CN114752858B - Alloy hand tool steel wire rod without martensite structure, preparation method and hand tool steel - Google Patents
Alloy hand tool steel wire rod without martensite structure, preparation method and hand tool steel Download PDFInfo
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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
- 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
- C21C7/072—Treatment with gases
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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
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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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
- C22C38/44—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
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
An alloy hand tool steel wire rod without martensite structure, a preparation method and hand tool steel, wherein the wire rod comprises the following components in percentage by weight: 0.57-0.67% of C, 1.11-1.20% of Si, 0.25-0.39% of Mn0.31-0.49% of Cr, 0.09-0.29% of Mo, 0.03-0.14% of V, 0.04-0.09% of Ni0.04-0.09% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities; the preparation method comprises a smelting process, a continuous casting process, a rolling process, a spinning process and a cooling process; the cooling process adopts sectional cooling. The invention designs the chemical components of the tool steel, adopts a proper rolling process and a sectional cooling technology after rolling, controls the ordered transformation of the tool steel structure into pearlite, ferrite and a small amount of bainite, avoids the generation of a martensite structure, particularly reduces the formation of obvious structure layering phenomena of the martensite, a residual austenite structure, the pearlite, the ferrite and the small amount of bainite, and avoids the easy occurrence of structure stress at the obvious layering part, thereby avoiding the formation of a crack source and the development of fracture.
Description
Technical Field
The invention relates to the field of tool steel, in particular to an alloy hand tool steel wire rod without a martensite structure and a preparation method thereof.
Background
The hand tool steel is mainly applied to manufacturing common daily hand tools such as a wrench, a pliers, a screwdriver, a hammer and the like, and has the characteristics of certain surface strength and toughness and no crack and fracture problems, so that the hand tool steel needs to contain different elements, adopts high-frequency quenching, improves the surface strength and hardness, and keeps the toughness of the steel. Because the alloy content of the steel grade is higher, the produced disc is easy to have self-breaking problem.
CN113151742A discloses a corrosion-resistant high-strength high-toughness alloy tool steel, its heat treatment method and production method, which comprises the following chemical components by weight percent: 0.70-1.00 percent of C, 0.80-1.10 percent of Si, 0.50-0.80 percent of Mn, 0.50-0.80 percent of Cr0.50, 0.30-0.50 percent of Mo0.20-0.40 percent of V, 0.020-0.040 percent of Nb0.030-0.050 percent of Ti, 0.15-0.35 percent of Ni, 0.15-0.35 percent of Cu, 0.05-0.25 percent of Re0.05, trace amounts of P, S, O and N, and the balance of Fe and other inevitable impurities.
CN103436687A discloses a controlled cooling process for high alloy tool steel, which specifies that the tool steel wire rod obtains fine-grained martensite by means of controlling water tank, blower, heat-insulating cover, etc., and the phase transition temperature is controlled below 600 ℃. The final structure of the wire rod produced by the method is martensite with poor plasticity, the proportion and the distribution of each structure in steel are not clear, and the risk of structure stress exists.
Although the research on the alloy tool steel products in China is more and the products are mature at present, the alloy components of the steel are higher, the chemical components are not properly designed, the process is improper in the production process, and the structure in the steel is easy to be abnormal, so that the steel is self-broken; the material is self-broken, which brings huge potential safety hazard.
Disclosure of Invention
In order to solve the problems of the prior art, one of the objects of the present invention is to provide an alloy tool steel wire rod without martensite structure, which can reach a suitable transformation temperature by adjusting the chemical composition of the tool steel wire rod under the condition of meeting the performance requirements of hand tool steel.
The invention also aims to provide a preparation method of the alloy tool steel wire rod without the martensite structure, which combines the chemical components of the tool steel, adopts a proper rolling process and a segmented cooling technology after rolling to control the orderly transformation of the structure into pearlite, ferrite and a small amount of bainite, avoids the generation of the martensite structure, causes the martensite, the residual austenite structure, the pearlite, the ferrite and the small amount of bainite to form an obvious structure layering phenomenon, and avoids the easy occurrence of structural stress at the obvious layering position, thereby causing a crack source and developing into fracture.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides an alloy hand tool steel wire rod without martensite structure, the wire rod comprises the following components by weight: 0.57-0.67% of C, 1.11-1.20% of Si, 0.25-0.39% of Mn, 0.31-0.49% of Cr, 0.09-0.29% of Mo, 0.03-0.14% of V, 0.04-0.09% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities; the microstructure of the wire rod is pearlite, ferrite and bainite, wherein the mass percentage of the ferrite and pearlite structure is more than or equal to 91%, and the mass percentage of the bainite structure is less than 9%.
