	US 12,286,682 B2
	High strength steel product and a process to produce a high strength steel product
Shangping Chen, Beverwijk (NL); Ashwath Ravi, Amsterdam (NL); and Theo Arnold Kop, Haarlem (NL)
Assigned to TATA STEEL NEDERLAND TECHNOLOGY B.V., Velsen-Noord (NL)
Appl. No. 17/604,221
Filed by TATA STEEL NEDERLAND TECHNOLOGY B.V., Velsen-Noord (NL)
PCT Filed Apr. 30, 2020, PCT No. PCT/EP2020/062100 § 371(c)(1), (2) Date Oct. 15, 2021, PCT Pub. No. WO2020/221889, PCT Pub. Date Nov. 5, 2020.
Claims priority of application No. 19171942 (EP), filed on Apr. 30, 2019.
Prior Publication US 2022/0205058 A1, Jun. 30, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C21D 9/46 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/58 (2006.01)

CPC C21D 9/46 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0247 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/58 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)]

20 Claims

1. A high strength steel product with a chemical composition comprising:

0.20-0.55 wt. % C;

1.00-3.50 wt. % Mn;

0.05-2.50 wt. % Cr;

0.50-3.00 wt. % Si;

0.01-1.00 wt. % Al;

1.00-4.00 wt. % of Σ (Si+Al);

1.50-6.00 wt. % of Σ (Cr+Mn);

at most 0.050 wt. % P;

at most 0.020 wt. % S;

at most 0.010 wt. % N;

and optionally one or more of:

0.05-0.50 wt. % Cu;

0.05-1.00 wt. % Ni;

0.05-0.50 wt. % Mo;

0.01-0.10 wt. % Nb;

0.01-0.10 wt. % Ti;

0.01-0.10 wt. % V;

0.0003-0.0050 wt. % B;

0.01-0.15 wt. % of Σ (Nb+Ti+V);

0.0003-0.0100 wt. % of Σ (Ca+REM);

remainder iron and inevitable impurities;

and wherein the microstructure comprises at least 40% partitioned martensite and 60-90% of Σ (partitioned martensite+bainitic ferrite) and 0-15% of proeutectoid ferrite and 0-5% of fresh martensite and 0-1.5% of carbides and 5-35% of retained austenite; and

wherein the retained austenite comprises an average C content of 0.90% or more, wherein the microstructure comprises partitioned martensite+bainitic ferrite as a matrix of a mixture of the partitioned martensite+bainitic ferrite.