CN112322868A - High-alloy tool and die steel and preparation method thereof - Google Patents
High-alloy tool and die steel and preparation method thereof Download PDFInfo
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- CN112322868A CN112322868A CN202011278291.2A CN202011278291A CN112322868A CN 112322868 A CN112322868 A CN 112322868A CN 202011278291 A CN202011278291 A CN 202011278291A CN 112322868 A CN112322868 A CN 112322868A
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- C—CHEMISTRY; METALLURGY
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- 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
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- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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Abstract
The invention relates to high alloy tool and die steel and a preparation method thereof, belonging to the technical field of die steel preparation. In order to solve the problem that the mechanical property of the high alloy tool and die steel is unqualified, the invention provides a preparation method of the high alloy tool and die steel, the heat treatment step comprises a secondary tempering treatment step, specifically, the steel material obtained after the forging tempering is heated to the quenching temperature and is kept warm for 1h, and oil cooling is carried out; heating the cooled steel material to a primary tempering temperature, preserving heat for 2 hours, and air cooling; and heating the cooled steel material to a secondary tempering state, preserving heat for 2 hours, and cooling in air. According to the invention, the secondary tempering heat treatment step is adopted to eliminate the residual austenite and newly-generated martensite in the steel structure, so that the tempered sorbite with better mechanical property is generated, the mechanical property of the high-alloy tool and die steel is obviously improved, the reduction of area can reach 41-44%, the reduction of area is improved by 46% compared with the prior art, and the requirement of the technical field of die steel on the mechanical property of the high-alloy tool and die steel is met.
Description
Technical Field
The invention belongs to the technical field of die steel preparation, and particularly relates to high-alloy tool and die steel and a preparation method thereof.
Background
The high alloy tool and die steel is alloy steel specially used for manufacturing dies of stamping, die forging, extrusion, die casting and the like. Because high-alloy tool and die steel contains a large amount of alloy elements, the hardenability of the steel is good, a large amount of retained austenite is retained in a structure after quenching, and the retained austenite can be continuously transformed into martensite only in the tempering and cooling processes, namely, the secondary quenching is carried out. After primary tempering, new internal stress is generated due to the formation of new martensite, and in addition, part of unconverted residual austenite still possibly exists, so that the mechanical property reduction of area of the steel is unqualified, and serious economic loss is caused.
Disclosure of Invention
The invention provides high-alloy tool and die steel and a preparation method thereof, aiming at solving the problem that the mechanical property of the existing high-alloy tool and die steel is unqualified.
The technical scheme of the invention is as follows:
a preparation method of high alloy tool and die steel comprises the following production processes: electric furnace → LF → VD → cast electrode blank → blank annealing → electrode blank cleaning → electroslag remelting → electroslag ingot heat-transfer annealing → steel ingot heating → forging → annealing after forging → heat treatment → polishing flaw detection → inspection, inspection → handing over; the heat treatment step comprises a secondary tempering treatment step, and specifically comprises the steps of heating the steel material obtained by post-forging tempering to the quenching temperature of 1050-1060 ℃, preserving heat for 1h, water quenching, and oil cooling to 50-100 ℃; heating the cooled steel material to 520-530 ℃ for primary tempering, keeping the temperature for 2h after temperature equalization, and air cooling; and heating the cooled steel material to 520-530 ℃ for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling in air.
Further, in the heat treatment step, the steel material is heated to the quenching temperature at a heating rate of 60-80 ℃/h.
Further, in the heat treatment step, the steel material is heated to the primary tempering temperature and the secondary tempering temperature at the heating rate of 60-80 ℃/h.
Furthermore, in the electric furnace step, the pig iron content is not less than 30 wt%, the molten steel temperature is not less than 1580 ℃, the C content of the steel is not less than 0.05%, and the P content is not more than 0.003%.
Furthermore, the white slag holding time in the LF refining and VD vacuum steps is not less than 30min, and S is not more than 0.003 percent before vacuum; after the white slag refining is finished, keeping the white slag at the vacuum degree of 67Pa for not less than 20min, adding a ladle covering agent after the white slag is diffused, and performing argon soft blowing on the slag surface by using micro motion without exposing molten steel, wherein the soft blowing time is not less than 20 min.
