CN115537671B - Preparation method of valve spring steel - Google Patents
Preparation method of valve spring steel Download PDFInfo
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- CN115537671B CN115537671B CN202110733860.6A CN202110733860A CN115537671B CN 115537671 B CN115537671 B CN 115537671B CN 202110733860 A CN202110733860 A CN 202110733860A CN 115537671 B CN115537671 B CN 115537671B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/002—Hybrid process, e.g. forging following casting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/076—Use of slags or fluxes as treating agents
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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Abstract
The invention discloses a preparation method of valve spring steel, which is prepared by primary smelting, LF furnace refining, VD furnace refining, continuous casting, electroslag remelting, forging and wire rolling. The preparation method of the valve spring steel can stably control inclusions in the steel, can lead the width of the inclusions of the valve spring steel to be comprehensively smaller than 6 mu m, lead the length-width ratio of 95 percent of the inclusions (larger than 2 mu m) to be larger than 2, can not contain brittle aluminum inclusions, lead the surface quality of a wire rod to be excellent, meet the requirement of the valve spring steel of a high-end passenger car, and reduce the failure risk of the valve spring steel to zero due to the inclusions.
Description
Technical Field
The invention belongs to the technical field of steelmaking, and particularly relates to a preparation method of valve spring steel.
Background
The valve spring steel is steel for an engine valve spring, and the valve spring is positioned between an engine cylinder cover and a valve rod tail end spring seat; the function of the valve seat is to ensure that the valve seat can be tightly attached to the valve seat or the valve retainer when the valve is closed, and overcome the inertia force generated by a valve mechanism when the valve is opened, so that the transmission parts are always controlled by the cam and are not separated from each other; because the valve spring is one of the core safety parts of the engine, strict requirements are imposed on steel for the valve spring, particularly the valve spring for a passenger car, the surface quality of the valve spring steel cannot be problematic, the fatigue life of the relevant spring is required to be stable for over 2000 ten thousand times, the steel is required to have ultrahigh purity, strict requirements are imposed on steelmaking, the total inclusion content of the steel is less than or equal to 10 mu m, the inclusion plasticity is good, and brittleness and non-deformation inclusion cannot be caused.
In order to be able to better smelt valve spring steel, publication number KR20000041267 (a) proposes that the valve spring steel inclusion control-related composition is less than 0.025wt% S and less than 0.010wt% Al and forms non-composite inclusions of less than 10 μm, the inclusion proportion in the steel slab being less than 0.05%, however this technique is silent about how to achieve inclusion control. The publication No. JPS62170460 (a) proposes to treat steel to obtain an extremely low oxygen content, thereby reducing the oxygen content to 15ppm or less, further treat steel to obtain a desired extremely low Ti and N content, thereby limiting the Ti content to 50ppm or less, limiting the N content to 60ppm or less, and then control the form of inclusions in the steel by adding calcium, thereby making the steel very clean and improving fatigue characteristics, and the present method proposes to strictly control the oxygen, titanium and nitrogen contents of the steel and control the inclusions by calcium treatment, however this patent does not mention how to control the inclusion size, and large-particle silicate inclusions, although plastic, are also detrimental to valve spring steel.
At present, enterprises for actually producing valve spring steel, especially passenger car valve spring steel, mainly produce wire rods through conventional electric furnaces (or converters), ladle furnace refining, vacuum refining (optional), square billet continuous casting, blooming (optional), finish rolling in Japan, and steel-making end control inclusions depend on control raw materials and refractory quality to ensure that harmful inclusions do not enter molten steel, so that the difficulty of steel-making end tissue production is high, smelting cost is high, and the produced valve spring steel wire rods still have the risk of large particle inclusions remained in steel despite reaching the control requirements of related inclusions; to circumvent this risk in engine manufacture, a dual valve spring is used to mount on the engine, and once one valve spring fails, the other valve spring can continue to operate.
In view of the above, there is a need in the industry to develop a new method for preparing valve spring steel, which can stably control inclusions in the steel, ensure the surface quality of the valve spring steel wire rod, and reduce the risk of failure of the valve spring steel due to the inclusions to zero.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a preparation method of valve spring steel, which can stably control inclusions in the steel, ensure the surface quality of a valve spring steel wire rod and reduce the risk of failure of the valve spring steel due to the inclusions to zero.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of a valve spring,
a preparation method of valve spring steel is characterized in that the valve spring steel is obtained through primary smelting, LF furnace refining, VD furnace refining, continuous casting, electroslag remelting, forging and wire rolling.
Preferably, the method specifically comprises the following steps:
(1) Primary smelting, namely primary smelting by adopting an electric furnace/converter to obtain molten steel, and adding high-purity ferrosilicon, low-carbon low-aluminum ferrochrome and electrolytic manganese into the molten steel in the tapping process to perform initial alloying treatment;
(2) Refining in an LF furnace, adding lime and synthetic slag into a ladle to perform slag formation, then adding alloy and carbon powder to adjust the components of molten steel to a target range, and prohibiting aluminum deoxidation, wherein the alkalinity of a final slag system is 0.8-1.2;
(3) Refining in a VD furnace, controlling the vacuum pressure to be 100-1000 Pa, and the vacuum treatment time to be 10-20 min;
(4) Continuous casting, namely directly casting molten steel into a continuous casting square billet;
(5) Electroslag remelting, cleaning the surface of the continuous casting square billet, preparing an electrode rod, and carrying out electroslag remelting by taking the electrode rod as a raw material to obtain an electroslag ingot, wherein the electroslag is guaranteedThe slag protection comprises the following components in percentage by mass: caF (CaF) 2 ：45～55wt％，CaO：10～15wt％，Al 2 O 3 ：5～15wt％，SiO 2 ：20～25wt％，Na 2 O：1～5wt％；
(6) Forging, namely forging the electroslag ingot into a forging square billet for rolling wires;
(7) Rolling wires, namely rolling the forged square billet to obtain a valve spring steel wire rod, wherein the valve spring steel wire rod comprises the following components in percentage by mass: c:0.5 to 0.6 percent of Mn:0.6 to 0.8 percent of Si: 1.45-1.55%, ti <0.001%, al <0.0015%, N <0.006%, cr 0.6-0.8%, S0.002-0.01%, and the balance being iron and unavoidable impurities.