Optionally, the wire rod further comprises, in weight percent: 0.57-0.67% of C, 1.11-1.20% of Si, 0.25-0.33% of Mn, 0.31-0.37% of Cr, 0.23-0.29% of Mo, 0.10-0.14% of V, 0.04-0.06% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities.
In a second aspect: the invention provides a preparation method of a hand alloy tool steel wire rod without a martensite structure, which comprises a smelting process, a continuous casting process, a rolling process, a spinning process and a cooling process; the cooling process adopts sectional cooling.
Optionally, the staged cooling is divided into four stages:
the cooling speed is controlled to be 5-12.5 ℃/s from the spinning temperature to 718 ℃;
the temperature is reduced from 718 ℃ to 613 ℃, and the cooling speed is controlled to be 5 ℃/s-10 ℃/s;
the temperature is reduced from 613 ℃ to 530 ℃, and the cooling speed is controlled to be 1 ℃/s-5 ℃/s;
the temperature is reduced from 530 ℃ to room temperature, and the cooling speed is controlled to be less than or equal to 8 ℃/s.
Optionally, the spinning temperature is controlled to be 820-840 ℃.
Optionally, the cooling speed is controlled by the air volume of the fan, the wire ring spacing and the heat preservation cover together.
Optionally, the smelting process comprises converter smelting and RH vacuum treatment, the terminal point P is controlled to be less than or equal to 0.015 percent, the vacuum degree is below 0.266kPa, the vacuum maintaining time is greater than or equal to 18min, the pure degassing time is greater than or equal to 10min, soft argon blowing is carried out after RH is finished, and the maintaining time is greater than or equal to 15min.
Optionally, the continuous casting process comprises: the process of electromagnetic stirring and soft pressing of the crystallizer is adopted, the pulling speed is controlled to be 0.62m/min, the superheat degree is controlled to be less than or equal to 35 ℃ for a casting furnace, and the continuous casting furnace is controlled to be less than or equal to 30 ℃.
Optionally, the rolling process comprises cogging rolling, rough rolling, pre-finishing rolling and finish rolling.
Optionally, the cogging rolling temperature is 900-980 ℃, the rough rolling temperature is 920-980 ℃, the pre-finish rolling temperature is 880-920 ℃, and the finish rolling temperature is 860-900 ℃; the temperature of the preheating section of the heating furnace is 550-850 ℃, the temperature of the heating section is 980-1100 ℃, and the temperature of the soaking section is 980-1100 ℃.
In a third aspect: the invention also provides hand tool steel prepared by the preparation method.
The inventor of the invention finds out in research that: alloying elements in the steel reduce the martensite start transformation temperature Ms and the martensite transformation end temperature Mf to different degrees, and increase the amount of retained austenite; martensite and residual austenite exist in the internal structure of the steel, obvious structure layering phenomenon occurs, a structure transition region exists, and the structure transition region generally has large structure stress, so that crack sources are generated in the region to cause disc breakage. Due to the characteristics of the hand tool steel, more alloy elements need to be added, so that the martensitic transformation temperature is reduced, and further the steel is often subjected to martensitic transformation when being cooled to room temperature; and the rolled steel has more retained austenite, the rolled steel is placed at room temperature under normal conditions, and the structure difference is more obvious under the condition of room temperature, the structure stress is increased, and the steel is broken.
The beneficial effects of the invention include:
the martensite transformation temperature is improved by researching and controlling chemical components; specifically, the martensitic transformation finishing temperature Mf of the steel is increased by controlling C and Ni in the steel, the martensitic transformation finishing temperature Mf of the steel is increased to be more than 300 ℃ from room temperature, the martensitic transformation at the normal temperature is stopped, the tendency that the steel is easy to generate martensite in the cooling process is avoided, the structure difference is improved, and the structure stress is reduced; by controlling Si element, the stability of super-cooled austenite is improved, mn, cr, mo and V elements are controlled, and the influence on the martensite transformation temperature is reduced; in addition, si, mn, cr, mo and V are controlled to further enhance the strength and wear resistance of the steel.