Further, the molten steel after the soft blowing in the step of casting the electrode blank is poured under the protection of argon at the pressure of 0.02-0.03 MPa in the whole process, and the temperature of the molten steel is 1505-1510 ℃ during pouring; when the ingot type is 2.4t, the pouring time of the ingot body is controlled to be 200-300 s, the feeding time of the cap opening is controlled to be 90-180 s, and the mold cooling time is controlled to be 30-60 min; when the ingot shape is 3.935t, the pouring time of the ingot body is controlled to be not less than 360s, the feeding time of the cap opening is controlled to be not less than 210s, and the mold cooling time is controlled to be 150 min; in the blank annealing step, the blank obtained by casting is heated to 600 ℃ and the temperature is equalized for 2 hours, the temperature is raised to 820 +/-10 ℃ at the speed of less than or equal to 100 ℃/h, the temperature is kept for 10 hours, then the temperature is lowered to 300 ℃ at the cooling speed of less than or equal to 50 ℃/h, and the blank is cooled to room temperature by air.
Further, in the electroslag remelting step, when the crystallizer is phi 600/630, the quaternary slag system is CaF242Kg、Al2O363Kg, 28Kg of CaO and 7Kg of MgO, and the refining time is 30 min; when the crystallizer is phi 640/680, the quaternary slag system is CaF2 51Kg、Al2O377Kg, 34Kg CaO and 8Kg MgO, with a refining time of 30 min.
Further, in the steps of heating, forging and annealing the steel ingot, annealing the electroslag ingot at 820 ℃, then cold-loading the electroslag ingot into a quick forging heating furnace, carrying out high-temperature homogenization heating at 1250 ℃, preserving heat for 12 hours, cooling to 1220 ℃, carrying out forging cogging by a quick forging machine after preserving heat for 2 hours, then forging the electroslag ingot into a material by a rotary forging machine, carrying out annealing by a rotary forging furnace of 15m after forging, and preserving heat for 15 hours under the normalizing condition of 1030 ℃; the spheroidizing annealing condition is that the temperature is 870 ℃ for 3h, and the temperature is 740 ℃ for 25 h.
The high alloy tool and die steel prepared by the preparation method of the high alloy tool and die steel comprises the following chemical components in percentage by weight: 0.47-0.52% of C, 0.80-1.00% of Si, 0.28-0.45% of Mn, less than or equal to 0.010% of P, less than or equal to 0.010% of S, 5.25-5.60% of Cr, 0.20-0.32% of Ni, 1.40-1.75% of Mo, 0.90-1.20% of V, less than or equal to 0.20% of Cu, and the balance of Fe and inevitable impurities.
Furthermore, the tensile strength is 1936-1948 MPa, the elongation after fracture is 10-11%, the reduction of area is 41-44%, the impact absorption energy KU2 is 24-26J, and the hardness is 58-59.
The invention has the beneficial effects that:
according to the preparation method of the high alloy tool and die steel, the secondary tempering heat treatment step is adopted to eliminate the residual austenite and the newly generated martensite in the steel tissue, the tempered sorbite with better mechanical property is generated, the mechanical property of the high alloy tool and die steel is obviously improved, the reduction of area can reach 41-44%, is improved by 46% compared with the prior art, and the requirement of the technical field of die steel on the mechanical property of the high alloy tool and die steel is met.
The invention solves the problem that the mechanical property of the existing high-alloy tool and die steel is unqualified, reduces the loss of 18500 yuan/ton per ton of steel, and has positive economic benefit and social benefit.
Drawings
FIG. 1 is a metallographic structure photograph of a high alloy tool and die steel obtained by a secondary tempering heat treatment in example 10;
FIG. 2 is a metallographic structure picture of a high alloy tool and die steel obtained by one tempering heat treatment in comparative example 1.
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention. The process equipment or apparatus not specifically mentioned in the following examples are conventional in the art, and if not specifically mentioned, the raw materials and the like used in the examples of the present invention are commercially available; unless otherwise specified, the technical means used in the examples of the present invention are conventional means well known to those skilled in the art.
Example 1
A preparation method of high alloy tool and die steel comprises the following production processes: electric furnace → LF → VD → cast electrode blank → blank annealing → electrode blank cleaning → electroslag remelting → electroslag ingot heat-transfer annealing → steel ingot heating → forging → annealing after forging → heat treatment → polishing flaw detection → inspection, inspection → handing over; the heat treatment step comprises a secondary tempering treatment step, and specifically comprises the steps of heating the steel material obtained by post-forging tempering to the quenching temperature of 1050-1060 ℃, preserving heat for 1h, water quenching, and oil cooling to 50-100 ℃; heating the cooled steel material to 520-530 ℃ for primary tempering, keeping the temperature for 2h after temperature equalization, and air cooling; and heating the cooled steel material to 520-530 ℃ for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling in air.
