Cr12Mov Rolling

　　Material :cr12mov

　　Ingredients:

　　C Si Mn P S Cr Ni Mo V Cu Nb Ti N

　　1.45 ~ 1.7 0.4 0.4 0.030 0.03 or less or less or less 11 ~ 12.5 0.25 0.40 0.60 0.15 ~ 0.30 or less

　　China GB standard grade: cr12mov, China Taiwan cNS standard grade SKD11. Germany DlN standard material number 1.26o1. Germany DIN standard grade x165CrM0v12. This Jis standard grade sKD11. Korean Ks standard grade sTD11. meaning? UN1 standard x165CrM0W12KU, Swedish SS standard 2310. Spanish? UNE standard X160CrM0V12. American AISi/sAE standard D3. Russian roCT standard x12M.

　　The hardness, strength and toughness of Cr12MoV die steel after quenching and tempering are higher than that of CR12. and the workpiece with a diameter of 300~400mm can be fully quenched, and the quenching deformation is small, but the high temperature plasticity is poor. Cr12MoV is mostly used to manufacture composite molds and tools with large cross sections, complex shapes and heavy workloads. Such as punching die, cutting die, piping die, steel plate and so on.

　　Heat treatment specification

　　Heat treatment specification: 1. Quenching,950 ~ 1000℃ oil cooling; 2. Quenching 1020℃,200℃ tempering 2h.

　　Metallographic structure: fine granular pearlite + carbide.

　　Delivery condition: Steel is delivered in annealed condition.

　　Softening specification for cold extrusion

　　Make... Iron filings protection heating, temperature 760~780°C, time 10h, furnace cold, hardness l96HBW, can successfully achieve cold extrusion forming

　　Standard for ordinary isothermal spheroidizing annealing

　　850 ~870℃×3~4h, with the furnace cooling to 740~760℃×4~5h isothermal, air cooling hardness ≤241HBW, eutectic carbide grade ≤3

　　The optimum isothermal temperature is 740~76o°C, and the time is ≥4 ~5h

　　Spheroidizing annealing specification

　　° C (860 + 1 u) x 2 ~ 4 h, at 30 ° C/h speed furnace cold, (740 +) 10 ° C x4-6 h, with the slow cooling furnace to 500 ~ 600 ° C, from air cooling. Hardness 207 ~255HBW.

　　Cryogenic treatment

　　Crl2MoV steel is cryogenic treatment, cryogenic treatment can make the quenching martensite precipitate highly dispersed ultra-fine carbide, and then after 200℃ low temperature tempering, these ultra-fine carbide can be transformed into carbide. After tempering at low temperature, the martensite without cryogenic treatment only precipitates a small amount of carbides in some local areas. Crl2MoV adopts low temperature chemical heat treatment method, on the basis of maintaining the high hardness and high wear resistance of Crl2MoV steel, ion nitriding, gas nitriding carburizing, salt bath sulfur cyanotizing common low temperature chemical heat treatment infiltration layer adhesion resistance. Three kinds of low temperature chemical heat treatment infiltration layer have obvious impact adhesion resistance, especially the salt bath sulfur cyanide infiltration is the best. Crl2MoV steel stainless steel ware tensile die after gas nitrocarburizing treatment, the service life of more than 30.000 pieces, than the conventional quenching, tempering treatment of similar die life increased by more than 10 times.

　　hardening

　　In order to increase the life of the die to more than 800.000 mold times, the hardening method of quenching and low temperature tempering can be implemented on the pre-hardened steel. Quenching at 500-600℃ preheat 2-4 hours, and then at 850-880℃ insulation for a certain time (at least 2 hours), into the oil cooling to 50-100℃ oil air cooling, hardness after quenching up to 50-52HRC, in order to prevent cracking should be immediately 200℃ low temperature tempering treatment, after tempering, hardness can be maintained above 48HRC