The inventors have also found that the use of alloy elements generally requires pearlite, ferrite, and bainite as the structure of steel materials, and that the structures are uniform and the grain size is appropriate; the poor matching of the alloy element proportion and the steel-making and steel-rolling processes can also cause abnormal structures, such as martensite structures, martensite + retained austenite structures, or mixed structures, and the like, and the problem of material self-breaking cannot be avoided.
In contrast, the controlled rolling and controlled cooling technology is utilized, and particularly, the segmented cooling technology is adopted on the controlled cooling process, the structure is controlled to be orderly transformed into pearlite, ferrite and a small amount of bainite, the martensite structure is avoided, the martensite transformation is stopped after the production is finished, the structure difference is reduced, and the structure stress is reduced, so that the problem of self-breaking is solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a microstructure of example 1 of the present invention;
FIG. 2 is a microstructure of example 2 of the present invention;
FIG. 3 is a microstructure of example 3 of the present invention;
FIG. 4 is a microstructure of example 4 of the present invention;
FIG. 5 is a microstructure of example 5 of the present invention;
FIG. 6 is a microstructure of comparative example 1 of the present invention;
FIG. 7 is a microstructure of comparative example 2 of the present invention;
FIG. 8 is a microstructure of comparative example 3 of the present invention;
FIG. 9 is a microstructure of comparative example 4 of the present invention;
FIG. 10 is a microstructure of comparative example 5 of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. The detection method is not particularly described, and the detection is carried out according to national standards or conventional detection methods.
The invention provides an alloy tool steel wire rod without martensite structure, which comprises the following components in percentage by weight: 0.57-0.67% of C, 1.11-1.20% of Si, 0.25-0.39% of Mn, 0.31-0.49% of Cr, 0.09-0.29% of Mo, 0.03-0.14% of V, 0.04-0.09% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities.
In the invention, the content of alloy elements in the steel is very critical, the content of the alloy elements influences the phase transition temperature, particularly the influence on the martensite transition temperature, is a factor for determining whether the steel grade can be successful, and is critical for solving the self-breaking problem by matching with the subsequent segmented cooling technology, and the steel with the proper structure transition temperature is obtained on the premise of ensuring that the service performance of the steel meets the requirement.
The concrete description is as follows:
c is a main element second only to iron, and directly influences the strength, plasticity, toughness, welding performance and the like of steel. When the carbon content in the steel is 0.8% or less, the strength and hardness of the steel are improved and the plasticity and toughness are reduced as the carbon content increases.
Researches find that when the carbon content is properly reduced under the condition of meeting the requirements, the martensite transformation end temperature Mf is favorably improved, the martensite transformation of steel is prevented from stopping at normal temperature, the structure difference is improved, and the structure stress is reduced; c0.57-0.67 wt.%, such as, but not limited to, any one of, or a range between any two of 0.57wt.%, 0.60wt.%, 0.63wt.%, 0.65wt.%, and 0.67 wt.%.
Si can be dissolved in ferrite and austenite to improve the hardness and strength of steel, and the effect is second to phosphorus and is stronger than elements such as manganese, nickel, chromium, tungsten, molybdenum, vanadium and the like. However, when the silicon content is too high, the plasticity and toughness of the steel are significantly reduced. Silicon can improve the elasticity of steelUltimate, yield strength and yield ratio (σ) s /σ b ) And fatigue strength and fatigue ratio (σ) -1 /σ b ) And the like. It has been found that silicon improves the stability of super-cooled austenite and that silicon has a small effect on the martensitic transformation temperature relative to other alloying elements, si 1.11-1.20 wt.%, such as, but not limited to, any one of 1.11wt.%, 1.12wt.%, 1.15wt.%, 1.17wt.%, 1.18wt.%, 1.19wt.% and 1.20wt.%, or a range between any two.
