CN109797343A - A kind of low-alloy high-strength hot strip rolling and preparation method thereof suitable for extremely cold area - Google Patents

Abstract

The low-alloy high-strength hot strip rolling and preparation method thereof that the invention discloses a kind of suitable for extremely cold area, by weight percentage, chemical analysis are as follows: C:0.06~0.10%, Si:0.6~0.7%, Mn:1.40~1.70%, Nb:0.015~0.025%, Ti:0.005~0.010%, Mg:0.004~0.007%, P≤0.010%, S≤0.010%, Al≤0.002%, N:0.002~0.005%, surplus are Fe and are inevitably mingled with.The preparation method comprises the following steps: KR method molten iron takes off that S → duplex converter takes off P, de- C → LF refining furnace → sheet billet continuous casting → Steel In Reheating Furnace base reheating → roughing, finish rolling → ultrafast cold → section cooling → batch.The present invention solves the problems, such as that stocking nonuniform organization phenomenon easily occurs in ultra-rapid cooling technique.

Description

A kind of low-alloy high-strength hot strip rolling and preparation method thereof suitable for extremely cold area

Technical field

The invention belongs to Strip production technical fields, and in particular to a kind of low-alloy high-strength suitable for extremely cold area Hot rolled strip and its production method.

Background technique

The minimum temperature of the extremely cold areas such as Siberia can reach -60 DEG C hereinafter, since this area stores a large amount of stone The resources such as oil, natural gas, also increasing to the exploitation dynamics of this area in the world, winning apparatus and its auxiliary building are most of It is made of steel, steel used in corresponding this area also needs have good mechanical property under -60 DEG C of low temperature.

There are ductile-brittle transition temperatures for steel, and lower than at this temperature, the fracture mode of steel is changed into brittleness by ductile rupture Fracture, that is, there is black brittleness phenomenon, the original good steel of toughness loses due toughness, become like glass bar it is equally crisp and It is easy to break, studies have shown that reduce steel in C, P element content, refinement stocking crystal grain, improve stocking tissue in acicular ferrite Content can reduce ductile-brittle transition temperature, so that steel also have good mechanical property in extremely cold area, but in actual steel How the steel of resistance to extremely cold area temperature are produced by the method for economical and efficient in production, and there is presently no disclosed technologies.

There is scholar to propose to induce the low temperature that intragranular acicular ferrite is precipitated to improve steel using Oxides Metallurgy Technology The theory of impact property, the theory are by forming a large amount of tiny MgO, TiO in steel₂、CaO、ZrO₂Type impurity lures Precipitation acicular ferrite is led, but there are no mature technologies in actual Steel Production Flow Chart to generate a large amount of tiny folders Sundries.It also has been reported that using rolling rear ultrafast refrigeration technique come Ferrite Refinement, but due to being rolled in During Ultra Fast Cooling at present Material surface and the center portion temperature difference are big, if ultrafast cold final temperature and cooling velocity control improper will appear stocking surface and core structure Inconsistent phenomenon.

Chinese patent 201610871499.2 " a kind of ship steel molten steel magnesium treatment process " improves a kind of magnesium processing technique, Technology are as follows: firstly, determining station and the opportunity of magnesium processing: being added after the fine tuning of LF process alloy or after the vacuum processing of RH process Mg-Al-Fe alloy claded wire；Secondly, guaranteeing Mg-Al-Fe alloy claded wire magnesium treatment effect according to steel grade acid-soluble aluminum content Under the premise of, coordinate configuration and feeds aluminum amount and magnesium processing line feeding amount；Then, magnesium processing is carried out: in LF or RH process, using cored Line feeds and Mg-Al-Fe alloy claded wire is added in normal direction ship steel molten steel, final to obtain finished product molten steel, applies in ship steel essence During refining, deck of boat steel cleanness and steel inclusion ingredient, quantity, granularity and its distribution can be controlled, it is clean to improve ship steel Cleanliness and non-metallic inclusion controlled level, so as to improve the mechanical property and its stability of ship steel.This application feeds Mg- Al-Fe alloy claded wire, the field trash of generation are magnesium aluminate spinel (MgOAl₂O₃), MgOAl₂O₃Field trash easily assembles length Big and easily blocking continuous casting submersed nozzle, field trash thinning effect is unobvious, and influences the normal operation of continuous casting.