Preferably, in the step (1):
the high-purity ferrosilicon comprises the following components in percentage by mass: si: 70-80%, al <0.02%, ti <0.05%, the balance being iron and unavoidable impurities; the addition amount of the high-purity ferrosilicon is 20-25 kg/t steel; and/or
The low-carbon low-aluminum ferrochrome comprises the following components in percentage by mass: cr: 50-70%, al <0.05%, ti <0.05%, the balance being iron and unavoidable impurities; the addition amount of the low-carbon low-aluminum ferrochrome is 11-13 kg/t steel; and/or
The addition amount of the low-carbon low-aluminum ferrochrome is 11-13 kg/t steel; the addition amount of the electrolytic manganese is 6-8 kg/t steel; and/or
And adding carbon powder according to the carbon content of converter or electric furnace tapping and the target carbon content of valve spring steel in the tapping process.
Preferably, in the step (2):
the synthetic slag comprises the following components: caO: 35-45 wt% of SiO 2 ：40～50wt％，Al 2 O 3 :0 to 3 weight percent of MgO: 3-5 wt%; and/or
In the slag forming process, the slag amount is controlled to be 15-25 kg/t of steel; and/or
In the final slag, al 2 O 3 Content of<5wt％。
Preferably, in the step (3), after the refining in the VD furnace is finished, the composition of molten steel meets the following requirements: c:0.5 to 0.6 percent of Mn:0.7 to 0.8 percent of Si: 1.5-1.55%, ti <0.001%, al <0.0015%, N <0.0055%, cr 0.6-0.8%, S0.002-0.01%, H <2ppm.
Preferably, in the step (4), the cross-sectional dimension of the continuous casting billet is (300 to 340 mm) × (400 to 430 mm).
Preferably, in the step (5):
adopting full argon gas for sealing protection; and/or
The diameter of the electroslag ingot is 0.6-0.65 m.
Preferably, in the step (6), the cross section of the forging square billet is square, and the side length of the cross section is 0.14-0.16 m; the length of the forging square billet is more than 10m.
Preferably, in the step (7), the diameter of the valve spring steel wire rod is 5-8 mm.
The process route of the invention is based on the traditional electric furnace or converter-refining-continuous casting process route, and electroslag smelting is newly added, so that large-particle inclusions in steel can be further removed through electroslag smelting, and the plasticity of inclusions is controlled through the electroslag covering slag mentioned later; meanwhile, for the traditional electroslag path, a die casting original ingot is generally used as an electrode rod, and the continuous casting square billet is directly used as the electrode rod, so that the die casting cost is far higher than that of continuous casting, and the continuous casting square billet is used as the electrode rod, so that the production cost can be greatly saved; after the continuous casting square billet is obtained by continuous casting through the brand new process path, a certain amount of continuous casting square billets can be selected selectively to smelt valve spring steel, and the continuous casting square billets obtained by the rest continuous casting can still be directly rolled to produce spring steel meeting the requirements, such as suspension spring steel.
In the primary smelting process, the lower the aluminum content is required to be, the better the aluminum content is required to realize that brittle alumina inclusions or magnesia-alumina spinel inclusions are not generated or are rarely generated, but the alloy materials used in the steelmaking process generally contain metal aluminum, so that the alloy containing a small amount of aluminum such as high-purity ferrosilicon, low-carbon low-aluminum ferrochrome and the like is added as much as possible in the tapping process of an electric furnace or a converter, the generation of the brittle alumina is avoided as much as possible by utilizing the condition that molten steel oxygen is still in a higher content in the tapping process, the addition of the high-purity ferrosilicon and the low-carbon low-aluminum ferrochrome are configured according to the upper limit required by the final components of the steel, specifically, the addition of the low-carbon low-aluminum ferrochrome is 11-13 kg/t, and the addition of electrolytic manganese is 6-8 kg/t. The high-purity ferrosilicon, low-carbon low-aluminum ferrochromium and the like are adopted, and the aluminum and titanium contents of the alloy added in tapping are controlled mainly to control the aluminum content and the titanium content in the final molten steel to be in a lower range;
in the refining process of the LF furnace, synthetic slag is added for smelting so as to facilitate slagging, if lime is difficult to melt due to the fact that lime slagging is only added, on one hand, the melting convenience of the synthetic slag is ensured, and on the other hand, the composition of the synthetic slag is set for the final slag system composition; the synthetic slag contains a small amount of MgO to prevent the synthetic slag from seriously corroding MgO-C furnace lining refractory materials of the LF furnace; controlling the slag amount to be 15-25 kg/t steel, which is relatively low, so as to ensure that the slag surface of the slag is easy to break in the subsequent VD vacuum refining treatment, so that the vacuum pressure of the VD furnace is relatively easy to reduce to a target range, if the slag amount is controlled to be lower than 15kg/t steel, the slag amount is too low to prevent an electric arc refined in the LF furnace, and if the slag amount is higher than 25kg/t steel, the slag amount is too high to ensure that the vacuum refining treatment pressure of the subsequent VD furnace is smoothly reduced; the aluminum addition deoxidization is forbidden in the invention because the valve spring steel cannot be mixed with aluminum oxide; the alkalinity of the final slag system is 0.8-1.2, and the final slag Al 2 O 3 Content of<5% is to ensure good fluidity of the slag and good plasticity of inclusions formed once the slag is involved in the molten steel.
The vacuum refining of the VD furnace mainly removes N and H in molten steel, but if the vacuum pressure is controlled to be too low (namely, the vacuum degree is too high), the vacuum melting loss falling off of the vacuum refractory in the VD furnace is triggered, so that the falling off of the refractory is prevented finally for ensuring denitrification and dehydrogenation, the vacuum pressure is controlled to be 100-1000 Pa finally, and the vacuum treatment time is 10-20 min. After the vacuum refining treatment of the VD furnace is finished, the composition of the molten steel is basically determined, so that the lower limit of the silicon content control of the molten steel is slightly higher than the lower limit of the silicon content of the final wire rod composition after the vacuum treatment is finished in order to prevent the attenuation of the silicon content in the subsequent electroslag remelting process, and the upper limit of the nitrogen content control of the molten steel after the end of the VD process is lower than the upper limit of the nitrogen content of the final wire rod in order to prevent the extremely small nitrogen increment in the electroslag remelting process. H can be determined after the vacuum refining of the VD furnace is finished, and for valve spring steel, because the specification is thinner, the H content requirement is not as strict as that of a thick-specification wire rod, and the H <2ppm can meet the requirement of no hydrogen induced crack in the wire rod.
