Another process involving intense heat, precautions must be taken to make the cut at a sufficient distance from the body of the casting to avoid defects being introduced in casting due to local heating. Such an operation must be done before the final heat treatment. 10.3 in the case of casting prove defective causes of foundry in preparation, machining or erection, such casting may be rejected notwithstanding any previous certification test andtor satisfactory inspection.
NOTES 1 the austenitization temperature relatively high in combination with a content of high canses of labeled carbon decarburization of surface by the furnace atmosphere and a certain loss of manganese. The skin can therefore be Martensitic partiafly which can lead to the formation of cracks fine and little deep surface. These cracks for most applications are not functionally harmful ordirmzy, less than serious constraints impact or traction ate involved. This is for informatidrr only.
2. changes that occur in the surface composition of castings during heat treatment can produce a magnetic skin. This surface magnetism developed is generally not dangerous. It can be significantly reduced by grinding, if necessary. This is for information only.
3 (a) after heat treatment, the microstructure of the material is usually fully austenitic. However, in the case of a high section thickness, due to the relatively slow building ground speed and cooling, a significant amount of carbides separate during casting of origin. These carbides are quite slow to dissolve back into the austenite during heat treatment. Try to eliminate carbides of microstructure, especially in the interior regions of thick-walled castings can call for sustained periods of soaking very at a temperature of austenitizatioa. [Such prolonged, in turn, immersion coa] D result to some extent of the degradation of the surface, in the nature of the level, decarbonization, etc. growth as also of grain that may be harmful. Sailandra, the presence of a small percentage uf carbides of heavy castings section thickness, especially in the Interior, is tolerated as a practical compromise and is generally not dangerous. It is open to the parties to agree on the extent of the presence of carbides for a given section thickness. However, unless specifically agreed between the pafiics, or then stipulated in the investigation and the agenda, examination of the microstructure 51 is not a criterion for acceptance of castings to thk standard. 3 (b) to overcome or at least reduce, the problem of the presence of carbides in the condition of heat treatment and the loss of the endurance to some degree, for applications involving heavy thicknesses and high impact grades 4 and 5 are recommended.
If specified at the time of the investigation and order, the analysis of the product can be made from a test piece or of a representative flow melt everyone. Drilling for the analysis must be taken from pitch less than 6 mm under the surface of the melt, and so as to not harm the usefulness of any casting selected. The variation permitted in the analysis of the product of the limits specified in table 1 is ‘ be given in IS 6601.
NOTE – Contamination of drilling by drilling chips should be avoided. Drills BAUKJE’s best high speed steel, or exercises some of new tool materials, will be generally satisfactory for drilling of manganese steel. Manganese steel can be drilled better after annealing for several hours at 500 to 600 “C.