Mn can improve the strength of steel and can be infinitely dissolved with Fe, and the influence on plasticity is relatively small while the strength of the steel is improved; mn can also improve the hardenability of steel and improve the hot workability of steel: mn can eliminate the influence of S (sulfur): mn can form MnS with a high melting point with S in steel smelting, thereby weakening and eliminating the adverse effect of S. Mn, when exerting the above effect, has less impact on lowering the martensitic transformation temperature, is determined to be in the range of 0.25 to 0.39wt.%, such as, but not limited to, any one of, or a range between any two of 0.25wt.%, 0.28wt.%, 0.30wt.%, 0.32wt.%, 0.34wt.%, 0.36wt.%, and 0.39 wt.%.
Cr has the main function of improving hardenability in steel, so that the steel has better comprehensive mechanical properties after quenching and tempering, and chromium-containing carbide can be formed in carburizing steel, thereby improving the wear resistance of the surface of the material.
Studies have found that Cr has less impact on lowering the martensitic transformation temperature when it does so, with Cr 0.31-0.49 wt.%, such as, but not limited to, any one of, or a range between any two of 0.31wt.%, 0.34wt.%, 0.35wt.%, 0.38wt.%, 0.41wt.%, 0.45wt.%, and 0.49 wt.%.
Mo improves hardenability and heat strength in steel, prevents temper embrittlement, increases remanence and coercivity and resists corrosion in certain media. In the quenched and tempered steel, molybdenum can enable parts with larger sections to be quenched deeply and thoroughly, improve the tempering resistance or tempering stability of the steel, and enable the parts to be tempered at higher temperature, so that the residual stress is effectively eliminated (or reduced), and the plasticity is improved. In addition to the above-mentioned effects, molybdenum in carburized steel can reduce the tendency of carbides to form a continuous network at grain boundaries in the carburized layer, reduce retained austenite in the carburized layer, and relatively increase the wear resistance of the surface layer. Mo has less impact on lowering the martensitic transformation temperature when it does so, with Mo 0.09 to 0.29wt.%, such as, but not limited to, any one of, or a range between any two of 0.09wt.%, 0.12wt.%, 0.13wt.%, 0.17wt.%, 0.21wt.%, 0.23wt.%, and 0.29 wt.%.
V has strong affinity with carbon, nitrogen and oxygen to form corresponding stable compounds. Vanadium is mainly present in steel in the form of carbides. The main function of the steel is to refine the structure and crystal grains of the steel and improve the strength and toughness of the steel. When the solid solution is dissolved at high temperature, hardenability is increased. Vanadium increases the temper stability of the quenched steel and produces a secondary hardening effect. Vanadium refines grains in the tool steel, reduces the overheating sensitivity, and increases the tempering stability and the wear resistance, thereby prolonging the service life of the tool. V has less effect on lowering the martensitic transformation temperature when it does so, V0.03 to 0.14wt.%, such as but not limited to any one of 0.03wt.%, 0.05wt.%, 0.08wt.%, 0.10wt.%, 0.11wt.% and 0.14wt.%, or a range between any two.
The beneficial effects of Ni are: the strength, toughness, hardenability, high resistance and corrosion resistance of the steel are improved. On the one hand, the strength of the steel is strongly improved, and on the other hand, the toughness of the iron is always kept at an extremely high level. When it is combined with Cr and Mo, the hardenability is especially increased. Nickel molybdenum steels also have a very high fatigue limit. Too high Ni tends to make the steel prone to martensite during cooling, and the Ni content is determined in the range of 0.04 to 0.09wt.%, such as, but not limited to, any one of 0.04wt.%, 0.05wt.%, 0.06wt.%, 0.08wt.%, and 0.09wt.%, or a range between any two.
It should be noted that the invention does not contain niobium, which reduces the martensite start temperature Ms, the martensite finish temperature Mf and increases the retained austenite amount, resulting in an obvious structure delamination phenomenon in the structure, a structure transition region, and further a crack source in the structure transition region to cause disc breakage, and the addition of niobium increases the production cost.
