The solid solution nitriding vacuum furnace for industrial applications can be a standard Ipsen VTTCK or VVTK vacuum furnace, which has been modified to meet the following requirements: (1) increase convection heating to 1200 °C; (2) temperature uniformity within ±10 °C; (3) nitrogen pressure setting It is set at 0.01~0.3MPa and can be controlled within ±10mbar; (4) The gas quenching pressure can be selected to 1MPa (10bar) nitrogen, and sometimes 1MPa helium gas may be required. For the VTTCK-924 vacuum furnace, the working chamber size is 1150 mm × 850 mm × 650 (height) mm, the weight of the loaded workpiece is 1000 kg, and the gas quenching pressure is 1 MPa (10 bar) of nitrogen.
Application examples: (1) Austenitic stainless steels such as SOLNIT-A, 1.4435, 1.4571, 1.4301 and 1.4539 are treated to obtain a tough high nitrogen austenite surface with a thickness of 0.3 to 2.5 mm, which has high corrosion resistance and fatigue resistance. The heart still maintains the strength of the solution treatment, and the hardness increases by 50 to 120 HV. This combination of properties gives the workpiece high fatigue strength in corrosive environments. (2) SOLNIT-M, 1.4021, 1.4104, 1.4024 and other martensitic stainless steels are treated to obtain a tough core and a hard surface layer to maintain and improve the corrosion resistance of the raw materials. The workpiece may have a thickness of 0.3 to 2.5 mm. The hardness is 58-60HRC, and it also has high fatigue strength.
2.3.2 Induction heating treatment:
In the past 25 years, the industrial application of induction heating has become more and more extensive. In addition to induction smelting, induction welding and special applications in some occasions, it focuses on induction heat treatment and heat transfer (including the heating of the billet in semi-solid forming). The induction heat treatment mainly has quenching. , tempering, stress relief, annealing, normalizing, spheroidizing and sintering, etc., the latest report should also include chemical heat treatment of liquid medium induction carburizing (US special issue). Here we mainly discuss the advanced level of induction heating quenching treatment, heating power supply and quenching equipment.
China applied induction heating in industry. It started in the 1950s and in the late 1950s, China made self-made tube-type high-frequency power supply and mechanical medium-frequency generator. After the 1960s, the thyristor intermediate frequency power supply (SCR thyristor) was developed. At present, the SCR intermediate frequency power supply has completely replaced the intermediate frequency generator set and the electromagnetic frequency multiplier in the range of 150 to 10 kHz. Since the reform and opening up, the introduction of modern induction heating technology in industrialized countries has made great progress in the induction heat treatment technology in China.
About induction heating power supply: At present, the IGBT (Insulated Gate Bipolar Transistor) generator of the Spanish GH Group has a maximum output power of 500 kW and an operating frequency of 5 to 50 kHz. The IGBT generator manufactured by Japan High Frequency Co., Ltd. has a power of 100 to 600 kW in 1 to 25 kHz and 50 kHz; 800 kW, 1000 kW and 1200 kW are only 1 to 25 kHz. The products of domestic production plants are below this level. EFD has a stronger strength. As one of the world's largest suppliers of induction heating equipment, the IGBT has been broken below the 150 kHz limit, and the frequency has been increased to 350 kHz for the first time. The company has now established a factory in Shanghai.
For high frequency bands above 100 kHz, MOSFET power devices (MOS field effect transistors) with fast mode and large capacity are mainly used. Spain GH Group's product output power of 25 ~ 50kW has 10 specifications, the output frequency is 50 ~ 100kHz, 100 ~ 200kHz and 200 ~ 300kHz. High-frequency power supply Another power device is SIT (static induction transistor), which is mainly based on Japanese products. At the end of the 1980s, it has reached the power level of 100kW, frequency of 200kHz and 400kW power of 400 kHz. The domestic level is much lower than this value. . The UHF power supply for solving special processes such as blades and saw blades is 27.12MHz, which mainly relies on imports. The domestic ultra-high frequency power supply of electronic tubes is 8~100kW.
About induction hardening equipment: general induction hardening machine, adapt to a wide variety of workpieces, complete functions, a wide range of applications, generally vertical and horizontal, more vertical.
