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What is spheroidizing annealing and isothermal annealing of seamless steel pipe?

The heat treatment methods of seamless steel pipes are spheroidizing annealing and isothermal annealing. What are their functions and purposes?

The effect of spheroidizing annealing

1. Obtain spherical pearlite and eliminate the slight network structure in the eutectoid

2. Reduce hardness, improve plasticity and toughness

3. Improve machinability

4. As a preliminary heat treatment before quenching


Application and description of spheroidizing annealing

Used to improve the structure of carbon tool steel, alloy tool steel and bearing steel with ωc greater than 0.65%. So as to obtain good processing performance, and prepare for the final thermal heat treatment


The effect of isothermal annealing

1. Using isothermal annealing, because the isothermal decomposition of austenite is carried out at a constant temperature, the resulting pearlite structure is uniform (especially for large cross-section parts), so as to obtain uniform mechanical properties

2. The use of isothermal annealing can make the steel which is difficult to obtain the pearlite structure by the general annealing method to obtain pearlite, so as to facilitate the cutting process and shorten the production cycle

Application and description of isothermal annealing

1. According to the purpose of isothermal annealing, it can be widely used in production, especially hypoeutectoid steel and eutectoid steel

2. For the annealing of alloy steel, isothermal annealing is almost used instead of full annealing.
 
3.The grain size and hardness obtained at different isothermal temperatures are different, the isothermal temperature is high, the crystal grains are coarser, and the hardness is low. On the contrary, the crystal grains are finer and the hardness is high.


Tips: ASTM A53 pipe (also referred to as ASME SA53 pipe) is intended for mechanical and pressure applications and is also acceptable for ordinary uses in steam, water, gas and air lines. It is suitable for welding and for forming operations involving coiling, bending, and flanging, subject to certain qualifications.
 

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