JPH0143018B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an austenitic stainless steel cast steel having high strength and high fatigue strength and used as a material for cast steel products such as runners, propellers, valves, etc., which are used in severe corrosive environments such as seawater and acidic rivers. In recent years, due to demands for resource and energy conservation, the conditions under which power plants are used have become more severe, and they are also forced to be used in environments with severe corrosive conditions that have not been used in the past. Conventionally, austenitic stainless cast steels such as SCS14 have been used in the above-mentioned corrosive environments, but these have low strength levels and do not have satisfactory corrosion fatigue strength. The purpose of the present invention is to reduce the Ni content and add N to the basic chemical composition of conventional austenitic stainless steel cast steel, namely SCS14, to achieve high strength and high corrosion fatigue. Our goal is to provide austenitic stainless cast steel that can be used in runners, propellers, valves, etc. used in corrosive environments. The austenitic stainless steel cast steel of the present invention includes, in weight percent, C0.12% or less, Si1.0-1.5%, Mn1.5% or less, Cr17-20%, Ni8-11%, Mo1-5%,
Consists of 0.05-0.15% N, the balance Fe and unavoidable impurities. Next, the reasons for limiting each component of the present invention will be explained. C is an essential element for increasing the strength level, but it forms carbides and significantly impairs corrosion resistance, so the content was limited to 0.12% or less in consideration of strength and corrosion resistance. Si is an effective deoxidizing agent and is inevitably included in the normal steelmaking process.
% or more, but if it is contained more than 1.5%, the sigma phase tends to precipitate and become brittle, so the content should be 1.5% or less. Like Si, Mn is effective as a deoxidizing agent and for improving oxidation resistance. However, increasing its content would result in a decrease in strength, so it was limited to 1.5% or less. Cr has a passivation effect in a corrosive environment and is an essential element for achieving the functionality of stainless steel.If it is less than 17%, appropriate strength cannot be obtained. If it exceeds, embrittlement becomes noticeable, so it was limited to 17 to 20%. Ni is dissolved in solid solution in the matrix to maintain corrosion resistance, strengthen it as a solid solution, and increase toughness. Further, although 8% or more is necessary to stabilize the austenite phase, it has the opposite effect on strength, so the upper limit was set at 11%. Mo is an element that significantly improves corrosion resistance against local corrosion when coexisting with Cr, but if it is less than 1%, it is insufficient, and if it is more than 5%, the effect will be saturated and it will become brittle, so it is limited to 1 to 5%. did. N is an effective element that not only strengthens the matrix but also secures strength without impairing toughness and ductility, and its effect appears at 0.05% or more. However, if it exceeds 0.15%, the ductility is inhibited, so it is limited to 0.05 to 0.15%. Next, examples of the present invention will be explained in comparison with conventional steel. Table 1 shows the chemical composition of the examples of the present invention in comparison with that of conventional steel. Table 2 shows the mechanical properties of each steel in Table 1. As is clear from Table 2, the tensile strength of the conventional steel is 42.2Kg/mm ² and 45.5Kg/mm ² , whereas that of the steel of the present invention is 55Kg/mm ² or more, which is significantly superior. , ductility and toughness (Sharpey impact value) are approximately the same, and the steel of the present invention is significantly superior in seawater corrosion fatigue strength.

【table】

[Table] As explained above, the steel of the present invention has a higher
It has excellent strength and corrosion fatigue strength, and exhibits extremely excellent performance as a material for runners, propellers, valves, etc. used in harsh corrosive environments such as seawater and acidic rivers.

Claims (1)

[Claims] 1 Weight% C0.12% or less, Si1.0-1.5%, Mn1.5
% or less, Cr17~20%, Ni8~11%, Mo1~5%,
Austenitic stainless steel cast steel with high strength and high corrosion fatigue strength, characterized by consisting of 0.05~0.15% N, the balance Fe and unavoidable impurities.