The output of alloy tool steel in China ranks among the top in the world, including about 100,000 tons of alloy die steel. China's mold industry consumes an annual total of 300,000 to 400,000 tons of mold materials, of which 130,000 to 150,000 tons of alloy mold steel.
China's current low die steel mold quality is low, the performance of the general quality of the mold steel, high quality mold steel less, a considerable part of the required mold steel must undergo vacuum refining and electroslag remelting, in order to ensure the high purity of steel Degree, high density, and high tropism, but China's share of mold steel remelted by electroslag is very small. There are many black bar, flat steel, fine materials, and pre-hardened materials, products, standard parts less. About 80% of China's die steel market is black bar. After users get the material, they also need to change their own forging system. The material utilization is low and the production cycle is long. It can not meet the needs of the mold manufacturing industry.
In the cost of mold manufacturing, the material cost only accounts for about 20% of the cost of the mold. Therefore, for the long-life molds with higher requirements, the mold materials are often required to be improved, for example, the degree of carbide unevenness is 5-6. The Cr12MoV steel reeling molds have a service life of less than 10,000 pieces, and the use of high-quality Cr12MoV steels with a carbide unevenness grade of 1 to manufacture the reeling molds can reach tens of thousands or even hundreds of thousands of pieces. Since domestic mold materials cannot fully meet the needs of the mold manufacturing industry, many molds with high performance, long life, and tight delivery dates still have to use imported mold materials. Such as the mold steel that Haier Group needs each year, 90% of which are imported from Sweden, Germany, Japan, mainly imported pre-hardened high-quality plastic mold steel and hot die steel, such as imported from Sweden 718 steel ( 3Cr2NiMo), 618 Steel (3Cr2Mo) and 8407 Steel (4Cr5MoSiV1), SKD11 (Cr12MoV) Cold Work Die Steel imported from Japan. The price of imported materials is very high, which is 3 to 5 times higher than that of domestic materials. The following introduces several common mold steels for reference.
1. 7Cr7Mo3V2Si
7Cr7Mo3V2Si referred to as LD steel is a kind of high strength and toughness cold work die steel, which has higher strength and toughness than Cr12 cold work die steel and W6Mo5Cr4V2 high speed steel, and has good wear resistance suitable for manufacturing cold under high load. Extrusion, cold heading, cold punching die.
Initial forging temperature: 1120°C Final forging temperature: ≥ 850°C, repeated stripping to eliminate banded structure, slow cooling after forging and immediate spheroidizing annealing. Isothermal spheroidizing annealing process: 860°C, holding temperature for 3 hours, cooling to 740°C for 4 hours, furnace cooling to 500°C. Hardness 212 HBS after annealing, tissue: spheroidal pearlite + eutectic carbide.
Mold quenching temperature: 1140 ° C, 550 ° C tempering 90min. Then after QPQ treatment, the heart hardness to maintain 61-63HRC, the surface hardness is higher, have better toughness.
2. Cr12Mo1V1 (US grade D2)
Cr12Mo1V1 is a high-carbon high-chromium cold work die steel widely used in the world. It is a high-carbon steel, has a high hardenability, hardenability, high wear resistance; high temperature oxidation resistance, quenching and polishing after anti-corrosion Good ability, small heat treatment deformation; suitable for the manufacture of high-precision, long-life cold work molds, cutting tools and measuring tools, such as the shape of the punching die, cold extrusion die, rolling round, reeling plate, cold shearing knife and Precision measuring tools and so on. See GB/T1299-2000 for chemical composition.
C Si Mn PS Cr Mo V Co
1.40-1.60 ≤ 0.60 ≤ 0.60 ≤ 0.03 ≤ 0.03 11.00-13.00 0.70-1.20 ≤ 1.10 ≤ 1.00
The steel can use two quench temperatures.
(1) Use a lower quenching temperature of 950-1040 °C 180-230 °C low temperature tempering hardness of 60-64HRC
(2) The higher quenching temperature of 1050-1100°C 510-540°C high temperature tempering 2 times hardness 60-64HRC treated by QPQ has better effect.
3. DC53- Japan Datong Special Steel Company Production Features:
(1) After heat treatment, the hardness is higher than that of SKD11, high temperature (520-530°C) can reach 62-63HRC after tempering, and exceeds SKD11 in terms of strength and wear resistance.
(2) Toughness is twice that of SKD11. The toughness of DC53 is more prominent in the cold work die steel. Therefore, cracks and cracks are rarely produced with DC53 and the service life is greatly improved.
(3) Residual stress after wire-cutting machining reduces the residual stress through high-temperature tempering. Therefore, cracks and deformations after large-scale molds and precision-required molds are cut in-line are suppressed.
