Introduction to the development of induction heat treatment equipment

1 Introduction

Induction heat treatment has many advantages such as fast heating speed, energy saving, non-oxidation and decarbonization, no pollution to the environment and high production efficiency. These advantages are widely recognized by heat treatment workers, so they have developed rapidly in the past decade. Of course, this actual demand has also greatly promoted the development and technological upgrading of domestic induction heat treatment equipment. Taking Changchun's “China FAW” as an example, the company has nearly 100 induction heat treatment equipment, of which 50 are newly added or updated in the past ten years, almost all of which are thyristor intermediate frequency equipment and IGBT super audio equipment. At present, the weight of induction heat treatment parts of the "FAW" medium-sized trucks reaches 291.3kg, accounting for 52% of all heat-treated parts. The induction heat treatment really stands up for half of the heat treatment.

2 Early induction heat treatment equipment in China

In the early and mid-1950s, with the construction of “FAW” and “one-to-one”, a number of high- and medium-frequency heat treatment equipments were introduced from the Soviet Union, with a total of about 20 units, and a very small number of Czech equipment. The Chinese have known the induction heat treatment since then. In the late 1950s, several factories in China developed high- and medium-frequency power equipment. For example, Tianjin Broadcasting Equipment Factory and Beijing Broadcasting Equipment Factory developed high-frequency electronic tube equipment; Xiangtan Electric Machinery Factory and Jinzhou Electric Machinery Factory developed mechanical medium-frequency generators; In the mid-1960s, the Tianjin Labor Bureau Technical School (later Tianjin Ninth Machine Tool Plant) began to produce simple quenching machine tools [1]. They opened the first place in China to develop and produce induction heat treatment equipment.

3 Current status and development of induction heat treatment power supply equipment in China

Medium and high frequency power supply equipment is the key equipment for induction heat treatment. At present, in China's heat treatment industry, except for the oldest spark gap type high-frequency power supply, several other power sources are used. Among them, the medium-frequency generator and the tube-type high-frequency power supply are behind, in some regions or factories. Still the main production equipment. The advantages and disadvantages of various power sources are as follows:

3.1 Mechanical IF Generator

The mechanical IF generator was successfully developed in about 1920. At that time, Clark Company of Ohio, USA, first used it for the quenching of the crankshaft journal. This was the first intermediate frequency power supply for industrial production. Its biggest advantage is its durability. It requires almost no maintenance except for the replacement of bearings for several years. Its shortcomings are fixed frequency, limited use range; large floor space; high noise; large water consumption; low electrical efficiency, about 70~75% [2].

2.2 Tube high frequency power supply

The tube high frequency power supply was born around 1930. Its main advantages are simple tuning and ease of use, despite the high frequency (after the development of super audio), the scope of application is still wide (without paying attention to heating efficiency). Its main disadvantage is that the electrical efficiency is low, about 50%; the working voltage is too high, the safety is poor; the single machine power is small [2].

2.3 Thyristor (SCR) type intermediate frequency power supply

The thyristor (SCR) intermediate frequency power supply is also called the thyristor intermediate frequency power supply. This kind of power supply was successfully developed around the world in about 1970 and began to be used in large quantities. China was successfully developed and started trials in the 1980s. It was fully mature in the early 1990s and some technical indicators have reached the international advanced level. The thyristor intermediate frequency power supply frequency for induction hardening is generally 2.5~8 kHz. Compared with the machine IF, it has many advantages: small size, light weight; no mechanical movement, low noise; convenient start-stop, frequency can be adjusted according to the needs of the parts, and automatically tracked during operation, keeping running at the highest power factor Easy to install, no special foundation required; single-machine power of quenching equipment can reach 1000kW; electrical efficiency can reach 90% [2].

2.4 Transistor Super Audio and High Frequency Power Supply

Transistor super audio and high frequency power supplies generally refer to: (1) IGBT super audio power supply, MOSFET high frequency power supply and SIT high frequency power supply. Transistor super-audio and high-frequency power supplies have been developed internationally in the mid to late 1970s. China developed successfully in the 1990s. At present, the domestic IGBT power supply is very mature. Some indicators of the IGBT power supply produced by our company have reached the international advanced level: the frequency can reach 500kW at 8~50kHz, and the power can reach 200kW at 50~100kHz. Domestic MOSFETs are 200kHz and 100kW. SIT high-frequency power has been produced in China for dozens of units, but due to the lack of spare parts, it has gradually been scrapped. SIT power supply is difficult to overcome due to shortcomings such as small single-tube power, and foreign companies have stopped research and development and production. The advantages of a transistor power supply are the same or similar to those of a thyristor power supply, but the frequency can be several hundred kilohertz. The following table summarizes the above:

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