Chinese patent 201610178135.6 " a kind of oxide control method for improving magnesium recovery rate " discloses a kind of raising The oxide control method of magnesium recovery rate, belongs to steelmaking technical field, in the inventive method, feeds in RH station into ladle Ti-Fe alloy core-spun yarn adds alloying element Ti, after ladle is hung to revolving platform, controls the free oxygen content in molten steel in 10- Within the scope of 18ppm, superheat of liquid steel is 20-30 DEG C, and Ni-Mg alloy claded wire addition alloy is fed into ladle in continuous casting station Element M g, and with the soft stirring 3min of the pressure of 0.4MPa, alloying element Mg recovery rate can be stablized in 1 5-30%, plate obtained Oxide in base is based on Mg-Ti series composite oxides, and wherein the oxide of size≤2.0 μm accounts for all above-mentioned oxides Ratio reach 83% or more, the bulk density of the oxide of size≤2.0 μm reaches 3.7 × 10⁵A/mm³Or more.But It finds in production practice, feeds the generation containing magnesium alloy within the scope of 10-18ppm in free oxygen content using the technical controlling Mg-Ti series composite oxides quantity is on the low side, and fine foreign matter quantity is inadequate, and intragranular acicular ferrite content is few in stocking, Free oxygen content feeds unreasonable containing magnesium alloy within the scope of 10-18ppm.

Summary of the invention

In order to solve the deficiency of the above technology, the present invention provides a kind of low-alloy high-strength hot suitable for extremely cold area and rolls Steel band and its production method.

In order to achieve the above objectives, the low-alloy high-strength hot strip rolling provided by the invention suitable for extremely cold area, with weight Measure percentages, chemical analysis are as follows:

C:0.06~0.10%, Si:0.6~0.7%, Mn:1.40~1.70%, Nb:0.015~0.025%, Ti: 0.005~0.010%, Mg:0.004~0.007%, P≤0.010%, S≤0.010%, Al≤0.002%, N:0.002~ 0.005%, surplus is Fe and is inevitably mingled with.

Influence of the chemical component to steel band performance in the present invention:

C: steel low temperature impact properties can be improved by reducing C content in molten steel, but can reduce steel yield strength, and C contains Amount will increase steel smelting cost lower than 0.05%, and C content is 0.06~0.10% in comprehensively considering lower control molten steel.

N: being impurity element in traditional nitrogen in steel, and still, N and Nb, Ti reaction generate (Nb, Ti) N, and (Nb, Ti) N can be prevented Austenite Grain Growth, plays the effect of refinement crystal grain, and (Nb, Ti) N can also play the effect that precipitation strength improves steel strength. Therefore nitrogen control range in the present invention are as follows: 0.002-0.005%.

Si: silicon can play the effect of solution strengthening, can improve steel strength, control molten steel oxygen using Si in the present invention Position, under refining furnace liquid steel temperature, the dissolved oxygen content of the Si balance with 0.6~0.7% is about 20~30ppm, therefore, this hair Bright middle control silicone content range are as follows: 0.6~0.7%.

S: sulphur is impurity element, can cause steel red brittleness, and causes the anisotropy of steel, and the lower S content the better, examines Consider smelting cost, the control range of S content in the present invention are as follows:≤0.010%.

Ti: titanium is the formation element of strong carbon, nitrogen and sulfide, and the binding ability of Ti and N are greater than Nb, and the generation of TiN can press down The generation of NbN at austenite grain boundary processed, to solve the slab of steel containing niobium crack problem, but the binding ability of Ti and O is stronger, for up to The effect for being about 20~30ppm to control steel content of oxygen dissolved in water, can only be added micro Ti, therefore, control in the present invention Ti content range are as follows: 0.005~0.01%.

Nb: niobium can play the effect of strong refined crystalline strengthening and precipitation strength, be needed in the application using Nb, Ti microalloy Change the strengthening effect for increasing 40Mpa, since Ti is controlled 0.005~0.010%, according to the strengthening effect of Nb, Ti, therefore, this Content of niobium range is controlled in invention are as follows: 0.015~0.025%.

