereby being beneficial to the formation of martensite and having higher alloy cost compared with deep drawing IF steel; (2) the martensite phase in the dual-phase steel is a hard phase structure, the ferrite phase is a soft phase structure, the proportion of ferrite and martensite determines the comprehensive performance of the dual-phase steel, the martensite is obtained by the technological parameters of C curve, cooling rate and the like of steel grade, the proportion of martensite cannot be too high or too low, the plasticity of the steel is reduced and the stamping performance of the steel is reduced, and the strength of the steel is reduced due to too low strength and cannot reach the required strength level. The martensite phase of the deep drawing dual-phase steel accounts for about 15 percent ideally, but the process parameter range is narrow by accurately controlling the martensite phase proportion, the control difficulty is high, the cost is high, and the quality qualified rate is low. (3) The dual-phase steel is obtained by heat treatment or controlled rolling of low-carbon steel or low-alloy high-strength steel in a critical zone. The 'window' of the critical area is narrow, proper tissues and processing conditions need to be prepared for subsequent annealing heat treatment during hot rolling and cold rolling, the corresponding process control parameter range is small, and the process control difficulty is increased; the allowable fluctuation range of parameters such as annealing heat treatment temperature, time and the like is small, the process parameter precision needs to be controlled, and the stability is kept. (4) The dual-phase martensite phase is obtained by controlling the quenching cooling rate, and the cooling rate of the surface layer and the core part of the steel is inconsistent, so that the formation amount and the structure size of martensite are inconsistent, the martensite and the ferrite structure are uneven, and the performance of the steel is unstable. Furthermore, the changes in the hot rolling, cold rolling and annealing parameters have an effect on the original structure of the steel sheet, which in turn has an effect on the formation of martensite. 3) Transformation induced plasticity steel (multi-phase steel): this type of steel consists of three phases of ferrite, bainite and retained austenite. Under the action of external load or deformation, the residual austenite in the structure induces the martensite to be transformed, so that the local hardness is improved; however, since it becomes difficult to continue the deformation, the deformation is transferred to the surrounding tissues, and the generation of necking is delayed, so that the material obtains high plasticity. The retained austenite is transformed into high-strength high-carbon martensite, simultaneously, the instability of plastic deformation is inhibited along with volume expansion, the uniformly extending range is increased, the strength and the plasticity are simultaneously improved, and the effect is called TRIP effect, which is also called TRIP steel for short. The steel is low-carbon high-alloy metastable austenitic steel containing a large amount of chromium, nickel, molybdenum, manganese and silicon. The martensite point Ms (the upper temperature limit at which deformation leads to martensitic transformation) of this steel is below room temperature. After low-temperature deformation heat treatment (deformation at 450 ℃ 76% -80%), the Md point becomes higher than room temperature, but the Ms point is still far lower than room temperature (lower than-196 ℃), and at the moment, the steel structure is austenite containing finely dispersed alloy carbide and high-density dislocation. The ferrite boundary is distributed with residual austenite and bainite, and the content of the residual austenite is about 10%. Ferrite is taken as a matrix and is distributed in equiaxial crystal; bainite is distributed in the grain boundary in a strip shape or a granular shape; the retained austenite is mainly distributed in three positions: (1) distributed in the ferrite grain or in the grain boundary in an island shape; (2) distributed in island shape at bainite ferrite grain boundary; (3) is distributed among the bainite ferrite bars in a membrane shape or a needle shape. Among them, island-like retained austenite size is large, and needle-like or film-like austenite size distributed among bainitic ferrite bars is small. The martensite which is very little in the structure is mainly transformed from austenite with relatively poor stability in the process of quenching and cooling to room temperature, and is distributed in island shapes. The steel is a new generation of high-strength steel plate for automobiles. The steel has the following disadvantages: (1) the steel belongs to low alloy steel, has high alloy content, contains manganese, silicon, chromium, nickel, molybdenum and other metals, has high alloy cost, and is not beneficial to reduction production and carbon peak carbon neutralization; (2) the steel grade is hot rolled and cold rolled to obtain a ferrite + pearlite structure. In order to finally obtain a multi-phase structure containing ferrite, bainite and residual austenite, a heat treatment process of annealing in a two-phase region and isothermal quenching in a bainite region and then cooling to room temperature is adopted, austenite is converted into bainite during isothermal treatment in a bainite region, a small amount of austenite is remained, and the finally obtained steel plate structure contains ferrite, bainite and residual austenite. The annealing heat treatment process is complex, the proportion of ferrite, bainite and residual austenite is appropriate, the transformation Ms from the residual austenite to the martensite is lower than the room temperature, the process control parameters are required to be accurate, the allowable fluctuation is small, and the operation control difficulty is high; (B) The two-phase region has higher heating and annealing temperature, which brings high energy consumption, high technical requirements on annealing equipment and high equipment investment. 4) The three types of high-strength cold-rolled stamping steel have the advantages that the stamping performance indexes, namely n value, r value, A value and Agt value, are not high, the qualification rate is low when complex parts are stamped, and the application of the steel is limited; in particular, the Rm value of transformation induced plasticity steel (multiphase steel) can exceed 1500MPa at most, but the stamping characteristic parameters of the steel are not too high, such as r value which is generally between 1.5 and 2.0, n value which is between 0.20 and 0.25 and elongation which is between 45 and 55 percent, and the application range of the steel is also limited.

Disclosure of Invention

Aiming at the problems of the prior art for producing high-strength deep-drawing cold-rolled steel sheets, in particular to the defects of low strength, cold-working brittleness, poor coating adhesion and the like of cold-rolled deep-drawing steel represented by IF steel; the invention provides a high-strength deep-drawing cold-rolled steel plate represented by bake-hardening steel, dual-phase steel, TRIP steel and multiphase ultrahigh-strength steel, which has the technical difficulties of complex production process parameters, long process control loop, large equipment investment, low deep-drawing index and the like. The high-strength deep-drawing steel plate provided by the invention meets the following characteristic indexes: the yield ratio Rel/Rm value is less than 0.65; the plastic strain ratio r is more than 3.0, the work hardening index n is more than 0.45, the elongation is more than 65%, the yield strength Rel is more than or equal to 500MPa, and the tensile strength Rm is more than or equal to 800MPa.

The second purpose of the invention is to provide a production method of the high-strength deep-drawing steel plate processed by nitrogen-vanadium-titanium-niobium rare earth microalloying.

The invention relates to a nitrogen-vanadium-titanium-niobium rare earth microalloyed high-strength deep-drawing steel plate, which comprises the following chemical components in percentage by weight: 0.001wt% -0.0020wt% of C, 0.03wt% -0.07wt% of Si, 0.10wt% -0.35wt% of Mn, 0.007wt% -0.011wt% of N, 0.02wt% -0.06wt% of Als, 0.0015wt% -0.0040wt% of Sigma Re, 0.015wt% -0.040wt% of V, 0.012wt% -0.025wt% of Nb, 0.035wt% -0.065wt% of Ti, 0.025wt% -0.055wt% of P, less than or equal to 0.0008wt% of S, and the balance of iron and inevitable impurity elements.

In a preferred embodiment, the Σ Re is selected fromLanthanum、Cerium (Ce)、NeodymiumOne or more of europium, gadolinium and holmium.

