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Key Points of Annealing, Normalizing,Quenching and Tempering of Seamless Steel Pipes

Date:2019-11-18    keywords:annealing, normalizing, quenching and tempering,seamless steel pipe
1. Seamless steel pipe annealing operation method: After heating the seamless steel pipe to Ac3+30~50 degrees or Ac1+30~50 degrees or below Ac1, it is generally cooled slowly with the furnace temperature.
Objective: 1. Reduce hardness, improve plasticity, improve cutting and pressure processing performance; 2. Refine grain, improve mechanical properties, prepare for the next step; 3. Eliminate internal stress generated by cold and processing.
Application points: 1. Suitable for alloy structural steel, carbon tool steel, alloy tool steel, high-speed steel forgings, welded parts and raw materials with unsatisfactory supply conditions; 2. Generally annealing in the blank state.

2. Seamless steel pipe normalizing operation method: The seamless steel pipe is heated to 30 to 50 degrees above Ac3 or Accm, and then cooled to a temperature slightly larger than the annealing cooling rate.

Objectives: 1. Reduce hardness, improve plasticity, improve cutting and pressure processing performance; 2. Refine grain, improve mechanical properties, prepare for the next step; 3. Eliminate internal stress generated by cold and hot processing.

Application points: Normalizing is usually used as a pre-heat treatment process for forgings, welded parts and carburized parts. For low-carbon and medium-carbon carbon structural steels and low-alloy seamless steel pipes with low performance requirements, it can also be used as the final heat treatment. For general medium and high alloy steels, air cooling can lead to complete or partial quenching and therefore cannot be used as the final heat treatment process.

3. Seamless steel pipe quenching operation method: heating the seamless steel pipe to the phase transition temperature Ac3 or Ac1, holding for a period of time, and then rapidly cooling in water, nitrate, oil, or air.

Purpose: Quenching is generally used to obtain high-hardness martensite structure. Sometimes, when quenching some high-alloy steels (such as stainless steel and wear-resistant steel), it is to obtain a single uniform austenite structure to improve wear resistance and corrosion resistance.

Application points: 1. Generally used for carbon steel and alloy steel with carbon content greater than 0.3%; 2. Quenching can fully exert the strength and wear resistance potential of steel, but at the same time it will cause great internal stress. To reduce the plasticity and impact toughness of steel, it is necessary to temper to obtain better comprehensive mechanical properties.

4. Seamless steel pipe tempering operation method: reheat the seamless steel pipe after quenching to a temperature below Ac1, and after cooling, cool in air or oil, hot water and water.

Objective: 1. Reduce or eliminate the internal stress after quenching, reduce the deformation and cracking of the workpiece; 2. Adjust the hardness, improve the plasticity and toughness, and obtain the mechanical properties required for the work; 3. Stabilize the workpiece size.
Application points: 1. Keep the steel high temperature and wear resistance after quenching with low temperature tempering; use medium temperature tempering to improve the elasticity and yield strength of steel under the condition of maintaining certain toughness; to maintain high impact toughness Degree and plasticity, and high temperature tempering when there is sufficient strength; 2. General steel should avoid tempering between 230~280 degrees and stainless steel between 400~450 degrees, because there will be a temper brittleness.

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