Mn: manganese can improve steel strength and will not reduce steel toughness, but Mn too high levels can cause stocking band occur Therefore shape tissue controls manganese content range are as follows: 1.40~1.70% in the present invention.

P: phosphorus significantly deteriorates the toughness of steel, and it is low as far as possible to need to control P in molten steel for the steel that cold district uses, In view of smelting cost, phosphorus content range is controlled in the present invention are as follows: P≤0.010%

Mg: the application is mingled with by generating MgO in steel come inductive formation intragranular acicular ferrite tissue, is improved with this The low temperature impact properties of steel, it is therefore desirable to have a certain range of content of magnesium in steel, it is contemplated that smelting cost, the present invention in control Content of magnesium range processed are as follows: Mg:0.004~0.007%

Al: the application is mingled with by generating MgO in steel come inductive formation intragranular acicular ferrite tissue, but MgO easily and Al₂O₃It is mingled with to react and generates magnesium aluminate spinel (MgOAl₂O₃), MgOAl₂O₃The easy agglomeration of field trash and easily blocking The submersed nozzle of continuous casting, therefore Al content in molten steel need to be reduced as far as possible, aluminium content range is controlled in the present invention are as follows: Al≤ 0.002%

The present invention also provides a kind of manufacturing methods of low-alloy high-strength hot strip rolling suitable for extremely cold area comprising Following steps:

Its process flow are as follows: KR method molten iron takes off S → duplex converter and takes off P, de- C → LF refining furnace → sheet billet continuous casting → heating furnace Interior steel billet reheating → roughing, finish rolling → ultrafast cold → section cooling → batch；Specific production technology are as follows:

1) using KR mechanical mixing method to molten iron carry out desulfurization, lime consumption amount be 5~8kg/ tons of iron, by molten iron sulphur take off to 0.01% or less；Then deep de- P and deep decarburization are carried out to molten iron through duplex converter, P in molten iron is taken off to 0.007% hereinafter, iron C takes off to 0.006% hereinafter, when decarburization converter molten steel goes out to 1/5th in water, and Si-Ca-Ba, silicomanganese, ferrosilicon, niobium is added portionwise Iron carries out deoxidation alloying, and molten steel adds when going out to 3/4ths, and Si-Ca-Ba additional amount is 3~5kg/t steel, silicomanganese additional amount 23 ~27kg/t steel, ferrosilicon additional amount 6~8kg/t steel, ferro-niobium additional amount 0.3~0.5kg/t steel；

2) adjustment for then carrying out temperature, composition, degree of purity to molten steel through LF refining furnace, using Si-Ca-Ba and CaC to steel Water carries out deoxidation, and the adjustment Ti composition of alloy containing Ti is added into molten steel after producing yellowish-white slag, refines in terminal clinker for refinery cinder TFe content≤1% controls steel oxygen in water oxygen position within the scope of 20~30ppm, in the entire system of steel billet before soft blow argon It makes and is added without the deoxidier containing aluminium in process, control Al≤0.002% in steel billet composition, molten steel composition, temperature, molten steel dissolved oxygen After oxygen position, refinery cinder oxidisability are met the requirements, promote molten steel progress soft blow argon operation the floating of large-sized inclusions, it is soft Magnesium manganese line is fed in Argon 7~9 minutes backward molten steel generates a large amount of tiny MgO field trashes, magnesium manganese line composition are as follows: Mg:10wt% ~15wt%, Mn:30wt%~80wt%, Fe are surplus, control Mg content in molten steel are as follows: 0.004~0.007%, feed magnesium Continue soft blow argon 2~3 minutes uniform molten steel compositions after manganese line, molten steel is then transported to continuous casting station and carries out slab casting.

Magnesium manganese line plays the role of deep deoxidation and refinement is mingled with, and MgO field trash generated is not easy agglomeration, and size is small 99% or more of field trash total quantity is accounted in 5 μm of the amount of inclusions, the amount of inclusions of 0.05~5 μ m in size of size in steel For 4000~10000/mm²。

3) whole process protection is cast during continuous casting operation, and crystallizer section is 175mm × (950~1350) mm, crystallizer Interior plus low carbon protective slag, Casting speed are 1.2~1.3m/min, keep stablizing pulling rate.