According to the nitrogen vanadium titanium niobium rare earth microalloying high-strength deep-drawing steel plate, microalloying elements of vanadium, titanium and niobium, rare earth, residual carbon elements in steel and added trace nitrogen elements are fully utilized to generate carbonitrides, the solid solubility of free interstitial carbon and nitrogen in the steel is reduced, the formation of {111}// ND textures is promoted, and the formation of non {111}// ND textures is reduced, so that the r value of a cold-rolled steel plate is greatly improved; due to different precipitation temperatures of different types of carbonitrides, under the action of factors such as temperature, heat preservation time and the like under different metallurgical conditions, the sizes of the precipitated carbonitrides are different, the coarse micron-sized precipitates are beneficial to forming {111}// ND textures, and the dispersed and uniformly distributed nano-scale vanadium carbonitride, titanium carbonitride, niobium carbonitride and rare earth carbonitride block dislocation movement and improve the strength of steel; under the condition of ensuring that crystal grains are properly coarsened, the formation of cake-shaped crystal grains is promoted, and the deep drawing performance is greatly improved under the condition of greatly improving the strength of the cold-rolled deep drawing steel.

In a preferred scheme, the high-strength deep-drawing steel plate is of a {111}// ND texture, and the yield ratio Rel/Rm value is less than 0.65; the plastic strain ratio r value is more than 3.0, the work hardening index n is more than 0.45, the elongation is more than 65%, the yield strength Rel value is more than or equal to 500MPa, and the tensile strength Rm value is more than or equal to 800MPa.

The invention relates to a production method of a high-strength deep-drawing steel plate processed by nitrogen-vanadium-titanium-niobium rare earth microalloying, which comprises the following steps:

the blast furnace molten iron is desulfurized outside the furnace and then blown in a converter, the molten steel is tapped when the end point molten steel of the converter meets the requirements, the molten steel is decarbonized and dehydrogenated through RH vacuum, deep desulfurization and inclusion removal are carried out at an LF station, the molten steel is taken out of the station and transferred to be continuously cast into a slab after reaching the target molten steel component, and the slab is hot rolled, acid-washed, cold rolled, annealed and leveled to obtain the high-strength deep-drawing steel plate.

In the preferable scheme, the KR method or the blowing method is adopted to carry out external desulfurization treatment on blast furnace molten iron to ensure that the sulfur content of the blast furnace molten iron is reduced to be below 0.0010 percent, and the desulfurization slag is removed;

further preferably, in the KR method, the used desulfurizing agent a comprises the following components in percentage by mass: caC ₂ 30-50 percent of desulfurizer A, 40-60 percent of CaO and 10-20 percent of Mg powder, wherein the addition amount of the desulfurizer A is 1.0-6.0Kg of desulfurizer A added in each ton of iron.

Preferably, the blowing method adopts nitrogen as a conveying medium, the used desulfurizer B is metal magnesium powder and/or metal calcium powder, and when the used desulfurizer B is the metal magnesium powder and the metal calcium powder, the metal magnesium powder accounts for 10-80% and the metal calcium powder accounts for 20-90% by mass percentage.

According to the preferable scheme, the proportion and the quantity of the molten iron and the scrap steel as well as the type and the quantity of the slag former added in the blowing process are determined according to the composition and the temperature of the molten iron entering the furnace and the composition and the temperature of the molten steel at the end point of the converter, and the oxygen lance carries out oxygen supply blowing according to a high-low-high-low system.

In the present invention, the high-low-high-low regime is a term of art: the height means that the distance between the oxygen lance contact head and the liquid level of the molten pool is larger, namely the height between the oxygen lance contact head and the liquid level in the molten pool is higher; conversely, low means that the distance between the oxygen lance contact head and the liquid level of the molten pool is smaller, namely the height between the oxygen lance contact head and the liquid level in the molten pool is lower.

The mass fraction of [ P ] in the molten steel at the converter terminal is 0.015-0.035 wt%, the mass fraction of [ C ] is 0.040-0.070 wt%, and the mass fraction of [ O ] is 0.040-0.080%; the tapping temperature is 1580-1640 ℃.

In the actual operation process, the oxygen lance position-grabbing, the oxygen supply pressure and flow and the oxygen supply time are controlled to carry out the smelting process and the end point component and temperature control, so that the phosphorus content in the molten steel at the end point of the converter is more than or equal to 0.015wt% and less than or equal to 0.035wt%, the phosphorus content in the molten steel is more than or equal to 0.040wt% and less than or equal to 0.070wt%, and the temperature meets the requirements of the RH vacuum treatment and LF refining treatment and continuous casting process in the subsequent working procedures.

When tapping from the converter, a proper amount of strong deoxidizer is added for primary deoxidation, wherein the strong deoxidizer comprises one or a combination of more of metal aluminum, aluminum-calcium alloy, metal calcium and the like, so that the oxygen content in the molten steel in the ladle is ensured to be slightly larger than the oxygen balance value balanced with the carbon content at the temperature.

Preferably, during RH vacuum treatment, the RH vacuum degree is controlled within 40KPa, according to the content of [ C ] and [ O ] in steel, oxygen is blown into molten steel for decarburization according to the target C being less than or equal to 0.0010%, the circulation frequency and time of oxygen blowing and decarburization of the molten steel are determined, the mass fraction of [ C ] in the RH outbound molten steel is less than or equal to 0.0010%, the mass fraction of [ O ] is less than or equal to 0.0010%, and metallic aluminum is added to ensure that the mass fraction of acid-soluble aluminum [ Als ] in the RH outbound molten steel is 0.020% -0.060%.

In the actual operation process, the added metal aluminum after decarburization comprises aluminum cakes or blocks, metal aluminum particles and the like

According to the preferable scheme, the molten steel treated by RH enters an LF station, carbon-free or low-carbon slagging materials such as lime and fluorite are added according to the sulfur content in the molten steel discharged from the RH station, the total content of C in the slagging materials is less than or equal to 0.50%, submerged arc power transmission operation is carried out, the slagging slag is subjected to deep desulfurization, and when S is less than or equal to 0.0005wt%, power is cut off, sampling and temperature measurement are carried out; according to the components in molten steel and the target component requirements of the end-point molten steel, one or more of rare earth nitrogen alloy, micro nitrogen alloy, vanadium nitride and manganese nitride are added, ferrovanadium, ferroniobium, ferrotitanium, manganese metal, rare earth alloy and the like are added, a carbon-free or low-carbon premelting slag ladle top slag calcium agent is added for top slag modification treatment, and submerged arc power transmission operation is performed again to ensure that the components reach the target values and are uniform and the temperature is uniform. Finally, according to the content of aluminum in the molten steel, feeding metal calcium wires into the molten steel for impurity deformation treatment to ensure that [ Ca ] in the molten steel]/[Al]=0.1-0.065, and molten steel discharged from LF (ladle furnace) is obtainedThe LF outbound molten steel comprises, by mass, 0.001-0.0020% of C, 0.03-0.07% of Si, 0.10-0.35% of Mn, 0.007-0.011% of N, 0.02-0.06% of Als, 0.0015-0.0040% of Sigma Re, 0.015-0.040% of Nb, 0.012-0.025% of Nb, 0.035-0.065% of Ti, 0.025-0.055% of P, less than or equal to 0.0008% of S, and the balance of iron and inevitable impurity elements; the pre-melted slag ladle top slag calcareous agent used in the top slag modification treatment is upper furnace ladle top slag or pre-melted calcium aluminate slag, and the top slag modification treatment comprises the following components: 45-60% of Al ₂ O ₃ ：30-40％，SiO ₂ :5-10％，CaF ₂ :3-8％。

Further preferably, the temperature of the LF outlet molten steel is 15-25 ℃ higher than the liquidus temperature according to the temperature of the continuous casting tundish molten steel. In the actual operation process, the temperature loss in the process from the LF outlet station to the continuous casting rotary table, the process from the large ladle to the tundish, the process from the tundish to the crystallizer and the like is considered, and the temperature of the molten steel in the LF outlet station is determined and controlled.

