45 steel tempering heat treatment process_45 steel.40Cr steel tempering heat treatment new process

45 steel, 40Cr steel tempering heat treatment new process in the non-ferrous metals and their alloys in the processing equipment, for the use of 45 steel, 40Cr steel manufactured by some of the wear and tear of the movable parts, the key is to improve its wear resistance and service life, which involves the selection of heat treatment process. 45 steel, 40Cr steel parts of the traditional heat treatment process is: the steel parts are heated to the required quenching temperature and then kept warm (the quenching temperature is usually calculated at 1.1-1.5mm/min). Usually 1.1-1.5mm/min), quenching and then low-temperature tempering. This traditional heat treatment process so that the steel parts at high temperatures for a long time insulation, testing and production, the workpiece is usually in the furnace without protective atmosphere, so the oxidation is serious, the surface decarburization, and the internal organization of the workpiece grain coarse. Shorten the quenching heating and holding time, has been the heat treatment workers research topics. The majority of scientific and technological workers after many years of research, although the development of surface pulse quenching, high frequency and medium frequency heating surface quenching and other new processes, but its equipment investment and process complexity, many small and medium-sized non-ferrous metal processing enterprises due to the funds and stop.

The new process introduced in the article is that the conventional quenching and heating furnace can be used - high-temperature box-type resistance furnace, 45 steel, 40Cr steel pieces of the center of the center part of the heating to the specified quenching and heating temperature, no longer hold, but immediately quenching, and then tempering. The steel parts of the new process were subjected to organizational observation, performance testing and on-site trial, and the organizational properties were compared with those of traditional heat treatment.

1 test conditions and test process

The test selected 020 ~ 90mm of 45 steel, 40Cr steel bar, the original organization of the hot rolled state.

Heating equipment for the SRJS-8-13 high-temperature box-type resistance furnace; XWB-101 automatic balance of the recorder to measure; in the XJB-1 microscope to observe the metallurgical organization; in the WJ-10 test machine to stretch the specimen.

The test process: the first to be quenched and heated round steel bar, at the center of one end of the surface drilling 010mm × 120mm hole, the temperature measurement thermocouple inserted to the top of the blind holes until, in addition to the thermocouple at the very top of the outside, the periphery of the tightly plugged aluminum silicate fiber refractory material, the end of the refractory mud sealing with the steel into the box-type resistance furnace, the thermocouple's compensation wire by the furnace observation holes lead, connected to the temperature measurement and recording device, the thermocouple is a good choice. Connected to the temperature measurement and recording device, connected to the power supply of the resistance furnace, and at the same time began to measure the surface temperature of the steel bar (furnace temperature) and the temperature of the center part of the steel bar.

Temperature measurement results show that Φ90mm 45 steel bar, the center part of the quenching temperature to 820 ℃ than the surface of the time lag 16-20min; Φ90mm 40Cr steel bar, to 860cC quenching temperature to lag 22-28min. 45 steel, 40Cr steel in the determination of the center and the surface of the quenching temperature of the heating time difference between the steel to determine Φ90mm 45 steel, 40Cr steel quenching temperature heating time difference between the surface of the steel, determine Φ90mm 45 steel, 40Cr steel quenching temperature heating time difference between the steel and the surface of the steel, determine Φ90mm 45 steel quenching temperature. steel, 40Cr steel tempering heat treatment process, the former when the surface to 820 ℃ and then heated for about 20min (to be the center part of the temperature) on the quenching, can shorten the holding time of 120min, and then tempering holding time from 90min to 60min; the latter when the surface to 860 ℃ and then heated for about 25min on the quenching, can shorten the holding time of 150min, holding Tempering time is shortened from 120min to 60min.

Test results and discussion

The organization and properties of 45 steel, 40Cr steel after tempering heat treatment are listed in Table l.

From Table l, it can be seen that, after shortening the time of tempering heat treatment of 45 steel, 40Cr steel, the strength and hardness of the workpiece is basically comparable to the traditional treatment process.

Table 145 steel.40Cr steel tempering heat treatment after the organization and performance

Steel tempering heat treatment tempering organization

45

40Cr 820 ℃ / 120S + T530 ℃ / 90min. air cooling 820 ℃ to temperature after water quenching; S + T + a small amount of carbon 813530 ℃ / 60 chemicals 860 ℃ / 150S 779560 ℃ / 120min. 860℃ to temperature after water quenching; S + T a small amount of carbon 787

560℃/60 chemical σa/Mpa805σb/Mpa[1 **********]5σ-1/Mpa--550570 Tempering mechanical properties δΨαk/%/%/J.cm - 213.148.285.311.444.193.162.770.6HRC 30.5(60.2)30.8(60.4)28.9(57.5)29.5(58.1)14.363.613.161.3

Note: (1) s is Soxhlet and T is flexural; (2) Data in parentheses in the column HRC is the Quenching hardness. The elongation is slightly decreased. The martensitic organization after quenching is 2~3 grades finer than that of conventional treatment. This is favorable for improving the surface hardness. After tempering heat treatment according to the new process, a small amount of carbide remains in 45 steel and 40Cr steel, which, in some cases, perhaps enhances their surface hardness and wear resistance. In order to verify the practicality of the new process of tempering heat treatment, with six Φ90mm × 500mm 40Cr steel bar, processed into Φ85mm × 482mm tie rolls, of which, each take four were respectively according to the traditional, new process of tempering heat treatment, and installed in a two-roll mill for aluminum strip with load operation. The results show that the new process of tempering heat treatment rollers, compared with the traditional process, the surface wear resistance is significantly enhanced, service life is extended.

3 Conclusion

45 steel, 40Cr steel in the quenching temperature, no insulation immediately quenching, and tempering treatment of the new process of tempering heat treatment, compared with the traditional tempering heat treatment process, the overall performance of the workpiece is roughly the same, but greatly shorten the insulation time, energy savings, cost reduction, and both to ensure the toughness of the center part of the workpiece, but also to improve the surface abrasion resistance, the majority of small and medium-sized non-ferrous metal processing enterprises. For the majority of small and medium-sized non-ferrous metal processing enterprises, is a reference to the new process of tempering heat treatment.