Al-Plated Welded Steel Pipe Structure to Suppress Scale During Hot Forming
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Solution Overview
Problem
The formation of cracks in the alloy layer during the formation of electric resistance welded steel pipes and the subsequent formation of iron oxides (scales) inside the plating layer due to these cracks, which reduces productivity and affects the corrosion resistance of the steel pipes.
Innovation Solution
The development of an Al plated electric resistance welded steel pipe with specific thickness ratios of the intermetallic compound layer and the Al plating layer, along with a surface film layer containing ZnO, to suppress the formation of scales and improve welding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel pipe is heated to high temperature for hot press working, then the steel pipe can be easily formed and mechanical strength is improved, but scale (oxides) forms on the surface and inside the plating layer
Solution Approach 1:
The patent applies preliminary action by forming an Al-Fe-Si intermetallic compound layer before hot press working. This layer is created during the plating process, prior to forming and welding operations. The intermetallic compound layer acts as a protective barrier that prevents oxidation of the base steel during subsequent high-temperature hot press working, thereby preventing scale formation while allowing the steel to be easily formed and gain mechanical strength.
Solution Approach 2:
The patent uses an Al-Fe-Si intermetallic compound layer as an intermediary between the base steel and the external environment during hot press working. This intermediate layer serves as a protective barrier that mediates the interaction between oxygen and the base steel, preventing direct oxidation and scale formation on the steel surface while allowing the necessary high-temperature forming process to occur.
2Productivity
If scale forms on the steel pipe surface during hot press working, then productivity decreases due to necessary descaling steps, but the steel pipe structure remains intact
Solution Approach 1:
The patent applies preliminary action by creating the Al-Fe-Si intermetallic compound layer before hot press working, which prevents scale formation in advance. This eliminates the need for subsequent descaling steps, thereby maintaining high productivity and simplifying the overall manufacturing process without requiring additional complexity for scale removal operations.
3Reliability
If Al plated steel plate is used for hot press working, then corrosion resistance is improved and scale deposition is prevented, but the plating layer may evaporate at high temperature
Solution Approach 1:
The patent applies parameter changes by controlling the composition of the plating layer to contain specific amounts of Fe and Si (0.1-10 wt% Fe and 0.01-5 wt% Si). This compositional adjustment changes the properties of the Al plating layer, forming an Al-Fe-Si intermetallic compound layer that remains stable at hot press working temperatures. The controlled composition prevents both excessive evaporation and excessive intermetallic growth, maintaining plating layer stability while preserving corrosion resistance.
Solution Approach 2:
The patent creates a composite plating layer structure consisting of Al-Fe-Si intermetallic compounds. This composite material combines the benefits of Al (corrosion resistance, high-temperature stability) with controlled amounts of Fe and Si (which modify the intermetallic phase formation). The resulting composite plating layer maintains its integrity at high temperatures, prevents scale formation, and preserves corrosion resistance properties.
4Object-generated harmful factors
If the intermetallic compound layer is too thick, then scale prevention is improved, but welding quality deteriorates due to excessive brittleness
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the intermetallic compound layer to be 3-15 μm and the Al plating layer to be 5-20 μm. These controlled parameters ensure that the intermetallic layer is thick enough to provide effective scale prevention during hot press working, while remaining thin enough to avoid excessive brittleness that would compromise welding quality. The specific parameter ranges optimize both scale prevention and weldability.
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 prevents the formation of scales inside the plating layer during hot press working, enhances the corrosion resistance, and improves the productivity of the steel pipes by eliminating the need for a descaling step.
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 pipe is produced by forming and seam welding the plated steel plate
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.