Paul J Kelly

US Patent:

20160177411, Jun 23, 2016

Filed:

Dec 18, 2015

Appl. No.:

14/974628

Inventors:

- Charlotte NC, US
Paul KELLY - Charlotte NC, US
David VAN AKINS - Charlotte NC, US
Christopher Ronald KILLMORE - North Sydney, AU

International Classification:

C21D 8/02
B22D 11/06
C21D 6/00
C22C 38/38
C22C 38/02
C22C 38/22
C22C 38/20
C22C 38/06
C22C 38/04
B22D 11/00
C22C 38/26

Abstract:

A hot rolled light-gauge martensitic steel sheet made by the steps comprising: (a) preparing a molten steel melt comprising: (i) by weight, between 0.20% and 0.35% carbon, less than 1.0% chromium, between 0.7% and 2.0% manganese, between 0.10% and 0.50% silicon, between 0.1% and 1.0% copper, less than 0.05% niobium, less than 0.5% molybdenum, and silicon killed containing less than 0.01% aluminum, and (ii) the remainder iron and impurities resulting from melting; (b) solidifying at a heat flux greater than 10.0 MW/mand cooling the molten melt into a steel sheet less than 2.0 mm in thickness in a non-oxidizing atmosphere to below 1080 C. and above Atemperature at a cooling rate greater than 15 C./s; and (c) hot rolling the steel sheet to between 15% and 50% reduction and rapidly cooling to form a steel sheet with a microstructure having by volume at least 75% martensite or martensite plus bainite, a yield strength of between 700 and 1300 MPa, a tensile strength of between 1000 and 1800 MPa and an elongation of between 1% and 10%.