In the continuous casting process, the section size of the continuous casting square billet is controlled to be (300-340 mm) x (400-430 mm); on one hand, the setting of the section size of the continuous casting square billet meets the section size requirement of normal mass production, and can also meet the size requirement of the continuous casting square billet serving as an electrode rod for electroslag removal remelting.
According to the electroslag remelting method, remelting treatment is carried out on the square billet electrode rod through the electroslag furnace, although the aluminum content and the inclusion morphology of molten steel are strictly controlled in the smelting process of electric furnace (or converter) -LF furnace-VD furnace-continuous casting, the risk of corrosion and falling of refractory materials or the risk of slag being involved in the smelting process exist in the process, inclusions larger than 10 mu m in steel cannot be completely eradicated, and finally the coil rod of the valve spring steel cannot be eradicated of inclusion exceeding the standard and finally losing efficacy; in the electroslag remelting smelting process, the floating speed of molten steel and molten casting powder in an electroslag furnace is extremely slow, the speed is about 0.07mm/s, impurities larger than 12 mu m are adsorbed and completely removed by slag according to the floating speed calculation of the impurities, meanwhile, the impurities cannot deform along with a steel matrix in the follow-up forging or rolling process when the size of the impurities is 2-3 mu m after the electroslag is considered, the impurities in the 95% proportion (larger than 2 mu m) of the valve spring steel can not deform along with the steel matrix due to the fact that the specific surface area of molten steel-slag contact is large, the impurities have the capability of converting into casting powder components, the setting of slag protecting components ensures that the impurities have low melting point and good plasticity, even if the impurities of exactly 12 mu m remain in the molten steel, the length-width ratio is larger than 2 after the impurities are deformed in the follow-up forging and rolling process, and the length-width of the impurities is smaller than or equal to 6 mu m. The protecting slag in electroslag process is mainly used for isolating molten steel from outsideAnd the contact can also be used for removing the melting electrode by electric heating to form a molten steel pool in the electroslag furnace, the molten steel pool is stored in a copper plate crystallizer, and the molten steel is gradually cooled into an electroslag ingot due to water cooling on the outer layer of the crystallizer. The composition of the covering slag is mainly ensured to be acid slag, so that the covering slag has stronger adsorption or modification capability of possibly remaining alumina inclusion in the original electrode rod, and the final composition of the covering slag is set as CaF by comprehensively considering 2 ：45～55％，CaO：10～15％，Al 2 O 3 ：5～15％，SiO 2 : 20-25%, na2O:1 to 5 percent of casting powder is added into CaF 2 The method mainly ensures that the slag has certain conductivity, and the other components of the protective slag have the extremely content of ensuring that the protective slag is in a low melting point and has the plastic inclusion capacity; the casting powder selected by the invention has a lower melting point, and is only about 1200 ℃, so that the casting powder can also well improve the heat transfer between a crystallizer and the steel solidification process in the electroslag remelting process, and the surface quality of the final electroslag ingot is good.
The components of the final wire rod in the rolling process are set according to the requirement of valve spring steel, the lower limit of the S in molten steel is required to be 0.002wt%, and MnS inclusion is mainly used for separating and wrapping oxide inclusion so as to reduce the harm of inclusion.
In addition, the invention mainly facilitates the production in the processes of continuous casting, electroslag remelting, forging and rolling for setting the sizes of the related electrode bars, electroslag ingots and wire rods.
The preparation method of the valve spring steel provided by the invention has the following beneficial effects:
1. the preparation method of the valve spring steel can stably control inclusions in the steel, ensure the surface quality of the valve spring steel wire rod and reduce the risk of failure of the valve spring steel due to the inclusions to zero;
2. the preparation method of the valve spring steel can lead the width of the inclusions of the valve spring steel to be comprehensively smaller than 6 mu m, lead the length-width ratio of 95 percent of the inclusions (larger than 2 mu m) to be larger than 2, lead the inclusions not to contain brittle aluminum inclusions, lead the surface quality of the wire rod to be excellent, meet the requirement of the valve spring steel of high-end passenger vehicles and lead the failure risk of the valve spring steel to be reduced to zero.
Detailed Description
In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below with reference to examples.
The process route of the valve spring steel provided by the invention is as follows: primary refining, LF refining, VD refining, continuous casting, electroslag remelting, forging and wire rolling.
The preparation method of the valve spring steel comprises the following specific steps:
(1) Primary refining: primary smelting by adopting an electric furnace/converter to obtain molten steel, and adding high-purity ferrosilicon, low-carbon low-aluminum ferrochromium and electrolytic manganese into the molten steel in the tapping process to perform initial alloying treatment;
the specific process is as follows: according to the requirements of finished products of valve spring steel, primary smelting is carried out through an electric furnace or a converter to obtain molten steel, and high-purity ferrosilicon, low-carbon low-aluminum ferrochromium and electrolytic manganese are added in the tapping process for initial alloying; the high-purity ferrosilicon comprises the following components in percentage by mass: si: 70-80%, al <0.02%, ti <0.05%, the balance iron and unavoidable impurities, the addition of high-purity ferrosilicon is 20-25 kg/t steel; the low-carbon low-aluminum ferrochrome comprises the following components in percentage by mass: cr: 50-70%, al <0.05%, ti <0.05%, the balance iron and unavoidable impurities, and the addition amount of low-carbon low-aluminum ferrochrome is 11-13 kg/t steel; the addition amount of electrolytic manganese is 6-8 kg/t. Carbon powder can be added according to the carbon content of molten steel in the tapping of the electric furnace or the converter and the target carbon content of valve spring steel in the tapping process.
(2) Refining in an LF furnace: adding lime and synthetic slag into a ladle to perform slagging, then adding alloy and carbon powder to adjust the components of molten steel to a target range, and prohibiting aluminum deoxidization, wherein the alkalinity of a final slag system is 0.8-1.2;
the specific process is as follows: adding lime and synthetic slag into molten steel to perform slagging, adding a small amount of alloy and carbon powder into the molten steel to adjust the components of the molten steel to a target range, and prohibiting aluminum deoxidization in the molten steel in the process; wherein the synthetic slag comprises the following components: caO: 35-45 wt% of SiO 2 ：40～50wt％，Al 2 O 3 :0 to 3 weight percent of MgO: 3-5 wt%; in the slag forming process, the slag amount is controlled to be 15-25 kg/t steel, the alkalinity of a final slag system is 0.8-1.2, and Al is contained in the final slag 2 O 3 Content of<5wt％.
