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Application case of induction heat treatment technology: Substitute carburizing

Induction heat treatment gradually replaces carburizing

Nowadays, people have higher and higher requirements for environmental protection. China has taken environmental protection as a basic national policy and started to promote clean production, requiring green heat treatment to produce clean products. Green heat treatment, the most fundamental is for the sustainable development of mankind. We should ensure the rational development and utilization of natural resources, and at the same time protect natural resources and the environment. For an enterprise, the relationship between development and efficiency, development and innovation, development and resources, development, and environment should also be handled well.

The production of traditional carburizing heat treatment will cause great environmental pollution, which is mainly the waste gas, wastewater, waste residue, noise, and the consumption of a large number of combustible gas and chemical raw materials. At the same time, the processing cycle of carburizing heat treatment is long, the deformation is large, it is difficult to achieve local accurate carburizing, which restricts the development of metal parts heat treatment technology and technology upgrade of China’s equipment manufacturing industry to a large extent.

Induction heating quenching, due to its rapid heating speed, belongs to the way of less and no oxidation heating. Meanwhile, induction heating quenching can precisely control the area of heat treatment of parts and the corresponding technological indicators. It has the characteristics of a short processing cycle, a wide range of parts, and small quenching deformation. According to statistics, compared with the traditional carburizing process, the processing cycle of inductor heat treatment is reduced by 90%. Small distortion of heat-treated workpiece; Heat treatment energy efficiency increased to 80%; The environmental impact of heat treatment is reduced to zero; Reduce heat treatment cost by 75%; Achieving high rates of return on productivity and profits; The working environment is clean, comfortable and safe. The induction heat treatment equipment of our company is developing towards the direction of automation, integration, flexibility, and intelligence, gradually replacing the traditional carburizing heat treatment process.

Replacement of carburizing process after the successful promotion of parts

Carburizing workpiece material is generally low carbon steel or low carbon alloy steel (carbon content is less than 0.25%). After carburizing steel surface chemical composition can be close to the high carbon steel, carburizing technology is widely used in aircraft, automobile and engineering machinery and other mechanical parts, such as gear, shaft, camshaft, ball cage, at present my company’s induction heat treatment equipment has been successfully applied to the crankshaft, camshaft, ring gear parts, shaft parts, CVJ, and other areas of the induction hardening, entirely replace the carburizing and quenching technology of these parts.

Induction heat treatment equipment still need to be improved

Advanced digital heating power supply, reliable control, accurate measurement sensor, complete set of an engineering system that can realize precise control (including instrument and meter, cutting, pump, execution action components, computer, software program design, etc.) is to ensure the accurate production of induction heat treatment equipment, stable and reliable quality assurance.

For example, the induction heat treatment equipment makes it possible to apply its rapid, high-energy density energy to the induction heat treatment of complex surface workpiece with similar gears, which will greatly save energy and reduce the deformation, thus reducing the machining allowance in the next step.At the same time, it will be completely customized according to the customer’s heat treatment system, it can be placed in the entire production line as a heat treatment unit, so as to become a complete production chain, integrated with the entire production line, to meet the cost savings, save time and energy and improve the efficiency of the integrated management requirements. This is also the direction of Shiyan Hengjin Technology Co., LTD.

Corresponding process substitution case

(1) Using the car steering knuckle, three column shell parts, the traditional is the whole carburizing process method to improve the surface hardness of the parts and mechanical properties of single product carburizing time in more than 15 h, which restricted the efficiency of the production of an auto parts manufacturer, Shiyan constant technology co., LTD. In 2009, patterned constant speed universal joint induction hardening equipment has successfully replaced the components of the carburizing and quenching process, the single heat treatment time only needs 35 s continuous scanning (quenching), a quenching heating time is less than 3 s, over 80% of energy and carburizing heat treatment, Its quenching quality has reached the advanced level of similar foreign products.

(2) the big gear ring gear quenching parts, traditional carburizing process, a single product of carburizing for a long time (generally more than 24 h), deformation of gear is high at the same time, the rejection rate is higher, in 2007 the company successfully developed the domestic first 1600 mm the whole tooth induction quenching equipment, has realized the single product of the whole tooth induction heat treatment, machining time just 5 min, can adapt to many specifications of the heat-treatment, save a lot of cost for manufacturer, has created considerable economic benefits.

(3) The bulldozer inner gear ring carburizing quenching to induction quenching process: the original process of the inner gear ring is carburizing quenching, the produced inner gear ring teeth shrinkage deformation is large, resulting in a high workpiece rejection rate.

The inner ring is made of 20CrMnTi, the hardening depth is 1.8-2.4mm, and the surface hardness is 58-63HRC. The main technological process of the inner gear ring is as follows: blanking → forging → normalizing → roughing → finishing → gear shaping → carburizing → shot blasting → hardening → tempering; Our company adopts 1200kW transistor power supply and inner hole one-time quenching inductor to realize the quenching process of inductor and adopts the process method of induction rapid heating workpiece and rapid spraying cooling to reduce the deformation of the gear ring. Only the tooth surface can be heated, and the other positions can still maintain good plasticity, and the heating time is very short (about 40S), which greatly reduces the deformation. The modified process route: blanking → forging → normalizing → roughing → tempering → shot blasting → finishing → gear shaping → induction hardening → tempering.

Effect comparison: induction quenching to get the inner gear ring to meet the requirements of the heat treatment, compared with the carburizing heat treatment workpiece surface hardness is slightly lower, but the depth of hardening layer is deeper, grain size and martensite level is the same, but does not contain higher wear resistance carbide. After the installation verification, the main engine is disassembled after working for 3000h, and the inner tooth ring wear is very small without any problem, which completely meets the requirements.The tempering time of 20CrMnTi inner gear ring after carburizing and the tempering time after secondary heating and quenching are 46h. The tempering time of 45 steel inner gear ring and the tempering time after induction quenching is the only 9.5h.Induction quenching process greatly shortens the manufacturing cycle of the workpiece and improves production efficiency. The production cost of 20CrMnTi steel is higher than that of 45 steel. Using 45 steel can reduce the production cost. Carburizing heat treatment needs to consume a lot of electric energy, cementing agent and so on, the production cost is high, and exhaust gas pollution environment; Induction heat treatment only consumes a small amount of electric energy, no emissions, no pollution, is an environmental protection technology, is the heat treatment industry focus on the promotion of energy conservation, emission reduction new technology.

There are four points to be considered when induction heat treatment replaces carburizing

(1) learning exchanges and technical cooperation, promote the application of the induction heat treatment in the field of metal parts heat treatment and recognition, especially in the special industries need to manufacturing companies and good cooperation, induction heat treatment plant to improve the traditional carburizing and quenching process, replace carburization equipment with induction heat treatment equipment, reduce energy consumption and environmental pollution.

(2) The limitation of the process, there are a lot of enterprises have made a clear provision for the process of heat treatment, can only take the carburizing quenching process, which greatly restricts the induction heat treatment equipment to replace the pace of carburizing process.

(3) With the support of technology and capital, induction heat treatment equipment is a complex system engineering, especially in the field with high requirements for heat treatment process indexes. The lack of high-end technical talents and capital is also a factor restricting the development of induction heat treatment equipment towards the high-end and intelligent direction. In order to accelerate the process of the induction hardening process instead of the traditional carburizing quenching process, the government should increase its efforts in capital investment, talent training, and introduction.

(4) Users should more explore the application of the induction hardening process in the traditional carburizing process, and gradually or partially replace the traditional process. At the same time, it is hoped that domestic iron and steel enterprises can develop more new materials for induction quenching instead of carburizing quenching.

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