The alloy elements in the steel reduce the martensite start transformation temperature Ms and the martensite finish transformation temperature Mf to different degrees, and increase the amount of retained austenite, so that the obvious structure layering phenomenon in the structure is caused, the structure transition region is generated, and further the crack source is generated in the structure transition region to cause the disc fracture. The tool steel is required to have a certain surface strength, a certain toughness, and no cracking or breaking problems, and a large amount of alloying elements are required to be added. Therefore, the decrease in the martensitic transformation temperature tends to cause martensitic transformation even after cooling to room temperature; and the rolled steel has more retained austenite, the rolled steel is placed at room temperature under normal conditions, and the structure difference is more obvious under the condition of room temperature, so that the fracture of the steel is further accelerated.
In the proportion of the elements of the steel, the contents of carbon, silicon, chromium, molybdenum and vanadium are mainly considered, so that the toughness and the surface hardenability are ensured.
According to the invention, the content of alloy elements is controlled through research, the martensite transformation temperature is increased, and the microstructure of the wire rod is controlled to be pearlite, ferrite and bainite, wherein the mass percent of the ferrite and pearlite structure is more than or equal to 91%, and the mass percent of the bainite structure is less than 9%.
The wire rod further comprises the following components in percentage by weight: 0.57-0.67% of C, 1.11-1.20% of Si, 0.25-0.33% of Mn, 0.31-0.37% of Cr, 0.23-0.29% of Mo, 0.10-0.14% of V, 0.04-0.06% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities.
The present invention further provides a method for producing an alloy tool steel wire rod including the martensite-free structure of the first aspect, including a smelting process, a continuous casting process, a rolling process, a spinning process, and a cooling process.
The production process flow of the steel grade further comprises the following steps: blast furnace molten iron → converter smelting → converter tapping → LF furnace refining → RH vacuum → continuous casting machine continuous casting → cogging rolling → rolling blank inspection, cleaning → rolling billet cold charging heating furnace heating → high speed wire controlled rolling → segmented cooling → finishing → inspection → packing → weighing → warehousing.
The smelting process comprises blast furnace molten iron → converter smelting → LF furnace refining → RH vacuum. The control of the smelting process mainly aims at improving the purity of steel, reducing inclusions, reducing casting blank segregation and the like, and creates conditions for subsequent steel rolling.
Description of key control points:
in some possible embodiments, the first furnace does not smelt the steel grade after the new furnace and the big fettling furnace, and the chemical components of the molten steel are controlled to comprise the following components in percentage by weight: 0.57-0.67% of C, 1.11-1.20% of Si, 0.25-0.39% of Mn, 0.31-0.49% of Cr, 0.09-0.29% of Mo, 0.03-0.14% of V, 0.04-0.09% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities, and the end point [ P ] is controlled to be less than or equal to 0.015%.
In some possible embodiments, good slag fluidity and whitening of the slag are ensured, while the slag surface is diffusion deoxidized. In RH vacuum treatment, illustratively, the vacuum degree is controlled to be below 0.266kPa, the vacuum maintaining time is more than or equal to 18min, the pure degassing time is more than or equal to 10min, soft argon blowing is carried out after RH is finished, the maintaining time is more than or equal to 15min, the slag surface is controlled to be slightly moved by soft argon blowing, and the molten steel is strictly forbidden to be exposed.
Description of key control points of the continuous casting process:
in some possible embodiments, the crystallizer electromagnetic stirring and soft reduction technology are adopted, the pulling speed is controlled at 0.62m/min, and the stability of the liquid level of the crystallizer can be ensured; the control target of the superheat degree of the tundish is as follows: the casting furnace is less than or equal to 35 ℃, and the continuous casting furnace is less than or equal to 30 ℃; and cutting off the continuous casting first furnace end blank by more than 0.9m, cutting off the tail blank by more than 2.0m, and cutting off the corresponding casting blank under the non-steady flow condition, such as the non-steady flow conditions of oxygen burning at a tundish nozzle, nozzle changing and the like.
And the rolling process comprises cogging rolling, rough rolling, pre-finish rolling and finish rolling.
