	US 12,129,533 B2
	Ultra-fine grained steels having corrosion- fatigue resistance
Martin Bühler, Villa Mercedes (AR); and Matias Gustavo Pereyra, Villa Mercedes (AR)
Assigned to Tenaris Connections B.V., Amsterdam (NL)
Filed by TENARIS CONNECTIONS B.V., Amsterdam (NL)
Filed on Aug. 7, 2020, as Appl. No. 16/987,786.
Application 16/987,786 is a division of application No. 14/686,071, filed on Apr. 14, 2015, abandoned.
Prior Publication US 2020/0370152 A1, Nov. 26, 2020
Int. Cl. C21D 6/00 (2006.01); C21D 8/06 (2006.01); C21D 9/00 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/22 (2006.01); C22C 38/24 (2006.01); C22C 38/26 (2006.01); C22C 38/28 (2006.01); C22C 38/32 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01)

CPC C22C 38/001 (2013.01) [C21D 6/002 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/065 (2013.01); C21D 9/0075 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C22C 38/32 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (2013.01)]

22 Claims

1. A method of manufacturing a steel sucker rod, the method including:

providing a steel having a composition comprising iron and:

0.15-0.4 wt. % carbon;

0.1-1.0 wt. % manganese;

0.5-1.5 wt. % chromium;

0.2-0.35 wt. % silicon;

0.1-1.0 wt. % molybdenum;

0.01-0.05 wt. % niobium;

0.005-0.03 wt. % titanium;

0.0001 to 0.0025 wt. % boron;

0.01 to 0.1 wt. % aluminum; and

processing the steel, wherein the processing consists essentially of:

hot rolling the steel at a forging ratio greater than about 15 to form a steel sucker rod;

austenitizing the hot rolled steel sucker rod at a heating rate greater than about 100° C./sec to a temperature between a critical temperature (Ac3) and a maximum temperature that satisfies a formula Tmax=1025° C.-210° C.*sqrt(wt % C)+50° ° C.*wt % Mo to form an austenitized steel sucker rod;

quenching the austenitized steel sucker rod below about 100° C. at a rate to produce a martensitic microstructure to form a quenched steel sucker rod; and

tempering the quenched steel sucker rod at a temperature between 565° C. and a lower critical temperature (Ac1) to form a tempered steel sucker rod comprising at least 90 volume % tempered martensite;

wherein a time between a maximum austenitizing and quenching is between 1 second and 10 seconds;

wherein an austenitic grain size prior to quenching is 5 microns or less, and

wherein the processing does not comprise additional austenitizing or quenching steps.