Example 2
The present embodiment is different from embodiment 1 only in that, in the step of heating the furnace in the present embodiment:
the electric furnace is charged with pig iron, molten iron or steel materials, and in order to reduce the content of harmful elements as much as possible, the amount of pig iron is required to be more than or equal to 30 wt% in the embodiment. When the temperature of the molten steel is more than or equal to 1580 ℃, the content of C is more than or equal to 0.05 percent, and the content of P is less than or equal to 0.003 percent, discharging the generated oxidizing slag, and beginning tapping, wherein the tapping amount is controlled according to 30 t. Deep oxygen blowing, decarbonization and degassing before tapping, and reducing the nitrogen content in steel. The steel tapping process is ensured to have no oxide slag.
During tapping, 100Kg of lime and 300Kg of synthetic refining slag are added along with molten steel.
Example 3
The difference between this example and example 1 is only that in the steps of LF refining and VD vacuum:
adding more than or equal to 300Kg of lime into a refining position, adding Al particles, carbon powder and silicon powder in batches after slagging is finished to whiten slag, sampling and fully analyzing the slag after the slag is white, feeding an aluminum wire according to a basic rule according to results, adjusting components according to sampling results to control component requirements, controlling the adding amount of the alloy to reach the lower limit of the specification by using chemical components in the LF refining position, and performing diffusion deoxidation by using the carbon powder and the silicon powder in the later refining stage. The white slag retention time is more than or equal to 30 min. And strictly prohibiting large flow of argon gas from stirring molten steel in the later stage of refining, wherein S is less than or equal to 0.003 percent before vacuum.
The target composition of this example is shown in table 1:
TABLE 1
After the white slag refining is finished, controlling the argon flow to be 20-40 NL/min under the vacuum degree of 67Pa, keeping the time to be more than or equal to 20min, adding a ladle covering agent to be more than or equal to 50kg after the white slag is dispersed, and carrying out argon soft blowing on the condition that the slag surface is slightly moved and is not exposed to molten steel, wherein the soft blowing time is more than or equal to 20 min.
Example 4
The present embodiment differs from embodiment 1 only in that in the cast electrode blank and blank annealing step of the present embodiment:
pouring the molten steel after soft blowing under the protection of argon gas with the pressure of 0.02-0.03 MPa in the whole process, wherein the temperature of the molten steel is 1505-1510 ℃ during pouring, adjusting the pouring flow after pouring, strictly prohibiting the flow adjustment which is suddenly large and small in the pouring process, and ensuring that the molten steel stably rises in the pouring process; when the ingot type is 2.4t, the pouring time of the ingot body is controlled to be 200-300 s, the feeding time of the cap opening is controlled to be 90-180 s, and the mold cooling time is controlled to be 30-60 min; when the ingot shape is 3.935t, the pouring time of the ingot body is controlled to be more than or equal to 360s, the feeding time of the cap opening is controlled to be more than or equal to 210s, and the mold cooling time is controlled to be 150 min.
Heating the blank obtained by casting to 600 ℃ for 2 hours, raising the temperature to 820 +/-10 ℃ at the speed of less than or equal to 100 ℃/h, preserving the temperature for 10 hours, then reducing the temperature to 300 ℃ at the speed of less than or equal to 50 ℃/h, and cooling in air to room temperature.
Example 5
The only difference between this example and example 1 is that in the electroslag remelting step of this example:
the electrode blank is annealed at 820 ℃ and then electroslag remelting is carried out, quaternary slag production is adopted, argon protection is carried out in the whole process, and a crystallizer and a bottom water tank are carefully checked before production, so that the phenomena of water seepage and water leakage are avoided. The quaternary slag system in this example is shown in table 2:
TABLE 2
The electroslag remelting in the embodiment specifically comprises the following steps:
when the crystallizer is phi 600/630, graphite electrode phi 250 and metal electrode phi 420: arc starting voltage 91(10 grades), slagging current 0-4.0 KA, refining current 4-4.5 KA, current increasing 11.5 +/-0.5 KA-8 grade voltage, process current 13.5 +/-0.5 KA-6 grade voltage, current reduction: the height from the ingot is 200mm, and the voltage is 12.0 +/-0.5 KA-8 grade;
the feeding control is 10.5KA (10 th voltage) 10min → 8.5KA (12 th voltage) 20min → 6.5KA (13 th voltage) 30min → 0 KA.
