Welcome India Customer to Duolin Accept the 2 Production Line of Long Bar Heat treatment

Welcome India Customer to Duolin Accept the 2 Production Line of Long Bar Heat treatment

This is the second time our customer visit us came in November 2025,first time to discuss with our engineer time for production line of long bar continous hardening and tempering solution.

After confirm the purchase order,Duolin took 2 months to finished the 2 production line,customer come in January to check the process of fully automatic long bar heat treatment line,they are very happy with the surface and core hardness,trust our new cooperation will bring new economy increase point for customer in 2026.

What is long bar Thread Bar heat treatment production line?

The steel bar induction hardening and tempering equipment is a non-standard customized heat treatment production line,mainly composed of a medium-frequency power supply,induction heater,spray cooling system,tempering system, roller conveyor,and PLC control system. Its core principle is to use the electromagnetic induction effect to rapidly heat the steel bar to the critical temperature,and then obtain ideal comprehensive properties through quenching and tempering.

Duolin long bar heat treatment line can process diameter 6 to 150mm length 1000 to14000mm,long bar thread bar  pipe can be heat treated.

Induction heating

Alternating current is converted into medium-frequency current by induction power supply,which flows into a ring inductor,generating an alternating magnetic field on the surface of the steel bar,forming an induced current and rapidly raising the temperature.The multi-zone heating design ensures uniform heating of the diameter 6 to 150mm steel bar,avoiding excessive temperature differences between the surface and the core.

Induction hardening process

After the steel bars are heated to 850 to 920 celcius degree,they immediately enter the spray system.Cooling water is sprayed evenly from spray water ring,and the cooling rate and the depth of the hardened layer are controlled by segmented flow rate adjustment,generally within the range of 2 to 6 mm.This step determines the high-hardness layer on the surface of the steel bars.

Induction tempering

The steel bar retains significant residual stress after quenching,making it prone to cracking if no tempering process.Induction tempering typically employs induction heating or resistance heating to raise the steel bar to 500 to 650 celcius degree,relieving stress and improving toughness. By carefully controlling the tempering temperature and time,a combination of high strength and high toughness can be achieved.

Automation and Monitoring

The entire production line utilizes PLC,infrared temperature measurement, and flow monitoring to achieve closed-loop control. Customer can monitor heating temperature,cooling flow rate,and tempering curves in real time,ensuring each bar same heat treatment quality.