Further preferably, the ferrovanadium alloy is selected from at least one of ferrovanadium, vanadium-nitrogen and metal vanadium;

the ferrocolumbium alloy comprises at least one of ferroniobium and metallic niobium;

the ferrotitanium alloy comprises at least one of ferrotitanium and metallic titanium;

the ferromanganese alloy comprises at least one of metal manganese and ferromanganese, wherein in the ferromanganese, the carbon content is less than 0.2 percent, and the silicon content is less than 0.1 percent

The rare earth alloy is at least one selected from rare earth nitrogen alloy and metal rare earth alloy.

In the preferable scheme, when the continuous casting is carried out, the superheat degree of molten steel is 15-25 ℃, the continuous casting pulling speed is controlled to be 0.8-2.0m/min, the width of the section of the continuous casting slab is 1200-2000mm, and the thickness is 180-220mm.

According to the preferable scheme, during continuous casting, a ladle long nozzle and a crystallizer submerged nozzle are adopted for protection casting, the crystallizer covering slag is alkaline covering slag, the mass fraction of carbon in the crystallizer covering slag is less than 0.2%, the mass fraction of silicon in the crystallizer covering slag is less than 0.3%, and the tail end and the solidification tail end of the continuous casting crystallizer are both stirred electromagnetically.

In the invention, full-protection casting is adopted, the alkaline protective slag with extremely low carbon and extremely low silicon is adopted, a crystallizer and a secondary cooling water distribution cooling system are determined according to the high-temperature mechanical property characteristics of the steel grade, a non-sinusoidal vibration mode is selected, and high-frequency and small-amplitude vibration parameters are adopted. The crystallizer and the solidification tail end both use an electromagnetic stirring device to ensure that components and tissues of a casting blank are uniform. And after the surface quality of the obtained continuous casting billet is checked and treated, hot rolling is carried out.

Preferably, the slab is heated first, and then the heated slab is hot-rolled, wherein the heating is divided into three sections of preheating treatment, heating treatment and soaking treatment, and the temperature of the preheating treatment is controlled as follows: 800-980 ℃, and the temperature of the heating treatment is controlled as follows: 980-1060 deg.C, the soaking temperature is 1020-1080 deg.C, the initial rolling temperature is 920-1000 deg.C, the final rolling temperature is 830-900 deg.C, and the coiling temperature is 650-710 deg.C.

In the preferable scheme, the pickling speed is 120-150m/min and the total pressure rate is 80-90% during pickling and cold rolling.

Preferably, the annealing is hood annealing or continuous annealing, when hood annealing is performed, the annealing temperature is 680-750 ℃, the heat preservation time is 12-16h, and when continuous annealing is performed: the temperature of the soaking section is 720-780 ℃, the temperature of the slow cooling section is 680-710 ℃, the temperature of the fast cooling section is 450-470 ℃ and the temperature of the overaging section is 330-380 ℃.

Preferably, during leveling, the leveling elongation is controlled according to 0.6-1.0%.

Principles and advantages

The principle of the invention is as follows: according to thermodynamic data, different types of carbonitrides are different in precipitation temperature, carbonitrides precipitated at a higher temperature, such as titanium nitride, begin to precipitate near the solidification point temperature of molten steel, do not dissolve back into austenite in the casting blank heating process, but the carbonitride precipitates of titanium grow and the original austenite grains of the casting blank grow by controlling the heating temperature and the heating time of the casting blank, and the precipitates are made to be oval or round under the coupling action of elements such as niobium, vanadium and trace rare earth which are added in reasonable proportion, and flat titanium nitride precipitates are formed under the condition of controlling each reasonable reduction in the deformation process, thicker original austenite grains are promoted to be transformed into cake-shaped grains, and the formation of {111}// ND textures is promoted; niobium carbonitride is precipitated at the next high temperature, the niobium carbonitride is dissolved back into austenite in the heating process of a casting blank, niobium carbonitride is precipitated from the austenite in the rolling deformation process and the cooling process, and the niobium carbonitride precipitate with proper size and uniform distribution can be ensured by controlling the temperature and the cooling parameters after rolling, so that the formation of {111}// ND texture can be promoted, and dislocation movement can be blocked; at a lower temperature, vanadium carbonitride is precipitated, and dispersed, fine and uniformly distributed carbonitride can be precipitated in steel through controlled rolling and controlled cooling, so that the effects of pinning dislocation and hindering grain growth are achieved; in addition, rare earth can promote the precipitation of rare earth carbonitride, promote the formation of {111}// ND texture, and trace rare earth elements can reduce the precipitation temperature of titanium, niobium and vanadium carbonitride, thereby being beneficial to controlling the precipitation and redissolution-precipitation of titanium, niobium and vanadium carbonitride, and simultaneously reducing the heating temperature of casting blanks and realizing energy conservation.

According to the invention, trace nitrogen and nitrogen in steel are fully utilized to combine elements vanadium, titanium, niobium and rare earth to generate carbonitride, the solid solubility of free interstitial carbon and nitrogen in steel is reduced, the formation of {111}// ND texture is promoted, and the formation of non {111}// ND texture is reduced, so that the r value of the cold-rolled steel sheet is greatly improved; due to different precipitation temperatures of different types of carbonitrides, under the action of factors such as temperature, heat preservation time and the like under different metallurgical conditions, the sizes of the precipitated carbonitrides are different, the coarse micron-sized precipitates are beneficial to forming {111}// ND textures, and the dispersed and uniformly distributed nano-scale vanadium carbonitride, titanium carbonitride, niobium carbonitride and rare earth carbonitride block dislocation movement and improve the strength of steel; under the condition of ensuring that crystal grains are properly coarsened, the formation of cake-shaped crystal grains is promoted, and the deep drawing performance is greatly improved under the condition of greatly improving the strength of the cold-rolled deep drawing steel. The deep drawing cold-rolled steel plate produced by the technology almost completely forms a {111}// ND texture, the non- {111}// ND texture can be ignored, and the deep drawing cold-rolled steel plate has a low yield ratio Rel/Rm value which is less than 0.65; the plastic strain ratio r value is more than 3.0, the work hardening index n is high, the value is more than 0.45, the elongation is more than 65%, a large amount of dispersed and uniformly distributed vanadium carbonitride, titanium carbonitride, niobium carbonitride and rare earth carbonitride are precipitated simultaneously, 25-15% of precipitates are in a nanometer level, dislocation movement is hindered, the strength of the steel is improved, 75-85% of the precipitates are in a micrometer level, the grain size is about 6 levels, the rare earth carbonitride promotes the formation of cake-shaped grains, and the deep drawing performance is greatly improved under the condition of greatly improving the strength of the cold-rolled deep drawing steel. The steel can meet the performance requirements of SEDDQ deep drawing steel, the yield strength Rel value is more than or equal to 500MPa, the tensile strength Rm value is more than or equal to 800MPa, the steel can be widely applied to parts and equipment with higher strength requirements and complicated punch forming, and the light weight and reduction equipment manufacturing can be realized.

Detailed Description

The present invention will be described in further detail with reference to examples, but the present invention is not limited thereto.