Example 6
The only difference between this example and example 1 is that in the electroslag remelting step of this example:
the electrode blank is annealed at 820 ℃ and then electroslag remelting is carried out, quaternary slag production is adopted, argon protection is carried out in the whole process, and a crystallizer and a bottom water tank are carefully checked before production, so that the phenomena of water seepage and water leakage are avoided. The quaternary slag system in this example is shown in table 3:
TABLE 3
The electroslag remelting in the embodiment specifically comprises the following steps:
when the crystallizer is phi 640/680, the graphite electrode phi 350 and the metal electrode phi 420: the arc striking voltage is 96(8 grades), the slagging current is 0-4.0 KA, the refining current is 4-4.5 KA, the extraction current is 13.0 +/-0.5 KA-6 grades of voltage, the extraction process current is 15.0 +/-0.5 KA-5 grades of voltage, and the current is reduced: the height from the ingot is 300mm, and the voltage is 12.0 +/-0.5 KA-7 grade;
the feeding control is 10.5KA (voltage level 8) 10min → 8.5KA (voltage level 10) 20min → 6.5KA (voltage level 12) 30min → 0 KA.
Example 7
The present embodiment differs from embodiment 1 only in that in the step of hot feeding annealing of an electroslag ingot → heating of a steel ingot → forging → annealing after forging:
annealing the electroslag ingot at 820 ℃, cold-loading the electroslag ingot in a rapid forging furnace, homogenizing and heating at 1250 ℃ at high temperature, preserving heat for 12h, reducing the temperature to 1220 ℃, preserving heat for 2h, forging and cogging the electroslag ingot to phi 400mm by a rapid forging machine, and forging the electroslag ingot to phi 203mm and phi 253mm by a rotary precision forging machine. After forging, turning to a finish forging 15m annealing furnace for annealing, wherein the normalizing condition is that the temperature is kept at 1030 ℃ for 15h, including the temperature equalization for 12 h; the spheroidizing annealing condition is that the temperature is 870 ℃ for 3h, and the temperature is 740 ℃ for 25 h. And polishing, inspecting and checking after annealing and discharging.
Example 8
The present example is different from example 1 only in that, in the heat treatment step of the present example:
heating the steel ingot obtained by post-forging annealing to a quenching temperature of 1050 ℃ at a heating rate of 60 ℃/h, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling to 50 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 520 ℃ at a heating rate of 60 ℃/h for tempering for one time, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air; heating the cooled steel material to 520 ℃ at a heating rate of 60 ℃/h for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling to 50 ℃ in air.
Example 9
The present example is different from example 1 only in that, in the heat treatment step of the present example:
heating the steel ingot obtained by post-forging annealing at a heating rate of 80 ℃/h to a quenching temperature of 1060 ℃, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling is carried out to 100 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 530 ℃ at a heating rate of 80 ℃/h for primary tempering, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air; heating the cooled steel material to 530 ℃ at a heating rate of 80 ℃/h for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling to 50 ℃ in air.
Example 10
The embodiment provides a preparation method of high alloy tool and die steel, and the production flow of the high alloy tool and die steel is as follows: electric furnace → LF → VD → cast electrode blank → blank annealing → electrode blank cleaning → electroslag remelting → electroslag ingot heat-transfer annealing → steel ingot heating → forging → post-forging annealing → heat treatment → polishing flaw detection → inspection, inspection → upward.
The electric furnace comprises the following steps:
the electric furnace is charged with pig iron, molten iron or steel materials, and in order to reduce the content of harmful elements as much as possible, the amount of pig iron is required to be more than or equal to 30 wt% in the embodiment. When the temperature of the molten steel reaches 1580 ℃, the content of C is more than or equal to 0.05 percent, and the content of P is less than or equal to 0.003 percent, discharging the generated oxidizing slag, and beginning tapping, wherein the tapping amount is controlled according to 30 t. Deep oxygen blowing, decarbonization and degassing before tapping, and reducing the nitrogen content in steel. The steel tapping process is ensured to have no oxide slag. During tapping, 100Kg of lime and 300Kg of synthetic refining slag are added along with molten steel.
