The actual use of steel, in addition to iron, carbon and alloying elements, in the smelting process, will inevitably have to bring some impurities (such as manganese, silicon, sulfur, phosphorus, non-metallic impurities, as well as certain gases such as nitrogen , hydrogen, oxygen, etc.). These impurities on the quality of steel has a great influence.
A. Manganese
Manganese as impurities in the steel, generally less than 0.8%. It comes from as a steel-making raw materials, pig iron and deoxidizer ferromanganese. Manganese deoxidation ability to have a good, but also with the sulfur in the formation of MnS, to eliminate the harmful effects of sulfur. These reaction products enter the slag was removed, a small part remains in the non-metallic inclusions in steel. In addition, at room temperature, manganese can be dissolved in ferrite, a certain strengthening effect on the steel. Manganese can be dissolved in cementite and the formation of alloy cementite. Of manganese as the presence of a small amount of impurities, the performance impact of its steel is not significant.
Two. Silicon
Silicon impurities in the steel, generally less than 0.4%, also from pig iron and deoxidizer. At room temperature, silicon can be dissolved in the ferritic steel have a strengthening effect. Silicon as the presence of a small amount of impurities, the performance impact of its steel is not significant.
3. Sulfur
Sulfur impurities from pig iron and fuel into the steel. In the solid state, the solubility of sulfur in the iron is extremely small, but the form of FeS present in the steel. Of FeS plastic, so that the sulfur content of more steel brittle. More serious is that of FeS and Fe can form low melting point (985 ° C) eutectic distribution in the austenite grain boundaries. When the steel is heated to about 1200 ° C heat-pressure processing on the grain boundary eutectic melting intergranular combination destroyed, so that the steel along the grain boundary cracking in the process, a phenomenon known as hot brittleness. In order to eliminate the harmful effects of sulfur, must increase the manganese content in steel. Priority manganese and sulfur to form a high melting point (1620 ° C), manganese sulfide, and granular distribution in the grain, it has a certain shape at a high temperature, thus avoiding the hot brittleness. Sulfide is a non-metallic inclusions will reduce the mechanical properties of steel, and the formation of the thermal processing of fibrous tissue in the rolling process. Therefore, under normal circumstances, the sulfur is harmful impurities. To strictly limit the sulfur content in steel. But more of the sulfur content of steel, can be formed more of MnS in machining and MnS can play chip-breaking effect can improve the machinability of steel, sulfur favorable.
4. Phosphorus
Phosphorus from pig iron into steel, under normal circumstances, the phosphorus in steel can all be dissolved in the ferrite. Phosphorus there is a strong solid solution strengthening effect, so that the strength of steel, the hardness increases, but the ductility, toughness is significantly lower. This embrittlement phenomenon is more severe at low temperatures, it is known as the cold brittleness. General cold-brittle transition temperature is lower than the operating temperature of the workpiece in order to avoid the cold crisp. Phosphorus in the crystallization process, prone to coring, so that the high phosphorus content of the local area, resulting in cold-brittle transition temperature, which occurred in the cold crisp. Cold brittle structure in the alpine zone, and other low-temperature conditions with serious harm, in addition, the segregation of phosphorus to the steel in the formation of banded structure after hot rolling. Therefore, under normal circumstances, phosphorus is harmful impurities. Should strictly control the phosphorus content in steel. The phosphorus content of more brittle in the manufacture of shells steel and to improve the steel machinability aspects are favorable.
5 Non-metallic inclusions in the steel making process, a small amount of slag, refractories and smelting reaction products may enter the liquid steel, the formation of nonmetallic inclusions. Such as oxides, sulfides, silicates, nitrides, etc.. They will reduce the mechanical properties of steel, in particular reducing the ductility, toughness and fatigue limit. Severe, but also the steel in a sudden brittle fracture in the crack or the use of thermal processing and heat treatment. Nonmetallic inclusions also contributed to the steel to form a thermal processing of fibrous tissue and banded structure, so that the material is anisotropic. In severe cases, the transverse plastic is only half of the vertical, and the impact toughness is greatly reduced. Therefore, the important use of steel (such as bearing steel, spring steel, etc.) To check the number of nonmetallic inclusions, shape, size and distribution. In addition, the steel smelting process, are in contact with air, thus the liquid steel will always absorb some gases such as nitrogen, oxygen, hydrogen. On the quality of steel will have a negative impact.



Other News:
Impurity to influence on the performance of the steel
Bearing parts quenching oil choice
The house will vote on the ＂Chinese exclusion act＂ apology case
The six role car lubricating oil
How to guarantee the quality of the measurement work bearing industry
SKF bearing reliable work should pay attention to
The United States congress to house will history apologized for the Chinese excl
UK top court rejects Assange bid to reopen case