Electric Resistance Welded Steel Pipe Cold Workability
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Solution Overview
Problem
Existing electric resistance welded steel pipes for automotive parts face challenges in achieving excellent cold workability, mold life, and moderate hardness after quenching, which are crucial for producing high-quality automotive parts like rack bars.
Innovation Solution
The development of an electric resistance welded steel pipe with a specific chemical composition and steel structure, including a ferrite-pearlite mixed structure and controlled hardness before quenching, which ranges from 110 to 150 Hv. This composition and structure enable the pipe to have improved cold workability and mold life while maintaining a moderate hardness after quenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the steel pipe has high hardness before quenching, then the strength of the automotive part is improved, but the cold workability and mold life deteriorate
Solution Approach 1:
The invention changes the chemical composition parameters of the steel pipe, specifically controlling C content at 0.20-0.50%, Si at 0.01-0.25%, Mn at 0.10-0.70%, and adding microalloying elements (Ti: 0.005-0.040%, B: 0.0005-0.0050%, Nb: 0.00-0.10%, V: 0.00-0.20%) to achieve a ferrite-pearlite mixed structure with hardness of 110-150 Hv, which provides optimal balance between cold workability and subsequent strength after quenching
2Strength
If the steel pipe has high hardness before quenching, then the strength of the automotive part is improved, but the mold life deteriorates
Solution Approach 1:
The invention optimizes the chemical composition parameters to achieve a ferrite-pearlite mixed structure with controlled hardness of 110-150 Hv before quenching, which reduces the mechanical stress and wear on the mold during cold working while ensuring the final part achieves the required strength after quenching
3Ease of manufacture
If the steel pipe has low hardness after quenching, then the machine processability is improved, but the hardness and strength of the automotive part deteriorate
Solution Approach 1:
The invention carefully controls the chemical composition parameters (C: 0.20-0.50%, Si: 0.01-0.25%, Mn: 0.10-0.70%, plus microalloying elements) to achieve a ferrite-pearlite mixed structure with hardness of 110-150 Hv before quenching, which transforms into an optimal hardness range after quenching that balances both strength requirements and machine processability
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 proposed solution effectively enhances the cold workability and mold life of the steel pipes, while ensuring a moderate hardness after quenching, thereby improving the overall quality and processability of automotive parts produced using these pipes.
Implementation Method 1
electric resistance welded steel pipe
Implementation Method 2
electric resistance welded portion
Data Source
AI summary
An electric resistance welded steel pipe for an automotive part, the pipe comprising a base metal portion and an electric resistance welded portion, wherein the base metal portion has a chemical composition comprising, in terms of % by mass: from 0.42 to 0.48% of C, from 0.01 to 0.20% of Si, from 0.10 to 0.70% of Mn, from 0 to 0.030% of P, from 0 to 0.030% of S, from 0.005 to 0.050% of Al, from 0.005 to 0.040% of Ti, from 0.0005 to 0.0050% of B, and a balance comprising Fe and impurities, wherein a steel structure of the base metal portion is a ferrite-pearlite mixed structure, and wherein the base metal portion has a hardness of from 110 to 150 Hv.