(4) Machinability and abrasiveness exceed SKD11. DC53's machinability and abrasiveness are superior to SKD11. Therefore, using DC53 can increase die life and reduce processing.
use:
(1) Precision stamping die: precision punching of wire cutting and punching die for various purposes;
(2) Plastic deformation tools for difficult-to-machine materials. Cold forging, deep drawing and rifling;
(3) Others. High speed punch punch, stainless steel punch.
Heat Treatment: DC53 is a new type of cold work die steel modified for SKD11. Its specification is contained in Japanese Industrial Standard (JIS) G4404. It overcomes the weakness of SKD11 high temperature tempering hardness and toughness, and will fully replace SKD11 in the field of general-purpose and precision molds.
After QPQ treatment better.
4. 4Cr5MoSiV1
China's 4Cr5MoSiV1 is similar to the United States' H13 steel. There are almost similar steel grades in the tool steel standards of various industrial countries in the world. At present, in addition to domestically produced 4Cr5MoSiV1 on the domestic mold steel market, foreign countries include Japan's SKD61, Sweden (ASSAB) 8407, Germany's X40CrMoV5-1, Korea's STD-61 and their improved models, although they have their own national brands. , but all appear as H13 steel numbers.
This type of steel is hot die steel, due to the difference in smelting technology, the quality of the gap is large, but after QPQ treatment can get more ideal results.
5. 5Cr2NiMoVSi
5Cr2NiMoVSi steel is better hot forging die steel than 5CrNiMo, and its smelting and processing are processed according to special high-grade steel (ie "E" steel). The conventional heat treatment process is preheated at 600-650°C, austenitized at 970-980°C, oil cooled to about 650-700°C and turned to 300-350°C for isothermal 3-4h, and the tempering temperature is 670-680°C. , Insulation 4-5h, tempered twice, air-cooled, hardness 40-44HRC. The final QPQ treatment of the mold can increase the heat-resistant fatigue strength, reduce the friction coefficient, and extend the life of the mold.
6. 3Cr2W8V
3Cr2W8V steel is a typical hot-strength steel hot die steel, the application of a long time and very extensive. The disadvantage is poor thermal conductivity, easy cracking, plasticity, toughness, thermal fatigue properties have declined. At present, 3Cr2W8V is used for a few days, and is replaced by new type of heat-strength hot work die steels, such as 3Cr3Mo3W2V, 4Cr3Mo3SiV, 5Cr4W5Mo2V, 5Cr4Mo3SiMnVAl and QRA45 of ASSAB, and H19 of the United States. The above steel molds are treated with QPQ after heat treatment, which can improve the thermal fatigue resistance, oxidation resistance, and greatly increase the life of the mold.
China's current low die steel mold quality is low, the performance of the general quality of the mold steel, high quality mold steel less, a considerable part of the required mold steel must undergo vacuum refining and electroslag remelting, in order to ensure the high purity of steel Degree, high density, and high tropism, but China's share of mold steel remelted by electroslag is very small. There are many black bar, flat steel, fine materials, and pre-hardened materials, products, standard parts less. About 80% of China's die steel market is black bar. After users get the material, they also need to change their own forging system. The material utilization is low and the production cycle is long. It can not meet the needs of the mold manufacturing industry.
In the cost of mold manufacturing, the material cost only accounts for about 20% of the cost of the mold. Therefore, for the long-life molds with higher requirements, the mold materials are often required to be improved, for example, the degree of carbide unevenness is 5-6. The Cr12MoV steel reeling molds have a service life of less than 10,000 pieces, and the use of high-quality Cr12MoV steels with a carbide unevenness grade of 1 to manufacture the reeling molds can reach tens of thousands or even hundreds of thousands of pieces. Since domestic mold materials cannot fully meet the needs of the mold manufacturing industry, many molds with high performance, long life, and tight delivery dates still have to use imported mold materials. Such as the mold steel that Haier Group needs each year, 90% of which are imported from Sweden, Germany, Japan, mainly imported pre-hardened high-quality plastic mold steel and hot die steel, such as imported from Sweden 718 steel ( 3Cr2NiMo), 618 Steel (3Cr2Mo) and 8407 Steel (4Cr5MoSiV1), SKD11 (Cr12MoV) Cold Work Die Steel imported from Japan. The price of imported materials is very high, which is 3 to 5 times higher than that of domestic materials. The following introduces several common mold steels for reference.
1. 7Cr7Mo3V2Si
7Cr7Mo3V2Si referred to as LD steel is a kind of high strength and toughness cold work die steel, which has higher strength and toughness than Cr12 cold work die steel and W6Mo5Cr4V2 high speed steel, and has good wear resistance suitable for manufacturing cold under high load. Extrusion, cold heading, cold punching die.
Initial forging temperature: 1120°C Final forging temperature: ≥ 850°C, repeated stripping to eliminate banded structure, slow cooling after forging and immediate spheroidizing annealing. Isothermal spheroidizing annealing process: 860°C, holding temperature for 3 hours, cooling to 740°C for 4 hours, furnace cooling to 500°C. Hardness 212 HBS after annealing, tissue: spheroidal pearlite + eutectic carbide.
