所属分类：公司动态 发布时间：2021-02-26 11:28:24 来源：http://www.lcnmb500.com 浏览量：
The content of H and N in Hardox400 liquid steel is higher than that of ordinary liquid steel. With the decrease of temperature and solidification of liquid steel, the solubility of H and N in steel decreases greatly. Especially during solidification, a large number of gases precipitate and form pores, especially hydrogen pores. The addition of rare earth can form more stable compounds with H and N in molten steel, such as re, reh3, Ren, etc., which can fix the gas in molten steel and reduce the porosity defects of wear-resistant plate castings.
Hardox400 wear-resistant plate is easy to oxidize in liquid state, and its main oxide inclusion is MnO, which distributes in the grain boundary and makes the grain boundary brittle. It is easy to produce hot cracking at high temperature, and its toughness decreases at room temperature and low temperature, and it is easy to crack under strong impact load. The addition of rare earth can further deoxidize the molten steel, reduce the oxygen content in the steel, reduce the distribution of MnO inclusions in the grain boundary, and improve the metallurgical quality of wear-resistant plate.
Because of the large radius of rare earth atoms, they mainly exist in the defects such as grain boundary holes after dissolving into Hardox400. Therefore, most of the rare earth atoms exist in the grain boundary in the form of internal adsorption, which reduces the interface energy of grain boundary and makes it difficult for carbides to nucleate at the grain boundary.
Rare earth elements are enriched on the grain boundary and filled with defects such as grain boundary holes, which prevent atoms from diffusing through the grain boundary holes and prevent carbides from growing along the grain boundary. Secondly, the addition of rare earth can reduce the amount of carbides in as cast grain boundary, inhibit the formation of continuous network of carbides in grain boundary, and reduce and eliminate the occurrence of needle like carbides in grain boundary.
The characteristics of the outer electron arrangement of rare earth elements are that the electrons in the SD layer are seriously unsaturated. Rare earth elements are strong carbide forming elements. Rec, rez, req and other special carbides can be formed between rare earth elements and carbon, and the melting point of the carbides is high, such as melting point higher than 2300 ℃, P absorption melting point higher than 2200 ℃, NDQ melting point higher than 2000 ℃.
When the system temperature drops to 960 ℃, these carbides become the crystal core of carbide precipitation, which increases the amount of dispersed carbides in austenite grains of wear-resistant plate.