Graphitic steel compositions
AssigneeThe Timken Company
InventorsJames A. Brusso, George T. Matthews
Life of this patent
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Abstract
A machinable, graphitic steel is disclosed having a composition in weight % of about 1.0 to 1.5 total C; 1.0 to Si; 0.3 to 1.0 Mn; up to 2.0 Ni; up to 0.5 Cr; up to 0.5 Mo; up to 0.1 S; up to 0.5 Al; balance Fe and incidental impurities. The steel is hot worked and cooled to precipitate a controlled amount of graphite for improved machinability and to achieve a controlled amount of matrix carbon for enhanced physical properties. A matrix carbon content of between about 0.2 to 0.8 weight % is desired. The steel may be further heat treated to yield further variations in the microstructure and physical properties.
Claims23
A highly machinable graphitic steel consisting essentially of in weight % about 1.0 to 1.3 total C;
- 1.0 to 2.5 Si;
- 0.3 to 1.0 Mn;
- up to 2.0 Ni;
- up to 0.5 Cr;
- up to 0.5 Mo;
- up to 0.1 S;
- up to 0.5 A1;
- balance Fe and incidental impurities, said steel having a controlled matrix carbon content in the range of about 0.2 to 0.8 weight and wherein a balance of the total carbon content is in the form of graphite in an amount greater than about 0.4 weight %;
- said steel further having a carbon equivalent "CE" value defined by the formula:
- CE=% C+1/3 % Si maintained in a range of about 1.75 to 2.1.
A highly machinable graphitic steel consisting essentially of in weight % about 1.15 to 1.3 total C;
- 1.75 to 2.0 Si;
- 0.35 to 0.70 Mn;
- less than 0.06 S;
- 0.02 to 0.20 A1;
- less than 0.50 Ni;
- less than 0.1 of Cr;
- less than 0.1 Mo;
- balance Fe and incidental impurities, said steel having a controlled matrix carbon content in the range of about 0.2 to 0.8 weight % and wherein a balance of the total carbon content is in the form of graphite in an amount greater than about 0.4 weight %;
- said steel further having a carbon equivalent "CE"value defined by the formula CE=% C+1/3 % Si maintained in a range of about 1.75 to 2.1.
A process for making a graphitic steel article comprising the steps of:
- (a) providing a steel alloy having a composition consisting essentially of in weight % about 1.0 to 1.3 total C;
- 1.0 to 2.5 Si;
- 0.3 to 1.0 Mn;
- up to 2.0 Ni;
- up to 0.5 Cr;
- up to 0.5 Mo;
- up to 0.1 S;
- up to 0.5 Al;
- balance Fe and incidental impurities;
- (b) hot working the steel at a temperature of at least 1000.degree. C. to produce a hot worked shape;
- (c) cooling the hot worked shape to develop a microstructure comprising ferrite, pearlite and graphite and having a matrix carbon content of from about 0.2 up to 0. 8 weight % C with a balance of the total carbon being in the form of graphite in an amount greater than about 0.4 weight %;
- and
- (d) machining said shape to produce a finished article.
A process for making a graphitic steel article comprising the steps of:
- (a) providing a steel alloy having a composition consisting essentially of in weight % about 1.0 to 1.3 total C;
- 1.0 to 2.5 Si;
- 0.3 to 1.0 Mn;
- up to 2.0 Ni;
- up to 0.5 Cr;
- up to 0.5 Mo up to 0.1 S;
- up to 0.5 Al;
- balance Fe and incidental impurities;
- (b) piercing and hot working the steel at a temperature of at least 1000.degree. C. to produce an elongated, seamless tubular shape;
- (c) cooling the pierced and hot worked seamless tubular shape to develop a microstructure comprising ferrite, pearlite and graphite and subsequently thermally treating the tubular shape to develop a desired matrix carbon content of between about 0.2 and 0.6 weight % with a balance of the total carbon being in the form of graphite in an amount between about 0.4 to 1.1 weight % and to develop desired physical properties.
A graphitic steel consisting essentially of in weight % about 1.0 to 1.3 total C, having a matrix carbon content of about 0.2 to 0.6 with a balance of the C present in the form of graphite in an amount between about 0.4 to 1.1;
- 1.0 to 2.5 Si;
- 0.3 to 1.0 Mn;
- up to 2.0 Ni;
- up to 0.5 Cr;
- up to 0.5 Mo;
- up to 0.1 S;
- up to 0.5 A1;
- balance Fe and incidental impurities, said steel having a microstructure comprising ferrite, pearlite and spheroidal graphite and being highly machinable.
A graphitic steel article according to claim 21.
A highly machinable graphitic steel in a hot worked and cooled condition consisting essentially of in weight % about 1.0 to 1.3 total C;
- 1.0 to 2.5 Si;
- 0.3 to 1.0 Mn;
- up to 2.0 Ni;
- up to 0.5 Cr;
- up to 0.5 Mo;
- up to 0.1 S;
- up to 0.5 A1;
- balance Fe and incidental impurities, said steel having a controlled matrix carbon content in the range of about 0.2 to 0.8 weight % and wherein a balance of the total carbon content is in the form of graphite in an amount greater than about 0.4 weight % and having a microstructure consisting of ferrite, pearlite and graphite.
A highly machinable graphitic steel in a hot worked and cooled condition consisting essentially of in weight % about 1.15 to 1.3 total C;
- 1.75 to 2.0 Si;
- 0.35 to 0.70 Mn;
- less than 0.06 S;
- 0.02 to 0.20 Al;
- less than 0.50 Ni;
- less than 0.1 of Cr;
- less than 0.1 Mo;
- balance Fe and incidental impurities, said steel having a controlled matrix carbon content in the range of about 0.2 to 0.8 weight % and wherein a balance of the total carbon content is in the form of graphite in an amount greater than about 0.4 weight % and having a microstructure consisting of ferrite, pearlite and graphite.
Dependencies are inferred from the claim text.