Manufacture method of vermicular cast iron steam cylinder cover

Abstract

The invention relates to a manufacture method of a vermicular cast iron steam cylinder cover. The vermicular cast iron steam cylinder cover is manufactured by the following ingredients according to the following mixture ratio: 75 percent to 85 percent of foundry returns and 15 percent to 25 percent of waste steel. External desulfurization is carried out after the melting, the melting temperature is controlled to be higher than 1500 DEG C, the weight percent of sulphur in desulfurized molten iron is 0.008 percent to 0.2 percent, and ingredients after the refining comprise 3.70 percent to 3.80 percent of carbon, 1.50 percent to 1.60 percent of silicon, at most 0.30 percent of manganese, at most 0.50 percent of phosphorus and 0.008 percent to 0.012 percent of sulphur. The molten iron can be perfectly subjected to vermicularizing treatment, the vermicularity is controlled to be in a proper range, the influence on the vermicularity caused by sulphur content fluctuation is avoided, the casting rejection caused by unqualified vermicularity is reduced, and the cost is reduced. In addition, the vermicular shape can be perfectly controlled, further, the mechanical performance of the vermicular cast iron can be regulated, and the performance requirement of the steam cylinder cover is met.

Description

technical field [0001] The invention relates to a manufacturing method of a vermicular graphite cast iron cylinder head. Background technique [0002] The cylinder head is a one-piece casting with complex structure and uneven wall thickness. It is subjected to high pressure and repeated thermal loads during work, often causing cracking and leakage problems. Previously, the cylinder head was mostly cast with gray cast iron. Due to the limited performance of gray cast iron, Vermicular graphite cast iron is currently being replaced by vermicular graphite cast iron, which is a new type of cast iron material that appeared in the 1960s. Cast iron can have good strength, thermal conductivity, wear resistance, corrosion resistance and thermal fatigue resistance under the harsh conditions of high temperature, high pressure and poor lubrication. These properties can well meet the working requirements of the cylinder head, but due to At present, when vermicular graphite cast iron is u...

AI Technical Summary

Problems solved by technology

[0002] The cylinder head is a one-piece casting with complex structure and uneven wall thickness. It is subject to high pressure and repeated thermal loads during work, often causing cracking and leakage problems. Previously, the cylinder head was mostly cast with gray cast iron. Due to the limited performance of gray cast iron, Vermicular graphite cast iron is currently being replaced by vermicular graphite cast iron, which is a new type of cast iron material that appeared in the 1960s. Cast iron can have good strength, thermal conductivity, wear resistance, corrosion resistance and thermal fatigue resistance under the harsh conditions of high temperature, high pressure and poor lubrication. These properties can well meet the working requirements of the cylinder head, but due to At present, when vermicular graphite cast iron is used to manufacture cylinder heads with complex structures, the requirements for the control of molten iron are high. During the manufacturing process, the morphology and creep rate of worms are often not well controlled. If the requirements are not met, the qualified rate of the vermicular graphite cast iron cylinder head will be reduced and the production cost will be increased.