(3) Refining by a VD furnace: controlling the vacuum pressure to be 100-1000 Pa, and the vacuum treatment time to be 10-20 min;
the specific process is as follows: vacuum refining is carried out in a VD furnace, the vacuum refining is controlled to be 100 Pa to 1000Pa, and the vacuum treatment time is 10 min to 20min; after refining in the VD furnace, the components of the molten steel meet the following requirements: c:0.5 to 0.6 percent of Mn:0.7 to 0.8 percent of Si: 1.5-1.55%, ti <0.001%, al <0.0015%, N <0.0055%, cr 0.6-0.8%, S0.002-0.01%, H <2ppm.
(4) Continuous casting: directly pouring molten steel into a continuous casting square billet;
obtaining a continuous casting square billet after continuous casting of molten steel, wherein the cross section size of the continuous casting square billet is (300-340 mm) x (400-430 mm);
(5) Electroslag remelting: cleaning the surface of a continuous casting square billet, preparing an electrode rod, and carrying out electroslag remelting by taking the electrode rod as a raw material to obtain an electroslag ingot, wherein the electroslag protection slag comprises the following components in percentage by mass: caF (CaF) 2 ：45～55wt％，CaO：10～15wt％，Al 2 O 3 ：5～15wt％，SiO 2 ：20～25wt％，Na 2 O：1～5wt％；
The specific process is as follows: cleaning the surface of a continuous casting square billet to prepare an electrode rod capable of being used for electroslag smelting, carrying out electroslag remelting by taking the electrode rod as a raw material, and smelting by an electroslag furnace to obtain a cylindrical electroslag ingot; in the electroslag remelting process, full argon gas is used for sealing protection, and the electroslag protection slag comprises the following components: caF (CaF) 2 ：45～55wt％，CaO：10～15wt％，Al 2 O 3 ：5～15wt％，SiO 2 ：20～25wt％，Na 2 O:1 to 5 weight percent; the length of the electrode rod is 2.5-3.5 m, and the diameter of the prepared electroslag ingot is 0.6-0.65 m; wherein the surface quality of the electroslag ingot is good.
(6) Forging: forging electroslag ingots into forging square billets with the section side length of 0.14-0.16 m for rolling wires, wherein the length of the forging square billets is more than 10m;
(7) The wire rod rolling process comprises the following steps: rolling the forged square billet into a valve spring steel wire rod with the diameter of 5-8 mm; the valve spring steel comprises the following components in percentage by mass: c:0.5 to 0.6 percent of Mn:0.6 to 0.8 percent of Si: 1.45-1.55%, ti <0.001%, al <0.0015%, N <0.006%, cr 0.6-0.8%, S0.002-0.01%, and the balance being iron and unavoidable impurities.
In the preparation method, the surface quality of the electroslag ingot prepared in the step (5) is good, and the surface quality of the finally rolled wire rod (valve spring steel) is good due to heredity.
The preparation method of the valve spring steel of the invention is further described below with reference to specific examples;
example 1
The process of this example is as follows: primary smelting of an electric furnace, refining of an LF furnace, refining of a VD furnace, continuous casting, electroslag remelting, forging and wire rolling to produce passenger car valve spring steel, wherein the main process steps are as follows:
(1) Primary refining: 150 tons of electric furnace is selected for primary smelting of molten steel, when the temperature of the primary smelting molten steel reaches 1640 ℃, the carbon content is measured to be 0.006%, the electric furnace is segregated, the furnace bottom is tapped, 3400kg of high-purity ferrosilicon, 1750kg of low-carbon low-aluminum ferrochromium and 1000kg of electrolytic manganese are added into a steel ladle in the tapping process, and 800kg of carbon powder is added; wherein the added high-purity ferrosilicon comprises the following components in percentage by mass: si:75%, al:0.015%, ti:0.02% of iron and the balance of unavoidable impurities, and low-carbon low-aluminum ferrochrome components (in mass percent) added: cr:60%, al:0.04%, ti:0.04%, the balance being iron and unavoidable impurities.
(2) Refining in an LF furnace: 150 tons of LF refining is selected, molten steel smelted in the previous working procedure is transported to an LF refining station through a ladle, the LF heats the molten steel through an electric arc, and the molten steel is stirred through ladle bottom blowing. 200kg of lime and 1400kg of synthetic slag are added in the early stage of LF smelting, and the slag quantity is controlled to be 2500kg. After the preliminary completion of slagging, temperature measurement and sampling are carried out, 30kg of high-purity ferrosilicon, 10kg of low-carbon low-aluminum ferrochrome and 100kg of carbon powder are added according to sampling components, the molten steel components reach the target range of valve spring steel,the final slag component CaO (in mass percent) is CaO:40%, siO 2 ：45％，Al 2 O 3 :3%, mgO:10%, other uncontrollable components: 2%. The LF furnace comprises the following synthetic slag components in percentage by mass: caO:44, siO 2 ：50％，Al 2 O 3 ：1％，MgO：5％。
(3) Refining by a VD vacuum furnace: transferring the ladle from the LF refining station to the VD furnace vacuum treatment station, vacuumizing to start vacuum treatment, controlling the high vacuum pressure to be about 200Pa, and carrying out vacuum treatment for 15 minutes. After the VD refining treatment is finished, the molten steel comprises the following components in percentage by mass: c:0.55%, mn:0.72%, si:1.51%, ti:0.0008%, al:0.0010%, N:0.0050%, cr 0.69%, S0.0052%, H:1.5ppm.
(4) Continuous casting: and cooling part of the continuous casting square billets according to the requirement of the subsequent electroslag treatment capacity after continuous casting, wherein the section size of the continuous casting square billets is 320mm multiplied by 420 mm.
(5) Electroslag smelting: cutting the cooled continuous casting bloom into a section of 3 meters, cleaning the surface, manufacturing an electrode rod for electroslag smelting, taking the electrode rod as a raw material, carrying out electroslag remelting smelting, introducing argon for protection in the whole smelting process, after the smelting starts, promoting casting slag to melt and the steel at the top end of the electrode rod to melt, enabling the melted steel melt drop to fall into a crystallizer through a slag bath to form a new molten steel metal bath, cooling and solidifying the metal bath into an electroslag ingot through the crystallizer, and obtaining electroslag casting powder components (in percentage by mass): caF (CaF) 2 ：45％，CaO：15％，Al 2 O 3 ：15％，SiO 2 ：22％，Na 2 O:3, the electrode rod can be smelted into a cylindrical electroslag ingot by using the protective slag through an electroslag furnace, and the diameter of the electroslag ingot is 610mm and the length of the electroslag ingot is 1.1 m.
