Heat Treatment Of Seamless Steel Tubes

Heat treatment of seamless steel tubes is a process to improve the properties of metal materials and their products.Depending on the use, the material and its workpiece are heated to the appropriate temperature, insulated, and then cooled in different ways to alter the internal structure to achieve the desired performance.Heat treatment of seamless steel tubes is generally divided into annealing, normalizing, quenching, tempering, failure, chemical heat treatment and vacuum heat treatment.By heat treatment, the efficiency or life of the steel can be improved, and in some cases, more expensive special materials can be used instead of cheaper ordinary metal materials.The basic heat treatment methods of seamless steel tubes mainly include the following four forms:

1. Annealing
Annealing is a process in which a seamless steel tube is heated to a slightly higher or lower critical temperature for a period of time (ie, heat preservation) and then slowly cooled. Common annealing processes are classified as: diffusion annealing, full annealing, isothermal annealing, spheroidizing annealing, incomplete annealing, recrystallization annealing, and stress relief annealing.

2. Normalizing

Normalizing is a process in which a metal is heated to a temperature below its melting point and allowed to cool in air in order to make it more ductile. Normalizing is a process in which a metal is cooled in air after being heated in order to relieve stress.

3. Quenching
Quenching is a process in which a seamless steel tube is heated to a suitable temperature, insulated, and then rapidly cooled (usually cooled in water, oil or air) to convert supercooled austenite into martensite structure. Generally used to improve the hardness and strength of parts, or to change their physical and chemical properties (such as electrical conductivity, magnetic properties, corrosion resistance, etc.). Generally, the quenching methods include single-liquid quenching, two-liquid quenching, fractional quenching, and is othermal quenching.

4. Tempering
Tempering is a heat treatment process that alters the mechanical properties (typically ductility and hardness) and relieves internal stresses of a steel. Tempering allows carbon trapped in a martensitic microstructure to disperse, and enables the internal stresses to be released from the steel that may have been created from prior operations.