In order to solve the problems, such as continuous casting sprue dross caused by MgO is mingled with easily, using not being mingled with chemically reactive and not with MgO The easily continuous casting sprue inner cavity liner that is mingled with of absorption MgO, tundish is to the submersed nozzle inner cavity between crystallizer in continuous casting process Liner material is zirconium oxide, and the liner ingredient of submersed nozzle inner cavity is zirconium oxide: 92%~95%, yttrium oxide: 3~5%, Carbon: 2~3%, aluminium oxide≤0.5%, magnesia≤0.5%.

4) steel billet is reheated in heating furnace, enters furnace plate base heating cycle specific requirement and is shown in Table 1.

1 heating of plate blank system of table

5) roughing is carried out to the steel billet of the reheating, roughing carries out round-trip 5 passes, roughing using singlestandmill Start rolling temperature: 1180~1220 DEG C, heat preservation and soaking are carried out to intermediate base using Coil Box after roughing, reduce intermediate base end to end The temperature difference, intermediate base temperature: 1050~1080 DEG C.Later in A_r3Finish rolling is carried out to intermediate base at a temperature of above, finish rolling uses 7 framves Milling train continuous rolling, finish rolling finishing temperature: 840~880 DEG C, the poker temperature difference controls within 30 DEG C, commercial stock with a thickness of 2~ 15mm。

Stocking is subjected to ultra-rapid cooling immediately after finish rolling, stocking mean temperature is cooled to 720~760 DEG C, cooling speed Degree is 100~200 DEG C/S, and stocking is then carried out section cooling, and stocking is cooled to 640~680 DEG C, cooling velocity is 10~ 15 DEG C/S, stocking is then air-cooled to coiling temperature, coiling temperature is 620~660 DEG C, and the stocking of different-thickness specification rolls rear cold But system requires to be shown in Table 2.

2 stocking roller repairing system of table

Compared with conventional smelting iron and steel technique, manufacturing method provided by the invention has the following different:

(1) using low-carbon, technical solution low-phosphorous, niobium titanium is compound when steel product ingredient designs, low-carbon low-phosphorous can improve steel Low temperature impact properties, crystal grain is refined by the way that a small amount of Nb, Ti is added and improves intensity, and a small amount of Ti is added to inhibit The generation of the slab crackle of steel containing niobium.

(2) deep de- P and deep decarburization are carried out to molten steel using duplex converter, P in molten steel is taken off to 0.007% hereinafter, molten steel Middle C takes off to 0.006% or less.

Duplex converter is to carry out deep dephosphorization and deep carbonization treatment to molten steel using two block converters, and molten steel is handled through dephosphorization converter Afterwards, the P content in molten steel taken off to 0.025% hereinafter, then molten steel by ladle turnover be blended into decarburization converter again, by It will not be introduced into decarburization converter in the dephosphorization clinker in dephosphorization converter, make after new clinker that phosphorus content is low in clinker in decarburization converter, So the dephosphorisation reaction in decarbonizing furnace between clinker and molten steel can continue, can continue to take off P content in molten steel to 0.007% hereinafter, phosphorus content low energy significantly improves the low temperature impact properties of steel.

(3) steel oxygen in water oxygen position is controlled before the soft blow argon of LF refining within the scope of 20~30ppm, in steel billet It is added without the deoxidier containing aluminium in entire manufacturing process, controls Al≤0.002% in steel billet composition.

The application refines field trash using magnesia deoxidier, so need to be pre- in molten steel before magnesia deoxidier is added It stays enough dissolved oxygens to be mingled with to generate MgO, is mingled with achieving the effect that generate sufficient amount of tiny MgO, so in LF essence Steel oxygen in water oxygen position is controlled before the soft blow argon of refining within the scope of 20~30ppm.Due to being generated after magnesia deoxidier deoxidation MgO field trash easily and Al₂O₃Generate magnesium aluminate spinel MgOAl₂O₃Field trash, MgOAl₂O₃The easy agglomeration of field trash and The easily submersed nozzle of blocking continuous casting, so needing Al content in strict control molten steel, in the entire manufacturing process of steel billet not The deoxidier containing aluminium is added.

