Process analysis of heat treatment using high-frequency induction annealing equipment for the steel guide rails of the SI-220 CNC lathe bed

The material of the steel guide rail of the SI-220 CNC lathe bed is GCr15 steel. The heat treatment technical requirements: the surface hardness is 61-66HRC, and the flatness error is ≤0.5mm. In order to meet the above requirements, many manufacturers use high-frequency annealing equipment for heat treatment, with good results.

(1) Process flow

Forging - normalizing - spheroidizing annealing - planing - high temperature aging - fine planing, rough grinding - drilling - quenching, tempering and fine grinding.

(2) Heat treatment process

1) Normalize the fire. High-frequency induction annealing equipment is used, the heating temperature is (910±10) ℃, and it is cooled in flowing air. After normalizing, the grain size of the guide rail material is ≥ grade 5, the network carbide is ≤ grade 3, and the hardness is 270-390HBW.

2) Isothermal spheroidizing annealing. After heating at 790-810℃, the furnace is cooled to 690-710℃ and kept for 4-6 hours, and then the furnace is cooled to below 500℃ and released. The hardness is 197-207HBW, and the pearlite spheroidization level is level 2.

3) High temperature aging. For hanging heating, the furnace loading temperature does not exceed 200-300℃, and is heated to 600-650℃ at a speed of ≤150℃/h. After heating for 3 hours, it is quickly cooled to below 350℃ at a speed of ≤50℃/h and is air-cooled.

4) Quenching and tempering. High-frequency induction annealing equipment is used. The guide rail is preheated at about 600°C, then heated to the quenching heating temperature (860°C) and kept warm for 40-50 minutes. The oil is cooled to about 170°C and the thermal correction is taken out. Then perform low temperature tempering at 140-160℃ for 2.5-3h. The surface hardness of the guide rail should be controlled at 61-66HRC, and the flatness error should be ≤0.5mm.

Many manufacturers use the above process for heat treatment, and the hardness and wear resistance of the produced steel guide rails are greatly improved, meeting the needs of the work. What's even better is that this process is suitable for large-scale production and can greatly improve workers' production efficiency.