(6) Forging: the electroslag ingot is forged into a forging square billet for rolling wires, the side length of the section of the forging square billet is 0.142m, 8% of the two ends of the forging square billet in the length direction are respectively cut off after forging in order to ensure the valve spring steel quality, and the final length of the forging square billet is 13.8m.
(7) Rolling wire rods: and rolling the forged square billet into a valve spring steel wire rod with the diameter of 5.5mm by a wire rod rolling mill. The final wire rod has no surface quality defect, and the final components are as follows (in mass percent): c:0.54%, mn:0.71%, si:1.5%, ti:0.0008%, al:0.0009%, N:0.0051%, cr:0.69%, S:0.004%, meets the requirements of valve spring steel components.
The valve spring steel wire rod prepared in the embodiment is detected, and the detection area is 1200mm 2 The widest inclusion is 5 μm, the aspect ratio is more than 2 by 96% of the inclusions (more than 2 μm), and the inclusions generally have good plasticity: the surface quality of the valve spring steel wire rod is detected to be defect-free. The fatigue life of 2500 ten thousand times of non-broken wires measured after the valve spring steel is subsequently drawn, and the valve spring steel meets the relevant requirements of the valve spring. The valve spring steel is used as raw material to manufacture the valve spring of passenger car in spring factory.
Example 2
The process of this example is as follows: primary smelting of a converter, refining of an LF furnace, refining of a VD furnace, continuous casting, electroslag remelting, forging and wire rolling to produce passenger car valve spring steel, wherein the main process steps are as follows:
(1) Primary refining: firstly smelting molten steel by using a 120-ton electric furnace, determining the carbon content to be 0.004% when the temperature of the initially smelting molten steel reaches 1650 ℃, stopping slag and tapping, adding 2580kg of high-purity ferrosilicon, 1300kg of low-carbon low-aluminum ferrochromium and 800kg of electrolytic manganese into a steel ladle in the tapping process, and adding 660kg of carbon powder; wherein the added high-purity ferrosilicon comprises the following components in percentage by mass: si:77%, al:0.014%, ti:0.02% of iron and the balance of unavoidable impurities, and low-carbon low-aluminum ferrochrome components (in mass percent) added: cr:65%, al:0.04%, ti:0.03%, the balance being iron and unavoidable impurities.
(2) Refining in an LF furnace: 120 tons of LF refining is selected, molten steel smelted in the previous working procedure is transported to an LF refining station through a ladle, the LF heats up the molten steel through electric arc, and the molten steel is stirred through ladle bottom blowing. 1600kg of lime and 1150kg of synthetic slag are added in the early stage of LF smelting, and the slag quantity is controlled to be 2100kg. After the primary slagging is finished, measuring the temperature and sampling, and supplementing 25kg of high-purity ferrosilicon, 7kg of low-carbon low-aluminum ferrochrome and 90kg of carbon powder according to sampling components, wherein the molten steel components reach the target range of valve spring steel, and finally the slag components CaO (according to mass percentRatio meter): caO:42%, siO 2 ：44％，Al 2 O 3 :2%, mgO:9%, other uncontrollable components: 3%. The LF furnace comprises the following synthetic slag components in percentage by mass: caO:44, siO 2 ：50％，Al 2 O 3 ：1％，MgO：5％。
(3) Refining by a VD vacuum furnace: transferring the ladle from the LF refining station to the VD furnace vacuum treatment station, vacuumizing to start vacuum treatment, controlling the high vacuum pressure to be about 200Pa, and carrying out vacuum treatment for 18 minutes. After the VD refining treatment is finished, the molten steel comprises the following components in percentage by mass: c:0.56%, mn:0.78%, si:1.53%, ti:0.0010%, al:0.0011%, N:0.0045%, cr 0.71%, S0.004%, H1.3 ppm.
(4) Continuous casting: and cooling part of the continuous casting square billets according to the requirement of the subsequent electroslag treatment capacity after continuous casting, wherein the section size of the continuous casting square billets is 320mm multiplied by 425 mm.
(5) Electroslag smelting: cutting the cooled continuous casting bloom into a section of 3.1 m, cleaning the surface, manufacturing an electrode rod for smelting electric slag, taking the electrode rod as a raw material, carrying out electroslag remelting smelting, introducing argon for protection in the whole smelting process, after the smelting starts, causing casting slag to melt and steel at the top end of the electrode rod to melt, dripping the molten steel into a slag bath to form a new molten steel metal bath, cooling and solidifying the molten metal bath into an electroslag ingot by the crystallizer, and forming electroslag casting slag components (according to mass percent): caF (CaF) 2 ：50％，CaO：13％，Al 2 O 3 ：12％，SiO 2 ：23％，Na 2 O:2, the electrode rod can be smelted into a cylindrical electroslag ingot by using the protective slag through an electroslag furnace, and the diameter of the electroslag ingot is 610mm and the length of the electroslag ingot is 1.12 m.
(6) Forging: the electroslag ingot is forged into a forging square billet for rolling wires, the side length of the section of the forging square billet is 0.145m, 8% of the two ends of the forging square billet in the length direction are respectively cut off after forging in order to ensure the valve spring steel quality, and the final length of the forging square billet is 13.3m.
(7) Rolling wire rods: and rolling the forged square billet into a valve spring steel wire rod with the diameter of 5.5mm by a wire rod rolling mill. The final wire rod has no surface quality defect, and the final components are as follows (in mass percent): c:0.55%, mn:0.78%, si:1.51%, ti:0.0009%, al:0.0008%, N:0.0046%, cr:0.7 percent and 0.004 percent of S, which meets the component requirements of valve spring steel.
The valve spring steel wire rod prepared in the embodiment is detected, and the detection area is 1200mm 2 The widest inclusion is 6 μm, the aspect ratio is more than 2 by 95% of the inclusions (more than 2 μm), and the inclusions generally have good plasticity: the surface quality of the valve spring steel wire rod is detected to be defect-free. The fatigue life of 2500 ten thousand times of non-broken wires measured after the valve spring steel is subsequently drawn, and the valve spring steel meets the relevant requirements of the valve spring. The valve spring steel is used as raw material to manufacture the valve spring of passenger car in spring factory.