(4) the soft blow argon that LF refining closes on end is divided into two stages, before soft blow argon effect in 7~9 minutes be promote it is big Sized inclusions, which float, to be removed, and feeding magnesium manganese line generates a large amount of tiny MgO and is mingled in soft blow argon 7~9 minutes backward molten steel, magnesium Manganese line composition are as follows: Mg:10wt%~15wt%, Mn:30wt%~80wt%, Fe are surplus, control Mg content in molten steel are as follows: 0.004~0.007%, continue soft blow argon 2~3 minutes uniform molten steel compositions after feeding magnesium manganese line, molten steel is then transported to continuous casting Station carries out slab casting.

Magnesium manganese line plays the role of deep deoxidation and refinement is mingled with, and MgO field trash generated is not easy agglomeration, and size is small 99% or more of field trash total quantity is accounted in the MgO the amount of inclusions of 5um, the field trash of 0.05~5um of size size in steel Quantity is 4000~10000/mm²。

The application refines field trash using magnesia deoxidier, and the MgO field trash generated after magnesia deoxidier deoxidation is mutual Between attraction it is small, MgO field trash is not easy agglomeration, and tiny MgO can induce precipitation during being mixed in roller repairing Intragranular acicular ferrite can divide austenite grain in multiple acicular ferrites that austenite crystal intragranular is formed, so that generate Acicular ferrite crystal grain more tinyization, and the position of the acicular ferrite crystal grain generated is to being arranged as different directions, it is needle-shaped Ferrite is in criss-cross pattern.Acicular ferrite heterogeneous nucleation at non-golden field trash under normal circumstances, then from this A nucleation sites are to many different direction radiation growths.Since its tissue is linkage structure, the expansion of crackle can be prevented well Exhibition, therefore there is good mechanical property, especially toughness, the low temperature impact properties of steel can be significantly improved.Typical needle-shaped iron Ferritic pattern is illustrated in fig. 1 shown below.

(5) the liner material of tundish to the submersed nozzle inner cavity between crystallizer is zirconium oxide in continuous casting process (ZrO₂), the liner ingredient of submersed nozzle inner cavity is zirconium oxide: 92%~95%, yttrium oxide: 3~5%, carbon: 2~3%, oxygen Change aluminium≤0.5%, magnesia≤0.5%.

Inclusion content in melting steel is controlled in the application offer technology and is mingled with for MgO, MgO and ZrO₂It is strong basic ion Close object, MgO and ZrO₂It is difficult to chemically reactive；And MgO and ZrO₂It is molten former according to phase patibhaga-nimitta for the substance of different molecular type Reason mutually melts principle, MgO and ZrO with dissimilar hardly possible₂It is difficult to fuse together mutually；So MgO be mingled be difficult to be in liner material matter Zirconium oxide (ZrO₂) submersed nozzle inner cavity on assemble growth, Submerged Nozzle Clogging Course phenomenon will not be occurred, continuous casting casting It can stable smooth operation.

(6) in hot-rolled process, control finish rolling finishing temperature within the scope of 840~880 DEG C, after finish rolling immediately by stocking into Stocking mean temperature is cooled to 720~760 DEG C by row ultra-rapid cooling, and cooling velocity is 100~200 DEG C/S, then by stocking Section cooling is carried out, stocking is cooled to 640~680 DEG C, cooling velocity is 10~15 DEG C/S, is then air-cooled to stocking and batches Temperature, coiling temperature are 620~660 DEG C.

Immediately by steel ultra-rapid cooling to ferritic phase height temperature after rolling, since cooling time is short, rolled piece leads to rapidly Austenitic area is crossed, the dislocation inside austenite grain has little time to reply, and keeps rolled piece austenite hardening state, the change inside stocking Shape can be saved, and the number of nuclei of subsequent ferrite transformation, fining ferrite grains can be greatly improved；Due to ultrafast quickly cooling But stocking surface temperature is lower than about 50~100 DEG C of stocking mean temperature during, and stocking mean temperature is cooled to 720~760 DEG C when, stocking surface temperature remains to reach 650 DEG C or more, and bainite transformation will not occur for stocking surface at such a temperature, can protect The uniformity for holding stocking tissue, it is the appearance of pearlite+ferrite phenomenon that prevent stocking surface, which be bainite, stocking center portion,.

