CN111876564A - Spheroidizing annealing process of hexagonal alloy tool steel S2 - Google Patents
Spheroidizing annealing process of hexagonal alloy tool steel S2 Download PDFInfo
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- CN111876564A CN111876564A CN202010674613.9A CN202010674613A CN111876564A CN 111876564 A CN111876564 A CN 111876564A CN 202010674613 A CN202010674613 A CN 202010674613A CN 111876564 A CN111876564 A CN 111876564A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/02—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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Abstract
The invention relates to a spheroidizing annealing process of hexagonal alloy tool steel S2, which comprises the steps of feeding tool steel S2 subjected to sand blasting into a bell-type annealing furnace; raising the temperature in the furnace to 593-600 ℃, and preserving the heat for two hours by using N2Purging is carried out; in a furnaceThe temperature is increased to 775-780 ℃ and is maintained for four hours, and N is added in the heat preservation process2The purge amount of (A) is 55-65m2H; cooling to 180-220 deg.c, raising the heating hood at 630-680 deg.c while turning off nitrogen and raising the inner hood at 180-220 deg.c; and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling. The tool steel S2 treated by the spheroidizing process has the advantages of reducing the hardness, facilitating subsequent drawing processing, improving the mechanical toughness after quenching and improving the cutting processing performance of a client.
Description
Technical Field
The invention relates to tool steel, in particular to a spheroidizing annealing process of hexagonal alloy tool steel S2.
Background
The tool steel is a kind of alloy steel, and S2 is a kind of tool steel, which is a high-grade steel for manufacturing tools. The S2 tool steel is used as a steel material for manufacturing tools, and is a special tool for manufacturing various high-quality electric tools such as hexagonal heads, hexagon socket head wrenches, screwdrivers and the like. In order to make the steel material have the required mechanical property, physical property and chemical property, besides reasonably selecting materials and forming process, the heat treatment process is often indispensable, which not only changes the appearance of the steel material, but also can fully exert the potential of the steel material through heat treatment, and endows the steel material with various required special properties, thereby achieving the purposes of improving the quality of the steel material, prolonging the service life and ensuring the safe and reliable operation of the machine. The spheroidizing annealing process is a common heat treatment process for steel, and selects a proper annealing process aiming at different annealing furnaces, so that the spheroidizing annealing process can ensure that lamellar pearlite disappears, and can also retain a part of carbide which is not completely dissolved in austenite to be used as a spheroidizing core, and finally forms a normal spheroidized structure of coarse granular carbide.
Disclosure of Invention
In order to overcome the defects, the invention provides a spheroidizing annealing process of hexagonal alloy tool steel S2, wherein the annealing process adopts twice heating and twice heat preservation procedures to treat tool steel S2, so that the hardness of the treated tool steel S2 is reduced, the subsequent drawing processing is facilitated, the mechanical toughness after quenching is improved, and the cutting processing performance of a client is improved.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a spheroidizing annealing process of hexagonal alloy tool steel S2 comprises the following steps:
the method comprises the following steps: feeding the tool steel S2 subjected to sand blasting into a hood-type annealing furnace;
step two: heating the furnace to 593-600 deg.C, holding at 593-600 deg.C for two hours, and using N2Purging is carried out, N2The purge amount of (a) is: 75m2/h-85m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage, namely heating the temperature in the furnace from 593-600 ℃ to 775-780 ℃, wherein the heating rate is 80-90 ℃/h, and N is generated in the heating process2The purge amount of (A) is 65-75m2H, maintaining the temperature of 775 and 780 ℃ for four hours, and keeping N in the heat preservation process2The purge amount of55-65m2/h；
Step four: cooling to 180-220 ℃ at the speed of 25-35 ℃/h, wherein N is generated in the cooling process2The purge amount of (2) is 25 to 35m2Lifting the heating cover and turning off nitrogen gas at the temperature of 630-680 ℃, and lifting the inner cover at the temperature of 180-220 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
Preferably, the hood-type annealing furnace comprises a base, an inner cover and a heating hood, wherein the base comprises a bottom plate, a heat insulation plate, a gas distribution disc and a bearing disc which are sequentially arranged from bottom to top.