The invention can adopt the processes of molten iron external desulphurization, converter (BOF) blowing, RH vacuum treatment, LF external refining, continuous casting, hot rolling, acid pickling and cold rolling, annealing, leveling and the like. The specific embodiment of the invention is implemented by adopting the processes of molten iron external desulphurization, oxygen converter smelting, RH vacuum degassing, LF external refining, continuous casting, hot rolling, cold rolling and leveling.

Example 1

Transferring 125 tons of blast furnace molten iron to a molten iron furnace external desulfurization station, and performing molten iron desulfurization treatment by adopting a KR method, wherein the entering molten iron temperature is 1405 ℃, and the molten iron components are as follows: 4.51 percent of C, 0.38 percent of Si, 0.41 percent of Mn0.101 percent of P and 0.042 percent of S; adding a desulfurizer (lime 55% + calcium carbide 35% +10% metal magnesium powder) into each ton of molten iron for 4.2 Kg/ton, stirring for 15 minutes, sampling the molten iron with the sulfur content of 0.00089%, removing the desulfurized slag, measuring the temperature of 1326 ℃, adding the molten iron into a converter with the nominal capacity of 150 tons, then adding 30 tons of steel scraps, starting blowing, properly increasing the position of an oxygen lance in the early stage, adding lime and sludge or iron scale containing iron protoxide, rapidly slagging and dephosphorizing, pressing down the position, starting a bottom blowing mode, and carrying out converter material preparation according to the components and the temperature of the molten iron after desulfurization and the components and the temperature of the molten steel at the end point of the converterAnd heat balance calculation, determining the addition of other furnace materials of the converter, and molten steel at the end point of the converter: [ P ]]0.032wt％，[C]0.043wt％，[S]0.0025 percent, the tapping temperature is 1648 ℃, 0.25Kg of metallic aluminum cake per ton of molten steel is added during tapping, primary deoxidation is carried out, and [ O ] is contained in the molten steel in a ladle]0.045％，[C]0.048％，[Si]0.047％，[Mn]0.12％，[P]0.036％，[S]0.0027% and 1602 deg.C; then transferring the steel ladle to an RH vacuum processing station to perform decarburization and dehydrogenation treatment on the molten steel, wherein the vacuum degree is 35Kpa, the molten steel is circularly processed for 8 minutes, oxygen blowing decarburization is performed according to the carbon oxygen content in the molten steel, the C content of an RH station is 0.00087%, proper metal aluminum particles are added to ensure that the acid aluminum content in the molten steel reaches 0.032%, the molten steel after RH processing enters an LF station again for temperature measurement sampling, lime, a carbon-free slag modifier, fluorite, aluminum powder and other slag materials (the carbon and silicon content in the slag materials are less than 0.5%), foam-making white slag deep desulfurization is performed, after power transmission is performed for 8 minutes, temperature measurement sampling is performed, according to the sampling component results, the control ranges of 0.001wt% to 0.0020wt%,0.03wt% to 0.07wt% to 0.060.10 wt% to 0.35wt%,0.007wt% to N% to 0.011wt%,0.02wt% to 0.0015wt% and 0.025wt% to 0.025wt% of Al, the rare earth alloy is less than 0.025wt%, and the contents of Mo and Nb are added to 0.025%, and 0.025% to 0.025%, vanadium to 0.025% of the molten steelNeodymiumSo that the contents of rare earth and nitrogen in the molten steel reach the target; adding relative alloy such as ferrovanadium, ferroniobium, ferrotitanium, metallic aluminum and metallic manganese to finely adjust the components of the molten steel so that the components of the molten steel meet the target requirements, performing temperature measurement and sampling after 10 minutes of secondary power transmission, blowing argon gas to the bottom of a steel ladle in the whole power transmission process for stirring, ensuring foaming of top slag of the steel ladle, finally feeding a calcium metal wire into the steel ladle, performing deformation treatment and modification treatment on inclusions to ensure that [ Ca ] in the steel is modified]/[Al]＝0.1-0.065。

LF ex-station temperature 1557 ℃ (continuous casting heat), C0.0014wt%, si0.036wt%, mn0.25wt%, N0.0086wt%, als0.038wt%, sigma Re 0.0017wt%, V0.028wt%, nb0.024wt%, ti0.038wt%, P0.035wt%, S0.0007wt%, and [ Ca ]/[ Al ] =0.090. Casting molten steel into a continuous casting slab with a proper section of 1500mm width and 220mm thickness, checking and processing the surface quality of the continuous casting slab, wherein the temperature of a preheating section is 830 +/-10 ℃, and the temperature of a heating section is as follows: 1010 +/-10 ℃, the temperature of a soaking section is controlled between 1040 +/-10 ℃, the initial rolling temperature is 930 +/-10 ℃, the final rolling temperature is controlled at 835 +/-5 ℃, the coiling temperature is 655 +/-5 ℃, the pickling speed is 122m/min, the total pressure rate is 86 percent, and when a hood-type annealing furnace is adopted for annealing: the annealing temperature is 740 +/-5 ℃, and the heat preservation time is 12 hours; the flat elongation was controlled at 0.72%.

The produced cold-rolled steel plate almost forms a {111}// ND texture, the texture except for {111}// ND texture is negligible, rel =496MPa, rm =856MPa, and the yield ratio Rel/Rm =0.58 of the deep drawing cold-rolled steel plate; plastic strain ratio r =3.3, work hardening index n =0.48, elongation greater than 66.7%, grain size 6.0. The steel can meet the performance requirements of SEDDQ deep drawing steel, is widely applied to parts and equipment with higher strength requirements and complicated punch forming, and can realize light weight and reduced equipment manufacturing.

Comparative example 1 example of a high-strength deep-drawing cold-rolled steel sheet containing no rare earth.

The other conditions are the same as the example 1, only the components do not contain rare earth, the cold-rolled steel plate is produced, the texture proportion of {111}// ND is only 83 percent, the texture proportion of non {111}// ND reaches 17 percent, rel =463MPa, rm =656MPa, and the yield ratio Rel/Rm =0.71 of the deep drawing cold-rolled steel plate; plastic strain ratio r =2.1, work hardening index n =0.22, elongation greater than 51.3%, grain size 7.3.

Example 2

Transferring 86 tons of blast furnace molten iron to a molten iron external desulfurization station, and performing molten iron desulfurization treatment by adopting a KR method, wherein the temperature of the molten iron entering the station is 1396 ℃, and the components of the molten iron are as follows: 4.38 percent of C, 0.42 percent of Si, 0.39 percent of Mn0.096 percent of P and 0.035 percent of S; adding 3.6 Kg/ton of desulfurizer (50% of lime, 32% of calcium carbide and 18% of metal magnesium powder) into one ton of molten iron, stirring for 12 minutes, sampling the molten iron to obtain a molten iron with the sulfur content of 0.00081%, scraping clean desulfurized slag, measuring the temperature of 1332 ℃, adding the molten iron into a converter with the nominal capacity of 100 tons, then adding 21 tons of scrap steel,

starting blowing, properly improving the position of an oxygen lance in the early stage, adding lime and sludge or iron oxide scale containing iron protoxide, rapidly slagging and dephosphorizing, then depressing the position, starting a bottom blowing mode, carrying out converter material and heat balance calculation according to the components and temperature of molten iron after desulfurization and the components and temperature of molten steel at the end point of the converter, and determining the addition of other furnace charges of the converter and the molten steel at the end point of the converter: 0.043wt%, [ C ]0.051wt%, [ S ]0.0015 wt% tapping temperature 1645 deg.C, 0.23Kg metallic aluminum cake per ton molten steel is added during tapping, primary deoxidation is performed, and metallic manganese is added for manganese alloying, 0.047%, 0.052%, 0.032%, 0.19%, 0.048%, 0.0030% of [ S ] in the molten steel in the ladle, 1610 deg.C;