Stocking carries out section cooling after ultra-rapid cooling, and cooling velocity is 10~15 DEG C/S, which is greater than Perlitic transformation cooling rate, but it is less than bainite transformation cooling rate, which is the cooling rate range of acicular ferrite, can promote crystalline substance Interior acicular ferrite is formed.

Coiling temperature is 620~660 DEG C, and bainite transformation does not occur for stocking at such a temperature, and stocking tissue is needle-shaped iron Ferritic+a small amount of pearlite.

Advantages of the present invention

1, the present invention induces the precipitation of intragranular acicular ferrite using Oxides Metallurgy Technology, and intragranular acicular ferrite has Conducive to the low temperature impact properties for improving steel.The present invention is mingled with to realize Oxides Metallurgy Technology by tiny MgO, discusses in detail Stated the method for a large amount of tiny MgO field trashes that generates, prevent MgO field trash from causing the method for Submerged Nozzle Clogging Course, roll after promote The cooling system that intragranular acicular ferrite is precipitated marches toward Oxides Metallurgy Technology practice from theory, realization Oxide Metallurgy The engineering of technology.

2, for the present invention using ultrafast refrigeration technique come fining ferrite grains, stocking terminates temperature to ferrite transformation in finish rolling It takes the cooling velocity being exceedingly fast to be cooled down in section between temperature, the deformation inside stocking is saved, it can pole The number of nuclei of the big subsequent ferrite transformation of raising, fining ferrite grains；Simultaneously in order to formed uniform acicular ferrite+ A small amount of pearlitic structrure prevents the inconsistent of stocking center portion and surface, and the final temperature that the application devises ultra-rapid cooling is 720~760 DEG C, the temperature on stocking surface is higher than bainite transformation temperature under the final temperature, in subsequent section cooling mistake The temperature gap on Cheng Zhong, stocking center portion and surface further reduces, the case where section cooling final temperature is 640~680 DEG C Under, it is able to achieve appearance of the surface without bainite structure in stocking Cooling Process, is able to maintain the uniformity of stocking tissue, prevents from rolling It is the appearance of pearlite+ferrite phenomenon that material surface, which is bainite, stocking center portion, solves ultra-rapid cooling technique and easily rolls The problem of material nonuniform organization phenomenon.

3, using low-carbon, technical solution low-phosphorous, niobium titanium is compound when steel product ingredient designs, low-carbon low-phosphorous can improve steel Low temperature impact properties, crystal grain is refined by the way that a small amount of Nb, Ti is added and improves intensity, and a small amount of Ti is added to inhibit The generation of the slab crackle of steel containing niobium.

Detailed description of the invention

Fig. 1 is typical acicular ferrite structure's shape appearance figure.

Specific embodiment

Any feature is disclosed to obtain in this specification, it unless specifically stated, can be equivalent or with similar purpose by other Alternative features are replaced.Unless specifically stated, each feature is an example in a series of equivalent or similar characteristics ?.It is described to understand the present invention just for the sake of help, it should not be considered as to concrete restriction of the invention.

The steel billet composition of embodiment see the table below 3；

3 embodiment steel billet composition of table

The process flow of embodiment is using process flow, the rolling of embodiment and roller repairing described in Summary Technique see the table below 4；

The rolling and roller repairing technique of 4 embodiment of table

Inclusion density, mechanical property, the tissue of embodiment stocking see the table below 5；

Inclusion density, mechanical property, the tissue of 5 embodiment stocking of table

The stocking mechanical property of Examples 1 to 5 is all satisfied Russia's mark GOST 19281-2014 and GOST 27772-2015 rule The mechanical property of the serial steel in fixed 345, and -60 DEG C of low-temperature impact toughness is greater than 200J, is much larger than standard requirements, shows Good low-temperature flexibility index；The inclusion density of 0.05~5um size is 5000~9000/mm inside stocking², tiny folder Sundries quantity is more, can play the effect that intragranular acicular ferrite is precipitated in good induction；Stocking surface is identical with the tissue of center portion, Since uniform tissue is presented in stocking in a thickness direction, the deformation of surface and center portion also can be equal in stocking loading process It is even, it is not in the phenomenon that stress is concentrated, stocking elongation percentage is high；10~12 grades of stocking grain size, crystal grain is thin, low temperature impact properties It is good.