In the steps of LF refining and VD vacuum:
adding more than or equal to 300Kg of lime into a refining position, adding Al particles, carbon powder and silicon powder in batches after slagging is finished to whiten slag, sampling and fully analyzing the slag after the slag is white, feeding an aluminum wire according to a basic rule according to results, adjusting components according to sampling results to control component requirements, controlling the adding amount of the alloy to reach the lower limit of the specification by using chemical components in the LF refining position, and performing diffusion deoxidation by using the carbon powder and the silicon powder in the later refining stage. The white slag is kept for 30 min. And strictly prohibiting large flow of argon gas from stirring molten steel in the later stage of refining, wherein S is less than or equal to 0.003 percent before vacuum.
The target components of this example are shown in Table 1.
After the white slag refining is finished, controlling the argon flow to be 20NL/min under the vacuum degree of 67Pa, keeping the time for 30min, adding a ladle covering agent to be more than or equal to 50kg after the white slag is diffused, and performing argon soft blowing on the slag surface with the condition that the slag surface is slightly moved without exposing molten steel, wherein the soft blowing time is 20 min.
Casting an electrode blank and annealing the blank:
pouring the molten steel after soft blowing under the protection of argon gas with the pressure of 0.02MPa in the whole process, wherein the temperature of the molten steel is 1510 ℃ during pouring, adjusting the pouring flow after pouring, strictly prohibiting the flow adjustment which is suddenly large and suddenly small in the pouring process, and ensuring that the molten steel stably rises in the pouring process; the ingot type is 2.4t, the pouring time of the ingot body is controlled to be 200s, the feeding time of the cap opening is controlled to be 90s, and the mold cooling time is controlled to be 30 min.
Heating the blank obtained by casting to 600 ℃ for 2 hours, raising the temperature to 820 ℃ at the speed of 80 ℃/h, preserving the temperature for 10 hours, then lowering the temperature to 300 ℃ at the speed of 50 ℃/h, and cooling in air to room temperature.
In the electroslag remelting step:
the electrode blank is annealed at 820 ℃ and then electroslag remelting is carried out, quaternary slag production is adopted, argon protection is carried out in the whole process, and a crystallizer and a bottom water tank are carefully checked before production, so that the phenomena of water seepage and water leakage are avoided.
The quaternary slag system in this example is shown in table 2.
The electroslag remelting in the embodiment specifically comprises the following steps:
when the crystallizer is phi 600/630, graphite electrode phi 250 and metal electrode phi 420: arc starting voltage 91(10 grades), slagging current 0-4.0 KA, refining current 4-4.5 KA, current increasing 11.5 +/-0.5 KA-8 grade voltage, process current 13.5 +/-0.5 KA-6 grade voltage, current reduction: the height from the ingot is 200mm, and the voltage is 12.0 +/-0.5 KA-8 grade;
the feeding control is 10.5KA (10 th voltage) 10min → 8.5KA (12 th voltage) 20min → 6.5KA (13 th voltage) 30min → 0 KA.
The electroslag ingot hot-feeding annealing → steel ingot heating → forging → post-forging annealing step:
annealing the electroslag ingot at 820 ℃, cold-charging a quick forging heating furnace, homogenizing at 1250 ℃, preserving heat for 12h, reducing to 1220 ℃, preserving heat for 2h, forging and cogging by a quick forging machine to
Turning a precision forging machine to forge
And
a material is provided. After forging, turning to a finish forging 15m annealing furnace for annealing, wherein the normalizing condition is that the temperature is kept at 1030 ℃ for 15h, including the temperature equalization for 12 h; the spheroidizing annealing condition is that the temperature is 870 ℃ for 3h, and the temperature is 740 ℃ for 25 h.
The heat treatment step comprises:
heating the steel ingot obtained by post-forging annealing to a quenching temperature of 1050 ℃ at a heating rate of 60 ℃/h, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling to 50 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 520 ℃ at a heating rate of 60 ℃/h for tempering for one time, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air; heating the cooled steel material to 520 ℃ at a heating rate of 60 ℃/h for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling to 50 ℃ in air.
Example 11
The embodiment provides a preparation method of high alloy tool and die steel, and the production flow of the high alloy tool and die steel is as follows: electric furnace → LF → VD → cast electrode blank → blank annealing → electrode blank cleaning → electroslag remelting → electroslag ingot heat-transfer annealing → steel ingot heating → forging → post-forging annealing → heat treatment → polishing flaw detection → inspection, inspection → upward.