then transferring the ladle to an RH vacuum treatment station for decarburization and dehydrogenation treatment, wherein the vacuum degree is 30Kpa, circulating the molten steel for 6 minutes, blowing oxygen for decarburization according to the carbon oxygen content in the molten steel, the C content of an RH outlet station is 0.00092%, adding proper metal aluminum particles to ensure that the acid aluminum content in the molten steel reaches 0.048%, then transferring the molten steel treated by RH into an LF station for temperature measurement sampling, adding lime, a carbon-free slag modifier, fluorite, aluminum powder and other slag materials (the carbon and silicon contents in the slag materials are less than 0.5%), performing foam white slag deep desulfurization, transmitting electricity for 9 minutes, measuring the temperature for sampling, controlling the control range of 0.001-0.0020 wt% of C, 0.03-0.07 wt% of Si, 0.10-0.35 wt% of Mn, 0.007-0.025 wt% of N, 0.02-0.06 wt% of Als, 0.0015wt% of Re, 0.025wt% of Nb, 0.025wt% of 0.025%, 0.025wt% of Nb, 0.025% of 0.025%, and 0.025% of Nb, adding rare earth into the steelCerium (Ce)And the rare earth europium. The contents of rare earth and nitrogen in the molten steel reach the target; adding relative alloy such as ferrovanadium, ferroniobium, ferrotitanium, metallic aluminum and metallic manganese to finely adjust the components of the molten steel so that the components of the molten steel meet the target requirements, performing secondary power transmission for 8 minutes, performing temperature measurement and sampling, blowing argon gas to the bottom of a steel ladle in the whole power transmission process for stirring, ensuring foaming of top slag of the steel ladle, finally feeding a calcium metal wire into the steel ladle, performing deformation treatment and modification treatment on inclusions to ensure that [ Ca ] in the steel is modified]/[Al]＝0.1-0.065；

LF outbound temperature 1554 deg.C (continuous casting heat), C0.0018wt%, si0.055wt%, mn0.33wt%, N0.0073wt%, als0.048wt%, sigma Re 0.0024wt%, V0.031wt%, nb0.015wt%, ti0.046wt%, P0.046wt%, and S0.0006wt%. [ Ca ]/[ Al ] =0.076; casting the molten steel into a continuous casting slab with a proper section of 1200mm width and 180mm thickness, and heating the casting slab after checking and processing the surface quality of the continuous casting slab: preheating section temperature of 870 +/-10 ℃, heating section temperature: 1030 +/-10 ℃, the temperature of a soaking section is controlled to be 1030 +/-10 ℃, the starting rolling temperature is 960 +/-10 ℃, the finishing rolling temperature is controlled to be 840 +/-5 ℃, the coiling temperature is 690 +/-5 ℃, the pickling speed is 136m/min, the total pressure rate is 90%, and when a hood-type annealing furnace is adopted for annealing: the annealing temperature is 670 +/-5 ℃, and the heat preservation time is 15 hours; the flat elongation was controlled at 0.62%.

The cold-rolled steel plate produced almost forms a {111}// ND texture, the texture except for {111}// ND texture can be ignored, rel =518MPa, rm =886MPa, and the deep drawing cold-rolled steel plate has a yield ratio Rel/Rm =0.58; plastic strain ratio r =3.2, work hardening index n =0.47, elongation greater than 65.3%, grain size 6.5. The steel can meet the performance requirements of SEDDQ deep drawing steel, is widely applied to parts and equipment with higher strength requirements and complicated punch forming, and can realize light weight and reduced equipment manufacturing.

Comparative example 2 example of a high-strength deep-drawing cold-rolled steel sheet having a low nitrogen content.

The other conditions were the same as in example 2, except that [ N ] =0.0051% in the composition, and a cold-rolled steel sheet was produced with a {111}// ND texture ratio of only 62%, a non {111}// ND texture ratio of 38%, rel =428mpa, rm =598mpa, and a deep-drawing cold-rolled steel sheet yield ratio Rel/Rm =0.72; plastic strain ratio r =1.8, work hardening index n =0.21, elongation greater than 53.7%, grain size 7.5.

Example 3

Transferring 180 tons of blast furnace molten iron to a molten iron external desulfurization station, and performing molten iron desulfurization treatment by adopting a KR method, wherein the temperature of the molten iron entering the station is 1453 ℃, and the components of the molten iron are as follows: 4.45% of C, 0.41% of Si, 0.42% of Mn0.102% of P and 0.055% of S; adding a desulfurizer (lime 85% + calcium carbide 15%) 4.5 Kg/ton into one ton of molten iron, stirring for 13 minutes, sampling the molten iron to have a sulfur content of 0.00085%, scraping clean desulfurized slag, measuring temperature 1393 ℃, adding the molten iron into a converter with a nominal capacity of 200 tons, then adding 28 tons of scrap steel, starting blowing, properly improving oxygen lance position control in the early stage, adding lime and sludge or oxidized iron sheet containing iron oxide, rapidly slagging and dephosphorizing, then pressing down the position control, starting a bottom blowing mode, carrying out converter material and heat balance calculation according to the molten iron components and temperature after desulfurization and the converter terminal molten steel components and temperature, determining the addition of other furnace materials of the converter, and determining the converter terminal molten steel: 0.051wt%, [ C ]0.062wt%, [ S ]0.0045%, the tapping temperature is 1651 ℃, 0.20Kg of metallic aluminum cake is added during tapping per ton of molten steel for primary deoxidation and manganese alloying is added, 0.051%, [ C ]0.065%, [ Si ]0.035%, [ Mn ]0.23%, [ P ]0.052%, [ S ]0.0046%, the temperature is 1620 ℃ in the molten steel in the steel ladle;

then transferring the steel ladle to an RH vacuum treatment station for decarburization and dehydrogenation treatment, wherein the vacuum degree is 25Kpa, circulating the molten steel for 10 minutes, blowing oxygen for decarburization according to the carbon oxygen content in the molten steel, the C content of an RH outbound station is 0.00082%, adding proper metal aluminum particles to ensure that the acid aluminum content in the molten steel reaches 0.056%, feeding the molten steel treated by RH into an LF station for temperature measurement and sampling, adding lime, slag modifier, fluorite, aluminum powder and other slag materials (the carbon and silicon content in the slag materials are less than 0.5%), performing foam white slag deep desulfurization, transmitting electricity for 8 minutes, performing temperature measurement and sampling, controlling the control range of 0.001wt% to 0.0020wt% of C, 0.03wt% to 0.07wt% of Si, 0.10wt% to 0.35wt% of Mn, 0.007wt% to 0.011wt% of N, 0.02wt% to 0.06wt% of Als, 0.0015wt% to 0.025wt% of Re, 0.025wt% to 0.025wt% of Nb, and 0.040wt% of Nb, adding rare earth and 0.025% to 0.025% of Nb, adding rare earth to 0.025% of Mo, and 0.025% to 0.025% of Mo, adding rare earth to 0.025% of Mo, and 0.025% to 0.025% of vanadium to 0.025% ofLanthanumAnd rare earth gadolinium, so that the contents of rare earth and nitrogen in the molten steel reach the target; adding related alloy such as ferrovanadium, ferroniobium, ferrotitanium, metallic aluminum and metallic manganese to finely adjust the components of the molten steel so that the components of the molten steel meet the target requirements, performing temperature measurement sampling after performing secondary power transmission for 10 minutes, blowing argon gas to the bottom of a ladle in the whole power transmission process for stirring, ensuring the foaming of top slag of the ladle, and finally feeding the ladle with the top slagA metal calcium wire for deforming the impurities and modifying the slag on the top of steel ladle, [ Ca ]]/[Al]＝0.1-0.065；