Mold quenching temperature: 1140 ° C, 550 ° C tempering 90min. Then after QPQ treatment, the heart hardness to maintain 61-63HRC, the surface hardness is higher, have better toughness.
2. Cr12Mo1V1 (US grade D2)
Cr12Mo1V1 is a high-carbon high-chromium cold work die steel widely used in the world. It is a high-carbon steel, has a high hardenability, hardenability, high wear resistance; high temperature oxidation resistance, quenching and polishing after anti-corrosion Good ability, small heat treatment deformation; suitable for the manufacture of high-precision, long-life cold work molds, cutting tools and measuring tools, such as the shape of the punching die, cold extrusion die, rolling round, reeling plate, cold shearing knife and Precision measuring tools and so on. See GB/T1299-2000 for chemical composition.
C Si Mn PS Cr Mo V Co
1.40-1.60 ≤ 0.60 ≤ 0.60 ≤ 0.03 ≤ 0.03 11.00-13.00 0.70-1.20 ≤ 1.10 ≤ 1.00
The steel can use two quench temperatures.
(1) Use a lower quenching temperature of 950-1040 °C 180-230 °C low temperature tempering hardness of 60-64HRC
(2) The higher quenching temperature of 1050-1100°C 510-540°C high temperature tempering 2 times hardness 60-64HRC treated by QPQ has better effect.
3. DC53- Japan Datong Special Steel Company Production Features:
(1) After heat treatment, the hardness is higher than that of SKD11, high temperature (520-530°C) can reach 62-63HRC after tempering, and exceeds SKD11 in terms of strength and wear resistance.
(2) Toughness is twice that of SKD11. The toughness of DC53 is more prominent in the cold work die steel. Therefore, cracks and cracks are rarely produced with DC53 and the service life is greatly improved.
(3) Residual stress after wire-cutting machining reduces the residual stress through high-temperature tempering. Therefore, cracks and deformations after large-scale molds and precision-required molds are cut in-line are suppressed.
(4) Machinability and abrasiveness exceed SKD11. DC53's machinability and abrasiveness are superior to SKD11. Therefore, using DC53 can increase die life and reduce processing.
use:
(1) Precision stamping die: precision punching of wire cutting and punching die for various purposes;
(2) Plastic deformation tools for difficult-to-machine materials. Cold forging, deep drawing and rifling;
(3) Others. High speed punch punch, stainless steel punch.
Heat Treatment: DC53 is a new type of cold work die steel modified for SKD11. Its specification is contained in Japanese Industrial Standard (JIS) G4404. It overcomes the weakness of SKD11 high temperature tempering hardness and toughness, and will fully replace SKD11 in the field of general-purpose and precision molds.
After QPQ treatment better.
4. 4Cr5MoSiV1
China's 4Cr5MoSiV1 is similar to the United States' H13 steel. There are almost similar steel grades in the tool steel standards of various industrial countries in the world. At present, in addition to domestically produced 4Cr5MoSiV1 on the domestic mold steel market, foreign countries include Japan's SKD61, Sweden (ASSAB) 8407, Germany's X40CrMoV5-1, Korea's STD-61 and their improved models, although they have their own national brands. , but all appear as H13 steel numbers.
This type of steel is hot die steel, due to the difference in smelting technology, the quality of the gap is large, but after QPQ treatment can get more ideal results.
5. 5Cr2NiMoVSi
5Cr2NiMoVSi steel is better hot forging die steel than 5CrNiMo, and its smelting and processing are processed according to special high-grade steel (ie "E" steel). The conventional heat treatment process is preheated at 600-650°C, austenitized at 970-980°C, oil cooled to about 650-700°C and turned to 300-350°C for isothermal 3-4h, and the tempering temperature is 670-680°C. , Insulation 4-5h, tempered twice, air-cooled, hardness 40-44HRC. The final QPQ treatment of the mold can increase the heat-resistant fatigue strength, reduce the friction coefficient, and extend the life of the mold.
6. 3Cr2W8V
3Cr2W8V steel is a typical hot-strength steel hot die steel, the application of a long time and very extensive. The disadvantage is poor thermal conductivity, easy cracking, plasticity, toughness, thermal fatigue properties have declined. At present, 3Cr2W8V is used for a few days, and is replaced by new type of heat-strength hot work die steels, such as 3Cr3Mo3W2V, 4Cr3Mo3SiV, 5Cr4W5Mo2V, 5Cr4Mo3SiMnVAl and QRA45 of ASSAB, and H19 of the United States. The above steel molds are treated with QPQ after heat treatment, which can improve the thermal fatigue resistance, oxidation resistance, and greatly increase the life of the mold.