Description of key control points:
in some possible embodiments, the cogging temperature is controlled in the range of 900-980 ℃, and in the process of heating the casting blank, the temperature of a preheating section of a heating furnace is 550-850 ℃, the temperature of a heating section is 980-1100 ℃, and the temperature of a soaking section is 980-1100 ℃; when the temperature is too high, the phenomenon of quenching appears during subsequent cooling, a martensite structure is generated, and the burning loss is increased due to the increase of the temperature, so that energy is wasted; the phenomenon of mixed crystals, directional organization and the like can be caused by rolling in a two-phase region due to low temperature, and the rolling mill equipment is damaged due to overlarge deformation resistance of the rough and medium rolling mill due to low temperature.
In some possible embodiments, the rough rolling adopts a high-speed wire rolling process, the initial rolling temperature is controlled to be 920-980 ℃, the preheating section temperature of a heating furnace is controlled to be 550-850 ℃, the heating section temperature is controlled to be 980-1100 ℃, and the soaking section temperature is controlled to be 980-1100 ℃;
in some possible embodiments, the pre-finishing temperature (BGV entry) is in the range of 880 to 920 ℃, such as, but not limited to, any one or any range between 880 ℃, 886 ℃, 893 ℃, 900 ℃, 905 ℃, 909 ℃, 915 ℃ and 920 ℃.
In some possible embodiments, the finish rolling temperature (TMB inlet) is in the range of 860 to 900 ℃, such as, but not limited to, any one or any two of 860 ℃, 865 ℃, 870 ℃, 874 ℃, 882 ℃, 893 ℃ and 900 ℃.
A spinning process:
in some possible embodiments, the laying temperature is controlled in the range of 820-840 ℃, such as but not limited to any one or any two of 820 ℃, 823 ℃, 827 ℃, 830 ℃, 835 ℃, 838 ℃ and 840 ℃.
In some possible embodiments, the temperature of the rolling process and the spinning process is controlled by water tank cooling to suppress the temperature rise phenomenon caused by high temperature rolling, and fine austenite grains are obtained.
A cooling process: and adopting sectional cooling.
The sectional cooling is divided into the following stages:
the cooling speed is controlled to be 5-12.5 ℃/s from the spinning temperature to 718 ℃;
the temperature is reduced from 718 ℃ to 613 ℃, and the cooling speed is controlled to be 5 ℃/s-10 ℃/s;
the temperature is reduced from 613 ℃ to 530 ℃, and the cooling speed is controlled to be 1 ℃/s-5 ℃/s;
the temperature is reduced from 530 ℃ to room temperature, and the cooling speed is controlled to be more than or equal to 8 ℃.
After the spinning process, in order to enter a phase transformation interval as soon as possible, the cooling speed is controlled to be between 5 ℃/s and 12.5 ℃/s, so that the steel enters the phase transformation interval as soon as possible, martensite is prevented from being transformed to generate a martensite structure, and grain growth and uneven grain generation are avoided.
When the temperature is between 718 ℃ and 613 ℃, the cooling speed is cooled according to a larger cooling speed of 5 ℃/s-10 ℃/s, so that the highest cooling speed can be ensured to pass through a ferrite precipitation line, and the precipitation of ferrite is reduced. Since ferrite is precipitated too much, network ferrite is formed, which has an influence on quenching properties and drawing properties.
And after the temperature is 613 ℃, the temperature starts to enter a pearlite transformation region, the cooling speed is properly reduced, and until the pearlite transformation is finished, the cooling speed is controlled to be not more than 5 ℃/s, so that the structure is transformed into pearlite and ferrite as far as possible, and the generation of a retained austenite structure is avoided.
The adoption of the sectional cooling method can realize that the structure of the coiled steel material is pearlite, ferrite and bainite, and prevent martensite and residual austenite from appearing in the structure.
In some possible embodiments, the cooling speed is controlled by the air volume of the fan, the wire ring distance and the heat preservation cover together.
Wherein, the calculation formula of the wire ring spacing is as follows: w = v 1 *π*d/v 2
In the formula: v. of 1 The roller table speed is m/s; w is the wire loop spacing, mm; d is the diameter of the wire loop, mm; v 2 The rolling speed is m/s.
In a third aspect: the invention also provides hand tool steel which is prepared by adopting the wire rod.
Specifically, the wire rod is drawn and reduced to the required diameter, and then is annealed and then straightened and ground to manufacture the hand tool steel.