LF outbound temperature 1576 ℃ (tundish open casting furnace 1), c0.0012wt%, si0.046wt%, mn0.28wt%, nj0.0106wt%, als0.057wt%, Σ Re 0.0036wt%, v0.018wt%, nb0.024wt%, ti0.063wt%, p0.053wt%, s0.0007wt%. [ Ca ]/[ Al ] =0.068; casting the molten steel into a continuous casting slab with a proper section of 2000mm width and 220mm thickness, and heating the casting slab after checking and processing the surface quality of the continuous casting slab: preheating section temperature 930 ± 10 ℃, heating section temperature: 1050 +/-10 ℃, the temperature of a soaking section is controlled to be 1070 +/-10 ℃, the rolling start temperature is 980 +/-10 ℃, the rolling finish temperature is 890 +/-5 ℃, the coiling temperature is 670 +/-5 ℃, the pickling speed is 148m/min, the total rolling rate is 88%, and when continuous annealing is adopted: a soaking section is 750 +/-5 ℃, a slow cooling section is 690 +/-5 ℃, a fast cooling section is 460 +/-5 ℃ and an overaging section is 340 +/-5 ℃; the leveling elongation was controlled at 1.0%.

The cold-rolled steel plate is produced, almost all the texture of {111}// ND is formed, the texture of non {111}// ND is negligible, rel =621MPa, rm =967MPa, and the deep-drawing cold-rolled steel plate has a yield ratio Rel/Rm =0.64; plastic strain ratio r =3.3, work hardening index n =0.50, elongation greater than 67.8%, grain size 6.0. The steel can meet the performance requirements of SEDDQ deep drawing steel, is widely applied to parts and equipment with higher strength requirements and complicated punch forming, and can realize light weight and reduced equipment manufacturing.

Comparative example 3 continuous annealing process deep drawing cold rolled steel sheet examples out of the specified range.

The other conditions are the same as those of the embodiment 3, continuous annealing is adopted, and the annealing process parameters are as follows: the temperature of the soaking section is 863 +/-5 ℃, the temperature of the slow cooling section is 766 +/-5 ℃, the temperature of the fast cooling section is 462 +/-5 ℃ and the temperature of the overaging section is 337 +/-5 ℃; the produced cold-rolled steel plate has the texture proportion of {111}// ND of only 76 percent, the texture proportion of non {111}// ND of 24 percent, rel =551MPa, rm =883MPa, and the yield ratio Rel/Rm =0.62 of a deep drawing cold-rolled steel plate; plastic strain ratio r =1.9, work hardening index n =0.21, elongation greater than 61.2%, grain size 7.1.

Example 4

165 tons of blast furnace molten iron are transferred to a molten iron external desulfurization station, molten iron desulfurization treatment is carried out by adopting a KR method, the temperature of the molten iron entering the station is 1462 ℃, and the components of the molten iron are as follows: 4.21 percent of C, 0.36 percent of Si, 0.38 percent of Mn0.098 percent of P and 0.051 percent of S; adding 4.8 Kg/ton of desulfurizer (lime 85% + calcium carbide 15%) into a ton of molten iron, stirring for 14 minutes, sampling an iron water sample for analysis, wherein the sulfur content is 0.00088%, removing desulfurized slag completely, measuring temperature 1401 ℃, adding the molten iron into a converter with the nominal capacity of 180 tons, then adding 21 tons of scrap steel, starting blowing, properly increasing the position of an oxygen lance in the early stage, adding lime and sludge or iron oxide scale containing iron protoxide, rapidly slagging and dephosphorizing, then pressing down the position, starting a bottom blowing mode, carrying out converter material and heat balance calculation according to the components and temperature of the molten iron after desulfurization and the components and temperature of molten steel at the end point of the converter, determining the adding amount of other furnace charges of the converter, and determining the end point of the molten steel of the converter: 0.028wt% of [ P ], 0.051wt% of [ C ] and 0.0033 wt% of [ S ], the tapping temperature is 1652 ℃, 0.22Kg of metallic aluminum cake is added in the tapping process per ton of molten steel, primary deoxidation is carried out, and metallic manganese is added for manganese alloying, 0.046% of [ C ], 0.055% of [ Si ], 0.032% of [ Mn ], 0.035% of [ P ], 0.0038% of [ S ] and the temperature is 1606 ℃;

then the ladle is transferred to an RH vacuum processing station for decarburization and dehydrogenation treatment, the vacuum degree is 20Kpa, the molten steel is circularly processed for 8 minutes, oxygen blowing decarburization is carried out according to the carbon and oxygen content in the molten steel, the C content of the RH station is 0.00085 percent, proper metal aluminum particles are added to ensure that the acid-soluble aluminum content in the molten steel reaches 0.025 percent, the molten steel processed by RH enters an LF station again for temperature measurement and sampling, lime, slag modifying agent, fluorite, aluminum powder slag materials and the like are added (the carbon and silicon content in the slag materials are less than 0.5 percent) for deep desulfurization of foaming white slag, measuring temperature and sampling after 10 minutes, controlling the range of 0.001wt% to 0.0020wt% of C, 0.03wt% to 0.07wt% of Si, 0.10wt% to 0.35wt% of Mn, 0.007wt% to 0.011wt% of N, 0.02wt% to 0.06wt% of Als, 0.0015wt% to 0.0040wt% of Sigma Re, 0.015wt% to 0.040wt% of V, 0.012wt% to 0.025wt% of Nb, 0.035wt% to 0.065wt% of Ti, 0.025wt% to 0.055wt% of P and 0.0008wt% of S according to the sampling component results, adding micro-nitrogen alloy, vanadium nitride and dilute Ti into the molten steelSoil noteCerium oxideAnd rare earth holmium, so that the contents of rare earth and nitrogen in the molten steel reach the target; adding relative alloy such as ferrovanadium, ferroniobium, ferrotitanium, manganese metal, aluminum metal and the like to finely adjust the components of the molten steel so that the components of the molten steel meet the target requirements, performing temperature measurement and sampling after performing secondary power transmission for 8 minutes, blowing argon gas to the bottom of a steel ladle in the whole power transmission process for stirring, ensuring foaming of top slag of the steel ladle, finally feeding calcium metal wires into the steel ladle, performing deformation treatment and modification treatment on the inclusions, and [ Ca ] for carrying out modification treatment on the top slag of the steel ladle]/[Al]＝0.1-0.065。

LF out-station temperature 1558 ℃ (continuous casting heat), C0.0015wt%, si0.030wt%, mn0.25wt%, N0.0096wt%, als0.038wt%, sigma Re 0.0028wt%, V0.024wt%, nb0.019wt%, ti0.044wt%, P0.028wt%, and S0.0006wt%. [ Ca ]/[ Al ] =0.098;

casting molten steel into a continuous casting slab with a proper section of 1800mm in width and 200mm in thickness, and heating the casting slab after checking and processing the surface quality of the continuous casting slab: the temperature of the preheating section is 840 +/-10 ℃, and the temperature of the heating section is as follows: 1060 +/-10 ℃, the temperature of a soaking section is controlled to be 1050 +/-10 ℃, the initial rolling temperature is 940 +/-10 ℃, the final rolling temperature is controlled to be 850 +/-5 ℃, the coiling temperature is 680 +/-5 ℃, the pickling speed is 132m/min, the total pressure rate is 87%, and when a hood-type annealing furnace is adopted for annealing: the annealing temperature is 690 +/-5 ℃, and the heat preservation time is 12 hours; the flat elongation was controlled at 0.98%.

