Cr12MoV steel has high hardenability, and those with a cross-sectional area below 300-400mm can be completely quenched. It can still maintain good hardness and wear resistance at 300-400 ℃, and has higher toughness than Cr12 steel. The volume change during quenching is minimal. It can be used to manufacture various molds and tools with large cross-sections, complex shapes, and withstand significant impact loads. For example, complex punching dies, inserts on complex molds, deep drawing dies for steel plates, wire drawing dies, thread filing plates, cold extrusion dies, cold cutting scissors, circular saws, standard cutting tools, measuring tools, etc. Cr12MoV steel is a low-carbon molybdenum martensitic steel. Its carbon content is much lower than that of Crl2 steel, and molybdenum and vanadium elements are added, which significantly improves the thermal treatment performance, impact toughness, and carbide distribution of the steel. This steel has high wear resistance, hardenability, hardenability, strength and toughness, thermal stability, compressive strength, as well as excellent micro deformation, comprehensive performance, and wide adaptability. The softening temperature upon heating is 520 ℃.
The steel can be completely quenched with a laser cutting jewelr edge of less than 4mm, and its wear resistance is 3-4 times higher than that of low alloy steel, resulting in volume deformation after quenching. Hardening depth: oil quenching 200-300mm. During the crystallization process, eutectic carbides (with a carbide content of about 20% and an eutectic temperature of about 1150 ° C) are formed, which are very hard and brittle.
Although the carbides have some degree of fragmentation after billet rolling, they are distributed in ribbons, clumps, blocks, and clusters along the rolling direction. The degree of segregation increases with the diameter of the steel. The severe supply varieties include hot-rolled, forged, cold-drawn, hot-rolled steel plates, and cold-drawn steel wires in the annealed state, with a hardness of 255-207HBW and an indentation diameter of 3.8-4.2mm. Chinese GB standard grade Cr12MoV, Taiwan, China, China cNS standard grade SKD11, German DlN standard material No. 1.26o1, German DIN standard grade x165CrM0v12, Japanese Jis standard grade sKD11, Korean KS standard grade sTD11, Italian UN1 standard grade x165CrM0W12KU, Swedish SS standard grade 2310, Spanish UNE standard grade X160CrM0V12, American AISi/SAE standard grade D3, Russian rocT standard grade x12M. Introduction to Characteristics of Cr12MoV: Alloy Tool Steel: Cr12MoV Steel Standard: GB/T 1299-1985 Scope of Application: Cold worked mold steel. The hardenability, hardness, wear resistance, and strength of the steel are higher than those of Cr12. Used for manufacturing various cold stamping molds and tools with large cross-sectional areas, complex shapes, and heavy working conditions, such as punching dies, trimming dies, rolling dies, steel plate deep drawing dies, circular saws, standard tools and gauges, thread rolling dies, etc. Chemical composition: carbon C: 1.45-1.70 silicon Si: ≤ 0.40 manganese Mn: ≤ 0.40 sulfur S: ≤ 0.030 phosphorus P: ≤ 0.030 chromium Cr: 11.00-12.50 nickel Ni: allowable residual content ≤ 0.25 copper Cu: allowable residual content ≤ 0.30 vanadium V: 0.15-0.30 molybdenum Mo: 0.40-0.60 mechanical properties: hardness: annealed, 255-207HB, indentation diameter 3.8-4.2mm; Quenching, ≥ 58HRCCr12MoV Purpose: Cr12MoV steel has higher hardenability, hardness, strength, and toughness after quenching and tempering compared to CR12. Work with a diameter of 300-400mm or less can be fully quenched, with small quenching deformation, but poor high-temperature plasticity. Cr12MoV is mostly used for manufacturing composite molds and tools with large cross-sections, complex shapes, and heavy workloads. Heat treatment specifications: 1) Quenching, oil cooling at 950~1000 ℃; 2) Quench at 1020 ℃, temper at 200 ℃ for 2 hours. Metallographic structure: fine-grained pearlite+carbide.
● Delivery status: The steel is delivered in an annealed state. Cold extrusion mold softening specification protects and heats the iron filings, with a temperature of 760-780 ° C and a time of 10 hours. The furnace is cooled with a hardness of l96HBW, which can smoothly achieve common isothermal spheroidization annealing during cold extrusion forming. The specification is 850~870 ° C for 3 to 4 hours, and the furnace is cooled to 740-760 ° C for 4 to 5 hours. The outlet air cooling hardness is ≤ 241HBW, and the eutectic carbide grade is ≤ 3. The optimal isothermal temperature is 740-760 ° C and the time is ≥ 4 to 5 hours. The spheroidization annealing meets the specification (860 ± 1 ü). C2-4h, furnace cooling at a cooling rate of 30 ° C/h, (740 ± 10) ° C x 4-6 hours, Slowly cool down to 500~600 ° C with the furnace, and air cool after discharge. The hardness is 207~255HBW. Ordinary quenching, return quenching, standard quenching temperature 1000-1050 ° C, oil quenching or quenching, hardness 260HRC; The annealing temperature is 160~180, the annealing time is 2 hours, or the annealing temperature is 325~375 ° C, and the Cr12MoV steel undergoes 2-3 deep cooling treatments. After deep cooling treatment, the quenched martensite can precipitate highly dispersed ultrafine carbides, which can be transformed into carbides after low-temperature tempering at 200 ℃. Martensite that has not undergone deep cooling treatment only precipitates a small amount of carbides in certain local areas after low-temperature cycling. Crl2MoV adopts a low-temperature chemical heat treatment method. While maintaining the high hardness and wear resistance of Crl2MoV steel, ion nitriding, gas nitrocarburizing, and salt bath thiocyaniding are commonly used to improve the adhesion resistance of the carburized layer during low-temperature chemical heat treatment. All three types of low-temperature chemical heat treatment layers have significant anti impact adhesion effects, among which salt bath sulfocyanide co infiltration is the best. After gas nitrocarburization treatment, the service life of the Crl2MoV stainless steel vessel drawing die can reach over 30000 pieces, which is more than 10 times longer than that of similar molds treated with conventional quenching and tempering. Hardening treatment can be applied to pre hardened steel by quenching and low-temperature tempering to increase the mold life to over 800000 mold cycles. When quenching, preheat at 500-600 ℃ for 2-4 hours, then hold at 850-880 ℃ for a certain period of time (at least 2 hours), cool in oil to 50-100 ℃ for oil air cooling. After quenching, the hardness can reach 50-52HRC. To prevent cracking, low-temperature tempering treatment at 200 ℃ should be carried out immediately. After tempering, the hardness can be maintained above 48HRC. The neutral salt bath vanadizing treatment process for Crl2MoV cold working steel is used, Crl2MoV can obtain a carbide layer through neutral salt bath vanadizing treatment
1、 Carbon vanadium compound, which has a uniform structure, good continuity and compactness, uniform thickness, dense structure, high micro hardness and high wear resistance, and greatly improves surface hardness, wear resistance, and adhesion resistance.
