Steel Pipe Inclusion Control for Deformability
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Solution Overview
Problem
Electric resistance welded steel pipes face challenges in maintaining deformability and fatigue properties after quenching without spheroidization heat treatment, which is costly and inefficient, and without carburization, which affects their strength and fatigue resistance.
Innovation Solution
Control the morphology and distribution of calcium-based inclusions in the steel pipe, specifically by adjusting the content and particle size of Ca, O, and S, to enhance deformability and fatigue properties, while maintaining the chemical composition within specific ranges to prevent deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spheroidization heat treatment is performed to improve deformability, then deformability is improved, but production cost and process complexity increase
Solution Approach 1:
The patent applies preliminary action by controlling the morphology and size of inclusions (spheroidizing them to 10μm or less) during the steelmaking process itself, so that the material is pre-prepared for good deformability without requiring subsequent spheroidization heat treatment. This eliminates the need for the additional heat treatment step while maintaining excellent deformability.
Solution Approach 2:
The patent changes the parameters of inclusions by controlling their morphology (spheroidization) and size (10μm or less) through specific compositional control (Ca: 0.0010-0.0030%, S: 0.0005-0.0050%, O: 0.0005-0.0050%) and processing, thereby achieving good deformability without additional heat treatment steps.
2Strength
If high carbon content is used to increase strength after quenching, then strength is improved, but deformability deteriorates
Solution Approach 1:
The patent changes the parameters of inclusions (morphology and size) rather than changing the carbon content. By spheroidizing inclusions to 10μm or less and controlling their composition, the material achieves both high strength after quenching and good deformability, avoiding the trade-off between carbon content and deformability.
Solution Approach 2:
The patent applies local quality by specifically controlling the properties of inclusions (making them spherical and 10μm or less) while maintaining appropriate carbon content (0.15-0.55%) for strength. The localized control of inclusion characteristics enables both strength and deformability without requiring high carbon content throughout the material.
3Stability of the object's composition
If heat treatment after pipemaking is performed to uniformize quality, then quality uniformity is improved, but production efficiency decreases
Solution Approach 1:
The patent applies preliminary action by ensuring uniform inclusion distribution and morphology (spheroidized, 10μm or less) during the steelmaking and piping processes themselves. This preliminary uniformization eliminates the need for subsequent heat treatment to achieve quality uniformity, thereby improving production efficiency while maintaining quality consistency.
Solution Approach 2:
The patent extracts the quality uniformization function from the post-pipemaking heat treatment process and transfers it to the steelmaking and piping processes. By controlling inclusion morphology and distribution during manufacturing, the need for corrective heat treatment is eliminated, improving productivity while maintaining quality uniformity.
4Ease of operation
If Ca is added to control MnS morphology for improved deformability, then deformability is improved, but inclusion morphology control becomes more difficult
Solution Approach 1:
The patent changes the parameters of multiple elements simultaneously (Ca: 0.0010-0.0030%, S: 0.0005-0.0050%, O: 0.0005-0.0050%) to achieve spheroidized inclusions of 10μm or less. This coordinated parameter control simplifies the overall process by establishing clear compositional ranges that reliably produce the desired inclusion morphology, making manufacturing more precise rather than more difficult.
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 solution ensures excellent deformability and fatigue properties after quenching, allowing for complex shape formation without heat treatment, thereby improving the quality and efficiency of auto and machine structure parts.
Implementation Method 1
by controlling the morphology of the oxides and sulfides and other calcium(Ca)-based inclusions present at the base material and weld zone of electric resistance welded steel pipe
Implementation Method 2
the practice has been to use electric resistance welding to make the pipe
Implementation Method 3
Hardened auto parts and machine structure parts are required to have strength and fatigue properties
Data Source
AI summary
Electric resistance welded steel pipe excellent in deformability and fatigue properties after quenching which enables working into complicated shapes without spheroidization and which improves the fatigue properties after cold working and quenching without carburization are provided. The electric resistance welded steel pipe is characterized by containing, by mass %, C: 0.15 to 0.55%, Si: 0.01 to 0.30%, Mn: 0.5 to 1.5%, Ca: 0.0010 to 0.0030%, S: 0.0005 to 0.0050%, and O: 0.0005 to 0.0050%, having contents of Ca, O, and S satisfying 0.10≦[Ca](1−124[O])/1.25[S]≦2.50, having Ca-based inclusions present at the base material and electric resistance weld zone with an average particle size of 1.0 to 10 μm and a density of 3 to 300/mm2, and having a difference ΔHv of the maximum hardness of the electric resistance weld zone and the average hardness of the base material part satisfying 100 to 500.