The produced cold-rolled steel plate almost forms a {111}// ND texture, the texture except for {111}// ND is negligible, rel =576MPa, rm =915MPa, and the deep drawing cold-rolled steel plate has a yield ratio Rel/Rm =0.63; plastic strain ratio r =3.2, work hardening index n =0.51, elongation greater than 67.6%, grain size 6.5. The steel can meet the performance requirements of SEDDQ deep drawing steel, is widely applied to parts and equipment with higher strength requirements and complicated punch forming, and can realize light weight and reduced equipment manufacturing.

Comparative example 4 example of deep drawn cold rolled steel sheet cold rolled at low total rolling rate.

The cold rolled steel sheet was produced under the same conditions as in example 4, except that the total rolling reduction was 71%, the texture ratio {111}// ND was 78%, the texture ratio {111}// ND was 22%, rel =537MPa, rm =819MPa, and the yield ratio Rel/Rm =0.656; plastic strain ratio r =2.3, work hardening index n =0.21, elongation greater than 62.3%, grain size 6.3.

Example 5

Transferring 138 tons of blast furnace molten iron to a molten iron external desulfurization station, and carrying out molten iron desulfurization treatment by adopting blown magnesium metal, wherein the temperature of the molten iron entering the station is 1468 ℃, and the components of the molten iron are as follows: 4.45 percent of C, 0.39 percent of Si, 0.42 percent of Mn0.108 percent of P and 0.045 percent of S; adding 0.6 Kg/ton of desulfurizer (metal magnesium powder) into a ton of molten iron, blowing and stirring for 7 minutes, then sampling an iron water sample for analysis, wherein the sulfur content is 0.00093%, removing desulfurized slag completely, measuring the temperature for 1421 ℃, adding the molten iron into a converter with the nominal capacity of 150 tons, then adding 22 tons of waste steel, starting blowing, properly improving the position of an oxygen lance in the early stage, adding lime and sludge or iron oxide scale containing ferric oxide, rapidly forming slag and dephosphorizing, then pressing down the position, starting a bottom blowing mode, carrying out converter material and heat balance calculation according to the components and the temperature of the molten iron after desulfurization and the components and the temperature of molten steel at the end point of the converter, determining the addition amount of other furnace charges of the converter, and the molten steel at the end point of the converter: 0.039wt%, [ C ]0.063wt%, [ S ]0.0041%, the tapping temperature is 1642 ℃, 0.18Kg of metallic aluminum cake is added during tapping per ton of molten steel for primary deoxidation and manganese alloying is added, 0.045%, [ C ]0.052%, [ Si ]0.035%, [ Mn ]0.29%, [ P ]0.045%, [ S ]0.0035%, the temperature is 1613 ℃ in the molten steel in the ladle; then the ladle is transferred to an RH vacuum processing station for decarburization and dehydrogenation treatment, the vacuum degree is 20Kpa, the molten steel is circularly processed for 7 minutes, oxygen blowing decarburization is carried out according to the carbon and oxygen content in the molten steel, the C content of the RH station is 0.00088 percent, proper metal aluminum particles are added to ensure that the acid-soluble aluminum content in the molten steel reaches 0.040 percent, the molten steel processed by RH enters an LF station again for temperature measurement and sampling, lime, slag modifying agent, fluorite, aluminum powder and other slag materials (the carbon and silicon content in the slag materials are less than 0.5 percent) are added for deep desulfurization of foaming white slag, after 9 minutes of power transmission, temperature measurement sampling is carried out, according to the results of sampling components, the control ranges of the control components are between 0.001wt% and 0.0020wt% of C, between 0.03wt% and 0.07wt% of Si, between 0.10wt% and 0.35wt% of Mn, between 0.007wt% and 0.011wt% of N, between 0.02wt% and 0.06wt% of Als, between 0.0015wt% and 0.0040wt% of Sigma Re, between 0.015wt% and 0.040wt% of V, between 0.012wt% and 0.025wt% of Nb, between 0.035wt% and 0.065wt% of Ti, between 0.025wt% of P and 0.055wt% of P, between 0.0008wt% of S, and between [ Ca ]/[ Al ] =0.1-0.065. Adding micro nitrogen alloy, vanadium nitride and rare earth europium into the molten steel in the ladle to enable the content of rare earth and nitrogen in the molten steel to reach a target; adding relative alloys such as ferrovanadium, ferroniobium, ferrotitanium, metallic aluminum, metallic manganese and the like to finely adjust the components of the molten steel so that the components of the molten steel meet the target requirements, performing secondary power transmission for 10 minutes, measuring the temperature, sampling, blowing argon to the bottom of a ladle in the whole power transmission process, stirring while ensuring the foaming of ladle top slag, finally feeding metallic calcium wires into the ladle, performing deformation treatment and ladle top slag modification treatment on inclusions, and performing continuous casting (LF) discharge at 1561 ℃, C0.0012wt%, si0.068wt%, mn0.12wt%, N0.0082wt%, als0.025wt%, sigma Re 0.0034wt%, V0.037wt%, nb0.021wt%, ti0.039wt%, P0.049wt% and S0.0007wt%. [ Ca ]/[ Al ] =0.091;

casting molten steel into a continuous casting slab with a proper section of 1600mm width and 220mm thickness, checking and processing the surface quality of the continuous casting slab, and heating the casting slab: preheating section temperature: 970 +/-10 ℃, heating section temperature: 1090 +/-10 ℃, the temperature of a soaking section is controlled to be 1060 +/-10 ℃, the initial rolling temperature is 960 +/-10 ℃, the final rolling temperature is controlled to be 880 +/-5 ℃, the coiling temperature is 700 +/-5 ℃, the pickling speed is 140m/min, the total pressure rate is 82%, and when a bell-type annealing furnace is adopted for annealing: the annealing temperature is 685 +/-5 ℃, and the heat preservation time is 13 hours; the flat elongation was controlled at 0.85%.

The cold-rolled steel plate is produced, almost all textures {111}// ND are formed, the textures other than {111}// ND are negligible, rel =721MPa, rm =1169MPa, and the deep drawing cold-rolled steel plate has a yield ratio Rel/Rm =0.62; plastic strain ratio r =3.3, work hardening index n =0.50, elongation greater than 66.8%, grain size 6.5. The steel can meet the performance requirements of SEDDQ deep drawing steel, is widely applied to parts and equipment with higher strength requirements and complicated punch forming, and can realize light weight and reduced equipment manufacturing.

Comparative example 5 an example of a high-strength deep-drawing cold-rolled steel sheet having a flat elongation is shown.

