Application of Filtration Technology in stainless Steel casting production
In recent years, China's casting industry has witnessed rapid development, with the annual output of casting reaching a new high, far ahead of other countries. The rapid increase of casting output in China, on the one hand, is caused by the substantial increase of casting demand in China, and on the other hand, it is the result of the transfer of casting production from developed countries and regions to China, resulting in the increase of casting export volume year by year.
While maintaining the status of casting as a major country, China's stainless steel casting technology has also been rapidly improved, gradually towards the goal of casting as a powerful country, although this road is still a long way. At present, China's new casting technology and new technology are mainly applied in: advanced molding line, more and more core making centers, a large number of applications of resin sand technology, casting steel VOD smelting, epc casting, computer simulation technology, and the application of rapid forming technology. The improvement of casting technology mainly benefits from several aspects:
1.Strict requirements for quality of export castings.
2. Domestic demand for high-quality castings is increasing rapidly, such as the rapid development of automobile industry and the rise of wind power industry.
3. Wholly foreign owned. Advanced and mature technology brought by the joint venture casting enterprise.
The application of filtration technology in casting has been developing rapidly in recent years. This technology can reduce inclusions, air holes and improve casting mechanical properties. In the 1950s, China reported the use of filtration technology. Filtering technology also experienced a development process: 60 s application of glass fiber filter, appeared many pass filter at the end of seventy, 78 foam ceramic filter, out in the eighty s honeycomb type filter, filtering technology application is the production of high quality casting a very main process method, widely applied in the western developed countries, China's awareness of its importance is becoming more and more profound.
Inclusions in casting
As is known to all, with a type is very important in the casting defects, account for about more than half of total defects, of all the castings are likely to have this kind of defects, but at different extent, the inclusion defect control standards based primarily on the casting performance. Use and decide, the more precision castings. Harsh working conditions more rigorous restrictions on inclusion defects of castings, such as automobile castings. Engine castings. Wind castings. Steam turbine castings. Machine tool castings...
The main inclusions of castings are: the slag of oxide containing calcium carbonate and iron, manganese, aluminum, unmelted inoculant particles, sulfide, magnesium silicate, residual solvent, sand and so on.
Sources of inclusions and methods of elimination
The generation of inclusions can be traced back to several links of casting production:
1. Charge: if the charge is seriously corroded or improperly stored, the inclusion content of metal liquid will exceed the standard;
2. Melting and solution treatment: in the process of inoculation, spheroidization and refining, if the process parameters are not appropriate, residues will enter the metal liquid;
3. Core sand strength: if the core sand strength is not enough to resist the impact of high-temperature metal liquid, it will cause sand washing;
4. Secondary oxidation: due to the casting structure or improper casting system design, the metal liquid splashes violently during the casting process to form secondary inclusions.
For the cause of inclusion, the corresponding methods to eliminate such defects mainly include:
1. Use qualified cleaning materials to avoid open storage;
2. Make reasonable melting and intermediate treatment process and strictly follow the regulations;
3. Ensure sufficient core strength, and use resin technology to use special materials in areas where the hot impact is strong;
4. Reasonably design the pouring system to avoid metal liquid splash, increase slag bag and extend the runner;
5. Use filters, etc.
6. Among them, the filter is the most effective measure to reduce and eliminate inclusions.
The following filters are commonly used in casting:
1. Glass fiber filter net: made of high-temperature glass fiber cloth with special treatment, poor filtering effect and cheap price
2. Straight hole filter: good filtering effect, high cost performance and wide application.
3. Foam ceramic filter: it is made of foam plastic as the skeleton, coated with ceramic paste and fired, with the best filtering effect and wide application.Refractory aggregate used for filtering different metals.
4. Silica gel foam ceramic filter for large casting.
5. Silica gel foam ceramic filter is a new type of filter, which has better high temperature performance than conventional foam ceramic filter. The size of the filter can be larger and filter large cast steel.
6. Filter mechanism
Taking foam ceramic filter as an example, the filtration mechanism is explained:
1. Mechanical filtration: when the metal liquid flows through the filter, inclusions larger than the aperture are blocked on the filter.
2. Rectification effect: the metal liquid is generally turbulent during pouring. After passing through the filter, the metal liquid tends to laminar flow state, which is conducive to the floating of the inclusions, reducing the impact on the shape and reducing the sand washing and secondary oxidation inclusions.
3. Filter cake: as the filtering process goes on, the filter hole will be gradually blocked and become smaller, so as to filter smaller inclusions.
4. Adsorption: foam ceramic filters have a large surface area, and the filter material has a strong adsorption effect on the inclusions. As the metal liquid flows through these curved channels, small inclusions can easily be absorbed onto the wall of the filter passage.
Filter usage principles
In principle, the filter can be placed in any position of the casting system, but the closer the casting is, the better the filtration effect. In order to prevent high-temperature iron water from crushing the filter, the bottom of the sprue should be avoided as much as possible.Due to the blocking effect of the filter on the metal liquid and the blocking of some mesh holes in the process of filtration, the filtering area should be 3-4 bits of the original gate area.
The benefits of filtering
1. Reduce inclusion defects: effectively reduce the number of inclusions, reduce and eliminate such wastes.
2. Improvement of mechanical properties: numerous tests have been conducted. Studies have shown that the mechanical properties of castings, especially plasticity, have been improved due to the reduction of inclusions
3. Improvement of machining performance: the reduction of the number of inclusions in the metal matrix can significantly improve the life of cutting tools.
