CN112458256B - 1.2746 (45 NiCrMoV or 4CrNi4 MoV) die steel annealing process - Google Patents
1.2746 (45 NiCrMoV or 4CrNi4 MoV) die steel annealing process Download PDFInfo
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- CN112458256B CN112458256B CN202011200975.0A CN202011200975A CN112458256B CN 112458256 B CN112458256 B CN 112458256B CN 202011200975 A CN202011200975 A CN 202011200975A CN 112458256 B CN112458256 B CN 112458256B
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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
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- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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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
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- C21D1/26—Methods of annealing
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Abstract
The invention provides a 1.2746 (namely 45NiCrMoV or 4CrNi4 MoV) die steel annealing process, which is realized by the following technical scheme. Heating homogenization time is calculated according to the effective thickness of the steel material for 1.2746 (45 NiCrMoV or 4CrNi4 MoV) die steel, and austenite homogenization heating is carried out above Ar 1; austenitizing by using a continuous roller-hearth heating furnace, coarsening crystal grains, then slowly cooling to below an A1 line for annealing, then slowly cooling to below a martensite point, discharging and cooling to room temperature; then continuing to anneal at the annealing temperature, finally slowly cooling to the temperature below the martensite point, discharging and cooling to room temperature. The technical key points of the invention are as follows: after the second-stage annealing, the hardness is greatly reduced, and the austenitizing and annealing are proved to lay a good foundation for the second-stage annealing. The invention has the following advantages: on the premise of meeting the annealing hardness standard, the turnover time of the heat treatment furnace is shortened by one half, the equipment utilization rate is improved, and the energy-saving and environment-friendly effects are realized.
Description
Technical Field
The invention belongs to the technical field of metal heat treatment, and particularly relates to a 1.2746 (45 NiCrMoV or 4CrNi4 MoV) die steel annealing process.
Background
1.2746 belongs to the alloy tool steel of the german standard, with the execution standard DIN EN ISO 4957-2001, and its chemical composition (%) is: 0.41 to 0.49 percent of carbon, 0.15 to 0.35 percent of silicon, 0.60 to 0.80 percent of manganese, no more than 0.025 percent of phosphorus, no more than 0.020 percent of sulfur, 1.40 to 1.60 percent of chromium, 0.73 to 0.85 percent of molybdenum, 0.45 to 0.55 percent of vanadium, nickel: 3.80 to 4.20, which is equivalent to 45NiCrMoV or 4CrNi4MoV in China and belongs to cold-work die steel; the square flat steel or the round bar is used for cutting, and is generally delivered in an annealed state, and has an annealing Hardness (HBW) of not more than 295 and a target value of about 270. In the localization process, in order to realize the annealing Hardness (HBW) not more than 295, the annealing process of the same type of steel is mainly referred at present, the steel is annealed or pit-cooled, then heated to 630-680 ℃ at a temperature not more than 80 ℃/h, kept for 15-30 h, cooled to a temperature not more than 300 ℃ in a furnace at a temperature not more than 40 ℃/h, and then discharged, and if the hardness of the first annealing is not enough, the annealing is carried out again. In order to reach the hardness standard in actual production, the first annealing is carried out for 55-70 h at 680 ℃, the test Hardness (HBW) after annealing and discharging is 320-341, and the hardness is not suitable; annealing is repeatedly carried out according to a planned annealing process system (shown in figure 1) until the hardness is qualified, secondary annealing is carried out, the temperature is maintained at 680 ℃ for 60-70 h, the test Hardness (HBW) after secondary annealing and discharging is 311-333, and the hardness is still not qualified; and carrying out third annealing, keeping the temperature at 680 ℃ for 55-60 h, and keeping the test Hardness (HBW) of the annealed material after discharge to be about 274 so as to meet the requirement of delivery state. The heat preservation time of the process is as long as 200 hours, the total time length reaches 260 to 300 hours by adding the temperature rise and reduction time, the annealing time is long, the energy consumption is high, and the production efficiency and the equipment utilization rate are reduced.
Disclosure of Invention
The invention discloses a 1.2746 annealing process of 45NiCrMoV or 4CrNi4MoV die steel, and aims to solve the problem of long period of standard annealing hardness of tool and die steel with high nickel and molybdenum contents.