The electric furnace comprises the following steps:
the electric furnace is charged with pig iron, molten iron or steel materials, and in order to reduce the content of harmful elements as much as possible, the amount of pig iron is required to be more than or equal to 30 wt% in the embodiment. When the temperature of the molten steel is 1600 ℃, the content of C is more than or equal to 0.05 percent and the content of P is less than or equal to 0.003 percent, the generated oxidizing slag is discharged, tapping is started, and the tapping amount is controlled according to 30 t. Deep oxygen blowing, decarbonization and degassing before tapping, and reducing the nitrogen content in steel. The steel tapping process is ensured to have no oxide slag. During tapping, 100Kg of lime and 300Kg of synthetic refining slag are added along with molten steel.
In the steps of LF refining and VD vacuum:
adding more than or equal to 300Kg of lime into a refining position, adding Al particles, carbon powder and silicon powder in batches after slagging is finished to whiten slag, sampling and fully analyzing the slag after the slag is white, feeding an aluminum wire according to a basic rule according to results, adjusting components according to sampling results to control component requirements, controlling the adding amount of the alloy to reach the lower limit of the specification by using chemical components in the LF refining position, and performing diffusion deoxidation by using the carbon powder and the silicon powder in the later refining stage. The white slag retention time is 40 min. And strictly prohibiting large flow of argon gas from stirring molten steel in the later stage of refining, wherein S is less than or equal to 0.003 percent before vacuum.
The target components of this example are shown in Table 1.
After the white slag refining is finished, controlling the argon flow to be 40NL/min under the vacuum degree of 67Pa, keeping the time for 40min, adding a ladle covering agent to be more than or equal to 50kg after the white slag is diffused, and performing argon soft blowing for 30min on the basis of the fact that the slag surface is slightly moved without exposing molten steel.
Casting an electrode blank and annealing the blank:
pouring the molten steel after soft blowing under the protection of argon gas with the pressure of 0.03MPa in the whole process, wherein the temperature of the molten steel is 1505 ℃ during pouring, adjusting the pouring flow after pouring, strictly prohibiting the flow adjustment which is suddenly large and suddenly small in the pouring process, and ensuring that the molten steel stably rises in the pouring process; the ingot type is 3.935t, the pouring time of the ingot body is controlled to be 360s, the feeding time of the cap opening is controlled to be 210s, and the mold cooling time is controlled to be 150 min.
Heating the blank obtained by casting to 600 ℃ for 2 hours, raising the temperature to 830 ℃ at the speed of 100 ℃/h, preserving the temperature for 10 hours, then lowering the temperature to 300 ℃ at the speed of 30 ℃/h, and cooling in air to room temperature.
In the electroslag remelting step:
the electrode blank is annealed at 820 ℃ and then electroslag remelting is carried out, quaternary slag production is adopted, argon protection is carried out in the whole process, and a crystallizer and a bottom water tank are carefully checked before production, so that the phenomena of water seepage and water leakage are avoided.
The quaternary slag system in this example is shown in table 3.
The electroslag remelting in the embodiment specifically comprises the following steps:
when the crystallizer is phi 640/680, the graphite electrode phi 350 and the metal electrode phi 420: the arc striking voltage is 96(8 grades), the slagging current is 0-4.0 KA, the refining current is 4-4.5 KA, the extraction current is 13.0 +/-0.5 KA-6 grades of voltage, the extraction process current is 15.0 +/-0.5 KA-5 grades of voltage, and the current is reduced: the height from the ingot is 300mm, and the voltage is 12.0 +/-0.5 KA-7 grade;
the feeding control is 10.5KA (voltage level 8) 10min → 8.5KA (voltage level 10) 20min → 6.5KA (voltage level 12) 30min → 0 KA.
The electroslag ingot hot-feeding annealing → steel ingot heating → forging → post-forging annealing step:
annealing the electroslag ingot at 820 ℃, cold-loading the electroslag ingot in a rapid forging furnace, homogenizing and heating at 1250 ℃ at high temperature, preserving heat for 12h, reducing the temperature to 1220 ℃, preserving heat for 2h, forging and cogging the electroslag ingot to phi 400mm by a rapid forging machine, and forging the electroslag ingot to phi 203mm and phi 253mm by a rotary precision forging machine. After forging, turning to a finish forging 15m annealing furnace for annealing, wherein the normalizing condition is that the temperature is kept at 1030 ℃ for 15h, including the temperature equalization for 12 h; the spheroidizing annealing condition is that the temperature is 870 ℃ for 3h, and the temperature is 740 ℃ for 25 h.