Other conditions were the same as in example 5, the temper rolling elongation was 0.31%, and the cold-rolled steel sheet produced had a {111}// ND texture ratio of 82% only, a non {111}// ND texture ratio of 18%, rel =668MPa, rm =959MPa, and a deep drawing cold-rolled steel sheet yield ratio Rel/Rm =0.697; plastic strain ratio r =2.2, work hardening index n =0.22, elongation greater than 58.1%, grain size 6.5.

Claims

1. A nitrogen vanadium titanium niobium rare earth microalloying processing high strength deep drawing steel plate is characterized in that: the high-strength deep-drawing steel plate comprises the following chemical components in percentage by weight: 0.001-0.0020 wt% of C, 0.03-0.07 wt% of Si, 0.10-0.35 wt% of Mn, 0.007-0.011 wt% of N, 0.02-0.06 wt% of Als, 0.0015wt% -0.0040wt% of Re0.015wt% -0.040wt%, 0.012wt% -0.025wt% of Nb0.035wt% -0.065wt% of P, 0.025-0.055 wt% of S, less than or equal to 0.0008wt% of S, and the balance of Fe and inevitable impurity elements;

the Re is selected from one or a combination of more of lanthanum, cerium, neodymium, europium, gadolinium and holmium;

the high-strength deep-drawing steel plate is of a {111}// ND texture, and the yield ratio Rel/Rm value is less than 0.65; the plastic strain ratio r value is more than 3.0, the work hardening index n is more than 0.45, the elongation is more than 65%, the yield strength Rel value is more than or equal to 500MPa, and the tensile strength Rm value is more than or equal to 800MPa.

2. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium and the niobium and the rare earth, which is characterized in that: the method comprises the following steps:

the blast furnace molten iron is desulfurized outside the furnace, blown in a converter, tapped when the molten steel at the end point of the converter meets the requirements, decarbonized and dehydrogenated by RH vacuum, deeply desulfurized and inclusion-removed at an LF station, taken out of the station and transferred to a continuous casting station after the molten steel reaches the target molten steel component, continuously cast into a plate blank, and the plate blank is subjected to hot rolling, acid pickling and cold rolling, annealing and leveling to obtain the high-strength deep-drawing steel plate.

3. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium and the niobium and the rare earth, which is characterized by comprising the following steps of:

performing external desulfurization treatment on blast furnace molten iron by using a KR method or a blowing method to ensure that the sulfur content of the blast furnace molten iron is reduced to below 0.0010 percent, and removing desulfurization slag;

in the KR method, the used desulfurizer A comprises the following components in percentage by mass: caC ₂ 30-50% of desulfurizer A, 40-60% of CaO and 10-20% of Mg powder, wherein the addition amount of the desulfurizer A is 1.0-6.0Kg per ton of iron;

the blowing method adopts nitrogen as a conveying medium, the used desulfurizer B is metal magnesium powder and/or metal calcium powder, and when the used desulfurizer B is the metal magnesium powder and the metal calcium powder, the metal magnesium powder accounts for 10-80% and the metal calcium powder accounts for 20-90% by mass percentage.

4. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium, the niobium and the rare earth, which is characterized by comprising the following steps of:

determining the proportion and the quantity of the molten iron and the scrap steel as well as the type and the quantity of the slag former added in the blowing process according to the composition and the temperature of the molten iron entering the furnace and the composition and the temperature of the molten steel at the end point of the converter, carrying out oxygen supply blowing at an oxygen lance according to a high-low-high-low system,

5. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium and the niobium and the rare earth, which is characterized by comprising the following steps of: during RH vacuum treatment, controlling the RH vacuum degree within 40KPa, blowing oxygen into the molten steel for decarburization to ensure that the mass fraction of [ C ] and [ O ] in the RH outbound molten steel is less than or equal to 0.0010% and 0.0010%, and adding metallic aluminum to ensure that the mass fraction of acid-soluble aluminum in the RH outbound molten steel is 0.020-0.060%.

6. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium and the niobium and the rare earth, which is characterized by comprising the following steps of: the molten steel treated by RH enters an LF station, a slagging material is added, the total content of C in the slagging material is less than or equal to 0.50 percent, white slag deep desulfurization is carried out, when S is less than or equal to 0.0005wt percent, one or a combination of more of rare earth nitrogen alloy, rare earth alloy, micro nitrogen alloy, vanadium nitride and manganese nitride is added according to the target components of the molten steel, ferrovanadium, ferroniobium, ferrotitanium, manganese and rare earth alloy are added, then top slag modification treatment is carried out, finally, a calcium metal wire is fed into the molten steel according to the content of aluminum in the molten steel for inclusion deformation treatment, ca/Al =0.1-0.065 in the molten steel, LF outlet station molten steel is obtained,

the LF outbound molten steel comprises, by mass, 0.001-0.0020% of C, 0.03-0.07% of Si, 0.10-0.35% of Mn, 0.007-0.011% of N, 0.02-0.06% of Als, 0.0015-0.0040% of Re, 0.015-0.040% of V, 0.012-0.025% of Nb, 0.035-0.065% of Ti, 0.025-0.055% of P, less than or equal to 0.0008% of S, and the balance of iron and inevitable impurity elements; the pre-melted slag ladle top slag calcareous agent used in the top slag modification treatment is upper-furnace ladle top slag or pre-melted calcium aluminate slag, and the pre-melted slag ladle top slag calcareous agent comprises the following components: 45-60% of Al ₂ O ₃ ：30-40%，SiO ₂ :5-10%，CaF ₂ :3-8%，

The temperature of the molten steel of the LF outlet station is controlled according to the temperature 25-35 ℃ higher than the liquidus temperature of the molten steel of the continuous casting tundish.

7. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium, the niobium and the rare earth, which is characterized by comprising the following steps of:

when in continuous casting, the superheat degree of the molten steel is 15-25 ℃, the continuous casting pulling speed is controlled at 0.8-2.0m/min, the width of the section of the plate blank is 1200-2000mm, and the thickness is 180-220mm;

during continuous casting, a ladle long nozzle and a crystallizer submerged nozzle are adopted for casting protection, the crystallizer casting powder is alkaline casting powder, the mass fraction of carbon in the crystallizer casting powder is less than 0.2%, the mass fraction of silicon is less than 0.3%, and the tail end of a continuous casting crystallizer and the tail end of solidification are both stirred electromagnetically.

8. The method for producing the high-strength deep-drawing steel plate through the microalloying treatment of the nitrogen, the vanadium, the titanium, the niobium and the rare earth, which is characterized by comprising the following steps of:

the method comprises the following steps of firstly heating a slab, and then carrying out hot rolling on the heated slab, wherein the heating is divided into three sections, namely preheating treatment, heating treatment and soaking treatment, and the temperature of the preheating treatment is controlled as follows: 800-980 ℃, and controlling the temperature of heating treatment in the following range: 980-1060 ℃, the soaking temperature is 1020-1080 ℃, the initial rolling temperature is 920-1000 ℃, the final rolling temperature is 830-900 ℃, and the coiling temperature is 650-710 ℃;

during acid pickling and cold rolling, the acid pickling speed is 120-150m/min, and the total pressure rate is 80-90%;

the annealing adopts hood type annealing or continuous annealing, when the hood type annealing is carried out, the annealing temperature is 680-750 ℃, the heat preservation time is 12-16h, and when the continuous annealing is carried out: the temperature of the soaking section is 720-780 ℃, the temperature of the slow cooling section is 680-710 ℃, the temperature of the fast cooling section is 450-470 ℃, and the temperature of the overaging section is 330-380 ℃;

and during leveling, the leveling elongation is controlled according to 0.6-1.0%.