The invention is realized by the following technical scheme. Calculating heating homogenization time of 1.2746 (namely 45NiCrMoV or 4CrNi4MoV die steel) according to effective thickness of the steel, carrying out austenite homogenization heating above Ar1, carrying out austenitization by adopting a continuous roller bottom heating furnace, coarsening crystal grains, then slowly cooling to below A1 line for annealing, then slowly cooling to below martensite point, taking out of the furnace and cooling to room temperature; then continuing to anneal at the annealing temperature, finally slowly cooling to below the martensite point, discharging and cooling to room temperature.
The specific process (as shown in fig. 2) comprises the following steps:
the method comprises the steps of heating steel in a continuous roller bottom heating furnace or a cover type heating furnace by adopting a combustible medium or electricity at a heating speed of not more than 100 ℃/h to 730-780 ℃ for austenitizing and heat preservation for 4-8 h;
after the heat preservation is finished, slowly cooling to 630-680 ℃ at the speed of not more than 40 ℃/h for annealing, after the heat preservation is carried out for 20-36 h, slowly cooling to not more than 250 ℃ at the speed of not more than 40 ℃/h, discharging and cooling to room temperature;
thirdly, the steel is heated by adopting combustible media or electricity in a continuous roller-hearth heating furnace or a bell-type heating furnace, the heating speed is not more than 100 ℃/h, the steel is heated to 630-680 ℃ for annealing, the temperature is kept for 20-36 h, then the steel is slowly cooled to be not higher than 250 ℃ at the speed of not more than 40 ℃/h, and then the steel is taken out of the furnace and cooled to room temperature.
Hardness of steel after each annealing:
austenitizing the steel, and then continuously annealing to obtain the steel with the Hardness (HBW) of 310-414;
the Hardness (HBW) of the steel is 260-280 after the steel is annealed for the second time.
The technical key points of the invention are as follows:
after the first annealing, the hardness of the steel is equivalent to that of the original process, but after the second annealing, the hardness is reduced greatly, and the result proves that the first austenitizing and annealing process lays a good foundation for the second annealing.
The invention has the following advantages:
on the premise of ensuring that the annealing hardness meets the requirement, the turnover time of the heat treatment furnace is shortened by one half, the equipment utilization rate is improved, and the energy-saving and environment-friendly effects are achieved.
Drawings
FIG. 1 is a heat treatment process curve of a conventional process;
figure 2 is a graph of the annealing process of the present invention.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
Example 1
1.2746 flat steel, size 60mm thickness, 120mm width, 6.0m length, weight 16.8 tons. After the steel is taken out of the pit, measuring Hardness (HBW) 410, 425 and 435;
carrying out first annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 780 ℃ and keeping the temperature for 8h; after the heat preservation is finished, slowly cooling to 680 ℃ at the speed of 35 ℃/h, preserving the heat for 25h, then slowly cooling to 250 ℃ at the speed of 35 ℃/h, discharging from the furnace, and cooling to room temperature; the test Hardness (HBW) was 370, 386, 410.
And carrying out secondary annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 630 ℃ and keeping the temperature for 36h; after the heat preservation is finished, slowly cooling to 250 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; the test Hardness (HBW) was 270, 276, 280.
Example 2
1.2746 flat steel, the size is 58mm in thickness, 118mm in width, 6.0m in length, and 13.7 tons in weight. After the steel is taken out of the pit, the Hardness (HBW) 414, 432 and 438 are measured;
carrying out first annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 780 ℃ and keeping the temperature for 8h; after the heat preservation is finished, slowly cooling to 650 ℃ at the speed of 40 ℃/h, preserving the heat for 25h, slowly cooling to 230 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; the test Hardness (HBW) was 375, 382, 414.
And carrying out secondary annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 630 ℃ and keeping the temperature for 36h; after the heat preservation is finished, slowly cooling to 240 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; the test Hardness (HBW) was 268, 270, 275.
Example 3
1.2746 flat steel, the size is 44mm thickness, 110mm width, 6.0m length, weight 12.6 tons. After the steel is taken out of the pit, measuring the Hardness (HBW) 411, 430 and 437;
carrying out first annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 740 ℃ and keeping the temperature for 6h; after the heat preservation is finished, slowly cooling to 650 ℃ at the speed of 40 ℃/h, preserving the heat for 30h, slowly cooling to 225 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; the test Hardness (HBW) was 380, 388, 410.
