Introduction of metal heat treatment process


Introduction of metal heat treatment process

1. Annealing

Purpose:1 reduce the hardness, improve the plasticity, improve the cutting and pressure processing performance; 2 refine the grain, improve the mechanical properties, to prepare for the next process; 3 eliminate the internal stress generated by cold and hot processing.

Application points:1 Suitable for alloy structural steel, carbon tool steel, alloy tool steel, high-speed steel forgings, weldments and raw materials with unqualified supply status; 2 generally annealed in the blank state.

2, normalizing

Purpose:1 reduce the hardness, improve the plasticity, improve the cutting and pressure processing performance; 2 refine the grain, improve the mechanical properties, to prepare for the next process; 3 eliminate the internal stress generated by cold and hot processing.

Application points: Positive fire is usually used as a pre-heat treatment process for forgings, welds, and carburized parts. For low-carbon and medium-carbon carbon structural steel and low-alloy steel parts with low performance requirements, it can also be used as the final heat treatment. For general medium and high alloy steel, air cooling can lead to complete or partial quenching, so it can not be used as the final heat treatment process.

3. Quenching

Objective: Quenching is generally to obtain high hardness martensite organization, sometimes for some high alloy steel quenching, it is to obtain a single uniform austenite organization, in order to improve wear resistance and corrosion resistance.

Application points:1 is generally used for carbon content greater than 0.3% carbon steel and alloy steel; 2 quenching can give full play to the strength and wear resistance of steel potential, but at the same time will cause great internal stress, reduce the plasticity and impact toughness of steel, so it is necessary to Tempering to obtain better comprehensive mechanical properties.

4. Tempering

Purpose: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 by the work; 3 stabilize the size of the workpiece.

Application points:1 to maintain the high hardness and wear resistance of steel after quenching, use low temperature tempering; Medium temperature tempering is used to improve the elasticity and yield strength of steel under the condition of maintaining a certain toughness. High temperature tempering is used when maintaining high impact toughness and plasticity and sufficient strength. General steel should try to avoid tempering between 230 and 280 degrees and stainless steel between 400 and 450 degrees, because this will produce a temper brittleness.

5. tempering

Purpose:1 Improve the cutting performance and improve the degree of surface finish; 2 Reduce the deformation and cracking during quenching; 3 Obtain good comprehensive mechanical properties

Application points:1 Suitable for high hardenability alloy structural steel, alloy tool steel and high-speed steel; 2 can not only be used as the final heat treatment of various more important structures, but also as a pre-heat treatment of some tight parts, such as screw rods, to reduce deformation.

6. Aging

Purpose:1 Stabilize the structure of the steel after quenching and reduce the deformation during storage or use; 2 reduce the internal stress after quenching and grinding, and stabilize the shape and size.

Application points:1 is suitable for all kinds of steel after quenching; 2 is commonly used for tight workpieces that require no change in shape, such as tight screw rods, measuring tools, lathe bed chassis, etc.

7、Cold treatment

Purpose:1 All or most of the residual austenite in the quenched steel is converted to martensite, thereby improving the hardness, strength, wear resistance and fatigue limit of the steel; 2 Stabilize the structure of the steel to stabilize the shape and size of the steel.

Application points:1 steel parts should be cold treatment immediately after quenching, and then by low temperature tempering, in order to eliminate the internal stress during low temperature cooling; 2 cold treatment is mainly applied to alloy steel tight tools, measuring tools and tight parts.

8、flame heating surface quenching

Objective: To improve the surface hardness, wear resistance and fatigue strength of steel parts, and keep the core toughness.

Application points:1 For medium carbon steel parts, the general quenching layer depth is 2 to 6mm.

9、induction heating surface quenching

Objective: To improve the surface hardness, wear resistance and fatigue strength of steel parts, and maintain the toughness of the heart

Application points:1 for medium carbon steel and medium carbon alloy structural steel parts; 2 due to the skin effect, high-frequency induction quenching quenching layer is generally 1~2mm, medium frequency quenching is generally 3~5mm, high-frequency quenching is generally greater than 10mm.

10、carburizing

Objective: To improve the surface hardness, wear resistance and fatigue strength of steel parts, and maintain the toughness of the heart

Application points:1 for low carbon steel and low alloy steel parts with carbon content of 0.15~0.25, the general carburizing layer depth is 0.5~2.5mm;2 after carburizing, quenching must be carried out to make the surface martensite, in order to achieve the purpose of carburizing.

11、nitriding

Objective: To improve the surface hardness, wear resistance, fatigue strength and corrosion resistance of steel.

Application points: mostly used for medium-carbon alloy structural steel containing aluminum, chromium, molybdenum and other alloying elements, as well as carbon steel and cast iron, the general nitride layer depth is.0.025~0.8mm。

12、nitrocarburizing

Objective: To improve the surface hardness, wear resistance, fatigue strength and corrosion resistance of steel.

Application points:1 mostly used for low carbon steel, low alloy structural steel and tool steel parts, generally nitrided layer depth of 0.02~3mm;2 after nitriding, quenching and low temperature tempering.

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