2、 The solubility of VC in austenite is higher than that in ferrite. As the temperature decreases, VC precipitates from the ferrite, strengthening the alloy and refining the grains. The compound layer exhibits higher hardness. Cr12MoV belongs to high carbon and high chromium ledeburite steel, with a high content of carbides, accounting for about 20%. It is often unevenly distributed in ribbons or networks, with severe segregation. However, conventional heat treatment is difficult to change the carbide segregation status, which seriously affects the mechanical properties of the steel and the service life of the mold. The shape and size of carbides also have a significant impact on the performance of steel, especially the large and sharp carbides that have a significant ceramic cutting effect on the steel matrix, often becoming the source of fatigue fracture. Therefore, it is necessary to modify and forge the raw material rolled steel, fully crush the eutectic carbides, and make them small and evenly distributed. The fiber structure is distributed around the mold cavity or directionally, thereby improving the transverse mechanical properties of the steel. During forging, the steel billet is subjected to multiple upsetting and drawing from different directions, and the “two light and one heavy” method is used for forging. That is, the billet should be lightly struck at the beginning of forging to prevent fracture, and can be heavily struck at a temperature between 980 and 1020 ℃ to ensure the breakdown of carbides. Cr12MoV steel is not modified for forging guide, and solid solution double refinement treatment is used , which means secondary preheating at around 500 ℃ and 800 ℃, solid solution treatment at 1100 to 1150 ℃, quenching in hot oil or isothermal quenching, and high-temperature tempering at 750 ℃, After machining, heating at 960 ℃ and oil cooling, the final heat treatment can also refine carbides, round edges, and refine grains.
Recommended Tempering Specification for Cr12MoV Steel Note:
1. Schemes II and III are used for workpieces that require high mechanical properties and small deformation, such as threaded rollers, thread rolling plates, molds with complex shapes and subjected to impact loads, etc;
2. Schemes IV and V are used for workpieces that require red hardness and wear resistance, but have poor mechanical properties and significant dimensional deformation, such as hot stamping dies working below 450 ℃;
3. This type of steel is very sensitive to decarburization, and the salt bath used for preheating and heating must undergo sufficient deoxidation before use; If heated in a regular electric furnace, the workpiece can be loaded into the box and filled with carburizing agent or pig iron powder (at this time, the workpiece may have a slight increase in carbon, and the hardness can be increased by HRC1-2).
Table 2-3-7 Structure Ratio in Quenched State
1) This steel can be used to make complex shapes of convex, concave, and insert blocks for punching molds with a material thickness of>3mm. It is recommended to have a hardness of 58~62HRC when making convex molds and 60~64HRC when making concave molds.
2) In the production of punching molds, wear-resistant convex molds and concave molds are required. When making convex molds, it is recommended to have a hardness of 60-62HRC, and when making concave molds, it is recommended to have a hardness of 62-64HRC.
3) For concave molds that require high resistance in the production of deep drawing molds, it is recommended to have a hardness of 62~64HRC
4) In the production of bending molds, wear-resistant and complex shaped convex molds, concave molds, and inserts are required. When making convex molds, it is recommended to have a hardness of 60-64HRC, and when making concave molds, it is recommended to have a hardness of 60-64HRC
5) Suitable for producing convex and concave molds for cold extrusion molds of aluminum parts. When making convex molds, it is recommended to have a hardness of 60-62HRC, and when making concave molds, it is recommended to have a hardness of 62-64HRC.
6) For the production of convex and concave molds for cold extrusion of copper parts, it is recommended to have a hardness of 62~64HRC.
7) The hardness of the convex and concave molds used for cold extrusion of steel parts is recommended to be 62~64HRC.
8) Spring steel plates with a mass fraction of 0.65% to 0.80% of formed carbon have a hardness of 37 to 42HRC, providing a lifespan of up to 150000 cycles
9) Spring steel plates with a mass fraction of 0.65% to 0.80% formed carbon have a hardness of 37-42HRC, and are subjected to additional nitriding treatment, resulting in a lifespan of up to 400000 cycles.
10) This steel is suitable for wire rolling, such as simple forging and forming with a carbide unevenness of 5-6 levels. The wire rolling die has a short lifespan and is prone to tooth loss. But when the multi-directional repeated forging process is used, the unevenness of the carbide is reduced to not less than level 2, the service life of the wire plate will be increased from thousands of pieces before to 20000 pieces, even reaching 500000 pieces. This steel can be used in the wire rolling die for adding 20Mn steel parts
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