Preferably, the step one: conveying the wire rack loaded with the tool steel S2 to a bearing disc of a base, covering an inner cover, locking the inner cover through hydraulic tongs, then starting to charge nitrogen and loading a heating cover;
step two: heating the furnace to 593 deg.C, maintaining at 593 deg.C for two hours, and adding N2Purging is carried out, N2The purge amount of (a) is: 80m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage from 593 deg.C to 775 deg.C at a heating rate of 88.5 deg.C/h, wherein N is added during heating2Purge amount of (3) is 70m2H, maintaining the temperature of 775 ℃ for four hours, and N in the heat preservation process2Purge amount of (2) is 60m2/h；
Step four: cooling to 200 ℃ at the speed of 30 ℃/h, wherein N is generated in the cooling process2Purge amount of (2) 30m2H, lifting the heating cover at about 650 ℃, turning off nitrogen, and lifting the inner cover at about 200 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
Preferably, in the step one, the chemical composition and mass percentage of the tool steel S2 include: c: 0.65-0.72%, Si: 0.4-1.5%, Mn: 0.3-0.8%, P: 0.02-0.2%, S: 0.0008-0.15%, Cr: 0.15-0.45%, Ni: 0.10-0.35%, Cu: 0-0.25%, Mo: 0.2-0.6%, V: 0.15-0.3%, and the balance of iron and inevitable impurity elements.
Preferably, in the step one, the chemical composition and mass percentage of the tool steel S2 include: c: 0.66-0.7%, Si: 1.0-1.2%, Mn: 0.4-0.6%, P: 0.04-0.15%, S: 0.008-0.018%, Cr: 0.2-0.4%, Ni: 0.12-0.3%, Cu: 0-0.25%, Mo: 0.4-0.5%, V: 0.17-0.25%, and the balance of iron and inevitable impurity elements.
The invention has the beneficial effects that:
1) in the spheroidizing process, the temperature is increased to 593 ℃ for the first time and is kept for two hours, and N is utilized in the process2Replacing oxygen in the furnace to ensure that no oxidizing gas is generated in the atmosphere in the furnace above 593 ℃, heating to 775 ℃ for the second time and preserving heat for four hours, completing austenitizing of the tool steel in the process, and finally completing the cooling process, wherein a spheroidized structure is generated in the cooling process to ensure the extensibility, uniformity and mechanical strength of a finished product;
2) the tool steel S2 treated by the spheroidizing process achieves the following technical effects: the spheroidizing annealing structure is uniform, the spheroidizing rate is more than 90 percent, the annealing HRB hardness value is less than 91, the fluctuation of the HRB hardness value is less than 3, the forming processes such as drawing, cold bending and the like are normal, and the fatigue life of the tool is long; the quenching deformation is reduced, the post-quenching hardness is stabilized, the cutting phenomenon of the workpiece is improved, the phenomena of quenching cracking, quenching bending and the like are inhibited, the strength, toughness and wear resistance of the tool steel are improved, and the service life is prolonged; the tool steel S2 has reasonable contents of carbon, silicon and manganese, thereby reducing the decarburization sensitivity of the tool steel S2 and ensuring the surface strength of the tool steel after heat treatment;
3) in the process, spheroidizing annealing is carried out to 20-30 ℃ above Ac1, heat preservation is carried out, furnace cooling is carried out at a certain cooling speed at regular time, carbide in steel is spherical, the purpose is to spheroidize reticular secondary cementite in steel and lamellar cementite in pearlite, so as to reduce hardness and improve machinability, austenite grains are not easy to coarsen during quenching and heating, deformation and cracking tendency of workpieces are small during cooling, and preparation on a structure is made for final heat treatment.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A spheroidizing annealing process of hexagonal alloy tool steel S2 comprises the following steps:
the method comprises the following steps: feeding the tool steel S2 subjected to sand blasting into a hood-type annealing furnace;
step two: heating the furnace to 593-600 deg.C, holding at 593-600 deg.C for two hours, and using N2Purging is carried out, N2The purge amount of (a) is: 75m2/h-85m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage, namely heating the temperature in the furnace from 593-600 ℃ to 775-780 ℃, wherein the heating rate is 80-90 ℃/h, and N is generated in the heating process2The purge amount of (A) is 65-75m2H, maintaining the temperature of 775 and 780 ℃ for four hours, and keeping N in the heat preservation process2The purge amount of (A) is 55-65m2/h；
Step four: cooling to 180-220 ℃ at the speed of 25-35 ℃/h, wherein N is generated in the cooling process2The purge amount of (2) is 25 to 35m2Lifting the heating cover and turning off nitrogen gas at the temperature of 630-680 ℃, and lifting the inner cover at the temperature of 180-220 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
The bell-type annealing furnace comprises a base, an inner cover and a heating cover, wherein the base comprises a bottom plate, a heat insulation plate, a gas distribution disc and a bearing disc which are sequentially arranged from bottom to top. The heat insulation plate is a ceramic fiber cotton plate heat insulation plate, and a layer of stainless steel plate is coated outside the heat insulation plate and used for separating the fan from a heating area, so that the service life of the fan is prolonged, and the temperature consistency can be promoted by the air distribution disc.
