According to the national standard GB / T 221-2008 agreement, alloy tool steel grades are as follows.
Alloy tool steel grades usually consists of two parts:
The first part, the average carbon mass fraction of less than 1.00%, the use of a figure that carbon content (in a few thousandths of dollars). When the average mass fraction of carbon is not less than 1.00%, the carbon content is not indicated.
The second part, alloying elements and content, with the chemical element symbols and Arabic numerals, said the second part of the same alloy steel. That is to say, when the average mass fraction is less than 1.50%, only the elements are indicated in the grades, and the content is generally not indicated; the average mass fraction is 1.50% -2.49%, 2.50% -3.49%, 3.50% -4.49%, 4.50% -5.49% Isochronism, the alloy elements after the corresponding write 1,2,3,4,5 and so on.
Therefore, the difference between the two grades of Cr12MoV and Cr12Mo1V1 lies in that Mo and V have different labeling methods. The former is clearly listed according to the national recommended standards, and the content of Mo and V is less than 1.50% The two elements of the method of expression does not belong to the national recommended standard expressly agreed series, there may be manufacturers use this representation, the mass fraction should be the same as the former.
Cr12MoV; Chemical composition%: C1.45 ~ 1.70, Si less than or equal to 0.040, Mn less than or equal to 0.040, Cr11.50 ~ 13.00, p less than or equal to 0.030 and S less than or equal to 0.030; delivery status: Brinell hardness HBW10 / 3000 Equal to 255 ~ 207), quenching temperature: 950 ~ 1000; coolant: oil; Rockwell hardness GRC greater than or equal to 58 ;. Uses: hardenability, hardness after quenching and tempering, strength, toughness higher than the CR12, the diameter of 300 ~ 400mm below the work can be fully hardened, quenching deformation is small, but poor high temperature plastic. More for the manufacture of large cross-section, complex shape, heavier workload of the mold and tools such as punching die, trimming die, trimming die, die, thread rolling mold, thread rolling plate, standard tools and measuring tools .
Cr12Mo1V1 steel chemical composition (GB / T 1299-2000) ω /%
Component C Si Mn Cr Mo P S V Co
% 1.40 ~ 1.60 ≤0.60 ≤0.60 11.0 ~ 13.0 0.70 ~ 1.20 ≤0.030 ≤0.030 ≤1.10 ≤1.10
This steel, also known as die steel D2
performance:
High-carbon, high-chromium type of martensitic steel, cobalt is not required as a plus element without special requirements. As the content of molybdenum and vanadium is higher than that of Crl2MoV, the microstructure and grain size of steel are further refined and the hardenability, strength and toughness of steel are improved, so that the comprehensive properties of steel are better.
use:
Used in the manufacture of large, complex cold dies requiring high abrasion resistance such as cold cut scissors, trimming dies, drawing dies, thread rolling dies, thread rolling dies, curling dies and dies and punches requiring high wear resistance.
Cr12MoV material heat treatment performance
Cr12MoV steel has two heat treatment process: the first process is called, low quenching low back, for the use of low temperature environment, has good toughness, with the tempering temperature, the hardness decreased the second is called high Quenching high, secondary hardening, with strong red hardness, and can be nitriding, the surface hardness to further improve, up to 68-72 ° heat treatment recommendations
Annealing: 820-880 ℃ Hardness: ≤ 229HB * Quenching temperature: 1010-1030 ℃, fast cooling.
Tempering temperature: 550-650 ℃, tempering three times, does not recommend the use of the maximum tempering temperature. * Hardness: 43 ~ 53 degrees HRC
This steel has high hardenability, cross-section can be completely hardened 400mm below, at 300-400 ℃ can still maintain good hardness and wear resistance. ※ This steel has a lower melting point, so the heating temperature should not be too high. ※ poor thermal conductivity, attention should be slow heating. ※ After forging must be slow to avoid cracks.
