First, lower the heating temperature.

Generally, the quenching heating temperature of hypereutectoid carbon steel is 30~50℃ above Ac3, and the quenching heating temperature of eutectoid and hypereutectoid carbon steel is 30~50℃ above Ac1. However, research in recent years has confirmed that heating and quenching hypoeutectoid steel in the α + γ two-phase region slightly lower than Ac3 (i.e., sub-temperature quenching) can improve the strength and toughness of the steel, reduce the brittle transition temperature, and eliminate temper brittleness. The heating temperature for quenching can be reduced by 40°C. Using low-temperature rapid short-time heating and quenching of high-carbon steel can reduce the carbon content of austenite and help obtain lath martensite with good strength and toughness. It not only improves its toughness but also shortens the heating time. For some transmission gears, carbonitriding is used instead of carburizing. The wear resistance is increased by 40% to 60% and the fatigue strength is increased by 50% to 80%. The co-carburizing time is equivalent, but the co-carburizing temperature (850°C) is higher than that of carburizing. The temperature (920℃) is 70℃ lower, and it can also reduce heat treatment deformation.

Second, shorten the heating time.

Production practice shows that the traditional heating time determined based on the effective thickness of the workpiece is conservative, so the heating coefficient α in the heating holding time formula τ = α·K·D needs to be corrected. According to traditional treatment process parameters, when heated to 800-900°C in an air furnace, the α value is recommended to be 1.0-1.8 min/mm, which is conservative. If the α value can be reduced, the heating time can be greatly shortened. The heating time should be determined through experiments based on the size of the steel workpiece, the amount of furnace charging, etc. Once the optimized process parameters are determined, they must be implemented carefully to achieve significant economic benefits.

Third, cancel tempering or reduce the number of tempering.

Cancel the tempering of carburized steel. For example, if the double-sided carburized piston pin of a 20Cr steel loader is used to cancel the tempering, the fatigue limit of the tempered one can be increased by 16%; if the tempering of the low carbon martensitic steel is canceled, the bulldozer pin will be replaced. The set is simplified to use the quenched state of 20 steel (low carbon martensite), the hardness is stable at around 45HRC, the product strength and wear resistance are significantly improved, and the quality is stable; high-speed steel reduces the number of temperings, such as W18Cr4V steel machine saw blades that use one tempering Fire (560℃×1h) replaces the traditional three times tempering of 560℃×1h, and the service life is increased by 40%.

Fourth, use low and medium-temperature tempering instead of high-temperature tempering.

Medium carbon or medium carbon alloy structural steel uses medium and low-temperature tempering instead of high-temperature tempering to obtain higher multi-impact resistance. The W6Mo5Cr4V2 steel Φ8mm drill bit is subjected to secondary tempering at 350℃×1h+560℃×1h after quenching, and the cutting life of the drill bit is increased by 40% compared with the drill bit tempered three times at 560℃×1h.

Fifth, reasonably reduce the depth of the seepage layer

The chemical heat treatment cycle is long and consumes a lot of power. If the depth of the penetration layer can be reduced to shorten the time, it is an important means of energy saving. The necessary hardened layer depth was determined by stress measurement, which showed that the current hardened layer was too deep and only 70% of the traditional hardened layer depth was sufficient. Research shows that carbonitriding can reduce the layer depth by 30% to 40% compared to carburizing. At the same time, if the penetration depth is controlled to the lower limit of the technical requirements in actual production, 20% of energy can be saved, and the time and deformation can also be reduced.

Sixth, use high temperature and vacuum chemical heat treatment

High-temperature chemical heat treatment is to increase the chemical heat treatment temperature under narrow conditions when the equipment operating temperature allows and the austenite grains of the steel to be infiltrated do not grow, thereby greatly accelerating the carburization speed. Increasing the carburizing temperature from 930℃ to 1000℃ can increase the carburizing speed by more than 2 times. However, because there are still many problems, future development is limited. Vacuum chemical heat treatment is carried out in a negative-pressure gas phase medium. Due to the purification of the workpiece surface under vacuum and the use of higher temperatures, the penetration rate is greatly increased. For example, vacuum carburizing can increase productivity by 1 to 2 times; when aluminum and chromium are infiltrated at 133.3× (10-1 to 10-2) Pa, the penetration rate can be increased by more than 10 times.

Seventh, ion chemical heat treatment

It is a chemical heat treatment process that uses glow discharge between the workpiece (cathode) and anode to simultaneously infiltrate the elements to be infiltrated in a gas-phase medium containing elements to be infiltrated at a pressure below one atmosphere. Such as ion nitriding, ion carburizing, ion sulfurizing, etc., which have the advantages of fast penetration speed, good quality, and energy saving.

Eighth, use induction self-tempering

Induction self-tempering is used instead of tempering in the furnace. Since induction heating is used to transfer heat to the outside of the quenching layer, the remaining heat is not taken away during quenching and cooling to achieve short-term tempering. Therefore, it is highly energy-saving and has been used in many applications. Under certain circumstances (such as high carbon steel and high carbon high alloy steel), quenching cracking can be avoided. At the same time, once each process parameter is determined, mass production can be achieved, and the economic benefits are significant.

Ninth, use post-forging preheating and quenching

Preheating and quenching after forging can not only reduce heat treatment energy consumption and simplify the production process, but also improve product performance. Using post-forging waste heat quenching + high-temperature tempering as pretreatment can eliminate the shortcomings of post-forging waste heat quenching as the final heat treatment of coarse grains and poor impact toughness. It takes a shorter time and has higher productivity than spheroidizing annealing or general annealing. In addition, The temperature of high-temperature tempering is lower than that of annealing and tempering, so it can greatly reduce energy consumption, and the equipment is simple and easy to operate. Compared with general normalizing, residual heat normalizing after forging can not only improve the strength of steel but also improve plastic toughness, and reduce cold-brittle transition temperature and notch sensitivity. For example, 20CrMnTi steel can be heated at 730~630℃ at 20℃/h after forging. Rapid cooling has achieved good results.

Tenth, use surface quenching instead of carburizing and quenching

A systematic study on the properties (such as static strength, fatigue strength, multiple impact resistance, residual internal stress) of medium and high carbon steel with a carbon content of 0.6% to 0.8% after high-frequency quenching shows that induction quenching can be used to partially replace carburizing. Quenching is entirely possible. We used 40Cr steel high-frequency quenching to manufacture gearbox gears, replacing the original 20CrMnTi steel carburizing and quenching gears, and achieved success.

11. Use local heating instead of overall heating

For some parts with local technical requirements (such as wear-resistant gear shaft diameter, roller diameter, etc.), local heating methods such as bath furnace heating, induction heating, pulse heating, and flame heating can be used instead of overall heating such as box furnaces. , can achieve appropriate coordination between the friction and engagement parts of each part, improve the service life of the parts, and because it is localized heating, it can significantly reduce quenching deformation and reduce energy consumption.

We deeply understand that whether an enterprise can rationally utilize energy and obtain maximum economic benefits with limited energy involves factors such as the efficiency of energy-using equipment, whether the process technology route is reasonable, and whether management is scientific. This requires us to consider comprehensively from a systematic perspective, and every link cannot be ignored. At the same time, when formulating the process, we must also have an overall concept and be closely integrated with the economic benefits of the enterprise. We cannot formulate the process just for the sake of formulating the process. This is particularly important today with the rapid development of the market economy.