The application of filtering technology in stainless steel casting production

The application of filtering technology in stainless steel casting production
In recent years,Casting industry in China is developing rapidly and cast production is reaching a new record, that is over 2800 ton in year 2006 and goes ahead of other countries. While maintaining the casting great-power status, stainless steel casting technology in China has a rapid ascension, gradually to the casting power goal. At present, the new casting technology and process in china is mainly manifested in:advanced molding line,more and more core-making centers, a large number of applications of resin sand process, cast steel VOD smelting,lost foam casting,computer analog technology and the application of rapid prototyping technology,ect. The improvement in casting technology mainly benefits from below several aspects:
1,Strict requirements for quality of export castings.
2,Domestic demand for high quality castings rapidly increases, for example the rapid development of automobile industry,the rise of the wind power industry, ect.
3,the advanced and mature technology from foreign invested joint venture foundry enterprises.

Filtering technology application in the foundry is developing quickly in recent years, that Can have a significant effect for reducing the inclusions and blowhole defects and Improving the mechanical properties and processing performance of casting and gets more and more attention from foundry enterprises. Filtering technology application is a very important casting process in the production of main production high quality casting process high quality castings, that is widly used in western developed country and understanding of its importance in our country is becoming more and more profound.
The inclusions in the castings
As we all know,inclusion is a kind of very important type casting defects and it’s quantity is more than half of total defects. All the casting may have this defect and only severity is different.Standards for Inclusion defects control is based primarily on the casting properties and application. The control for inclusion defects is more strict for casting of harsh working conditions, for example, automobile castings,engine castings,wind power castings,the steam turbine castings and machine tool castings.
The main inclusions in casting:contains calcium carbonate and iron, manganese, aluminium oxide in the slag,not melt inoculant particles,sulfide,magnesium silicate,residual solvents and sand, ect.
The source of the inclusions and elimination methods
The generation of inclusions can be traced to multiple link of foundry production:
1,furnace burden:Serious corrosion or improper storage can make the metal fluid inclusions content exceeds;
2,Melting liquid processing:It will cause the child into the liquid metal under improper parameters and operation in the process of inoculation,spheroidizing,refining;
3,The strength of core sand:If the strength of core sand is insufficient to resist the impact of high temperature metal liquid, it will cause sand washing;
4,reoxidation:Because of the casting structure or improper pouring system design, liquid metal splash forms secondary inclusions in the process of pouring.
In view of the cause of inclusions, the corresponding methods to eliminate such defects are below:
1,Use qualified clean furnace charge, avoid in open air;
2,Formulate reasonable melting, intermediate process and strictly follow the operation;
3,Ensure enough the core strength of resin process, resin technology can be used and special materials can be used in heat shock strong part.
4,Reasonable design of gating system, avoid metal splash, increasing slag package, extend the sprue;
5,Using filters;
6,filter is he most effective measures to reduce the inclusion and blowhole defect.