Ovako Sweden Ab

Ovako Steel Ab

Jan-Erik Andersson

Joakim Fagerlund

A method for manufacturing a steel ingot in a casting arrangement employs a vacuum vessel; an ingot mold arranged within the vacuum vessel, and a stirrer arranged to stir liquid steel in the ingot mold. The method employs the following steps: providing a liquid steel melt; filling the ingot mold with the liquid steel melt; applying a reduced pressure within the vacuum vessel; allowing the liquid steel melt to solidify into an ingot; and allowing the liquid steel melt to solidify under stirring within the ingot mold at a reduced pressure during solidification of the steel melt. The liquid steel melt includes a predetermined amount of carbon and; incidental impurity elements in the form of oxides. During stirring, the oxides are reduced by carbothermic reaction in which oxygen in the oxides and carbon in the steel melt form carbon-monoxide.

Method for manufacturing a steel ingot

There is provided a precipitation hardening stainless steel with the composition: C: 0.05-0.30 wt %, Ni: 9-10 wt %, Mo: 0.5-1.5 wt %, Al: 1.75-3 wt %, Cr: 10.5-13 wt %, V: 0.25-1.5 wt %, Co: 0-0.03 wt %, Mn: 0-0.5 wt %, Si: 0-0.3 wt %, and remaining part up to 100 wt % is Fe and impurity elements, with the additional proviso that the amounts of Al and Ni also fulfil Al=Ni/4&#xb1;0.5 in wt %. Further Cris in the interval 11-15.4 wt % and Niis in the interval 10.5-15 wt %. There is the possibility to have very low amounts of cobalt, well below 0.01 wt %. The precipitation hardening stainless steel displays, low segregation, high yield strength at elevated temperatures, and can also suitably be nitrided. The precipitation hardening stainless steel is more economical to manufacture compared to stainless steel according to the state of the art with the same strength at elevated temperatures.

Precipitation hardening stainless steel and its manufacture

There is provided a precipitation hardening steel with the composition: C: 0.05-0.30 wt %, Ni: 3-9 wt %, Mo: 0.5-1.5 wt %, Al: 1-3 wt %, Cr: 2-14 wt %, V: 0.25-1.5 wt %, Co: 0-0.03 wt %, Mn: 0-0.5 wt %, Si: 0-0.3 wt %, and remaining part up to 100 wt % is Fe and impurity elements, with the additional proviso that the amounts of Al and Ni also fulfil Al=Ni/3&#xb1;0.5 in wt %. There is the possibility to have very low amounts of cobalt, well below 0.01 wt %. The precipitation hardening steel displays, low segregation, high yield strength at elevated temperatures, high resistance against corrosion, and can also suitably be nitrided. The precipitation hardening steel is more economical to manufacture compared to steel according to the state of the art with the same strength at elevated temperatures.

Precipitation hardening steel and its manufacture

A process for production of a steel component having a hard, carbon rich dissolved surface and a tough, low carbon dissolved core, incorporating the following steps:

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Falun, Sweden

Jan-Erik Andersson