Example 3
The process of this example is as follows: primary smelting of a converter, refining of an LF furnace, refining of a VD furnace, continuous casting, electroslag remelting, forging and wire rolling to produce passenger car valve spring steel, wherein the main process steps are as follows:
(1) Primary refining: firstly smelting molten steel in a 150 ton electric furnace, determining the carbon content to be 0.1% when the temperature of the initially smelting molten steel reaches 1640 ℃, tapping the steel at the segregation furnace bottom of the electric furnace, adding 3300kg of high-purity ferrosilicon, 1740kg of low-carbon low-aluminum ferrochromium and 1000kg of electrolytic manganese into a steel ladle in the tapping process, and adding 660kg of carbon powder; wherein the added high-purity ferrosilicon comprises the following components in percentage by mass: si:75%, al:0.015%, ti:0.02% of iron and the balance of unavoidable impurities, and low-carbon low-aluminum ferrochrome components (in mass percent) added: cr:60%, al:0.04%, ti:0.04%, the balance being iron and unavoidable impurities.
(2) Refining in an LF furnace: 150 tons of LF refining is selected, molten steel smelted in the previous working procedure is transported to an LF refining station through a ladle, the LF heats the molten steel through an electric arc, and the molten steel is stirred through ladle bottom blowing. 230kg of lime and 1400kg of synthetic slag are added in the early stage of LF smelting, and the slag quantity is controlled to be 2530kg. After the primary slagging is finished, measuring temperature and sampling, and supplementing 20kg of high-purity ferrosilicon, 12kg of low-carbon low-aluminum ferrochrome and 80kg of carbon powder according to sampling components, wherein molten steel components reach the target range of valve spring steel, and finally the slag components CaO (in percentage by mass): caO:44, siO 2 ：50％，Al 2 O 3 :1%, mgO:5%, other uncontrollable components: 3%. The LF furnace comprises the following synthetic slag components in percentage by mass: caO:44, siO 2 ：50％，Al 2 O 3 ：1％，MgO：5％。
(3) Refining by a VD vacuum furnace: transferring the ladle from the LF refining station to the VD furnace vacuum treatment station, vacuumizing to start vacuum treatment, controlling the high vacuum pressure to be about 200Pa, and carrying out vacuum treatment for 12 minutes. After the VD refining treatment is finished, the molten steel comprises the following components in percentage by mass: c:0.54%, mn:0.72%, si:1.55%, ti:0.0008%, al:0.0013%, N:0.0052%, cr 0.7%, S0.0032%, H1.7 ppm.
(4) Continuous casting: and cooling part of the continuous casting square billets according to the requirement of the subsequent electroslag treatment capacity after continuous casting, wherein the section size of the continuous casting square billets is 320mm multiplied by 425 mm.
(5) Electroslag smelting: cutting the cooled continuous casting bloom into a section of 3 meters, cleaning the surface, manufacturing an electrode rod for electroslag smelting, taking the electrode rod as a raw material, carrying out electroslag remelting smelting, introducing argon for protection in the whole smelting process, after the smelting starts, promoting casting slag to melt and the steel at the top end of the electrode rod to melt, enabling the melted steel melt drop to fall into a crystallizer through a slag bath to form a new molten steel metal bath, cooling and solidifying the metal bath into an electroslag ingot through the crystallizer, and obtaining electroslag casting powder components (in percentage by mass): caF (CaF) 2 ：55％，CaO：10％，Al 2 O 3 ：10％，SiO 2 ：22％，Na 2 O:3, the electrode rod can be smelted into a cylindrical electroslag ingot by using the protective slag through an electroslag furnace, and the diameter of the electroslag ingot is 610mm and the length of the electroslag ingot is 1.1 m.
(6) Forging: the electroslag ingot is forged into a forging square billet for rolling wires, the side length of the section of the forging square billet is 0.142m, 8% of the two ends of the forging square billet in the length direction are respectively cut off after forging in order to ensure the valve spring steel quality, and the final length of the forging square billet is 13.8m.
(7) Rolling wire rods: and rolling the forged square billet into a valve spring steel wire rod with the diameter of 6mm by a wire rod rolling mill. The final wire rod has no surface quality defect, and the final components are as follows (in mass percent): c:0.54%, mn:0.71%, si:1.48%, ti:0.0007%, al:0.0008%, N:0.0055%, cr:0.69%, S:0.003 percent, which meets the component requirement of valve spring steel.
The valve spring steel wire rod prepared in the embodiment is detected, and the detection area is 1200mm 2 The widest inclusion is 5 μm, the aspect ratio is more than 2 by 97% of the inclusions (more than 2 μm), and the inclusions generally have good plasticity: the surface quality of the valve spring steel wire rod is detected to be defect-free. The fatigue life of 2500 ten thousand times of non-broken wires measured after the valve spring steel is subsequently drawn, and the valve spring steel meets the relevant requirements of the valve spring. The valve spring steel is used as raw material to manufacture the valve spring of passenger car in spring factory.
Example 4
The process of this example is as follows: primary smelting of a converter, refining of an LF furnace, refining of a VD furnace, continuous casting, electroslag remelting, forging and wire rolling to produce passenger car valve spring steel, wherein the main process steps are as follows:
(1) Primary refining: 150 tons of electric furnace is selected for primary smelting of molten steel, when the temperature of the primary smelting molten steel reaches 1640 ℃, the carbon content is measured to be 0.1%, the electric furnace is segregated, the furnace bottom is tapped, 3000kg of high-purity ferrosilicon, 1650kg of low-carbon low-aluminum ferrochromium and 900kg of electrolytic manganese are added into a steel ladle in the tapping process, and 660kg of carbon powder is added; wherein the added high-purity ferrosilicon comprises the following components in percentage by mass: si:70%, al:0.018%, ti:0.04% of iron and the balance of unavoidable impurities, and low-carbon low-aluminum ferrochrome components (in mass percent) are added: cr:50%, al:0.03%, ti:0.03%, the balance being iron and unavoidable impurities.
(2) Refining in an LF furnace: 150 tons of LF refining is selected, molten steel smelted in the previous working procedure is transported to an LF refining station through a ladle, the LF heats the molten steel through an electric arc, and the molten steel is stirred through ladle bottom blowing. 230kg of lime and 1400kg of synthetic slag are added in the early stage of LF smelting to carry out slag formation, and the slag quantity is controlled to be 2550kg. After the primary slagging is finished, measuring temperature and sampling, and supplementing 20kg of high-purity ferrosilicon, 12kg of low-carbon low-aluminum ferrochrome and 80kg of carbon powder according to sampling components, wherein molten steel components reach the target range of valve spring steel, and finally the slag components CaO (in percentage by mass): caO:44, siO 2 ：50％，Al 2 O 3 :3%, mgO:5%, other uncontrollable components: 1%. The LF furnace comprises the following synthetic slag components in percentage by mass: caO:42%, siO 2 ：50％，Al 2 O 3 ：3％，MgO：5％。
(3) Refining by a VD vacuum furnace: transferring the ladle from the LF refining station to the VD furnace vacuum treatment station, vacuumizing to start vacuum treatment, controlling the high vacuum pressure to be about 200Pa, and carrying out vacuum treatment for 12 minutes. After the VD refining treatment is finished, the molten steel comprises the following components in percentage by mass: c:0.52%, mn:0.72%, si:1.51%, ti:0.0008%, al:0.0012%, N:0.0055%, 0.65% Cr, 0.0025% S, and 1.3ppm H.