4. Improve the process export rate: the effective function of filtration allows to simplify the complex pouring system originally designed to eliminate inclusions and improve the process output rate.
conclusion
Filtration technology is an effective method to reduce and eliminate inclusions in casting production. With the continuous improvement of casting technology and the continuous improvement of casting quality in China, people will have a deeper understanding of filtration technology and its application will be more and more
extensive.
While maintaining the status of casting as a major country, China's stainless steel casting technology has also been rapidly improved, gradually towards the goal of casting as a powerful country, although this road is still a long way. At present, China's new casting technology and new technology are mainly applied in: advanced molding line, more and more core making centers, a large number of applications of resin sand technology, casting steel VOD smelting, epc casting, computer simulation technology, and the application of rapid forming technology. The improvement of casting technology mainly benefits from several aspects:
1.Strict requirements for quality of export castings.
2. Domestic demand for high-quality castings is increasing rapidly, such as the rapid development of automobile industry and the rise of wind power industry.
3. Wholly foreign owned. Advanced and mature technology brought by the joint venture casting enterprise.
The application of filtration technology in casting has been developing rapidly in recent years. This technology can reduce inclusions, air holes and improve casting mechanical properties. In the 1950s, China reported the use of filtration technology. Filtering technology also experienced a development process: 60 s application of glass fiber filter, appeared many pass filter at the end of seventy, 78 foam ceramic filter, out in the eighty s honeycomb type filter, filtering technology application is the production of high quality casting a very main process method, widely applied in the western developed countries, China's awareness of its importance is becoming more and more profound.
Inclusions in casting
As is known to all, with a type is very important in the casting defects, account for about more than half of total defects, of all the castings are likely to have this kind of defects, but at different extent, the inclusion defect control standards based primarily on the casting performance. Use and decide, the more precision castings. Harsh working conditions more rigorous restrictions on inclusion defects of castings, such as automobile castings. Engine castings. Wind castings. Steam turbine castings. Machine tool castings...
The main inclusions of castings are: the slag of oxide containing calcium carbonate and iron, manganese, aluminum, unmelted inoculant particles, sulfide, magnesium silicate, residual solvent, sand and so on.
Sources of inclusions and methods of elimination
The generation of inclusions can be traced back to several links of casting production:
1. Charge: if the charge is seriously corroded or improperly stored, the inclusion content of metal liquid will exceed the standard;
2. Melting and solution treatment: in the process of inoculation, spheroidization and refining, if the process parameters are not appropriate, residues will enter the metal liquid;
3. Core sand strength: if the core sand strength is not enough to resist the impact of high-temperature metal liquid, it will cause sand washing;
4. Secondary oxidation: due to the casting structure or improper casting system design, the metal liquid splashes violently during the casting process to form secondary inclusions.
For the cause of inclusion, the corresponding methods to eliminate such defects mainly include:
1. Use qualified cleaning materials to avoid open storage;
2. Make reasonable melting and intermediate treatment process and strictly follow the regulations;
3. Ensure sufficient core strength, and use resin technology to use special materials in areas where the hot impact is strong;
4. Reasonably design the pouring system to avoid metal liquid splash, increase slag bag and extend the runner;
5. Use filters, etc.
6. Among them, the filter is the most effective measure to reduce and eliminate inclusions.
The following filters are commonly used in casting:
1. Glass fiber filter net: made of high-temperature glass fiber cloth with special treatment, poor filtering effect and cheap price
2. Straight hole filter: good filtering effect, high cost performance and wide application.
3. Foam ceramic filter: it is made of foam plastic as the skeleton, coated with ceramic paste and fired, with the best filtering effect and wide application.Refractory aggregate used for filtering different metals.
4. Silica gel foam ceramic filter for large casting.
5. Silica gel foam ceramic filter is a new type of filter, which has better high temperature performance than conventional foam ceramic filter. The size of the filter can be larger and filter large cast steel.
6. Filter mechanism
Taking foam ceramic filter as an example, the filtration mechanism is explained:
1. Mechanical filtration: when the metal liquid flows through the filter, inclusions larger than the aperture are blocked on the filter.
2. Rectification effect: the metal liquid is generally turbulent during pouring. After passing through the filter, the metal liquid tends to laminar flow state, which is conducive to the floating of the inclusions, reducing the impact on the shape and reducing the sand washing and secondary oxidation inclusions.
3. Filter cake: as the filtering process goes on, the filter hole will be gradually blocked and become smaller, so as to filter smaller inclusions.
4. Adsorption: foam ceramic filters have a large surface area, and the filter material has a strong adsorption effect on the inclusions. As the metal liquid flows through these curved channels, small inclusions can easily be absorbed onto the wall of the filter passage.
Filter usage principles
In principle, the filter can be placed in any position of the casting system, but the closer the casting is, the better the filtration effect. In order to prevent high-temperature iron water from crushing the filter, the bottom of the sprue should be avoided as much as possible.Due to the blocking effect of the filter on the metal liquid and the blocking of some mesh holes in the process of filtration, the filtering area should be 3-4 bits of the original gate area.
The benefits of filtering
1. Reduce inclusion defects: effectively reduce the number of inclusions, reduce and eliminate such wastes.
2. Improvement of mechanical properties: numerous tests have been conducted. Studies have shown that the mechanical properties of castings, especially plasticity, have been improved due to the reduction of inclusions
3. Improvement of machining performance: the reduction of the number of inclusions in the metal matrix can significantly improve the life of cutting tools.
4. Improve the process export rate: the effective function of filtration allows to simplify the complex pouring system originally designed to eliminate inclusions and improve the process output rate.
conclusion
Filtration technology is an effective method to reduce and eliminate inclusions in casting production. With the continuous improvement of casting technology and the continuous improvement of casting quality in China, people will have a deeper understanding of filtration technology and its application will be more and more
extensive.
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