A spheroidizing annealing process of hexagonal alloy tool steel S2 comprises the following steps:
the method comprises the following steps: conveying the wire rack loaded with the tool steel S2 to a bearing disc of a base, covering an inner cover, locking the inner cover through hydraulic tongs, then starting to charge nitrogen and loading a heating cover;
step two: heating the furnace to 593 deg.C, maintaining at 593 deg.C for two hours, and adding N2Purging is carried out, N2The purge amount of (a) is: 80m2H, replacing all the original gas in the furnace; at 593 deg.C, using N2To displace oxygen in the furnace to ensure that no oxidizing gas is generated in the furnace atmosphere above 593 ℃, wherein N is2Is high purity N2Oxygen is not contained;
step three: heating the furnace for the second stage from 593 deg.C to 775 deg.C at a heating rate of 88.5 deg.C/h, wherein N is added during heating2Purge amount of (3) is 70m2H, maintaining the temperature of 775 ℃ for four hours, and N in the heat preservation process2Purge amount of (2) is 60m2H; austenitizing is completed in the process;
step four: cooling to 200 ℃ at the speed of 30 ℃/h, wherein N is generated in the cooling process2Purge amount of (2) 30m2H, lifting the heating cover at about 650 ℃, turning off nitrogen, and lifting the inner cover at about 200 ℃; better, the cooling process produces spheroidized structure, which ensures the extensibility and uniformity of the steel and the mechanical strength of the finished product;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
In the first step, the tool steel S2 comprises the following chemical components in percentage by mass: c: 0.65-0.72%, Si: 0.4-1.5%, Mn: 0.3-0.8%, P: 0.02-0.2%, S: 0.0008-0.15%, Cr: 0.15-0.45%, Ni: 0.10-0.35%, Cu: 0-0.25%, Mo: 0.2-0.6%, V: 0.15-0.3%, and the balance of iron and inevitable impurity elements.
