Induction heating technology is widely used in the forging industry because of its energy-saving, pollution-free, and easy to realize temperature control of forging heating. The application of induction heating technology in China can be traced back to the 1960s. In the late 1960s, the induction heating thyristor intermediate frequency power supply was developed. Due to its many technical advantages over the intermediate frequency generator set, it has been more and more widely used.
First, the induction heating equipment in the present stage of the application
(1) The application of induction heating equipment at the present stage is mainly reflected in the overall diathermy of the blank. At the present stage, applied to the automobile connecting rod, crankshaft, and steering knuckle are induction heating, the scraper in the coal machine, the chain link on the mining machine are forged through induction heating. Even if there were previously units using gas heating, they were basically transformed into induction heating through technical transformation.
With the domestic investment in the automobile industry in recent years, many large forging lines have been built in China, so many large induction heating equipment has been born. However, most of them are provided by foreign enterprises, and only a few production lines use domestically made induction heating equipment. For example, Liaoning May 18 internal combustion engine accessories Co., LTD. 14000T hot die forging press with 5600kW intermediate frequency heating equipment is provided by a domestic equipment manufacturer.
(2) With the increasing requirements of users on forgings, equipment manufacturers should not only be satisfied with heating the equipment but also go deep into the production management process of users to solve various problems encountered by users in the forging process.
Similarly, the oxide scale generated in the heating process has been a headache for many users, especially for gear forgings, many users have tried various ways to remove the oxide scale. Here is a brief introduction of several user experiences: using the atmosphere protection, in the induction furnace filled with nitrogen as a protective atmosphere, to achieve the purpose of removing oxide scale; At the exit of the induction furnace, the flame generated by hydrogen spontaneous combustion is used to isolate the oxygen into the induction furnace and remove the oxide scale. There are also some users who first heat the blank to a certain temperature, then spray graphite, and then enter the induction furnace heating to reach the forging temperature, this process has been relatively mature.
The heating of different parts encountered by users in the process of use is also a problem to be solved by equipment manufacturers, among which the sensor design is a difficulty, and it is even more difficult to consider the automation of production.
(3) How to improve the power of the power supply. The power of a single machine is limited by its internal conditions, it is difficult to improve the power up to a certain extent, can only try to improve the power through other ways, to meet the requirements of production. An experience here is that the power can be increased to more than twice by the way of a parallel machine.
Second, the development direction of induction heating technology
1. Power will be more energy efficient
At present, many domestic manufacturers are still using thyristor power, and IGBT power has been introduced abroad. Compared with thyristor, IGBT energy saving effect is more obvious. Now domestic manufacturers began to try to develop IGBT power, but the power is not very big, the effect is not very ideal.
2. More intelligent and automatic equipment control
Due to the increase in labor cost, many forging factories are trying to improve the automation of production lines, trying to avoid the use of personnel operation.
(1) How to solve the feeding problem
Depending on the size of the blank heated, a variety of methods can be used. The following methods have been widely used by many manufacturers (see figure below)
(a) Vibration feeding mode
(b) Step feeding method
(2) Solve the interface between the oven and various presses and robots
In recent years, with the increase of labor costs, many manufacturers have begun to consider using robots to replace labor, so manufacturers of induction heating equipment should consider the transmission of blank between intermediate frequency furnace and robot, as shown in the video below.
(3) Interface with various presses
Because the forging process of various forgings is different, the user has used different presses, and the interface between the intermediate frequency furnace and the press is also the issue that the intermediate frequency furnace manufacturer needs to consider (see the following figure).
The interface between presses A
The interface between presses B