Can be placed in preheated pit, cooled to 400-500 ° C. After cooling can be annealed. ※ Usually three tempering, each 1-1.5h
Cr12MoV steel is a high-carbon, high-chromium, austenitic steel with a lower carbon content than Cr12 steel. The steel has high hardenability, cross-section can be completely hardened 300mm below the quenching volume change than Cr12 steel to be small. Therefore, 65mm will be able to get martensite. performance:
High-carbon, high-chromium type of martensitic steel, cobalt is not required as a plus element without special requirements. As the content of molybdenum and vanadium is higher than that of Crl2MoV, the microstructure and grain size of steel are further refined and the hardenability, strength and toughness of steel are improved, so that the comprehensive properties of steel are better. use:
Used in the manufacture of large, complex cold dies requiring high abrasion resistance such as cold cut scissors, trimming dies, drawing dies, thread rolling dies, thread rolling dies, curling dies and dies and punches requiring high wear resistance. The heat treatment system for the steel bar and forgings 960 degrees air + 700 ~ 720 degrees tempering, air cooling. The final heat treatment process, due to more, can give you a set of typical process: Quenching:
The first preheat: 300 ~ 500 ℃, the second preheat 840 ~ 860 ℃; quenching temperature: 1020 ~ 1040 ℃; cooling medium: oil, medium temperature: 20 ~ 60 ℃, cooled to oil temperature; , HRC = 60 ~ 63. Tempering:
After the above quenching process, can reduce the hardness effect, the specific tempering process is as follows: heating temperature 400 ~ 425 ℃, get HRC = 57 ~ 59.
Cr12MoV steel is a high-carbon, high-chromium, austenitic steel with a lower carbon content than Cr12 steel. The steel has high hardenability, cross-section can be completely hardened 300mm below the quenching volume change than Cr12 steel to be small.
The heat treatment system for the steel bar and forgings 960 degrees air + 700 ~ 720 degrees tempering, air cooling. The final heat treatment process, due to more, can give you a set of typical process: Quenching:
The first preheating: 300 ~ 500 ℃, the second preheating 840 ~ 860 ℃; Quenching temperature:
1020 ~ 1040 ℃; cooling medium: oil, medium temperature: 20 ~ 60 ℃, cooled to oil temperature; then, air cooling, HRC = 60 ~ Tempering:
After the above quenching process, can reduce the hardness effect, the specific tempering process is as follows: heating temperature 400 ~ 425 ℃, get HRC = 57 ~ 59.
Process performance of die steel
In the mold production cost, material cost usually accounts for 10%~20%, and mechanical processing, heat treatment, assembly and management costs accounted for more than 80%, so the process performance of the die material is one of the main factors affecting the mold production cost and manufacturing difficulty.
Machinability
– hot workability, refers to thermoplastic, processing temperature range, etc.;
Hot work die steel
Hot work die steel
– cold working performance, refers to cutting, grinding, polishing, cold drawing and other processing properties.
Cold working die steels are mostly eutectoid steels and bainitic steels, and the hot and cold working properties are not very good. Therefore, it is necessary to strictly control the technological parameters of hot working and cold working to avoid defects and waste products. On the other hand, by improving the purity of steel, reducing the content of harmful impurities, improving the microstructure of steel, to improve the hot processing and cold processing performance of steel, thereby reducing the production cost of the die.
To improve the performance of cold working die steel, since the beginning of 1930s, on S, Pb, adding graphite Ca and Te cutting elements or resulting in die steel die steel to carbon element in the development of a variety of free cutting steel, to further improve the cutting performance and grinding performance, reduce abrasive tool consumption and low cost.
Hardenability and hardenability
Hardenability depends mainly on the chemical composition of the steel and the original microstructure before hardening. The hardenability is mainly determined by the carbon content in the steel. For most cold work die steels, hardenability is often one of the major considerations. For hot work die steel and plastic die steel, the general mold size is larger, especially the manufacture of large mold, its hardenability is more important. In addition, the complex shape is easy to produce all kinds of mold heat treatment deformation, in order to reduce the quenching deformation of quenching medium, often as far as possible the use of cooling ability, such as air cooling, oil cooling or cooling bath, in order to get the required hardness and depth of hardened layer, requires the use of high hardenability die steel.
Quenching temperature and deformation of heat treatment
In order to facilitate production requirements of die steel after quenching temperature range as far as possible to relax some, especially when the mold by flame heating partial quenching, because it is difficult to accurately measure and control temperature, requires a wide range of quenching temperature of die steel.
Die during the heat treatment, especially in the quenching process, to produce the volume change, shape warping, distortion and so on, in order to ensure the quality of the mould and heat treatment requirements of die steel with small deformation, especially for precision mould with complicated shape, it is difficult to repair after quenching, heat treatment for deformation of the more demanding. It should be the choice of micro deformation of die steel.
Oxidation and decarburization sensitivity
During the heating process, if the oxidation and decarburization occur, the hardness, wear resistance, service performance and service life of the mold will be reduced. Therefore, the oxidation and decarburization sensitivity of the die steel will be better. Because of the high sensitivity of oxidation and decarburization, special heat treatment, such as vacuum heat treatment, controllable atmosphere heat treatment and salt bath heat treatment, should be adopted for die steels with high molybdenum content.