More preferably, in the step one, the chemical composition and mass percentage of the tool steel S2 include: c: 0.66-0.7%, Si: 1.0-1.2%, Mn: 0.4-0.6%, P: 0.04-0.15%, S: 0.008-0.018%, Cr: 0.2-0.4%, Ni: 0.12-0.3%, Cu: 0-0.25%, Mo: 0.4-0.5%, V: 0.17-0.25%, and the balance of iron and inevitable impurity elements. The interstitial solid solution formed by dissolving carbon in alpha-Fe is called ferrite and has the characteristics of good plasticity, low strength and low hardness; the interstitial solid solution formed by dissolving carbon in gamma-Fe is named as austenite, and has the characteristics of good plasticity, strength and hardness slightly higher than those of ferrite and no magnetism; if the solubility of carbon is too high, cementite can be formed, and the existence of the cementite can improve the hardness and the wear resistance of the alloy, so that the plasticity and the toughness of the alloy are reduced; effect of carbon on mechanical properties: carbon affects the hardness, wear resistance, toughness and hardenability of steel, and improves the strength and hardness of steel, forms carbide with alloy elements, and under normal austenitizing conditions, the carbide is often insufficiently dissolved and diffused, so that the stability of austenite is reduced and the hardenability is poor. The carbon content is increased, the toughness of the steel is reduced, and the excessively high carbon content is unfavorable, but the carbon content is excessively low, the hardenability of the steel is poor, and the wear resistance is low;
SI silicon is used as an alloy element in steel, the mass percentage of the SI silicon is generally not less than 0.4 percent, the SI silicon exists in ferrite or austenite in a solid solution form, and an austenite phase region is reduced; the annealing, normalizing and quenching temperatures are increased, and the hardenability is improved in the hypoeutectoid steel; silicon can not form carbide, has strong function of promoting graphitization of carbon, and is easy to graphitize under a certain temperature condition in medium carbon and high carbon steel with higher silicon content if the medium carbon and the high carbon steel do not contain strong carbide forming elements; in carburization, silicon reduces carburized layer thickness and carbon concentration; the silicon has good deoxidation effect on the molten steel;
effect of SI on mechanical properties of steel: the hardness and strength of ferrite and austenite are improved, and the effect is stronger than that of Mn, Ni, Cr, W, Mo, V and the like; obviously improving the elastic limit, the yield strength and the yield ratio of the steel, and improving the fatigue strength and the fatigue ratio; when the mass fraction of silicon exceeds 3%, the plasticity and toughness of the steel are remarkably reduced; silicon raises the ductile-brittle transition temperature; silicon tends to form a banded structure in the steel, making the transverse properties lower than the longitudinal properties;
mn is a good deoxidizer and desulfurizer; manganese sharply reduces Ar1 and martensite transformation temperature (second only to carbon) of the steel and the transformation rate in the steel, improves the hardenability of the steel, and increases the content of retained austenite; the quenched and tempered structure of the steel is uniform and refined, the aggregation and blocking of carbides in the carburized layer are changed, and the high overheating sensitivity and the tempering brittleness tendency are increased; manganese is a weak carbide former;
effect of Mn manganese on mechanical properties of steel: the manganese strengthening ferrite or austenite has no effect on ductility while enhancing strength as compared with carbon, phosphorus and silicon; manganese can refine pearlite, the strength of the low-carbon pearlite steel and the medium-carbon pearlite steel is obviously improved, and the ductility is reduced; the mechanical property of the quenched and tempered sorbite steel is improved by improving the hardenability; under the premise of strictly controlling the heat treatment process and avoiding the growth of crystal grains and the temper brittleness during overheating, the manganese can not reduce the toughness of the steel;
p phosphorus is a harmful impurity element in the conventional steel, but is a useful element for the weathering steel, and when the phosphorus in the weathering steel accounts for 0.04-0.15% by mass, P and Cu are added into the steel simultaneously, so that the inner rust layer is obviously banded, and the corrosion resistance of the steel is improved;
s sulfur can improve the cutting processing performance of steel in steel, and sulfur element is added in the steel. The sulfide shows beneficial effect in a certain range, the S content is increased from 0.0008 percent to 0.013 percent to 0.018 percent by mass, and the fatigue performance can be obviously improved along with the increase of the sulfur;
cr and Cr: cr and Fe form a continuous solid solution to reduce an austenite phase region, chromium and carbon form various carbides, the affinity with carbon is higher than that of iron and manganese and lower than that of tungsten, molybdenum and the like, and Cr and Fe can form an intermetallic compound sigma phase (FeCr); cr reduces the carbon concentration in pearlite and the limiting solubility of carbon in austenite; the austenite decomposition rate is slowed down, the hardenability of the steel is obviously improved, and the temper brittleness tendency of the steel is also increased.
Effect of Cr chromium on mechanical properties of steel: the strength and the hardness of the steel are improved, and meanwhile, when other alloy elements are added, the effect is obvious; obviously improves the ductile-brittle transition temperature of the steel; in the Fe — Cr alloy containing a high amount of chromium, if the σ phase is precipitated, the impact toughness is rapidly lowered.