　　Salt bath vanadium treatment

　　Crl2MoV cold work die steel neutral salt bath vanadium treatment process, Crl2MoV steel through neutral salt bath vanadium treatment can obtain carbide infiltration layer, a, vanadium carbide compound, the infiltration layer uniform organization, with good continuity and density, uniform thickness, dense structure, with high microhardness and high wear resistance, The surface hardness, wear resistance and adhesion resistance are greatly improved. Second, the solubility of VC in austenite is higher than its solubility in ferrite, with the decrease of temperature, VC precipitates from the ferrite, so that the alloy is strengthened and the grain is refined, and the compound layer shows a higher hardness. Cr12MoV belongs to high-carbon high-chromium letenite steel, the carbide content is high, accounting for about 20%, and often in a ribbon or network uneven distribution, serious segregation, and conventional heat treatment is difficult to change the status of carbide segregation, seriously affecting the mechanical properties of steel and die life. The shape and size of carbides also have a great impact on the performance of steel, especially the large block sharp Angle carbides have a relatively large splitting effect on the steel matrix, and often become the source of fatigue fracture. Therefore, it is necessary to change the forging of the raw material rolled steel to fully break the eutectic carbides, so that it is fine and evenly distributed, and the fiber structure is around the cavity or has no directional distribution. Thus improving the transverse mechanical properties of steel.

　　When forging, the billet is upset and drawn several times 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 the intermediate temperature of 980 ~ 1 020 ℃ can be hit hard to ensure that the carbide is crushed. Cr12MoV steel has not been changed to forge, and it adopts solid solution double refinement treatment [5], that is, secondary preheating at about 500 ℃ and 800 ℃, solid solution treatment at 1 100 ~ 1 150 ℃, quenching into hot oil or isothermal quenching, tempering at 750 ℃, and final heat treatment after machining at 960 ℃ after heating oil and cooling. The carbide can also be refined, rounded edges, grain refinement.

　　temper

　　quench

　　Recommended tempering specification for Cr12MoV steel

　　Scheme First preheating /℃ Second preheating /℃ quenching temperature /℃ cold hardness

　　Solution quenching temperature /℃ tempering

　　quench

　　(HRC)

　　Heating temperature /℃ Medium hardness HBW Medium hardness HRC

　　Medium The medium temperature / ° C is subsequently cooled in the medium

　　I 1020~1040 Stress relief 150~170 oil or nitrate 61~63

　　I 550~660 840~860 950~1000 Oil 20~60 to room temperature air cooling 58~62

　　ⅱRemove stress, reduce hardness 200~ 275-57 ~59

　　Ⅱ1020 ~1040 Oil 20~60 to oil temperature air cooling 62~63

　　Ⅲ Remove stress, reduce hardness 400~ 425-55 ~57

　　Ⅲ 1020~1040 Molten nitrate 40~55 5~10min Air cooling 62~63

　　Ⅳ1115 ~1130 Remove stress and form secondary hardening 510~520℃ multiple tempering - 60~61

　　Ⅳ 1115~1130 Oil 20~60 to oil temperature air cooling 42~50

　　Ⅴ Stress removal and secondary hardening -78℃ cold treatment - 60~61

　　Ⅴ1115 ~1130 Molten nitrate 40~45 5~10min air cooling 42~50

　　Ⅵ To remove the stress and form a secondary hardening plus 510~520℃ a tempering -61 ~6

　　Note: 1. Program II and III are used for workpieces requiring high mechanical properties and small deformation, such as thread rollers, wire rolling plates, moulds with complex shapes subject to impact load, etc. 2. Program Ⅳ and Ⅴ are used for workpieces requiring red hardness and wear resistance, but the mechanical properties are poor and the size deformation is large, such as hot stamping dies working below 450℃; 3. This steel is very sensitive to decarbonization, and the salt bath used for preheating and heating must be fully deoxidized before use; If heated in an ordinary electric furnace, the workpiece can be loaded into the box

　　Inside, it is filled with carburizing agent or pig iron powder (at this time, the workpiece may have a little carburization phenomenon, and the hardness can increase HRC1~2).

　　-78℃ cold treatment plus a 510~520℃ tempering, and then -78℃ cold treatment

　　Table 2-3-1 Microstructure ratio in quenched state

　　Quenching program cooling carbide /% martensite /% austenite /%

　　I, II oil, nitrate 12 73~68 20~23