US 9,284,635 B2 · Recrystallization, refinement, and strengthening mechanisms for production of advanced high strength metal alloys

Recrystallization, refinement, and strengthening mechanisms for production of advanced high strength metal alloys

AssigneeThe NanoSteel Company, Inc.

InventorsDaniel James Branagan, Grant G. Justice, Andrew T. Ball, Jason K. Walleser, Brian E. Meacham, Kurtis Clark, Longzhou Ma, Igor Yakubtsov, Scott Larish, Sheng Cheng, Taylor L. Giddens, Andrew E. Frerichs, Alla V. Sergueeva

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Abstract

This disclosure deals with a class of metal alloys with advanced property combinations applicable to metallic sheet production. More specifically, the present application identifies the formation of metal alloys of relatively high strength and ductility and the use of one or more cycles of elevated temperature treatment and cold deformation to produce metallic sheet at reduced thickness with relatively high strength and ductility.

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Claims19

Dependent claims

A method comprising:

a. supplying a metal alloy wherein said alloy contains Fe at a level of 55.0 to 88.0 atomic percent, B at a level of 0.5 to 3.8 atomic percent, Si at a level of 0.5 to 12.0 atomic percent and Mn at a level of 1.0 to 19.0 atomic percent;
b. melting said alloy and solidifying to provide a matrix grain size of 200 nm to 200,000 nm wherein said solidified alloy has a thickness of 1 mm to 500 mm;
c. heating said alloy to form a refined matrix grain size of 50 nm to 5000 nm where the alloy has a yield strength of 200 MPa to 1225 MPa and a thickness of 1 mm to 500 mm;
d. stressing said alloy by cold rolling, cold stamping, hydroforming or roll forming that exceeds said yield strength of 200 MPa to 1225 MPa wherein said alloy after stressing results in a thickness reduction to produce a thickness of 0.1 mm to 25 mm and indicates a tensile strength of 400 MPa to 1825 MPa and an elongation of 1.0% to 59.2%;
e. wherein said alloy in step (d) is heated to a temperature in the range 700° C. and below the melting point of said alloy and grain growth occurs and forming an alloy having grains of 100 nm to 50,000 nm, borides of 20 nm to 10000 nm in size, precipitations of 1 nm to 200 nm in size and said alloy has a yield strength of 200 MPa to 1650 MPa;
and
f. wherein said alloy formed in step (e) is stressed above yield and forms an alloy having grain sizes of 10 nm to 2500 nm, borides of 20 nm to 10000 nm in size, precipitations of 1 nm to 200 nm in size and indicates a yield strength of 200 MPa to 1650 MPa, tensile strength of 400 MPa to 1825 MPa and an elongation of 1.0% to 59.2%.

4 more elements

A method comprising:

a. supplying a metal alloy comprising Fe at a level of 55.0 to 88.0 atomic percent, B at a level of 0.5 to 3.8 atomic percent, Si at a level of 0.5 to 12.0 atomic percent and Mn at a level of 1.0 to 19.0 atomic percent;
b. melting said alloy and solidifying to provide a matrix grain size of 200 nm to 200,000 nm and borides having a size of 20 nm to 10,000 nm and said alloy has a thickness of 1 mm to 500 mm;
c. heating said alloy to form a refined matrix grain size of 50 nm to 5000 nm where the alloy has a yield strength of 200 MPa to 1225 MPa and a thickness of 1 mm to 500 mm;
d. stressing said alloy by cold rolling, cold stamping, hydroforming or roll forming that exceeds said yield strength of 200 MPa to 1225 MPa wherein said alloy after stressing results in a thickness reduction and indicates a tensile strength of 400 MPa to 1825 MPa and an elongation of 1.0% to 59.2% and a thickness of 0.1 mm to 25 mm;
e. wherein said alloy in step (d) has a melting point and is heated to a temperature in the range of 700° C. and below said melting point of said alloy and grain growth occurs and forming an alloy having grains of 100 nm to 50,000 nm, borides of 20 nm to 10,000 nm in size, precipitations of 1 nm to 200 nm in size and said alloy has a yield strength of 200 MPa to 1650 MPa;
f. wherein said alloy formed in step (e) is stressed above yield and forms an alloy having grain sizes of 10 nm to 2500 nm, borides of 20 nm to 10000 nm in size, precipitations of 1 nm to 200 nm in size and indicates a yield strength of 200 MPa to 1650 MPa, tensile strength of 400 MPa to 1825 MPa and an elongation of 1.0% to 59.2%.

3 more elements

Dependencies are inferred from the claim text.

Description38,831 words

Summary1,041 words

#This application deals with a class of metal alloys with advanced property combinations applicable to metallic sheet production. More specifically, the present application identifies the formation of metal alloys of relatively high strength and ductility and the use of one or more cycles of elevated temperature treatment and cold deformation to produce metallic sheet at reduced thickness with relatively high strength and ductility.

