US 5,849,116 A · Production method for steel material and steel pipe having excellent corrosion resistance and weldability

Abstract

A steel material and a steel pipe each exhibiting an excellent corrosion resistance in an environment containing a wet carbon dioxide and a small amount of hydrogen sulfide are produced at low cost and with high productivity, a steel slab which contains, in wt %, 0.01 to 0.6% of Si, 0.02 to 1.8% of Mn, 7.5 to 14.0% of Cr, 1.5 to 4.0% of Cu and 0.005 to 0.1% of Al, which reduces C to not more than 0.02%, N to not more than 0.02%, P to not more than 0.025% and S to not more than 0.01%, and whose balance consists of Fe and unavoidable impurities, is heated to a temperature of 1,100.degree. to 1,300.degree. C., hot rolling is finished at a rolling finish temperature of not less than 800.degree. C. and a cumulative rolling reduction quantity at a temperature not more than 1,050.degree. C. is at least 65%, and cooling is carried out at a cooling rate of less than 0.02.degree. C./sec to at least 500.degree. C. so as to substantially convert the metallic structure to ferrite.

Claims16

Dependent claims

A production method for a steel material having excellent corrosion resistance and weldability comprising the steps of:

heating a steel slab containing, in terms of percent by weight:
Si:
0.01 to 0.6%,
Mn:
0.02 to 1.8%,
Cr:
7.5 to 14.0%,
Cu:
1.5 to 4.0%,
Al:
0.005 to 0.10%, and reducing
C:
to not more than 0.02%,
N:
to not more than 0.02%,
P:
to not more than 0.025%,
S:
to not more than 0.01%, and
the balance consisting of Fe and unavoidable impurities, to a temperature within the range of 1,100.degree. to 1,300.degree. C.;
finishing hot rolling having a cumulative rolling reduction quantity at a temperature not more than 1,050.degree. C. of at least 65% and at a rolling finish temperature of not less than 800.degree. C.;
carrying out cooling at a cooling rate of less than 0.02.degree. C./sec to at least 500.degree. C.;
and
obtaining a steel material the metallic structure of which substantially consists of ferrite.

21 more elements

A production method for a steel pipe having excellent corrosion resistance and weldability, comprising serially making a steel pipe through the following steps 1 and 2 from a steel slab which contains, in terms of percent by weight, the following elements:

Si:
0.01 to 0.6%,
Mn:
0.02 to 1.8%,
Cr:
7.5 to 14.0%,
Cu:
1.5 to 4.0%, and
Al:
0.005 to 0.10%,
which reduces the following elements:
C:
to not more than 0.02%,
N:
to not more than 0.02%,
P:
to not more than 0.025%, and
S:
to not more than 0.01%, and
the balance of which consists of Fe and unavoidable impurities:
1 heating the slab to a temperature within the range of 1,100.degree. to 1,300.degree. C., finishing hot rolling within a temperature range where the metallic structure substantially comprises an austenite monophase, and also finishing hot rolling where a cumulative rolling reduction quantity at a temperature not more than 1,050.degree. C. is at least 65%, to thereby form a hot coil having a strip thickness of 3.0 to 25.4 mm, coiling said hot coil within a temperature range where the metallic structure substantially comprises the austenite monophase, and carrying out cooling at a cooling rate of less than 0.02.degree. C./sec. to at least 500.degree. C., and forming a steel strip the metallic structure of which substantially comprises ferrite;
and
2 slitting said hot coil into a selected width, continuously shaping it into a cylindrical shape and welding both ends of the steel strip by electric resistance welding to thereby form an electric resistance seam welded pipe.

20 more elements

Dependencies are inferred from the claim text.

Production method for steel material and steel pipe having excellent corrosion resistance and weldability

Life of this patent

Production method for steel material and steel pipe having excellent corrosion resistance and weldability

Life of this patent

Abstract

Claims16