The effect of Cr chromium on the physical, chemical and technological properties of steel: the wear resistance of the steel is improved, and a lower surface roughness value is easily obtained through grinding; the conductivity of the steel is reduced, and the resistance temperature coefficient is reduced; the coercive force and residual magnetic induction of the steel are improved, and the method is widely used for manufacturing permanent magnet steel; chromium promotes the surface of the steel to form a passive film, and when a certain content of Cr exists, the corrosion resistance of the steel (particularly nitric acid) is obviously improved;
ni and Ni: nickel and iron can be in infinite solid solution, and nickel expands the austenite zone of iron, namely, raises the A4 point and lowers the A3 point, so that the nickel is the main alloy element for forming and stabilizing austenite; the critical transition temperature is reduced, the diffusion rate of each element in the steel is reduced, and the hardenability is improved; the carbon content of the eutectoid pearlite is reduced, and the effect is stronger than that of nitrogen only than that of manganese. Half as much manganese acts in lowering the martensitic transformation temperature;
effect of Ni nickel on mechanical properties of steel: strengthening ferrite, thinning and increasing pearlite, improving the strength of steel and not obviously influencing the plasticity of the steel; the carbon content of the nickel-containing steel can be properly reduced, so that the toughness and the plasticity can be improved; the fatigue resistance of the steel is improved, and the sensitivity of the steel to the notch is reduced;
cu, which is an element for expanding an austenite phase region, but has low solid solubility in iron, and does not form carbide with carbon; the influence of copper on critical temperature and hardenability and the solid solution strengthening effect of copper are similar to those of nickel, and can be used for replacing a part of nickel;
effect of Cu copper on mechanical properties of steel: the strength, particularly the yield ratio, of the steel is improved; with the increase of the copper content, the room temperature impact toughness of the steel is slightly improved; copper also improves the fatigue strength of the steel;
effect of Cu on physical, chemical and technological properties of steel: the addition of a small amount of copper into the steel can improve the atmospheric corrosion resistance of low-alloy structural steel and rail steel, the effect is more obvious when the copper is used in combination with phosphorus, and the copper does not obviously improve the soil and seawater corrosion resistance of the steel. Copper also can slightly improve the high-temperature oxidation resistance of the steel; the fluidity of the molten steel is improved, and the casting performance is facilitated;
mo and molybdenum: mo is an element which can be dissolved in ferrite, austenite and carbide in solid solution in steel and which reduces the austenite phase region; when the content of Mo is lower, the Mo can form a composite cementite with carbon and iron; when the content is higher, special carbide of molybdenum can be formed; molybdenum increases the hardenability of steel, and its effect is stronger than chromium and slightly inferior to manganese; molybdenum improves the tempering resistance of the steel. Increases the temper brittleness of the steel when present as a single alloying element; when the molybdenum coexists with chromium, manganese and the like, the temper brittleness caused by other elements is reduced or inhibited;
the effect of Mo molybdenum on the mechanical properties of steel: molybdenum has a solid solution strengthening effect on ferrite, and simultaneously improves the stability of carbide, thereby improving the strength of steel; molybdenum has a beneficial effect on improving the ductility, toughness and wear resistance of steel; molybdenum increases the softening and recovery temperature after deformation strengthening and the recrystallization temperature, strongly improves the creep resistance of ferrite, effectively inhibits the aggregation of cementite at 450-600 ℃, promotes the precipitation of special carbide, and thus becomes the most effective alloy element for improving the heat strength of steel.
V vanadium, V and Fe form a continuous solid solution, and an austenite phase region is strongly reduced; vanadium has strong affinity with carbon, nitrogen and oxygen, and mainly exists in the form of carbide, nitride or oxide in steel; the hardenability of the steel can be adjusted by controlling the austenitizing temperature to change the content of vanadium in austenite, the quantity of undissolved carbide and the actual grain size of the steel; because vanadium forms stable and refractory carbide, the steel still keeps a fine crystalline structure at higher temperature, and the overheating sensitivity of the steel is greatly reduced.
Effect of vanadium V on mechanical properties of steel: a small amount of vanadium can refine steel grains, increase toughness and is particularly beneficial to low-temperature steel; higher vanadium levels lead to lower strength when aggregated carbides are present; precipitation of carbides in the crystal reduces room temperature toughness; when proper treatment is carried out to ensure that carbide is dispersed and separated out, vanadium can improve the high-temperature endurance strength and creep resistance of steel; vanadium carbides are the hardest and most wear resistant of the metal carbides. The dispersed vanadium carbide improves the hardness and wear resistance of the tool steel.
