Al-Plated Welded Pipe Layer Control to Suppress Hot-Forming Scale
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Solution Overview
Problem
The formation of cracks in the Al—Fe—Si-based alloy layer during the formation of Al plated steel pipes leads to oxidation and scale formation inside the plating layer, reducing productivity and corrosion resistance, especially in electric resistance welded steel pipes with large t/D ratios.
Innovation Solution
An Al plated electric resistance welded steel pipe with a specific composition and thickness ratio of the intermetallic compound layer and Al plating layer, along with a ZnO surface film, is used to suppress scale formation, ensuring good electric resistance welding and rapid cooling to prevent crack-related oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Al plated steel plate is used for hot press working, then scale formation on steel surface is prevented and productivity is improved, but at high temperatures (800-1000°C) the plating layer evaporates and surface properties deteriorate
Solution Approach 1:
The invention changes the compositional parameters of the steel plate to suppress scale formation. Specifically, it controls C content (0.15-0.40%), Si content (0.01-0.80%), Mn content (0.60-3.00%), and Al content (0.10-0.50%) to prevent excessive intermetallic compound layer formation and scale deposition during hot press working, while maintaining productivity benefits of Al plating.
Solution Approach 2:
The invention creates a composite structure with controlled intermetallic compound layer (Al-Fe-Si-based) between the steel base material and Al plating layer. This composite layering prevents scale formation on the steel surface while controlling evaporation effects at high temperatures through proper thickness ratios and composition control.
2Ease of manufacture
If steel plate is heated to high temperature for hot press working, then material softens for easy forming, but iron oxidizes and scale forms requiring additional processing steps
Solution Approach 1:
The invention changes the chemical composition parameters of the steel plate (C: 0.15-0.40%, Si: 0.01-0.80%, Mn: 0.60-3.00%, Al: 0.10-0.50%) to control oxidation behavior during heating. This prevents scale formation while maintaining the ability to soften and form at high temperatures.
Solution Approach 2:
The invention converts the potentially harmful oxidation process into a beneficial controlled intermetallic compound formation. The controlled formation of Al-Fe-Si-based intermetallic compounds during heating protects the steel surface from scale formation, turning the oxidation that would normally be harmful into a protective mechanism.
3Productivity
If Al plated steel plate is formed into steel pipe shape, then productivity is improved, but cracks form in the alloy layer leading to oxidation and scale formation inside plating layer
Solution Approach 1:
The invention changes the compositional parameters (Si: 0.01-0.80%, Mn: 0.60-3.00%, Al: 0.10-0.50%) and intermetallic compound layer thickness (5-20 μm) to prevent crack formation during forming. This maintains the productivity benefits while preventing the reliability issues caused by cracks.
Solution Approach 2:
The invention applies local quality control by creating a specific intermetallic compound layer with controlled thickness (5-20 μm) and composition (Al-Fe-Si-based) at the interface between steel and Al plating. This localized controlled structure prevents crack propagation that would otherwise lead to oxidation and scale formation inside the plating layer.
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 effectively prevents scale formation inside the plating layer during hot press working, maintaining the mechanical strength and corrosion resistance of the Al plated steel pipe, even when subjected to high temperatures.
Implementation Method 1
By applying an Al-based metal covering, it is possible to prevent deposition of scale on the steel surface
Implementation Method 2
the material to be formed is heated once to a high temperature (austenite region), the steel pipe softened by the heating is formed by bending
Implementation Method 3
the steel pipe is cooled. Due to this hot bending method, the material is heated once to a high temperature to make it soften, so the material can be easily bent, and furthermore, the material can be raised in mechanical strength due to the effect of hardening by cooling after forming
Implementation Method 4
the productivity of the plated steel plate is affected. For example, a galvanized coating with a sacrificial corrosion prevention action is being broadly used
Data Source
AI summary
An Al plated electric resistance welded steel pipe for hardening use suppressing the formation of scale to the inside of the plating layer while performing hot forming and an Al plated hollow member using that Al plated electric resistance welded steel pipe, wherein the Al plated electric resistance welded steel pipe for hardening use is comprised of a base material made of a tubular steel plate and having a predetermined chemical composition and an electric resistance welded zone provided at a seam portion of the steel plate and extending in a longitudinal direction of the steel plate, the base material is further provided with an intermetallic compound layer positioned on the surface of the steel plate and including an Al—Fe—Si-based intermetallic compound and an Al plating layer positioned on the surface of the intermetallic compound layer and containing Al and Si, and 70×X/D≤Y/t≤30 is satisfied, wherein X (μm) is a thickness of the intermetallic compound layer, Y (μm) is a thickness of the Al plating layer, t (mm) is a pipe thickness of the steel pipe, and D (mm) is an outside diameter of the steel pipe.