Cold Treating High-Strength Low-Alloy Steel for Strength Control
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Solution Overview
Problem
Conventional methods do not effectively address the treatment of high-strength, low-alloy steel, as there is a lack of understanding and significant benefit in cold treating this type of steel, particularly in achieving predictable increases in crystal structure and strength.
Innovation Solution
A method involving austenitizing, quenching, and cold treating high-strength, low-alloy steel within a specific temperature range to control and increase the minimum ultimate tensile strength while maintaining the maximum ultimate tensile strength, thereby altering the crystal structure for improved physical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional heat treating methods are used on high-strength, low-alloy steel, then the steel achieves basic strength properties, but the minimum ultimate tensile strength cannot be predictably increased without over-strengthening
Solution Approach 1:
The invention applies parameter changes by introducing a new temperature parameter range (−50°F to −150°F) for cold treating that is distinct from conventional heat treating temperatures. This parameter change enables predictable increases in minimum ultimate tensile strength (by 3-10 ksi) while maintaining maximum ultimate tensile strength within specification, thereby resolving the contradiction between improving strength and controlling strength range precision.
2Strength
If cold treating is applied to high-strength, low-alloy steel, then the crystal structure is modified to increase strength, but conventional understanding suggests no significant benefit
Solution Approach 1:
The invention applies preliminary action by performing cold treating at −50°F to −150°F after austenitizing and quenching but before final tempering. This preliminary cold treating step modifies the crystal structure in advance to achieve predictable strength increases (3-10 ksi) with controlled effects, resolving the reliability concern about unpredictable treatment outcomes that has plagued conventional approaches.
3Strength
If the minimum ultimate tensile strength is increased closer to the maximum ultimate tensile strength, then the strength range narrows, but this may compromise the steel's ability to meet specification requirements
Solution Approach 1:
The invention applies feedback by implementing a controlled cold treating process where the temperature (−50°F to −150°F) and duration are precisely regulated to achieve predictable strength increases of 3-10 ksi. This feedback-controlled approach ensures that the minimum ultimate tensile strength increases without exceeding the maximum ultimate tensile strength specification, thereby maintaining specification compliance while improving the minimum strength property.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for predictable and repeatable increases in minimum ultimate tensile strength, enabling the use of high-strength, low-alloy steel in various applications with thinner cross sections and improved crystal structure, reducing weight and enhancing performance in aerospace and other demanding environments.
Implementation Method 1
austenitizing the steel according to a selected material specification... quenching the steel... achieve a desired crystal structure of the steel
Implementation Method 2
cold treating the steel within a desired temperature range to achieve a desired crystal structure of the steel, wherein the desired temperature range is about 70 degrees Fahrenheit above zero degrees Fahrenheit to about 110 degrees Fahrenheit below zero degrees Fahrenheit
Data Source
AI summary
A method for treating high-strength, low-alloy steel includes controlling material responses, such as the crystal structure of the steel, through various processing steps. More specifically, the method includes cold treating the steel to achieve predictable increases in a minimum ultimate tensile strength or desired changes in the crystal structure of the steel. In one embodiment, cold treating the steel operates to controllably increase the minimum ultimate tensile strength of the steel within increasing a specified maximum ultimate tensile strength of the steel. Stated otherwise, cold treating the steel may reduce or narrow a minimum-to-maximum ultimate tensile strength range such that the minimum ultimate tensile strength is closer to the specified maximum ultimate tensile strength.