And carrying out secondary annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 650 ℃ and keeping the temperature for 36h; after the heat preservation is finished, slowly cooling to 210 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; the test Hardness (HBW) was 266, 269, 275.
Claims (4)
1. The 1.2746 (45 NiCrMoV or 4CrNi4 MoV) die steel annealing process is characterized in that: the specific process steps are as follows:
the method comprises the steps of heating steel in a continuous roller-bottom heating furnace or a bell-type heating furnace by adopting a combustible medium or electricity at a heating speed of not more than 100 ℃/h to 730-780 ℃ for austenitizing and preserving heat for 4-8 h;
after the heat preservation is finished, slowly cooling to 630-680 ℃ at the speed of not more than 40 ℃/h for annealing, after the heat preservation is carried out for 20-36 h, slowly cooling to not more than 250 ℃ at the speed of not more than 40 ℃/h, discharging and cooling to room temperature;
thirdly, the steel is heated in a continuous roller-hearth heating furnace or a bell-type heating furnace by coal gas or electricity, the heating speed is not more than 100 ℃/h, the steel is heated to 630-680 ℃ for annealing, the temperature is kept for 20-36 h, then the steel is slowly cooled to be not higher than 250 ℃ at the speed of not more than 40 ℃/h, and then the steel is taken out of the furnace and cooled to room temperature.
2. The annealing process of 1.2746 (45 NiCrMoV or 4CrNi4MoV die steel according to claim 1, wherein: the annealing process comprises the following steps of: heating combustible media in a continuous roller hearth heating furnace at the heating speed of 80 ℃/h to 780 ℃ and preserving heat for 8h; after the heat preservation is finished, slowly cooling to 680 ℃ at the speed of 35 ℃/h, preserving the heat for 25h, slowly cooling to 250 ℃ at the speed of 35 ℃/h, discharging and cooling to room temperature; and (3) second annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 630 ℃ and keeping the temperature for 36h; after the heat preservation is finished, the temperature is slowly cooled to 250 ℃ at the speed of 30 ℃/h, and then the product is taken out of the furnace and cooled to the room temperature.
3. The annealing process of 1.2746 (45 NiCrMoV or 4CrNi4MoV die steel according to claim 1, wherein: the annealing process comprises the following steps of: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 780 ℃ and keeping the temperature for 8h; after the heat preservation is finished, slowly cooling to 650 ℃ at the speed of 40 ℃/h, preserving the heat for 25h, slowly cooling to 230 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; and (3) second annealing: heating with coal gas in a continuous roller hearth heating furnace at a heating rate of 80 ℃/h to 630 ℃ and keeping the temperature for 36h; after the heat preservation is finished, the temperature is slowly cooled to 240 ℃ at the speed of 30 ℃/h, and then the product is taken out of the furnace and cooled to the room temperature.
4. The annealing process of 1.2746 (45 NiCrMoV or 4CrNi4MoV die steel according to claim 1, wherein: the annealing process comprises the following steps of: heating in a continuous roller hearth heating furnace with coal gas at a heating rate of 80 ℃/h to 740 ℃ and keeping the temperature for 6h; after the heat preservation is finished, slowly cooling to 650 ℃ at the speed of 40 ℃/h, preserving the heat for 30h, slowly cooling to 225 ℃ at the speed of 30 ℃/h, discharging and cooling to room temperature; and (3) second annealing: heating in a continuous roller hearth heating furnace with coal gas at the heating rate of 80 ℃/h to 650 ℃ and keeping the temperature for 36h; after the heat preservation is finished, the mixture is slowly cooled to 210 ℃ at the speed of 30 ℃/h, and then is taken out of the furnace and cooled to the room temperature.
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| JP3188791B2 (en) * | 1993-05-06 | 2001-07-16 | 株式会社神戸製鋼所 | Soft annealing method for high alloy tool steel |
| CN1283811C (en) * | 2004-09-17 | 2006-11-08 | 宝钢集团上海五钢有限公司 | Softening annealing heat treating method for 1Cr17Ni2 stainless steel |
| CN1277938C (en) * | 2004-09-29 | 2006-10-04 | 宝钢集团上海五钢有限公司 | Softening treatment of moderate alloy nickle serial cold working mold steel |
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| CN110257601A (en) * | 2019-07-12 | 2019-09-20 | 河冶科技股份有限公司 | The secondary ultra-soft spheroidizing method of high speed steel |
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