The features and properties of the present invention are further described in detail below with reference to examples:
a method for preparing an alloy tool steel wire rod without a martensite structure comprises a smelting process, a continuous casting process, a rolling process, a wire laying process and a cooling process.
Example 1:
provides a preparation method of an alloy tool steel wire rod without martensite structure, and the specification phi of the alloy tool steel wire rod is 6.5mm.
The method comprises the following steps: smelting: the converter control molten steel comprises the following chemical components in percentage by weight: c:0.57%, si:1.12%, mn:0.33%, cr:0.37%, mo:0.28%, V:0.14%, ni:0.05%, P:0.015%, S:0.015%, cu:0.01%, and the balance Fe and inevitable impurities; and continuing LF furnace refining, RH furnace refining and vacuum treatment, controlling the vacuum degree to be 0.238kPa, keeping the vacuum for more than or equal to 18min, keeping the pure degassing time for more than or equal to 10min, and carrying out soft argon blowing after RH is finished, wherein the keeping time is more than or equal to 15min.
Step two: continuous casting: adopting crystallizer electromagnetic stirring and soft pressing technology, controlling the pulling speed at 0.62m/min, wherein the furnace is a casting furnace, the superheat degree of a tundish controls the casting furnace to be less than or equal to 35 ℃, and the continuous casting furnace is less than or equal to 30 ℃; and cutting off the first furnace end blank of the continuous casting by more than 0.9m, and cutting off the tail blank by more than 2.0 m.
Step three: rolling: the cogging rolling temperature is controlled to be 942 ℃, the roughing rolling temperature is controlled to be 935 ℃, the preheating section temperature of the heating furnace is 761 ℃, the heating section temperature is 1085 ℃ and the soaking section temperature is 1086 ℃; the pre-finish rolling temperature (BGV inlet) was 889 ℃ and the finish rolling temperature (TMB inlet) was 884 ℃. In the process of heating the casting blank, the temperature of a preheating section of a heating furnace is 761 ℃, the temperature of a heating section is 1085 ℃ and the temperature of a soaking section is 1085 ℃.
Step four: spinning: the spinning temperature was 832 ℃.
Step five: and (3) cooling: the cooling speed is controlled to be 11.4 ℃/s from 832 to 718 ℃;
the temperature is reduced from 718 ℃ to 613 ℃, and the cooling speed is controlled at 7.2 ℃/s;
the temperature is reduced from 613 ℃ to 530 ℃, and the cooling speed is controlled at 2.3 ℃/s;
the temperature is reduced from 530 ℃ to room temperature, and the cooling speed is controlled to be 4.8 ℃/s
The fan air volume, roller table speed and heat preservation cover parameter control are shown in table 4. Through the procedures, the prepared wire rod is detected according to a metal microstructure detection method of GB/T13298-1991, and the microstructure detection evaluation is carried out according to a microstructure evaluation method of GB/T13299-1991 steel. According to the present invention, the wire rod structure was obtained with 62.78% of pearlite P, 33.13% of ferrite F, and 4.09% of bainite B, and did not contain martensite and retained austenite.
The ingredients of the wire rods and the preparation process parameters of examples 2-5 and comparative examples 1-5 are shown in tables 1-5.
TABLE 1 ingredient content of wire rod (wt.%) and wire rod specification (mm)
TABLE 2 Rolling and spinning Process parameters (. Degree. C.)
TABLE 3 Cooling procedure Process parameters after wire rod spinning
TABLE 4 Cooling control Process parameters
TABLE 5 micro-structure of wire rod (%)
As can be seen from tables 1 to 5, in examples 1 to 5, the martensitic transformation temperature is increased from room temperature to 300 ℃ or higher by controlling the composition of the wire rod and the cooling process, and the sectional cooling technique is adopted, so that the martensitic transformation and the formation of the obvious delamination phenomenon are avoided, and the structural difference and the structural stress are reduced, thereby solving the self-breaking problem.