The heat treatment step comprises:
heating the steel ingot obtained by post-forging annealing at a heating rate of 80 ℃/h to a quenching temperature of 1060 ℃, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling is carried out to 100 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 530 ℃ at a heating rate of 80 ℃/h for primary tempering, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air; heating the cooled steel material to 530 ℃ at a heating rate of 80 ℃/h for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling to 50 ℃ in air.
Example 12
Example 12 differs from example 10 only in that in the heat treatment step:
heating the steel ingot obtained after the forging and annealing at the heating rate of 70 ℃/h to the quenching temperature of 1050 ℃, preserving the heat for 1h, discharging the steel ingot out of a furnace for quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling the steel ingot to 100 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 530 ℃ at a heating rate of 70 ℃/h for primary tempering, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air; heating the cooled steel material to 530 ℃ at a heating rate of 70 ℃/h for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling to 50 ℃ in air.
Example 13
Example 13 differs from example 10 only in that in the heat treatment step:
heating the steel ingot obtained after the forging and annealing at a heating rate of 75 ℃/h to a quenching temperature of 1060 ℃, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling is carried out to 100 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 530 ℃ at a heating rate of 75 ℃/h for primary tempering, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air; heating the cooled steel material to 530 ℃ at a heating rate of 75 ℃/h for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling to 50 ℃ in air.
Comparative example 1
The present comparative example differs from example 10 only in that in the present comparative example heat treatment step:
heating the steel ingot obtained by post-forging annealing to a quenching temperature of 1050 ℃ at a heating rate of 60 ℃/h, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling to 50 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 520 ℃ at a heating rate of 60 ℃/h for tempering once, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air.
FIG. 1 is a structural picture of a high alloy tool and die steel obtained by a secondary tempering heat treatment in example 10; FIG. 2 is a structural picture of a high alloy tool and die steel obtained by one tempering heat treatment in comparative example 1. As can be seen from fig. 1, after the secondary tempering treatment, the martensite and austenite in the high alloy tool and die steel are substantially eliminated, and the structure becomes tempered sorbite composed of equiaxed ferrite and fine-grained carbide, while the tempered martensite still exists in the structural picture after the primary tempering heat treatment shown in fig. 2. Compared with tempered martensite, tempered sorbite has better mechanical property, so that the heat treatment step of secondary tempering can obviously improve the mechanical property of steel, particularly the reduction of area.
Comparative example 2
The present comparative example differs from example 10 only in that in the present comparative example heat treatment step:
heating the steel ingot obtained by post-forging annealing to the quenching temperature of 1040 ℃ at the heating rate of 60 ℃/h, preserving heat for 1h, discharging and quenching, wherein the quenching medium is water, the cooling medium is 20# mechanical oil, cooling to 50 ℃, and the cooling time is 0.5 h; heating the cooled steel material to 540 ℃ at a heating rate of 60 ℃/h for tempering once, keeping the temperature for 2h after temperature equalization, and cooling the steel material to 50 ℃ in air.
According to the national standard GB/T228 "Metal Material, Room temperature tensile test method", the mold steel of type H13E, produced by southern electromechanical manufacturing Co., Ltd., the RM tensile strength, the elongation after A fracture, the Z reduction of area, the KU2 impact absorption energy and the HRC strength of examples 10 to 13 and comparative examples 1 and 2 were measured, and the results are shown in Table 4.
TABLE 4
As can be seen from the comparison of data in Table 4, the mechanical property of the high-alloy tool and die steel prepared by the method is obviously superior to that of a comparative example and the conventional product, particularly the reduction of area can reach 41-44%, the reduction of area is improved by 46% compared with the prior art, and the requirement of the technical field of die steel on the mechanical property of the high-alloy tool and die steel is met.
Claims (10)
1. The preparation method of the high alloy tool and die steel is characterized in that the production process of the high alloy tool and die steel comprises the following steps: electric furnace → LF → VD → cast electrode blank → blank annealing → electrode blank cleaning → electroslag remelting → electroslag ingot heat-transfer annealing → steel ingot heating → forging → annealing after forging → heat treatment → polishing flaw detection → inspection, inspection → handing over; the heat treatment step comprises a secondary tempering treatment step, and specifically comprises the steps of heating the steel material obtained by post-forging tempering to the quenching temperature of 1050-1060 ℃, preserving heat for 1h, water quenching, and oil cooling to 50-100 ℃; heating the cooled steel material to 520-530 ℃ for primary tempering, keeping the temperature for 2h after temperature equalization, and air cooling; and heating the cooled steel material to 520-530 ℃ for secondary tempering, keeping the temperature for 2h after temperature equalization, and cooling in air.