The transmission type of the quenching equipment is hydraulic and full mechanical, but the hydraulic type has a tendency to eliminate. The latter uses a variable frequency speed regulating motor, a stepping motor or a servo motor to move through a ball screw drive, a T-type screw or a linear moving guide. The speed is uniform and accurate, and it is easy to realize shifting movement. Now the repeating positioning accuracy can reach 0.03 or 0.025mm, and the spindle positioning can reach ±0.01°. The control adopts PLC and NG control mode (CNC). In addition, according to the name of the moving parts, the workpiece movement and the sensor movement are divided into two ways. The domestic machine is often the moving method of the workpiece, and the foreign machine tool is basically the transformer moving except for the short length of the workpiece, which should become the development direction of the domestic general quenching machine.
The special quenching machine should be changed according to the specific quenching workpiece. We can elaborate and help choose the heat treatment parts according to the investment company. The imported equipment is advanced, reliable, stable, durable, safe and beautiful, but the price is quite expensive.
The important thing of foreign quenching equipment is to solve the high-efficiency, automation and reproducible process requirements, and is developing into complete sets, compact, online, numerical control, flexible and automatic. The equipment also gradually solves the following problems: (1) The energy controller is used to monitor the heating temperature of the workpiece, and the reproducibility is ±1%. According to Toggo's developed coil monitor, the input energy kW-S on the sensor is directly measured, replacing the original method of monitoring the energy of the oscillating component of the device. For example, the imported crankshaft quenching machine is provided with a pulsating heating or energy distributor. When the crankshaft is quenched, the different energy is allocated to achieve uniform temperature at the top dead center and the bottom dead center. (2) With the measurement and display instrument to increase the intelligent control: If the ball screw is induction hardened, it can automatically measure the elongation of the screw. If the elongation exceeds the difference, the heating power can be automatically reduced to reduce the elongation, and the relevant data can be printed and recorded; For example, the crankshaft quenching machine is equipped with a crankshaft bending deformation gauge to control the quenching deformation; the metering flowmeter directly displays the quenching liquid flow rate to control the quenching speed, and the water conductivity value of the water can be used to monitor the soft water quality. (3) It is equipped with a draft device to improve the working environment and reduce the error of measuring temperature. (4) Multi-axis devices, such as Weltductoin, which introduces 2-axis and 4-axis quenching machines, which can simultaneously process multiple workpieces with a length of 0.508m (20 in) and a weight of 9.08kg or less to improve production efficiency. (5) Random tempering treatment. Quenching on a quenching machine, followed by tempering with lower power, the two processes are completed on a quenching machine, which also saves loading and unloading and transportation, improves production efficiency, completes quenching and tempering in time, and guarantees quality. (6) One machine multi-station or one power supply quenching device with multiple machine tools. (7) The quenching machine and the flexible quenching machine tool of the processing part family appear, can automatically program a variety of quenching workpieces, automatically identify the quenching workpiece, and convert the workpiece in only 2 to 5 minutes, according to the selected parameters of the storage process for production, improve work efficiency.
About sensor design and manufacturing: When the foreign quenching equipment is provided, it is responsible for providing the sensor. This special sensor uses computer simulation technology to determine the main structure of the effective circle. According to the test, it can save 13~37% energy, not only for inner hole, plane heating, but also for outer ring workpiece heating. Fluxtrol Inc. has a sensor that can process magnetizers, called Power Inductors. In addition, because the sensor is exchanged, the switching chuck and the water and electricity are connected in one (3 to 15) s, which is already produced in China.
Recent advances in induction heat treatment processes (Mechanical Workers (Hot Working)): (1) Simultaneous Dual-Frequency Induction Heating Technology (SDF) for Gears: Inductive Hardening of Gears, People have been pursuing “contoured hardened layersâ€. The aim is to obtain high wear resistance of the tooth flanks and high fatigue resistance of the root portion under residual compressive stress. Although people have already understood the double-frequency gear quenching process, (in many places, it is also introduced as an advanced process), the two frequencies are obtained by converting two sets of coils, and the intermediate frequency is 3 to 10 kHz to heat the roots, and then the high frequency is 100 to 250 kHz. To heat the tooth surface, switch quickly. When the tooth surface reaches the quenching temperature, cut off the high frequency power supply, reduce the gear rotation speed, and spray the quenching water in the quenching water jacket to rapidly cool the tooth surface, the tooth top and the tooth root. Tooth-shaped quenching layer, there are also machine tools for this kind of process in foreign countries, but the process is complicated and the control must be strictly implemented.
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