The martensite transformation temperature is improved by researching and controlling chemical components; specifically, the martensite finish temperature Mf is increased by controlling C and Ni in steel, the martensite finish temperature Mf of steel is increased to more than 300 ℃ from room temperature, the martensite transformation at normal temperature is stopped, the tendency that the steel is easy to generate martensite in the cooling process is avoided, the tissue difference is improved, and the tissue stress is reduced; by controlling Si element, the stability of super-cooled austenite is improved, mn, cr, mo and V elements are controlled, and the influence on the martensite transformation temperature is reduced; in addition, si, mn, cr, mo and V are controlled to further enhance the strength and the wear resistance of the steel.
The inventors have also found that the use of alloy elements generally requires pearlite, ferrite, and bainite as the structure of steel materials, and that the structures are uniform and the grain size is appropriate; the poor matching of the alloy element proportion and the steel-making and steel-rolling processes can also cause abnormal structures, such as martensite structures, martensite + retained austenite structures, or mixed structures, and the like, and the problem of material self-breaking cannot be avoided.
In contrast, the controlled rolling and controlled cooling technology is utilized, and particularly, the segmented cooling technology is adopted on the controlled cooling process, the structure is controlled to be orderly transformed into pearlite, ferrite and a small amount of bainite, the martensite structure is avoided, the martensite transformation is stopped after the production is finished, the structure difference is reduced, and the structure stress is reduced, so that the problem of self-breaking is solved.
The above description is only exemplary of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. An alloy hand tool steel wire rod without martensite structure, characterized in that the wire rod comprises the following components by weight percentage: 0.57-0.58% of C, 1.11-1.20% of Si, 0.25-0.39% of Mn, 0.31-0.49% of Cr, 0.09-0.29% of Mo, 0.03-0.14% of V, 0.04-0.09% of Ni, trace P, S, O and N, and the balance of Fe and other inevitable impurities;
the microstructure of the wire rod is pearlite, ferrite and bainite, wherein the mass percentage of the ferrite and pearlite structure is more than or equal to 91%, and the mass percentage of the bainite structure is less than 9%.
2. The method for preparing the alloy hand tool steel wire rod without the martensite structure according to claim 1, which is characterized by comprising a smelting process, a continuous casting process, a rolling process, a spinning process and a cooling process;
the cooling process adopts sectional cooling, and the sectional cooling is divided into four stages:
the cooling speed is controlled to be 5-12.5 ℃/s from the spinning temperature to 718 ℃;
the temperature is reduced from 718 ℃ to 613 ℃, and the cooling speed is controlled to be 5 ℃/s-10 ℃/s;
the temperature is reduced from 613 ℃ to 530 ℃, and the cooling speed is controlled to be 1 ℃/s-5 ℃/s;
the temperature is reduced from 530 ℃ to room temperature, and the cooling speed is controlled to be less than or equal to 8 ℃/s.
3. The method according to claim 2, wherein the spinning temperature is controlled to 820 to 840 ℃.
4. The preparation method of claim 2, wherein the cooling speed is controlled by the combination of fan air volume, wire loop spacing and heat-insulating cover.
5. The method according to claim 2,
the smelting process comprises converter smelting and RH vacuum treatment, the terminal point P is controlled to be less than or equal to 0.015 percent, the vacuum degree is controlled to be less than 0.266kPa, the vacuum maintaining time is more than or equal to 18min, the pure degassing time is more than or equal to 10min, soft argon blowing is carried out after RH is finished, and the maintaining time is more than or equal to 15min;
the continuous casting process comprises the following steps: the process of electromagnetic stirring and soft pressing of the crystallizer is adopted, the pulling speed is controlled to be 0.62m/min, the superheat degree is controlled to be less than or equal to 35 ℃ for a casting furnace, and the continuous casting furnace is controlled to be less than or equal to 30 ℃.
6. The production method according to claim 2, wherein the rolling process includes cogging rolling, rough rolling, pre-finish rolling, and finish rolling.
7. The production method according to claim 6, wherein the cogging rolling temperature is 900 to 980 ℃, the rough rolling temperature is 920 to 980 ℃, the pre-finish rolling temperature is 880 to 920 ℃, and the finish rolling temperature is 860 to 900 ℃; the temperature of the preheating section of the heating furnace is 550-850 ℃, the temperature of the heating section is 980-1100 ℃, and the temperature of the soaking section is 980-1100 ℃.
8. A hand tool steel, characterized by being produced by the production method according to any one of claims 2 to 7.
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