2. The method for preparing high alloy tool and die steel according to claim 1, wherein the heating rate of the heat treatment step for heating the steel material to the quenching temperature is 60-80 ℃/h.
3. The method for preparing high alloy tool and die steel according to claim 1 or 2, wherein the heat treatment step heats the steel material to the primary tempering temperature and the secondary tempering temperature at a heating rate of 60-80 ℃/h.
4. The method for producing a high alloy tool and die steel as claimed in claim 3, wherein the amount of pig iron in the electric furnace step is not less than 30 wt%, the temperature of molten steel at tapping is not less than 1580 ℃, and the C content at tapping is not less than 0.05%, and P is not more than 0.003%.
5. The method for preparing high alloy tool and die steel according to claim 4, wherein the white slag holding time in the steps of LF refining and VD vacuum is not less than 30min, and S before vacuum is not more than 0.003%; after the white slag refining is finished, keeping the white slag at the vacuum degree of 67Pa for not less than 20min, adding a ladle covering agent after the white slag is diffused, and performing argon soft blowing on the slag surface by using micro motion without exposing molten steel, wherein the soft blowing time is not less than 20 min.
6. The method for preparing high alloy tool and die steel according to claim 5, wherein the molten steel after the soft blowing in the step of casting the electrode blank is poured under the protection of argon gas with the pressure of 0.02-0.03 MPa in the whole process, and the temperature of the molten steel is 1505-1510 ℃ during pouring; when the ingot type is 2.4t, the pouring time of the ingot body is controlled to be 200-300 s, the feeding time of the cap opening is controlled to be 90-180 s, and the mold cooling time is controlled to be 30-60 min; when the ingot shape is 3.935t, the pouring time of the ingot body is controlled to be not less than 360s, the feeding time of the cap opening is controlled to be not less than 210s, and the mold cooling time is controlled to be 150 min; in the blank annealing step, the blank obtained by casting is heated to 600 ℃ and the temperature is equalized for 2 hours, the temperature is raised to 820 +/-10 ℃ at the speed of less than or equal to 100 ℃/h, the temperature is kept for 10 hours, then the temperature is lowered to 300 ℃ at the cooling speed of less than or equal to 50 ℃/h, and the blank is cooled to room temperature by air.
7. The method for preparing high alloy tool and die steel as claimed in claim 6, wherein in the electroslag remelting step, when the crystallizer is phi 600/630, the quaternary slag system is CaF2 42Kg、Al2O363Kg, 28Kg of CaO and 7Kg of MgO, and the refining time is 30 min; when the crystallizer is phi 640/680, the quaternary slag system is CaF2 51Kg、Al2O377Kg, 34Kg CaO and 8Kg MgO, with a refining time of 30 min.
8. The method for preparing high alloy tool and die steel according to claim 7, wherein in the steps of ingot heating, forging and annealing after forging, the electroslag ingot is annealed at 820 ℃, then is cold-mounted in a rapid forging furnace, the high temperature homogenization heating temperature is 1250 ℃, the temperature is kept for 12h, is reduced to 1220 ℃, is kept for 2h, then is forged and unbaked by a rapid forging machine, then is forged into a material by a rotary forging machine, and is annealed by a rotary forging 15m annealing furnace after forging, and the normalizing condition is kept for 15h at 1030 ℃; the spheroidizing annealing condition is that the temperature is 870 ℃ for 3h, and the temperature is 740 ℃ for 25 h.
9. The high alloy tool and die steel prepared by the preparation method of the high alloy tool and die steel according to any one of claims 1 to 8, wherein the chemical components of the high alloy tool and die steel comprise the following components in percentage by weight: 0.47-0.52% of C, 0.80-1.00% of Si, 0.28-0.45% of Mn, less than or equal to 0.010% of P, less than or equal to 0.010% of S, 5.25-5.60% of Cr, 0.20-0.32% of Ni, 1.40-1.75% of Mo, 0.90-1.20% of V, less than or equal to 0.20% of Cu, and the balance of Fe and inevitable impurities.
10. The high alloy tool and die steel as claimed in claim 9, wherein the high alloy tool and die steel has a tensile strength of 1936 to 1948MPa, an elongation after fracture of 10 to 11%, a reduction of area of 41 to 44%, an impact absorption energy KU2 of 24 to 26J, and a hardness of 58 to 59.
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