ERW Steel Pipe Heat Treatment for Weld Hardness and Fatigue
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Solution Overview
Problem
Conventional electric resistance welded steel pipes or tubes lack fatigue durability, particularly in the electric resistance weld portion, due to insufficient hardenability after rapid and short-time heating quenching treatment.
Innovation Solution
The technique involves controlling heating conditions during rapid and short-time heating quenching treatment to suppress a decrease in quenching hardness in the electric resistance weld portion by adjusting the heating rate, peak temperature, soaking time, and primary cooling rate based on the bond width of the electric resistance weld portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid and short-time heating quenching treatment is applied to improve productivity and suppress decarburization, then productivity increases and decarburization is suppressed, but the quenching hardness of the electric resistance weld portion becomes insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling heating rate, peak temperature, soaking time, and cooling rate to achieve sufficient quenching hardness in the weld portion while maintaining rapid and short-time heating characteristics. The heating rate is controlled at 10°C/s or more, peak temperature at 900°C or more, soaking time at 1 minute or less, and cooling rate at 30°C/s or more, which resolves the contradiction between rapid heating and adequate hardening.
2Weight of moving object
If conventional electric resistance welded steel pipes are used for hollow parts, then weight reduction is achieved, but fatigue durability is insufficient
Solution Approach 1:
The patent improves fatigue durability through parameter changes in the heat treatment process, specifically controlling the heating rate (10°C/s or more), peak temperature (900°C or more), soaking time (1 minute or less), and cooling rate (30°C/s or more). These parameter changes ensure sufficient quenching hardness in the electric resistance weld portion, thereby enhancing fatigue durability while maintaining the weight benefits of hollow parts.
3Ease of manufacture
If the bond width of the electric resistance weld portion is increased to 40 μm or more for typical applications, then ease of manufacture is improved, but quenching hardness becomes insufficient
Solution Approach 1:
The patent resolves this contradiction by changing the heat treatment parameters: heating rate of 10°C/s or more, peak temperature of 900°C or more, soaking time of 1 minute or less, and cooling rate of 30°C/s or more. These parameter changes enable sufficient quenching hardness even in weld portions with bond width of 40 μm or more, maintaining both ease of manufacture and mechanical properties.
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
This method achieves improved quenching hardness and fatigue durability in the electric resistance weld portion while preventing decarburization, even for steel pipes or tubes with a typical bond width of 40 μm or more.
Implementation Method 1
rapid and short-time heating quenching treatment... heated rapidly for a short time by electrical resistance heating
Implementation Method 2
subjecting the steel pipe or tube to quenching or quenching-tempering to impart required strength
Implementation Method 3
C (carbon) enough to ensure sufficient quenching hardness diffuses from the base metal portion into the electric resistance weld portion during heating
Data Source
AI summary
An electric resistance welded steel pipe or tube comprises: a base metal being a steel sheet having a specific chemical composition and an electric resistance weld portion having a bond width of 40×10−6 m or more and 120×10−6 m or less, wherein C0-C1 is 0.05 mass % or less, where C0-C1 is a difference between C1 in mass % which is a minimum C content of the electric resistance weld portion and Co in mass % which is a C content of the steel sheet, and a depth of a total decarburized layer in each of an inner surface layer and an outer surface layer of the electric resistance welded steel pipe or tube is 50×10−6 m or less.