How to solve pores and slag inclusion in stainless steel precision casting
Stainless steelPrecision castingStoma solution? First of all, you have to understand the cause of the pores, that is, the incomplete deoxygenation leads to the pores, and then carry out effective deoxygenation. Stainless steel casting generally requires two deoxidation, initial deoxidation and final deoxidation. The deoxidizer and deoxidation process must be reasonable to ensure the quality of stainless steel castings.
1,For the deoxidation of stainless steel smelting stage, firstly use manganese (electrolytic manganese flakes)99.7, Which all have national standards) and75#Ferrosilicon undergoes initial deoxidation, which can remove most of the oxygen in the molten steel. For example, it can reach70-80%, But you must not think that everything is going well and everything is fine. The culprits that cause the casting defect rate are often those who are "silent" and "stubborn".10%Oxygen molecules free from the French Open.
2, For those stubborn oxygen, the initial deoxidation process or electrolytic manganese and ferrosilicon are powerless. Temperature and deoxidation capacity determine that the initial deoxidizer has completed its task. Then who will complete the fatal blow to the residual oxygen? The answer is: final deoxidizer or final deoxidizer! The final deoxidizer is generally a so-called composite deoxidizer with two or more components. A large number of practices have shown that when a composite deoxidizer containing multiple elements enters the molten steel, it not only cooperates with each other to perform their duties, but more importantly, they also congest each other. Compared with fighting alone, it can significantly increase its own deoxidation efficiency. Therefore, when designing composite deoxidizer products, how to do this1+1=3The idea of is a very important design element. Of course, there are other important indicators for composite deoxidizers, which seem not worth mentioning, but they are indispensable.
For example, aluminum has a very high oxygen affinity and has a particularly good deoxidation effect, but the problem is that aluminum has a small specific gravity and burns seriously. What should I do? Now we know that it can be added through large cans of bulk aluminum,The caisson method of adding aluminum and aluminum wire feeding process achieves the maximum deoxidation efficiency. If it is only the deoxidizing ability of aluminum itself, there is no doubt about it, and inserting into the bottom of molten steel becomes a key issue. Of course, aluminum deoxidation may also bring alumina insoluble fine particles to stainless steel. In addition, the aging time for aluminum deoxidation is very short. Therefore, it is very cautious to use aluminum for stainless steel deoxidation.
Some deoxidizers will be compounded with rare earth elements to achieve special purposes. However, in my own experience, we must be more careful. Whether there are rare earths is a problem. Second, are you sure that adding rare earths is appropriate? It may be just a gimmick!
3,The price of deoxidizer, the electrolytic manganese used for initial deoxidation is general12000Up, ferrosilicon6000-8000, At present, the price of ferroalloys has risen rapidly. Many brothers in the surrounding industrial areas have stopped working. Of course, the prices of other raw materials have also risen. Environmental protection is also closely watched. The price mainly depends on the amount you purchase. Generally speaking, stainless steel casting companies don’t use much. Our casting output is monthly100A single purchase of about ton is no more than one ton and two tons. Composite deoxidizers, such as the rare earth deoxidizer of Baotou Rare Earth Institute, are currently not available3The effect is good, especially for castings that require mechanical properties. Its Ganghua brand stainless steel composite deoxidizer has good effect. The price is not bad.1.9About ten thousand yuan, there are many deoxidizer companies in Henan. They have not tried it and there is no need to test them. The price is surprisingly low, only a few thousand yuan to ten thousand yuan, think about the price of ferrosilicon.6000-8000It is estimated that it is used in the large furnace of the crude steel plant, and it has nothing to do with casting. Some companies say that the deoxidizer sold is imported, which is pure nonsense! China is the number one country exporting ferroalloys, including deoxidizers, including rare earths, okay? Our current smelting process is electrolytic manganese99.7with75Initial deoxidation of silicon, adding amount0.10-0.15%, Ganghua brand stainless steel composite deoxidizer for final deoxidation, dosage0.2%,150The kilo stove does not carry the bag. It is important to measure the temperature and keep a record.
4, It is worth noting that the stainless steel casting deoxidizing process and deoxidizing agent are completely different from those used by steel mills. Please don’t put your heads on them. Especially some masters in front of the furnace who work in steel mills have this inertial thinking. Slag diffusion deoxidation, while the foundry does not require direct precipitation deoxidation without slagging. In addition, the quality standard liquid is incomparable.
5, The small amount of pores in precision casting stainless steel is due to secondary oxidation or entrapment of molten steel during the pouring process, so pay attention to the design of the pouring system. Of course, there are other reasons such as mold shell baking, etc., which will not be discussed.