Bainitic steel materials and methods of making such materials

Patent metadata

Field	Value
Publication number	US-2016348200-A1
Application number	US-201414566455-A
Country	US
Kind code	A1
Filing date	Dec 10, 2014
Priority date	Dec 10, 2013
Publication date	Dec 1, 2016
Grant date	—

Abstract

Methods of making bainitic steels may involve austenitizing a quantity of steel by exposing the quantity of steel to a first temperature. A composition of the quantity of steel may be configured to impede formation of non-bainite ferrite, pearlite, and Widmanstätten ferrite. The quantity of steel may be heat-treated to form bainite by exposing the quantity of steel to a second, lower temperature. The second, lower temperature may be stabilized by exposing the quantity of steel to the second, lower temperature in the presence of a thermal ballast.

First claim

What is claimed is:

1 . A bainitic steel material, comprising:
between 0.62% and 0.78% by weight carbon;
between 1.5% and 2.5% by weight silicon;
between 1.75% and 2.5% by weight manganese;
between 0.22%and 0.5% by weight molybdenum;
between 1.0% and 1.8% by weight chromium;
between 0.0% and 0.3% by weight cobalt;
between 0.25% and 1.0% by weight aluminum; and
the balance consisting essentially of iron.

2 . The material of claim 1 , wherein:
the carbon occupies 0.7% by weight;
the silicon occupies 1.9% by weight;
the manganese occupies 2% by weight;
the molybdenum occupies 0.25% by weight;
the chromium occupies 1.4% by weight;
the cobalt occupies 0.15% by weight;
the aluminum occupies 0.75% by weight; and
the balance consists essentially of iron.

3 . The material of claim 1 , wherein the bainitic steel is free of nickel.

4 . The material of claim 1 , wherein a microstructure of the bainitic steel is between about 10% and about 20% by volume austenite, the austenite being interspersed throughout a bainite phase.

5 . The material of claim 1 , wherein a hardness of the bainitic steel is at least substantially uniform throughout the bainitic steel.

6 . The material of claim 5 , wherein the hardness of the bainitic steel is about 50 HRC or greater.

7 . The material of claim 6 , wherein the hardness of the bainitic steel is about 56 HRC or greater.

8 . The material of claim 1 , wherein a yield strength of the bainitic steel in tension is greater than about 1.5 GPa.

9 . The material of claim 1 , wherein an ultimate tensile strength of the bainitic steel is greater than about 2 GPa.

10 . The material of claim 1 , wherein a maximum strain at failure of the bainitic steel is about 4% or greater.

11 . A method of making a bainitic steel, comprising:
austenitizing a quantity of steel by exposing the quantity of steel to a first temperature, a composition of the quantity of steel being configured to impede formation of non-bainite ferrite, pearlite, and Widmanstätten ferrite;
heat-treating the quantity of steel to form bainite by exposing the quantity of steel to a second, lower temperature;
stabilizing the second, lower temperature by exposing the quantity of steel to the second, lower temperature in the presence of a thermal ballast; and
permitting the quantity of steel to cool.

12 . The method of claim 11 , further comprising homogenizing the quantity of steel by exposing the quantity of steel to a temperature greater than about 1,000° C. before austenitizing the quantity of steel.

13 . The method of claim 11 , wherein austenitizing the quantity of steel by exposing the quantity of steel to the first temperature comprises exposing the quantity of steel to a temperature of about 1,000° C.

14 . The method of claim 11 , austenitizing the quantity of steel, the composition of the quantity of steel being configured to impede formation of non-bainite ferrite, pearlite, and Widmanstätten ferrite, comprises austenitizing the quantity of steel, the composition of the quantity of steel being between 0.62% and 0.78% by weight carbon, between 1.5% and 2.5% by weight silicon, between 1.75% and 2.5% by weight manganese, between 0.22% and 0.5% by weight molybdenum, between 1.0% and 1.8% by weight chromium, between 0.0% and 0.3% by weight cobalt, between 0.25% and 1.0% by weight aluminum, and the balance consisting essentially of iron.

15 . The method of claim 14 , wherein austenitizing the quantity of steel comprises austenitizing the quantity of steel, the quantity of steel being free of nickel.

16 . The method of claim 11 , wherein heat-treating the quantity of steel comprises maintaining the quantity of steel exposed to the second, lower temperature for 2 days or more.

17 . The method of claim 16 , wherein maintaining the quantity of steel exposed to the second, lower temperature for 2 days or more comprises maintaining the quantity of steel exposed to the second, lower temperature for at least 4 days.

18 . The method of claim 11 , wherein exposing the quantity of steel to the second, lower temperature comprises exposing the quantity of steel to a temperature of between 200° C. and 300° C.

19 . The method of claim 11 , wherein exposing the quantity of steel to the second, lower temperature in the presence of a thermal ballast comprises surrounding the quantity of steel with pre-heated alumina when exposing the quantity of steel to the second, lower temperature.

20 . The method of claim 19 , wherein permitting the quantity of steel to cool comprises air-cooling the quantity of steel.

Assignees

• Battelle Energy Alliance Llc

Inventors

• Bakas Michael Paul
• Chu Henry Shiu-Hung
• Zagula Thomas Andrew
• Langhorst Benjamin Robert

Classifications

• C22C38/06

  containing aluminium · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D1/34 Primary

  Methods of heating (C21D1/06 takes precedence) · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title

• C21D6/008

  containing Si · CPC title