(4) Continuous casting: and cooling part of the continuous casting square billets according to the requirement of the subsequent electroslag treatment capacity after continuous casting, wherein the section size of the continuous casting square billets is 320mm multiplied by 425 mm.
(5) Electroslag smelting: cutting the cooled continuous casting bloom into a section of 3 meters, cleaning the surface, manufacturing an electrode rod for electroslag smelting, taking the electrode rod as a raw material, carrying out electroslag remelting smelting, introducing argon for protection in the whole smelting process, after the smelting starts, promoting casting slag to melt and the steel at the top end of the electrode rod to melt, enabling the melted steel melt drop to fall into a crystallizer through a slag bath to form a new molten steel metal bath, cooling and solidifying the metal bath into an electroslag ingot through the crystallizer, and obtaining electroslag casting powder components (in percentage by mass): caF (CaF) 2 ：55％，CaO：10％，Al 2 O 3 ：10％，SiO 2 ：22％，Na 2 O:3, the electrode rod can be smelted into a cylindrical electroslag ingot by using the protective slag through an electroslag furnace, and the diameter of the electroslag ingot is 610mm and the length of the electroslag ingot is 1.1 m.
(6) Forging: the electroslag ingot is forged into a forging square billet for rolling wires, the side length of the section of the forging square billet is 0.142m, 8% of the two ends of the forging square billet in the length direction are respectively cut off after forging in order to ensure the valve spring steel quality, and the final length of the forging square billet is 13.8m.
(7) Rolling wire rods: and rolling the forged square billet into a valve spring steel wire rod with the diameter of 6mm by a wire rod rolling mill. The final wire rod has no surface quality defect, and the final components are as follows (in mass percent): c:0.52%, mn:0.69%, si:1.45%, ti:0.0007%, al:0.0007%, N:0.0057%, cr:0.62%, S:0.0021 percent, which meets the requirements of valve spring steel composition.
The valve spring steel wire rod prepared in the embodiment is detected, and the detection area is 1200mm 2 The widest inclusion is 4 μm, the aspect ratio is more than 2 by 96% of the inclusions (more than 2 μm), and the inclusions generally have good plasticity: the surface quality of the valve spring steel wire rod is detected to be defect-free. The fatigue life of 2500 ten thousand times of non-broken wires measured after the valve spring steel is subsequently drawn, and the valve spring steel meets the relevant requirements of the valve spring. The valve spring steel is used as raw material to manufacture the valve spring of passenger car in spring factory.
Example 4
The process of this example is as follows: primary smelting of a converter, refining of an LF furnace, refining of a VD furnace, continuous casting, electroslag remelting, forging and wire rolling to produce passenger car valve spring steel, wherein the main process steps are as follows:
(1) Primary refining: firstly smelting molten steel in a 150 ton electric furnace, determining the carbon content to be 0.1% when the temperature of the initially smelting molten steel reaches 1640 ℃, tapping the steel at the segregation furnace bottom of the electric furnace, adding 3600kg of high-purity ferrosilicon, 1950kg of low-carbon low-aluminum ferrochromium and 1100kg of electrolytic manganese into a steel ladle in the tapping process, and adding 660kg of carbon powder; wherein the added high-purity ferrosilicon comprises the following components in percentage by mass: si:79%, al:0.016%, ti:0.04% of iron and the balance of unavoidable impurities, and low-carbon low-aluminum ferrochrome components (in mass percent) are added: cr:69%, al:0.034%, ti:0.03%, the balance being iron and unavoidable impurities.
(2) Refining in an LF furnace: 150 tons of LF refining is selected, molten steel smelted in the previous working procedure is transported to an LF refining station through a ladle, the LF heats the molten steel through an electric arc, and the molten steel is stirred through ladle bottom blowing. 230kg of lime and 1400kg of synthetic slag are added in the early stage of LF smelting to carry out slag formation, and the slag quantity is controlled to be 2880kg. After the primary slagging is finished, measuring temperature and sampling, and supplementing 25kg of high-purity ferrosilicon, 10kg of low-carbon low-aluminum ferrochrome and 85kg of carbon powder according to sampling components, wherein molten steel components reach the target range of valve spring steel, and finally the slag components CaO (in percentage by mass): caO:43, siO 2 ：51％，Al 2 O 3 :2%, mgO:3%, other uncontrollable components: 1%. The LF furnace comprises the following synthetic slag components in percentage by mass: caO:45%, siO 2 ：50％，Al 2 O 3 ：2％，MgO：3％。
(3) Refining by a VD vacuum furnace: transferring the ladle from the LF refining station to the VD furnace vacuum treatment station, vacuumizing to start vacuum treatment, controlling the high vacuum pressure to be about 200Pa, and carrying out vacuum treatment for 12 minutes. After the VD refining treatment is finished, the molten steel comprises the following components in percentage by mass: c:0.58%, mn:0.78%, si:1.53%, ti:0.0008%, al:0.0011%, N:0.0052%, cr 0.78%, S0.008%, H1.2 ppm.
(4) Continuous casting: and cooling part of the continuous casting square billets according to the requirement of the subsequent electroslag treatment capacity after continuous casting, wherein the section size of the continuous casting square billets is 340mm multiplied by 430 mm.
(5) Electroslag smelting: cutting the cooled continuous casting bloom into a section with the length of 3.4 meters, cleaning the surface, manufacturing an electrode rod for smelting electroslag, taking the electrode rod as a raw material, carrying out electroslag remelting smelting, introducing argon for protection in the whole smelting process, after the smelting starts, causing casting slag to melt and the steel at the top end of the electrode rod to melt, dripping the molten steel drops into a slag bath to form a new molten steel metal bath, cooling and solidifying the molten metal bath into an electroslag ingot by the crystallizer, and forming electroslag casting slag components (in percentage by mass): caF (CaF) 2 ：45％，CaO：15％，Al 2 O 3 ：10％，SiO 2 ：25％，Na 2 O:5, the electrode rod can be smelted into a cylindrical electroslag ingot by using the protective slag through an electroslag furnace, and the diameter of the electroslag ingot is 610mm and the length of the electroslag ingot is 1.1 m.
