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Treatment of tempering machine castings and attention matters


Treatment of tempering machine castings and attention matters
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Aerospace, shipbuilding, automobile manufacturing, power generation equipment is to promote the development of machine tool casting industry accelerator they are the main customers of machine tool casting industry, also has a great role in promoting the development of national economy, all become the key to promote the development of machine tool casting industry. Machine tool castings in four key areas of demand in China “national medium and long-term science and technology development plan outline (2006-2020)” specified “high-end CNC machine tools and basic manufacturing equipment” science and technology major projects to “focus on development of aerospace, shipbuilding, automobile manufacturing, power generation equipment manufacture and so on need to high-grade CNC machine tool” and “gradually improve China’s high-end CNC machine tools based manufacturing complete sets of equipment with independent development ability, satisfy the basic requirement of domestic main industry of manufacturing equipment”. By 2020, the independent development ability of high-grade CNC machine tool and basic manufacturing equipment, including machine tool casting, machine tool workbench and assembly platform, will be formed. The overall technical level will enter the international advanced ranks, and some products will be internationally leading. Set up a complete functional component research and development and supporting capacity; Forming a technological innovation system with enterprises as the main body and the combination of production, education and research; To cultivate and establish a high-quality research and development team, no matter from the perspective of market, or to promote the development of national economy, China should focus on the development of aerospace, shipbuilding, automobile manufacturing, power generation equipment in the four fields of machine tool casting.


Principle of casting method selection for machine tool castings: sand mold casting is preferred for machine tool castings. The main reason is that sand mold casting has lower cost, simpler production process and shorter production cycle than other casting methods.When the wet type can not meet the requirements, then consider the use of clay sand table dry sand type, dry sand type or other sand type.The weight of a wet sand clay casting can range from a few kilograms to dozens of kilograms, while that of a dry clay casting can reach dozens of tons.Machine tool casting casting method should be suitable for mass production, low-pressure casting, die-casting, centrifugal casting and other casting methods, because of the expensive equipment and mold, so only suitable for mass production, machine tool casting can be a single casting can also be mass production.

  Large machine tool casting is one of the necessary structures for industrial development. The design improvement method of machine tool casting for mechanical stability is to clean up the castings. The cleaning is to improve the surface quality of castings.For small pieces, first use hexagonal drum for a rough cleaning, and then use shot blasting cleaning turntable on the second fine treatment, and finally use their own dust removal equipment grinding machine finishing, qualified brush anti-rust paint into the warehouse.

The influence of cast iron smelting and molten iron casting quality on casting surface quality is mainly reflected in two aspects:

  1. The content of impurities in molten iron, especially the content of iron oxide, is easy to produce slag inclusion or slag porosity on the surface of castings;
  2. Gas content in molten iron, high gas content makes it easy for casting to produce pores on the surface or under the skin.The main measures we take are to raise the temperature of molten iron, establish a perfect cupola detection system, and ensure the cupola is in a normal state.The selection of process parameters has a great influence on the dimension precision and profile resolution of casting.After many process tests, each process parameter is carefully selected.

Matters we have pay more attention to during the production of high-quality machine tool casting:

  1. Design technology of machine tool casting.During design, in addition to according to the working conditions and the metal material performance to determine machine tool castings geometric shape, size, also must from the perspective of the casting alloy and casting characteristics to consider the rationality of the design, namely the obvious size effect and solidification, shrinkage, stress and other problems, in order to avoid or reduce casting copper pieces composition segregation, deformation, cracking and other defects.
  2. Reasonable casting process. According to the casting structure, weight and size, casting alloy characteristics and production conditions, choose the appropriate parting surface and modeling, core method, reasonable setting of casting bars, cooling iron, riser and casting system.To ensure high quality casting.
  3. Quality of raw materials for casting. The quality of metal charging, refractory, fuel, flux, metamorphant and casting sand, molding sand binder, coating and other materials is not up to standard, which will cause the machine tool casting defects such as porosity, pinhole, slag inclusion, sand adhesion, affect the appearance and internal quality of the casting, serious casting scrap.

 4.  Process operation, to develop reasonable process operation procedures, improve the technical level of workers, so that the process procedures are correctly implemented.

Usage of tempering of machine tool castings.

1. Reduce brittleness, eliminate or reduce the internal stress, there is a lot of internal stress and brittleness after quenching steel pieces, such as not timely tempering will often make steel pieces deformation or even cracking.

2, Obtain the mechanical properties required by the workpiece, the workpiece after quenching high hardness and brittleness is large, in order to meet the requirements of different properties of various workpieces, the hardness can be adjusted through appropriate tempering coordination, reduce brittleness, get the required toughness, plasticity.

3, Stable workpiece size.

4, For some alloy steels that are difficult to soften after annealing, high temperature tempering is often used after quenching, so that the carbides in the steel are properly gathered, the hardness is reduced, to facilitate cutting.

Why iron parts of large machine tools need tempering treatment:

Iron and steel is the most widely used material in the mechanical industry, steel micro-structure is complex, can be controlled by heat treatment, so the heat treatment of steel is the main content of metal heat treatment. In order to meet the requirements of mechanical, physical and chemical properties of machine tool castings, heat treatment process is necessary in addition to rational selection of materials and various forming processes. In addition, aluminum, copper, magnesium, titanium and other alloys can also change their mechanical, physical and chemical properties through heat treatment, in order to obtain different performance. Integral heat treatment is a metal heat treatment process in which the castings are heated as a whole and then cooled at an appropriate rate to change the overall mechanical properties of the machine tool castings.

Tempering treatment is through a process of cast iron platform will demand, after processing of cast iron platform features are: first, to get artifacts of the mechanical functions of the requested, cast iron platform after quenching hardness, high brittleness is big, in order to satisfied the request of the different functions of various casting can be adjust by appropriate tempering hardness, decrease the brittleness, get needs patience, plastic; Secondly, it can reduce the brittleness of cast iron platform, eliminate or reduce the internal stress, there is a great deal of internal stress and brittleness after quenching steel pieces, such as not timely tempering usually makes steel pieces deformation and cracking; Finally, as for the alloy steels that are difficult to soften after annealing, high temperature tempering is often used after quenching to make the carbides in cast iron platform steels properly gather, so as to reduce the hardness and facilitate cutting. Therefore, we must not only request tempering treatment, but also do a good job in this process, so as to facilitate the development of our company and career.

Any type of cast iron platform equipment on the market, need to be specially tempered and aging process and the importance of dealing with cast iron platform any type of cast iron platform equipment on the market, all need through special tempering and aging fixture processing, all regular cast iron platform production process is complicated, to producers need to be taken seriously. However cast equipment of the tempering treatment is necessary, in the fixture tempering treatment needs to be placed within the kiln and the kiln internal temperature to 550 ℃ in eight hours and need to keep five hours. And then need to be dropped to below 200 ℃ within the kiln need to be able to keep two to four days. This is the process of tempering the cast iron platform fixture. Through these special tempering treatments, the corresponding HB and HT parameter standards can be met.

 All of main casting of producing CNC machines in  WMTCNC are all processed with Treatment of tempering 

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