Technological parameter (such as temperature, time) section bound value of the invention and interval value can realize this law, Embodiment numerous to list herein.

Ordinary skill in the art knowledge can be used in the unspecified content of the present invention.

It should be noted last that the above examples are only used to illustrate the technical scheme of the present invention and are not limiting.Although ginseng It is described the invention in detail according to embodiment, it will be apparent to an ordinarily skilled person in the art that technical side of the invention Case is modified or replaced equivalently, and without departure from the spirit and scope of technical solution of the present invention, should all be covered in the present invention Scope of the claims in.

Claims (5)

1. a kind of low-alloy high-strength hot strip rolling suitable for extremely cold area, which is characterized in that by weight percentage, change Study part are as follows:

C:0.06~0.10%, Si:0.6~0.7%, Mn:1.40~1.70%, Nb:0.015~0.025%, Ti:0.005~ 0.010%, Mg:0.004~0.007%, P≤0.010%, S≤0.010%, Al≤0.002%, N:0.002~0.005%, Surplus is Fe and is inevitably mingled with.

2. the preparation method described in claim 1 suitable for the low-alloy high-strength hot strip rolling of extremely cold area, the preparation side Method the following steps are included:

KR method molten iron take off S → duplex converter take off P, de- C → LF refining furnace → sheet billet continuous casting → Steel In Reheating Furnace base reheat → it is thick It rolls, finish rolling → ultrafast cold → section cooling → is batched；

Wherein,

Field trash is refined using magnesia deoxidier, controlled before the soft blow argon of LF refining steel oxygen in water oxygen position 20~ Within the scope of 30ppm；

The soft blow argon that LF refining closes on end is divided into two stages, and effect in 7~9 minutes is that large scale is promoted to be mingled with before soft blow argon Object, which floats, to be removed, and feeding magnesium manganese line generates a large amount of tiny MgO and is mingled in soft blow argon 7~9 minutes backward molten steel, is controlled in molten steel Mg content are as follows: 0.004~0.007%, continue soft blow argon 2~3 minutes uniform molten steel compositions after feeding magnesium manganese line, then by molten steel It is transported to continuous casting station and carries out slab casting；

The liner material of tundish to the submersed nozzle inner cavity between crystallizer is zirconium oxide material in continuous casting process.

3. preparation method according to claim 2, which is characterized in that desulfurization is carried out to molten iron using KR mechanical mixing method, Lime consumption amount is 5~8kg/ tons of iron, and molten iron sulphur is taken off to 0.01% or less；Then deep de- P is carried out to molten iron through duplex converter With deep decarburization, P in molten iron is taken off to 0.007% hereinafter, C takes off to 0.006% hereinafter, going out in decarburization converter molten steel to five in molten iron When/mono-, Si-Ca-Ba, silicomanganese, ferrosilicon, ferro-niobium being added portionwise and carries out deoxidation alloying, molten steel adds when going out to 3/4ths, Si-Ca-Ba additional amount is 3~5kg/t steel, silicomanganese additional amount 23~27kg/t steel, ferrosilicon additional amount 6~8kg/t steel, ferro-niobium addition Measure 0.3~0.5kg/t steel.

4. preparation method according to claim 2, which is characterized in that Steel In Reheating Furnace base reheats, and enters furnace heating of plate blank System specifically:

1180-1220 DEG C of tapping temperature；Soaking section temperature controls 1200-1260 DEG C, and bringing-up section temperature controls 1210-1280 DEG C, Preheating section temperature controls 1000-1150 DEG C；Cold base heating time >=130min, hot base heating time >=100min.

5. preparation method according to claim 2, which is characterized in that in hot-rolled process, control finish rolling finishing temperature exists Within the scope of 840~880 DEG C, stocking is subjected to ultra-rapid cooling immediately after finish rolling, stocking mean temperature is cooled to 720~760 DEG C, cooling velocity is 100~200 DEG C/S, and stocking is then carried out section cooling, stocking is cooled to 640~680 DEG C, cooling Speed is 10~15 DEG C/S, and stocking is then air-cooled to coiling temperature, and coiling temperature is 620~660 DEG C.