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Seamless Steel Pipe Normalizing, Quenching and Tempering Process

Date:2021-04-22    keywords:seamless steel pipe normalizing, quenching and tempering process
1) Normalizing of seamless steel pipe
Process: The steel parts are heated to 40~60°C above the critical temperature, kept for a certain period of time, and then cooled and heat treated in the air.

Purpose: 
①Improve the organization structure and cutting performance;
②For parts with low requirements for mechanical properties, normalizing is often used as the final heat treatment;
③ Eliminate internal stress.

2) Seamless steel pipe quenching treatment
Process: The steel parts are heated to the quenching temperature, kept for a period of time, and then rapidly cooled in water, salt water or oil (individual materials are in the air).

Purpose: 
①To obtain higher hardness and wear resistance of steel parts;

②Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness, etc.



Seamless steel pipe quenching category:
a. Single liquid quenching
Process: The steel parts are heated to the quenching temperature, and after heat preservation, they are cooled in a quenching agent. Single-liquid quenching is only suitable for carbon steel and alloy steel parts with simple shapes and low technical requirements. When quenching, for carbon steel parts with a diameter or thickness greater than 5-8mm, use salt water or water cooling: alloy steel parts use oil cooling.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
② Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

b. Double liquid quenching of seamless steel pipe
Process: The steel parts are heated to the quenching temperature. After heat preservation, they are quickly cooled to 300~400C in water, and then moved into oil for cooling.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
② Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

c. Flame surface quenching of seamless steel pipe
Process: Spray a flame of mixed combustion of acetylene and oxygen on the surface of the part to quickly heat the part to the quenching temperature, and then immediately spray water on the surface of the part. Flame surface hardening is suitable for single-piece or small batch production. The surface requires hard and wear-resistant large-scale medium-carbon steel and medium-carbon alloy steel parts, such as crankshafts, gears and guide rails, which can withstand impact loads.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
② Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

d. Surface induction heating quenching
Process: Put the steel part in the inductor, the inductor generates a magnetic field under the action of a certain frequency of alternating current, and the steel part generates an induced current under the action of the magnetic field, so that the surface of the steel part is rapidly heated (2~10min) to the melting temperature. At this time, water is immediately sprayed onto the surface of the seamless steel pipe. The seamless steel pipe quenched by surface induction heating has a hard and wear-resistant surface, while the core maintains good strength and toughness. Surface induction heating quenching is suitable for medium carbon steel and alloy steel pipes with medium carbon content.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
②Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

3) Tempering treatment of seamless steel pipe
Process: The quenched steel parts are heated to below the critical temperature, kept for a period of time, and then cooled in air or oil. Tempering is carried out immediately after quenching and is also the last process of heat treatment.

Purpose:
① Obtain the required mechanical properties. Under normal circumstances, the strength and hardness of parts after quenching are greatly improved, but the plasticity and toughness are significantly reduced, and the actual workpiece conditions of the parts require good strength and initial properties. After selecting an appropriate tempering temperature for tempering, the required mechanical properties can be obtained.
② Stable organization and stable size.

③ Eliminate internal stress.


Tips: ASTM/ASME A53/SA53 seamless and welded steel pipe is a general, all-purpose pipe used in generator plants, refineries, compressor stations, natural gas transmission, and steam conduction. It is acceptable for welding, flanging, and bending.

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