The effect of V vanadium on the physical, chemical and technological properties of steel is that vanadium is added into high-iron nickel alloy, and after proper heat treatment, the magnetic permeability can be improved. Vanadium is added into the permanent magnet steel, so that the magnetic coercive force can be improved; the addition of vanadium in sufficient quantity to fix carbon in vanadium carbide can greatly increase the stability of steel to hydrogen under high temperature and high pressure, and its strong action is similar to that of Nb, Zr and Ti. In the stainless acid-resistant steel, vanadium can improve the performance of resisting intergranular corrosion, but the effect is not as remarkable as that of Ti and Nb; the vanadium-containing steel obviously increases the deformation resistance when the processing temperature is lower; vanadium improves the weldability of steel.
Therefore, the contents of the alloy elements such as C, Si, Mn, P, S, Cr, Ni, Cu, Mo and V are reasonably controlled, and the low-temperature controlled rolling and cooling control procedures of a steel mill are combined to obtain the high-quality tool steel S2.
The chemical composition of the tool steel S2 was analyzed, and the results are shown in Table 1;
table 1: chemical composition List of tool Steel S2
| Element(s) | C | Si | Mn | P | S | Cr | Ni | Cu | Mo | V |
| Content (a) of | 0.67 | 1.08 | 0.5 | 0.12 | 0.01 | 0.23 | 0.16 | 0.04 | 0.42 | 0.19 |
Example 1:
the method comprises the following steps: conveying the wire rack loaded with the tool steel S2 with the diameter of 8mm to a bearing disc of a base, covering an inner cover, locking the inner cover through a hydraulic clamp, then starting to charge nitrogen, and loading a heating cover;
step two: heating the furnace to 593 deg.C, maintaining at 593 deg.C for two hours, and adding N2Purging is carried out, N2The purge amount of (a) is: 80m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage from 593 deg.C to 775 deg.C at a heating rate of 88.5 deg.C/h, wherein N is added during heating2Purge amount of (3) is 70m2H, maintaining the temperature of 775 ℃ for four hours, and N in the heat preservation process2Purge amount of (2) is 60m2/h；
Step four: cooling to 200 ℃ at the speed of 30 ℃/h, wherein N is generated in the cooling process2Purge amount of (2) 30m2H, and is lifted at about 650 DEG CHeating the cover, turning off nitrogen, and lifting the inner cover at about 200 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
Example 2:
the method comprises the following steps: feeding the tool steel S2 subjected to sand blasting into a hood-type annealing furnace;
step two: heating the furnace to 596 deg.C, maintaining the temperature at 596 deg.C for two hours, and using N2Purging is carried out, N2The purge amount of (a) is: 75m2/h-85m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage from 596 deg.C to 778 deg.C at a heating rate of 85 deg.C/h, wherein N is the amount of nitrogen in the heating process2Purge amount of 65m2H, maintaining the temperature of 778 ℃ for four hours, and keeping N in the heat preservation process2Purge amount of (2) is 55m2/h；
Step four: cooling to 180 ℃ at the speed of 25 ℃/h, wherein N is generated in the cooling process2Purge amount of (2) is 25m2H, lifting the heating cover and turning off nitrogen gas at about 630 ℃, and lifting the inner cover at about 180 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
Example 3:
the method comprises the following steps: feeding the tool steel S2 subjected to sand blasting into a hood-type annealing furnace;
step two: heating the furnace to 600 deg.C, maintaining the temperature at 600 deg.C for two hours, and adding N2Purging is carried out, N2The purge amount of (a) is: 85m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage, wherein the temperature in the furnace is increased from 600 ℃ to 780 ℃, the heating rate is 90 ℃/h, and N is generated in the heating process2Purge amount of (2) is 75m2H, maintaining at 780 ℃ for four hours, and N in the heat preservation process2Purge amount of 65m2/h；
Step four: cooling to 220 deg.C at a rate of 35 deg.C/h, wherein N is added during cooling2Purge amount of (2) is 35m2H, lifting the heating cover at about 680 ℃ and turning off nitrogen, and lifting the inner cover at about 220 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
The tool steel S2 processed in the examples 1-3 has uniform spheroidizing and annealing structure, spheroidization rate more than 90%, annealing HRB hardness value less than 91, HRB hardness value fluctuation less than 3, normal forming processes such as drawing, cold bending and the like, and high tool fatigue life.
