Method of using rods resistant to hydrosulfuric acid

DETAILED DESCRIPTION I claim: 1.
A method of using a high-strength steel rod in an acid environment, comprising immersing and using said rod in an acid-environment in which the H.
sub.
2 S partial pressure in gaseous phase is at least 300 Pa or in which the H.
sub.
2 S content in liquid phase has a corresponding equilibrium pressure, said steel being carbon steel or low-alloyed steel in a cold-deformed condition wherein the degree of cold-deformation is at least 5% to increase resistance to sulfide stress cracking, and wherein said rod is used in said acid-environment in the cold deformed condition without subsequent toughening by austenitizing, said steel having a lower yield point of 550 MPa and consisting essentially of by weight: C 0-1.
20% Si 0-1.
0% Mn 0-3.
0% Cr 0-2.
0% Ni 0-1.
0% Mo 0-1.
0% Cu 0-1.
0% V 0-0.
3% Nb 0-0.
2% Ca 0-0.
05% Fe together with incidental ingredients and impurities up to 100%.
2.
A method according to claim 1, wherein the steel has the following composition by weight: C 0.
05-0.
55% Si 0.
10-0.
50% Mn 0.
6-2.
0% Cr 0.
0-0.
50% Ni 0.
0-1.
0% Cu 0.
0-0.
50% V 0.
0-0.
20% Nb 0.
0-0.
10% Ca 0.
0-0.
005% Fe together with incidental ingredients and impurities up to 100%.
3.
A method according to claim 1, including the step of pumping oil from an acid oil well, and wherein said rod is a pump rod in an oil well pump.
4.
A method according to claim 1 wherein the steel has been annealed following cold-deformation at a temperature of from between about 400.
degree.
C.
and about 675.
degree.
C.
5.
A method according to claim 4 wherein the steel has been annealed following cold-deformation at a temperature of from between about 500.
degree.
C.
and about 650.
degree.
C.
6.
A method according to claim 1 wherein the steel contains not more than 0.
005% by weight S.




Description:
The present invention relates to high-strength rods for use in acid environment, in which the H.
sub.
2 S partial pressure in gaseous phase may exceed 300 Pa or in which the H.
sub.
2 S content in liquid phase may have a corresponding equilibrium pressure and/or in which CO