Energy shortage and environmental pollution are two major problems facing mankind today. Therefore, how to reduce energy consumption and pollutant emission has become a hot topic in China’s heat treatment industry in recent years, which is also related to the sustainable development of China’s equipment manufacturing industry.
Among many heat treatment processes, induction heat treatment has been labeled as “green heat treatment” due to its low energy consumption and less pollution, although it has been less than 100 years since its birth.
Comparison of the two processes
Induction heat treatment is far superior to traditional carburizing, another surface strengthening process, in terms of low energy consumption and less pollution. The appearance of vacuum low pressure carburizing process, although compared with controlled atmosphere carburizing shorten the process cycle, save the cleaning process, reduce the emission of pollutants, but its energy consumption is still high is an indisputable fact. Therefore, in the field of surface layer strengthening technology, induction heat treatment instead of carburizing heat treatment research has not stopped; In addition to the above energy and environmental factors, the equipment investment cost is also another important factor to promote induction heat treatment instead of carburizing heat treatment research.
Taking medium carbon steel or medium carbon low alloy steel as an example, medium carbon steel or medium carbon low alloy steel is selected for the copying induction quenching with the internationally advanced synchronous dual-frequency induction heating equipment, whose equipment price is about 8 million yuan. And choose low carbon steel or low carbon alloy steel manufacturing, the use of the international advanced horizontal double chamber vacuum low pressure carburizing furnace carburizing quenching, its equipment price is about 20 million yuan. Similarly, small and medium modulus gears are used for induction quenching with a complete set of equipment consisting of domestically produced transistor induction heating power supply, CNC quenching machine tool and cooling system. The equipment price is about RMB 1 million. And the use of controlled atmosphere carburizing furnace complete set of equipment for carburizing quenching, the price of the equipment is about 2 million yuan.
The surface layer needs to obtain high enough hardness, wear resistance, but the heart still to maintain good strength and toughness of the gear workpiece heat treatment, you can choose in the carburizing heat treatment and induction heat treatment of these two processes.
After synchronous double frequency induction quenching (SDF), the surface hardness and effective hardened layer depth of the gear can be achieved with the carburizing quenching, and in increasing the tooth bottom surface residual compressive stress, improve the fatigue strength and reduce the tooth shape tooth deformation are better than carburizing quenching; Induction quenching can also achieve online production, greatly reducing logistics costs.
By analyzing and comparing the economic value and social value of the two technical solutions, the balance of the technical solutions will undoubtedly incline to the side of induction heat treatment.
Foreign examples of induction heat treatment instead of carburizing
From the application technology and development trend of induction heat treatment in domestic and foreign machinery manufacturing industry, induction heat treatment is more and more applied in the field of heat treatment dominated by carburizing and other chemical treatments at present.
In the 1980s, Industrial Corporation of Japan in Hitachi and Komatsu manufacturing used induction heating for the construction machinery gear quenching, successfully replacing the carburizing quenching.
The impact quenching (SRIQ) method, which changes the power density, was introduced by Japan High Frequency thermal Smelting Co., LTD., which was applied to small gears such as gearbox gears of the automobile, medium joint gear used in diesel engines, and construction machinery to obtain the hardening layer along with the tooth profile, successfully replacing the carburizing quenching.
According to ElDEC, “Aerospace engineering is the most demanding in terms of cost control, safety, and quality standards. Based on the requirements of product quality and the insistence of environmental protection, the Boeing company of the United States chose to use synchronous two-frequency induction quenching technology (SDF) instead of the original carburizing quenching technology for some gears such as straight umbrella (cone) gear.
In addition to the already mentioned gear induction hardening, Michigan auburn hills sensing technology center nie, who valentine Dr. Give us the masterpieces of heavy metallurgical equipment used in the example of local hardening, a long time in the past carburizing method to ensure the inner hole of the workpiece, a gain of 4 mm or hardening layer to avoid inner hole surface hardening, seepage prevention treatment must be carried out in the outside to correct after carburizing and quenching heat treatment deformation, still need to deep grinding. Induction quenching, on the other hand, can use cheap steel and selectively harden the inner hole, which not only greatly reduces the heat treatment time and energy consumption, but also reduces the distortion of the workpiece, thus eliminating the need for expensive and laborious deep grinding.
An example of induction heat treatment instead of carburizing in China
For many years, domestic enterprises are also actively expanding the field of induction quenching research.
Qishuyan locomotive Technology Research Institute to carry out the high power electric locomotive elastic traction is driven gear 50CrMoA full tooth profile induction quenching instead of carburizing quenching process has achieved not only meet the use requirements and simplify the process, energy saving, reduce the production cost of satisfactory results.
Chongqing Gearbox Co., LTD. Adopts induction quenching to solve the large gear carburizing quenching deformation, high production cost, and production cycle are too long.
Dongfeng Motor Company has realized induction quenching in some gearbox gears and has obtained good economic benefits by replacing the high price carburized gear steel with the cheap medium carbon alloy steel.
Shanghai by Mr. Fu steering system co., LTD is the largest scale and highest market share of steering machine manufacturing enterprises, their production of the pretreatment of the steering rack using controlled atmosphere multi-purpose furnace to conditioning, for reasons of energy saving and environment, for the collaboration of Shanghai HuaYuan co., LTD. To switch to induction hardening and induction tempering heat treatment processing, according to statistics, only energy consumption was reduced by 35%.
The diesel engine rocker arm produced by Shanghai Youshun Automobile Parts Co., Ltd. used to be treated with nitrogen carburizing, but it has been changed to the induction hardening process since 2014, realizing online clean production.
It can be predicted that with the innovation and development of induction heating equipment and process, its application field will be continuously expanded. But induction heat treatment can not completely replace carburizing, one is that carburizing equipment and technology are also in innovation and development;Second, because for some of the induction heat treatment can not achieve the effect of carburizing, such as: for the complex shape of the workpiece and the thickness of the workpiece change greatly, the induction hardening of the hardening layer can not do such as carburizing quenching basic profile;Induction hardening of the tooling cost is higher, need to design and manufacture according to the different shape of workpiece induction quenching parts of different sensors, some special parts also need to design and manufacture special positioning fixture, unlike chemical heat treatment under the condition of the technical requirements and material are basically the same, without being limited by the shape and size can be a variety of workpiece with the furnace process,Induction heat treatment for a large number of a single variety of the workpiece to reflect its efficiency, but the need for its design and manufacture of special quenching machine;For the inner hole less than 12mm, it is not possible to conduct induction quenching, and for the gear larger than 6 modules, it is not possible to use synchronous dual-frequency induction quenching for processing at present.
Therefore, in the field of surface layer strengthening technology, induction heat treatment and carburizing and other chemical heat treatment to supplement each other will exist for a long time.
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