It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (5)
1. A spheroidizing annealing process of hexagonal alloy tool steel S2 is characterized in that: the method comprises the following steps:
the method comprises the following steps: feeding the tool steel S2 subjected to sand blasting into a hood-type annealing furnace;
step two: heating the furnace to 593-600 deg.C, holding at 593-600 deg.C for two hours, and using N2Purging is carried out, N2The purge amount of (a) is: 75m2/h-85m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage, namely heating the temperature in the furnace from 593-600 ℃ to 775-780 ℃, wherein the heating rate is 80-90 ℃/h, and N is generated in the heating process2The purge amount of (A) is 65-75m2H, maintaining the temperature of 775 and 780 ℃ for four hours, and keeping N in the heat preservation process2The purge amount of (A) is 55-65m2/h；
Step four: cooling to 180-220 ℃ at the speed of 25-35 ℃/h, wherein N is generated in the cooling process2The purge amount of (2) is 25 to 35m2A heating cover is lifted and closed at the temperature of between 630 and 680 DEG CRemoving nitrogen, and lifting the inner cover at about 180-220 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
2. The spheroidizing annealing process of hexagonal alloy tool steel S2 according to claim 1, characterized in that: the bell-type annealing furnace comprises a base, an inner cover and a heating cover, wherein the base comprises a bottom plate, a heat insulation plate, a gas distribution disc and a bearing disc which are sequentially arranged from bottom to top.
3. The spheroidizing annealing process of hexagonal alloy tool steel S2 according to claim 2, characterized in that: the method comprises the following steps:
the method comprises the following steps: conveying the wire rack loaded with the tool steel S2 to a bearing disc of a base, covering an inner cover, locking the inner cover through hydraulic tongs, then starting to charge nitrogen and loading a heating cover;
step two: heating the furnace to 593 deg.C, maintaining at 593 deg.C for two hours, and adding N2Purging is carried out, N2The purge amount of (a) is: 80m2H, replacing all the original gas in the furnace;
step three: heating the furnace for the second stage from 593 deg.C to 775 deg.C at a heating rate of 88.5 deg.C/h, wherein N is added during heating2Purge amount of (3) is 70m2H, maintaining the temperature of 775 ℃ for four hours, and N in the heat preservation process2Purge amount of (2) is 60m2/h；
Step four: cooling to 200 ℃ at the speed of 30 ℃/h, wherein N is generated in the cooling process2Purge amount of (2) 30m2H, lifting the heating cover at about 650 ℃, turning off nitrogen, and lifting the inner cover at about 200 ℃;
step five: and (4) lifting the spheroidized tool steel S2 out of the annealing furnace, placing the spheroidized tool steel in a cooling area, and discharging the spheroidized tool steel after cooling.
4. The spheroidizing annealing process of hexagonal alloy tool steel S2 according to claim 1, characterized in that: in the first step, the tool steel S2 comprises the following chemical components in percentage by mass: c: 0.65-0.72%, Si: 0.4-1.5%, Mn: 0.3-0.8%, P: 0.02-0.2%, S: 0.0008-0.15%, Cr: 0.15-0.45%, Ni: 0.10-0.35%, Cu: 0-0.25%, Mo: 0.2-0.6%, V: 0.15-0.3%, and the balance of iron and inevitable impurity elements.
5. The spheroidizing annealing process of hexagonal alloy tool steel S2 according to claim 4, characterized in that: in the first step, the tool steel S2 comprises the following chemical components in percentage by mass: c: 0.66-0.7%, Si: 1.0-1.2%, Mn: 0.4-0.6%, P: 0.04-0.15%, S: 0.008-0.018%, Cr: 0.2-0.4%, Ni: 0.12-0.3%, Cu: 0-0.25%, Mo: 0.4-0.5%, V: 0.17-0.25%, and the balance of iron and inevitable impurity elements.
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