(6) Forging: the electroslag ingot is forged into a forging square billet for rolling wires, the side length of the section of the forging square billet is 0.142m, 8% of the two ends of the forging square billet in the length direction are respectively cut off after forging in order to ensure the valve spring steel quality, and the final length of the forging square billet is 13.8m.
(7) Rolling wire rods: and rolling the forged square billet into a valve spring steel wire rod with the diameter of 6mm by a wire rod rolling mill. The final wire rod has no surface quality defect, and the final components are as follows (in mass percent): c:0.57%, mn:0.78%, si:1.52%, ti:0.0007%, al:0.0007%, N:0.0055%, cr:0.77%, S:0.007 percent, which meets the requirements of valve spring steel composition.
The valve spring steel wire rod prepared in the embodiment is detected, and the detection area is 1200mm 2 The widest inclusion is 5 μm, the aspect ratio is more than 2 by 97% of the inclusions (more than 2 μm), and the inclusions generally have good plasticity: the surface quality of the valve spring steel wire rod is detected to be defect-free. The fatigue life of 2500 ten thousand times of non-broken wires measured after the valve spring steel is subsequently drawn, and the valve spring steel meets the relevant requirements of the valve spring. The valve spring steel is used as raw material to manufacture the valve spring of passenger car in spring factory.
In summary, the preparation method of the valve spring steel can stably control inclusions in the steel, ensure the surface quality of the valve spring steel wire rod and reduce the risk of failure of the valve spring steel due to the inclusions to zero; the preparation method of the valve spring steel can lead the width of the inclusions of the valve spring steel to be comprehensively smaller than 6 mu m, lead the length-width ratio of 95 percent of the inclusions (larger than 2 mu m) to be larger than 2, lead the inclusions not to contain brittle aluminum inclusions, lead the surface quality of the wire rod to be excellent, meet the requirement of the valve spring steel of high-end passenger vehicles and lead the failure risk of the valve spring steel to be reduced to zero.
It will be appreciated by persons skilled in the art that the above embodiments are provided for illustration only and not for limitation of the invention, and that variations and modifications of the above described embodiments are intended to fall within the scope of the claims of the invention as long as they fall within the true spirit of the invention.
Claims (4)
1. A preparation method of valve spring steel is characterized in that the valve spring steel is obtained through primary smelting, LF furnace refining, VD furnace refining, continuous casting, electroslag remelting, forging and wire rolling,
the method specifically comprises the following steps:
(1) Primary smelting, namely primary smelting by adopting an electric furnace/converter to obtain molten steel, and adding high-purity ferrosilicon, low-carbon low-aluminum ferrochrome and electrolytic manganese into the molten steel in the tapping process to perform initial alloying treatment, wherein the high-purity ferrosilicon comprises the following components in percentage by mass: si: 70-80%, al <0.02%, ti <0.05%, the balance being iron and unavoidable impurities; the addition amount of the high-purity ferrosilicon is 20-25 kg/t steel; the low-carbon low-aluminum ferrochrome comprises the following components in percentage by mass: cr: 50-70%, al <0.05%, ti <0.05%, the balance being iron and unavoidable impurities; the addition amount of the low-carbon low-aluminum ferrochrome is 11-13 kg/t steel; the addition amount of the electrolytic manganese is 6-8 kg/t steel;
(2) Refining in an LF furnace, adding lime and synthetic slag into a ladle to perform slag formation, then adding alloy and carbon powder to adjust the components of molten steel to a target range, and prohibiting aluminum deoxidation, wherein the alkalinity of a final slag system is 0.8-1.2, and the components of the synthetic slag are as follows: caO: 35-45 wt% of SiO 2 ：40～50wt%，Al 2 O 3 :0 to 3 weight percent of MgO: 3-5 wt%; in the slag forming process, the slag amount is controlled to be 15-25 kg/t of steel; slag Al 2 O 3 Content of<5wt%；
(3) Refining in a VD furnace, controlling the vacuum pressure to be 100-1000 Pa, and the vacuum treatment time to be 10-20 min, wherein after the refining in the VD furnace is finished, the components of molten steel meet the following requirements: c:0.5 to 0.6 percent of Mn:0.7 to 0.8 percent of Si: 1.5-1.55%, ti <0.001%, al <0.0015%, N <0.0055%, cr 0.6-0.8%, S0.002-0.01%, H <2ppm;
(4) Continuous casting, namely directly casting molten steel into a continuous casting square billet;
(5) And (3) electroslag remelting, namely cleaning the surface of the continuous casting square billet, and preparing an electrode rod, wherein the electrode rod is used as a raw material to carry out electroslag remelting to obtain an electroslag ingot, and the electroslag protection slag comprises the following components in percentage by mass: caF (CaF) 2 ：45～55wt%，CaO：10～15 wt %，Al 2 O 3 ：5～15 wt %，SiO 2 ：20～25 wt %，Na 2 O：1～5 wt %；
(6) Forging, namely forging the electroslag ingot into a forging square billet for rolling wires;
(7) Rolling the wire rod, rolling the forged square billet to obtain the valve spring steel wire rod,
the valve spring steel comprises the following components in percentage by mass: c:0.5 to 0.6 percent of Mn:0.6 to 0.8 percent of Si:1.45 to 1.55 percent, ti <0.001 percent, al <0.0015 percent, N <0.006 percent, cr 0.6 to 0.8 percent, S0.002 to 0.01 percent, the balance being iron and unavoidable impurities,
the width of the inclusions in the valve spring steel is less than 6 mu m comprehensively.
2. The method for producing valve spring steel according to claim 1, wherein in the step (1):
and adding carbon powder according to the carbon content of converter or electric furnace tapping and the target carbon content of valve spring steel in the tapping process.
3. The method for producing valve spring steel according to claim 1, wherein in the step (4), the cross-sectional dimension of the continuous casting billet is (300 to 340 mm) × (400 to 430 mm).
4. The method of producing valve spring steel according to claim 1, wherein in the step (7), the diameter of the valve spring steel wire rod is 5 to 8mm.
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| CN202110733860.6A CN115537671B (en) | 2021-06-30 | 2021-06-30 | Preparation method of valve spring steel |
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