What kinds of heat treatment process can improve the wear resistance of high manganese steel?
1. Conventional heat treatment process for high manganese steel
Normal heat treatment: 1000 ~ 1100 ℃ heating, heat preservation or heating to 650 ~ 700 ℃ heat preservation for a period of time and then heating to 1050 ~ 1100 ℃ and then quenched. Large, of which the thickness disparity, complicated shape in 650 ~ 700 ℃ heat preservation for a period of time, is good for reduce the deformation and cracking, and of uniform thickness, shape, simple not easy cracking of the small,, no heat preservation is necessary. It is economical and effective to apply ordinary heat treatment to ordinary high manganese steel.
1) ZGMn13 heat treatment process of high manganese steel castings, high manganese steel ZGMn13 casting belongs to a small, simple thing, and no accumulation of heat, can be in the < 750 ℃ charging to medium and high speed up directly to the quenching temperature, the maximum thickness of 1.3 ~ 1.4 mm/min) (flame furnace heat preservation after quenching, austenitic organization can be a single.
Simple large heavy thick pieces, accumulation of furnace, moderately complex parts, can at 650 ℃ or less charging, in 650 ~ 700 ℃ maximum thickness of 1.5 mm/min, and revise according to the thickness of accumulation, temperature after plastic deformation has been improved, appropriate USES faster heating up. Flame furnace temperature, heating rate can be used 250 ~ 250 ℃ / h; Furnace is relatively uniform, can use 300 ~ 650 ℃ / h; The temperature of the salt bath furnace is more even. Thickness of 50 mm ball mill lining board, electric furnace after 680 ℃ preheat, directly into the 1070 ℃, salt bath furnace, heat preservation for 15 min quenching, does not crack, and get a single austenitic organization. Practical experience shows that: the high-temperature insulation coefficient of flame furnace and electric furnace is calculated as 0.8min/mm; The single austenite structure can be obtained by calculating the salt bath furnace at 0.3~ 0.4min /mm without causing cracks.
Special big, weight, thickness disparity of complex parts, such as large jaw crusher teeth plate, shape size 50 ~ 100 mm Χ Χ 1500 mm and 850 mm thickness of 50 ~ 100 mm, a single weight 900 kg, by flame furnace heating. The heat treatment process for: the < 300 ℃ charging, to 300 ℃ 2 h, reoccupy temperature 60 ℃ / h 6 h, 650 ~ 650 ℃ heat preservation 3 h, again with 100 ℃ / h up 4 h, 1050 ~ 1100 ℃ heat 6 h quenching, cracks were not found. High temperature insulation coefficient can be 1.5~1.8min/mm; Thermal insulation 2.5~3h, even using thermal insulation coefficient 1~1.2min/mm; Heat preservation for 1.67~2h can make the carbides dissolve and diffuse evenly, and obtain single austenite structure, reduce surface decarbonization and demanganization, improve wear resistance, reduce crack rejection rate and reduce energy consumption.
2) water toughening treatment process high manganese steel, high manganese steel casting wear-resisting, subject to 1050 ~ 1100 ℃ high temperature heating water toughening treatment, in order to obtain high toughness austenitic organization; Under the action of high impact load, the austenite structure on the surface of steel parts is continuously deformed and hardened, and has good wear resistance. The former high manganese steel water toughening process, the process cycle is long, the energy consumption is large. High manganese steel water toughening treatment process is: after the workpiece loading furnace with 70 ℃ / h or less heat slowly heated to 700 ℃, and then to 100 ℃ / h or less heated to a temperature of 1050 ~ 1100 ℃, 2 h are temperature, heat preservation 2 ~ 3.5 h, ensure enough soaking time, facilitate carbide dissolves.
Due to the elimination of low-temperature residence and intermediate holding time, the process cycle is shortened from 16h to 14h, and the gas consumption is reduced from 11694m3/ furnace to 8256 m3/ furnace. The product quality is qualified and no cracks have occurred.
2. Energy saving heat treatment process of high manganese steel -- direct quenching with casting waste heat
After casting pouring shakeout, direct quenching in 1050 ~ 1100 ℃ or high temperature type out immediately after loading furnace temperature of 1050 ~ 1100 ℃ after homogenization melt quenching.
In order to obtain single austenite structure of high manganese steel (Mn13) castings, it is necessary to conduct water toughening treatment to improve the service life. Is after casting in a sand mold casting cooling before, after clear out again into the kiln heating to 1050 ~ 1100 ℃, the heat preservation for a period of time the austenite quenching in water after homogenization, austenitic organization for room temperature. However, due to the use of coal burning heating kiln, the heating speed and holding time are not accurate, often resulting in over-burning or under-burning and quenching scrap, and long processing time, consuming a lot of coal, electricity and manpower. After the high manganese steel castings pouring, in sand mold temperature is 1000 ~ 1100 ℃, also has a single austenitic organization, then such as quenching in water can also achieve the goal of water toughening treatment. Therefore, without adding any equipment, the manufacturing process of high manganese steel teeth plate was improved, and direct water was used.
According to the weight and thickness of the tooth plate, the casting mold with the tooth plate is lifted to the sand cleaning department from half an hour to one hour after the tooth plate is poured. In the lifting process, the box is not opened. Casting temperature is about 1100 ℃ or so high at this time, will immediately with the tooth plate sand box into the water pool for water blasting. Because of the casting of higher temperature and mould temperature is low, so the beginning does not produce water blasting, detonation measures must be taken, the sand box hit several times in the pool wall, cause water, in the water cooling 15 ~ 20 min, when tooth plate temperature is below 200 ℃, can the tooth plate lift, such direct water quench process is completed. And then the second and third... Until it's done. In the process of water burst, tooth plate into the water depth control in 400 ~ 600 mm below the water, the water temperature is not more than 40 ℃, the water silt content less than 7% (mass fraction).
3. Fine grain treatment of high manganese steel
Fine-grain heat treatment: heat the casting of 1000 ~ 1200 ℃ after solution treatment, again in 500 ~ 500 ℃ in pearlite, finally in 950 ~ 1100 ℃ and then to solid solution treatment, to achieve grain refinement, enhance toughness and wear resistance.