The heat treatment processes commonly used for steel pipes mainly include quenching, tempering, normalizing and annealing. The purpose is three: the final heat treatment to meet the performance requirements of the product, the heat treatment in the heat treatment state according to the requirements of the user and the standard, and the steel pipe manufacturing process. Heat treatment between processes. 
The heat treatment of steel pipes is to use a heating furnace, mainly including a quenching furnace and a tempering furnace. In the heat treatment process of steel pipe, the requirements for the heating furnace of steel pipe are: the temperature difference of the quenching furnace is ±10 °C, the temperature difference of the tempering furnace is ±5 °C, and the heating and heat preservation of different temperatures are carried out according to the process requirements and the steel grade (species) requirements. Commonly used heating furnaces include step-and-step retort furnaces and longitudinal pass-through furnaces. 
1. The step-and-step traverse heating furnace 
adopts a heat-resistant cast steel beam with a curvature to support the steel pipe. The steel pipe can rotate at an angle in each movement of the furnace, and the walking beam has a light-handling function during the movement. The utility model has the function of stopping the middle position and “stepping”, thereby ensuring uniform heating temperature of the steel pipe, and avoiding the large bending deformation of the steel pipe during the heat preservation or waiting time, and reducing the black mark of the steel pipe during the heating process. 
The continuous heat treatment production line can adopt the stepwise traverse heating furnace as the quenching and normalizing heating, and the fuel can be natural gas, mixed gas or blast furnace gas, etc., and the output thereof is high. 
2. The longitudinal-pass type heating furnace 
is arranged with an intermediate frequency induction heating device in the gap of the roller channel, and the steel pipe is heated and insulated by the intermediate frequency induction heating device during the conveying process of the roller conveyor. The intermediate frequency induction heating device can convert the ordinary AC power source into an intermediate frequency power source. When the steel pipe passes through the intermediate frequency induction heating device, an induced current is formed in the steel pipe, and the heat generated by the steel pipe is heated by the induced current. 
The medium frequency induction device is used as a heat treatment heating furnace for steel tubes, which has the advantages of low engineering investment, short construction period, fast heating speed, less oxidative decarburization, uniform heating and high temperature precision. In developed countries, medium frequency induction heating has been used as a mature process for steel tube heat treatment heating furnaces; in China, induction heating furnaces are mostly used in continuous heat treatment production lines for medium and small size steel pipes, and their production capacity is generally low.

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