When the carbon content dissolved in the matrix has increased to a certain extent, the matrix of the high vanadium high-speed steel in the
J55 casing pipe plant has been transformed into a composite matrix containing mainly martensite and austenite, together with the strengthening effect of carbides. Niobium vanadium high speed steel thus obtains sufficient hardness and certain toughness. This high-vanadium high-speed steel wear resistance is good, the author believes that this should be attributed to the composite matrix containing martensite-based austenite, this composite matrix itself has a certain degree of hardness, can resist the intrusion of foreign objects, In addition, it also provides a strong support for strengthening the carbides of the matrix.
As the carbon content continues to increase, the martensite in the matrix transforms to high-carbon martensite, while the M7C3-type complex carbides, which are dominated by chromium and molybdenum, appear as fish bones at the grain boundaries. Thus, the low-toughness high-carbon martensite occurs. With the addition of fish bone M7C3-type composite carbides to the matrix, the toughness of high-speed vanadium high-speed steel decreases, and cracks in the J55 casing pipe plant are easily generated at the M7C3-type composite carbide. In other words, the M7C3 type complex carbide carbide casing plant mainly based on chrome key is disadvantageous for improving the impact wear performance of high vanadium high speed steel.
In summary, to obtain high-vanadium high-speed steel with better wear resistance, the carbon content must be controlled within a suitable range.
