Role, methods and process characteristics of heat treatment

Steel in the solid state of the heating to the booking temperature of the conduct, and in the temperature to maintain a period of time, and then it is cooled down at a certain rate, such a heat treatment process is called heat treatment, the machinery manufacturing industry to be widely used in this article to be a small editor of the Xianjie net to show to introduce to you, is the role of the method and process characteristics of these aspects of the situation, a piece to Understand it!

The role of heat treatment:

1. The purpose is to change the internal organisational structure of steel in order to improve its properties.

2、With the help of appropriate heat treatment, can greatly improve the steel'smechanical propertyThis will prolong the life of the machine parts.

3, the heat treatment process can strengthen metal materials, fully tap the potential of material performance, reduce structural weight, saving materials and energy, but also improve the quality of mechanical products, significantly extend the service life of machine parts, to achieve a top several or even a dozen.

4, the appropriate heat treatment process can remove the casting, forging, welding these thermal process brought about by various types of defects, so that the grain refinement, the segregation eliminated, so that the internal stress can be reduced, which allows the steel organisation and performance to become more uniform.

5, machine parts processing technology, heat treatment is an important process. Like the manufacture of high-speed steel for drilling, have to be prepared for heat treatment, improve the organisation of the forging blank, reduce the hardness to 207 to 255HB, before cutting. After processing the finished drill bit also have to carry out the final heat treatment, improve the hardness of the drill bit to HRC60 to 65, enhance wear resistance, and then fine grinding, used for cutting other metals.

In addition, heat treatment provides the surface of the workpiece with special physico-chemical properties, including but not limited to resistance to wear and corrosion.

Methods of heat treatment:

Firstly, normalising is a heat treatment process in which steel or steel parts are heated to a temperature above the critical point AC3 or ACM, which corresponds to the appropriate and suitable temperature, and then kept for a certain period of time, and then cooled down in an air-filled environment, to obtain the result of pearlitic type of organisation.

Annealing is such a heat treatment process, which is aimed at sub-eutectic steel workpieces, which are first heated to 20 degrees to 40 degrees above AC3, then undergoes a period of holding time, and then slowly cooled with the furnace, where the slow cooling can also be buried in sand or in lime, and then finally cooled in the air when it reaches below 500 degrees.

3, solid solution heat treatment is such a heat treatment process, the alloy is heated to a high temperature single-phase region, so that its constant temperature to maintain, to promote the excess phase can be fully dissolved into solid solution, followed by rapid cooling, in order to get the supersaturated solid solution.

4, aging: alloy after solution heat treatment, or after cold plastic deformation, after this, placed at room temperature, or in the case of slightly above room temperature to maintain, there will be such a phenomenon, that is, its properties will change over time.

5. Solid solution treatment, the purpose of which is to allow the various phases in the alloy can be fully dissolved, thereby strengthening the solid solution, and improve the toughness of the alloy as well as corrosion resistance, but also to eliminate stress and soften the treatment, in order to facilitate the alloy can continue to carry out the processing of moulding.

6、Ageing treatment: Heat at the temperature where the reinforcing phase precipitates, and keep warm to let the reinforcing phase precipitate and precipitate, so as to harden and improve the strength.

7, quenching: steel austenitising, with the appropriate cooling rate to cool, resulting in the workpiece in the cross-section, all or within a certain range, the occurrence of martensite and other unstable organisational structure transformation of a heat treatment process.

8, tempering: after quenching the workpiece is heated, so that it reaches a lower than the critical point AC1 appropriate temperature, to maintain a certain length of time, and then according to meet the requirements of the way to be cooled, so as to obtain the required organisation and properties of the heat treatment process.

9, steel for carbon and nitrogen co-infiltration: carbon and nitrogen co-infiltration embodied in the surface layer of steel at the same time into the carbon and nitrogen, this process. In the customary carbonitriding is also called cyanide, nowadays because the medium temperature gas carbonitriding and low temperature gas carbonitriding (also known as gas nitrocarburising) is more widely used. The main objective of gas nitrocarburising is to improve the hardness, wear resistance and fatigue strength of the steel. Low-temperature gas nitrocarburising uses nitriding as the main aspect, and its main objective is to improve the steel's resistance to wear and galling.

10, tempering treatment: In general, the quenching and high-temperature tempering combination of the heat treatment, customarily known as the tempering treatment. Tempering treatment will be used for a variety of important structural parts, especially like those in the alternating load conditions of the work of the connecting rod, bolts, gears and shafts. After tempering, a tempered sohnite organisation is obtained, which, when compared, has better mechanical properties than a normalised sohnite organisation of the same hardness. The hardness is determined by the high tempering temperature and is related to the tempering stability of the steel as well as to the cross-section size of the workpiece, which is usually in the range of HB200 to 350.

11, brazing: with brazing material will be two kinds of workpiece bonded together heat treatment process.

Process characteristics of heat treatment:

Heat treatment of metals is one of the most important processes in mechanical manufacturing. Compared with other processes, heat treatment usually does not change the shape and overall chemical composition of the workpiece, but rather changes the internal microstructure of the workpiece or changes the chemical composition of the surface of the workpiece to give or improve the performance of the workpiece, which is characterised by improving the intrinsic quality of the workpiece, which is generally not visible to the naked eye.

In order for metal workpieces to have the required mechanical properties, physical properties, and chemical properties, heat treatment is often indispensable in addition to the proper selection of materials and the use of various forming processes. Iron and steel are the most widely used materials in the mechanical industry, and the microstructure of iron and steel is so diverse that it can be controlled with the help of heat treatment, so the heat treatment of iron and steel is a major part of the metal heat treatment. In addition, aluminium, copper, magnesium, titanium and their alloys can also be heat-treated to change their mechanical properties, physical properties and chemical properties, so as to obtain different performance.

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