#Steels have been used by mankind for at least 3,000 years and are widely utilized in industry comprising over 80% by weight of all metallic alloys in industrial use. Existing steel technology is based on manipulating the eutectoid transformation. The first step is to heat up the alloy into the single phase region (austenite) and then cool or quench the steel at various cooling rates to form multiphase structures which are often combinations of ferrite, austenite, and cementite. Depending on steel compositions and thermal processing, a wide variety of characteristic microstructures (i.e. polygonal ferrite, pearlite, bainite, austenite and martensite) can be obtained with a wide range of properties. This manipulation of the eutectoid transformation has resulted in the wide variety of steels available nowadays.

#Currently, there are over 25,000 worldwide equivalents in 51 different ferrous alloy metal groups. For steel produced in sheet form, broad classifications may be employed based on tensile strength characteristics. Low-Strength Steels (LSS) may be defined as exhibiting ultimate tensile strengths less than 270 MPa and include types such as interstitial free and mild steels. High-Strength Steels (HSS) may be steel defined as exhibiting ultimate tensile strengths from 270 to 700 MPa and include types such as high strength low alloy, high strength interstitial free and bake hardenable steels. Advanced High-Strength Steels (AHSS) steels may have ultimate tensile strengths greater than 700 MPa and include types such as martensitic steels (MS), dual phase (DP) steels, transformation induced plasticity (TRIP) steels, complex phase (CP) steels and twin induced plasticity (TWIP) steels. As the strength level increases, the ductility of the steel generally decreases. For example, LSS, HSS and AHSS may indicate tensile elongations at levels of 25% to 55%, 10% to 45% and 4% to 50%, respectively.

Brief description of the drawings31 figures

#The detailed description below may be better understood with reference to the accompanying FIGS. which are provided for illustrative purposes and are not to be considered as limiting any aspect of this invention.

#FIG. 1 illustrates the formation of Class 1 Steel.

#FIG. 2 is a stress v. strain diagram illustrating mechanical response of Class 1 Steel with Modal Nanophase Structure.

Detailed description36,983 words

#The steel alloys herein are such that they are initially capable of formation of what is described herein as Class 1 or Class 2 Steel which are preferably crystalline (non-glassy) with identifiable crystalline grain size morphology and mechanical properties. The present disclosure focuses upon improvements to the Class 2 Steel and the discussion below regarding Class 1 is intended to provide clarifying context.

#Class 1 Steel

#The formation of Class 1 Steel herein is illustrated in FIG. 1. As shown therein, a Modal Structure (Structure #1, FIG. 1) is initially formed as a result of starting with a liquid melt of the alloy and solidifying by cooling, which provides nucleation and growth of particular phases having particular grain sizes. Reference herein to “modal” may therefore be understood as a structure having at least two grain size distributions. Grain size herein may be understood as the size of a single crystal of a specific particular phase preferably identifiable by methods such as scanning electron microscopy or transmission electron microscopy. Accordingly, Structure #1 of the Class 1 Steel may be preferably achieved by processing through either laboratory scale procedures as shown and/or through industrial scale methods involving chill surface processing methodology such as twin roll processing, thick or thin slab casting.

Facts

Application

14/575,301Filed 18 Dec 2014 · continuation

Priority

2 Oct 2013

Published

US 2015/0090372 A116 Apr 2015

Granted

15 Mar 2016

Term ends

2 Oct 2034

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification32 codes

C22C 38/58
With nickel: with more than 1.5% by weight of manganese
C21D 6/004
Heat treatment of ferrous alloys: containing Cr and Ni
C21D 6/005
Heat treatment of ferrous alloys: containing Mn
C21D 6/008
Heat treatment of ferrous alloys: containing Si

Family

Application61/885,842Us provisional application · filed 2 Oct 2013

Application14/505,175Parent of this continuation · filed 2 Oct 2014

US 2015/0101714 A1Pre-grant publication · published 16 Apr 2015

US 2015/0090372 A1Published application

US 9,284,635 B2This patent

From the US filing history. Foreign family members aren’t listed.

Timeline

2 Oct 2013Priority claimedParent application 61/885,842
18 Dec 2014Application filedUS 14/575,301
16 Apr 2015PublishedUS 2015/0090372 A1
11 Jun 2015Assigned to Horizon Technology Finance Corporationsecurity interest
15 Mar 2016GrantedUS 9,284,635 B2
3 Dec 2018Assigned to Horizon Technology Finance Corporationsecurity interest
17 Feb 2021Assigned to United States Steel Corporationassignment of assignor's interest
1 Aug 2021Assigned to The Nanosteel Company, Inc.assignment of assignor's interest
12 Oct 2026TodayWithin its term
2 Oct 2034Term endsEstimated