SAND CASTING EQUIPMENT.

Preventing porosity in cast steel is the primary problem in casting production. However, porosity defects in castings produced by many steel casting plants are still high. Based on its own casting experience, xinyuanzhu group made the following summary of the causes of porosity in castings, hoping to be helpful to colleagues in casting enterprises
1. Furnace workers are inexperienced. They used to do cast iron. The hero is bold. He promised the boss that he did it if he hadn''t done cast steel. As a result, he was dumbfounded. If you can''t do it, just do it recklessly. As a result, there was a lot of waste.
2. In some cases, the smelting materials purchased by the steel casting plants are particularly poor, such as rusty materials, paint materials, thin materials, and coated materials. All these waste materials are filled into the electric furnace. They think that as long as these waste materials are turned into molten iron, they Can produce qualified steel castings! As a result, the products that came out were all waste products, wasted electric energy and labor.
3. Lack of laboratory equipment and laboratory personnel. In casting production, many foundries do not have laboratory equipment or have equipment without professional laboratory personnel. The data obtained by the test has large errors and has no reference value.
4. The process is extensive, and the ingredients, smelting and pouring are almost all right. A little bit here, a little bit there, the yield rate of cast steel parts produced by the whole process is very low. Therefore, only by strictly following the process requirements can the pore defects and other defects of steel castings be minimized.

Combining the above 4 points, Xinyuanzhu Group combined its own casting practice to summarize the reasons for the porosity of cast steel and the measures it took:
The production of steel castings is a work that can be completed through the joint efforts of multiple processes. There are many factors that affect product quality, and the causes of pores are also various. In order to enable people to better understand the causes and prevention methods of pores , We need to analyze and find solutions one by one from all aspects in order to reduce the occurrence of such problems.

The control of raw materials for smelting is a very important link. Let’s talk about raw materials for smelting. Try to avoid using all kinds of scrap materials recovered from the society, because the impurities in them are too complicated and will easily cause problems in the smelting process. The necessary trouble is to extend the smelting time, and the smelting process is not to cook the porridge as long as possible. With the extension of time, the content of various components in the molten steel changes at all times. For example, after the explosion in Tianjin last year, many cars reported It’s a waste. It’s said that it was sent to a steelmaking plant to make steel. Those who have done smelting must know how bad the scrap is. It is estimated that the masters who work at the units who have received this batch of scrap will be sad. It must be difficult to make such things into good steel.

Although most units now use the refining process, for some alloy materials that need to be added in the later stage of smelting, you must pay attention to the degree of baking, and it is strictly forbidden to add moisture, because the water will increase more than 1,000 times when it becomes a gas. Volume, which is a very big trouble for the degassing of molten steel.

The current ladle refining unit does not have the problem of baking ladle, but there will be a ladle baking problem when large pieces are cast in the furnace, especially those ladle that has not been used for a period of time, must be baked to the required temperature Otherwise, there will be a lot of gas involved in the molten steel.

Quality control of modeling materials is also a very important factor. The moisture content of quartz sand must be below the specified requirements, the modulus of the water glass adhesive must meet the process requirements, and the dust content of limestone sand must not exceed the specified requirements. Waste sand should be thrown away if the amount of dust exceeds the regulations. All of these are factors that affect gas generation and sand mold exhaust. If these things do not meet the requirements, it is impossible to solve the pore problem.

Process design is also a very important link. The determination of the position of the inner gate has a great influence on whether the molten steel enters the cavity smoothly. Improper setting will cause the turbulent flow of molten steel to easily involve the gas and cause the internal pores. The height of the inner nozzle is also The main reason for splashing is that this kind of pores are distributed in many parts of the casting and are internal, so the repair is extremely difficult and the casting is most likely to be scrapped, which is extremely harmful.
The setting of the riser and the air eye is also very important. In addition to the feeding function, the riser has a very important task is the exhaust function. If the air eye of some dark risers is not large enough, it will also make the mold The gas was not discharged in time and was re-entered into the molten steel. When using limestone sand as the inner cavity core, the air hole must be large enough. Because this kind of sand generates a large amount of air at high temperatures, it is very easy to cause choking during the casting process due to poor exhaust of the inner cavity core. The fire phenomenon eventually causes a large area of honeycomb pores on the upper surface of the casting, which is easy to make the casting scrap.

The control of the modeling operation process also plays a vital role in reducing the generation of pores. Some things in the operating procedures must be strictly implemented. The process does not make special requirements for the operating details of some conventional products, because those basic operating procedures have been The operation method has made detailed regulations and implementation methods, so the position and distance of the vent holes around the sand mold and the bottom must be made in accordance with the regulations. The vent holes at the bottom must be plugged with molding sand after baking. Their function is In the pouring process, the gas generated by the sand mold is smoothly discharged. If the gas is not discharged smoothly, it is easy to drill into the molten steel that has been filled with the sand mold to cause pores in the casting.

The pouring link is also a very important node. The hot air baking used now is a very good method. The hot air must be blown in from the gate, which will drive away the moisture in the refractory brick pipe. If it blows from the riser Hot air, the moisture in the horizontal gate cannot drive away the molten steel when it enters, it will be brought into the casting. The hot air can be removed within 30 minutes before pouring, and it should not take too long, otherwise the cooling process will be a moisture absorption process. Controlling the pouring temperature is also one of the important factors for the generation of pores. Lowering the temperature is of great significance to the reduction of intrusive pores and precipitating pores. The high temperature of molten steel will increase the amount of gas generated by sand and the high temperature of molten steel. The air volume will increase, so low-temperature pouring is a principle that must be followed in the production process of large castings.

The shortcomings of large ladle pouring of small parts, many thin-walled small castings are easy to form entangled pores if the pouring speed is too fast, because they do not have time to be discharged from the molten steel and solidify, such as the pores in some cylinder castings. They are pressure-bearing castings that need to be inspected by flaw detection. The repair of these defects is very difficult. It often causes the casting to be scrapped, which is a more difficult problem.

The calming time after the large-scale pouring hits the furnace and turns over the ladle also has a certain impact on the porosity of the castings. It is an involved process, which is also the reason for the porosity of many large castings after processing. As long as the production organization fully considers these factors affecting the quality of castings, this situation can be completely avoided.

All the problems and solutions mentioned above need to be taken seriously by every employee involved in this work, because these problems are no longer simply a product quality problem. In today''s fierce market competition, product quality is directly related to When the company survives, any problem that affects product quality is a big problem. It must be brought to the attention of relevant departments. As long as we pay attention to it, there will be no difficulties that cannot be solved, and all problems will not be problems. Xinyuanzhu Group is a Casting Supplier that can undertake: Steel casting, Pig iron gray iron casting, Ductile iron castings, Precision foundry, samples or drawings are welcome, and guests are welcome to visit the factory.