Causes and Solutions for Common Defects in Spiral Welded Steel Pipe Joints

Release date:

2019-08-10

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Steel Pipe Knowledge

The common defects in spiral steel pipe welds mainly arise from the following causes. Let’s take a look at what they are and how to address them. The first common issue is uneven weld bead width or curvature. This can result from inconsistent welding speed, unstable welding voltage, uneven wire feed rate, poor conductivity of the welding wire, contamination on the wire surface, unreliable conductivity of the contact tip, excessive oxide scale along the groove edges, improper flux cup and rubber baffle, or overly large flux particles and excessive powder. To remedy this, maintain stable welding parameters, troubleshoot any malfunctions in the wire‑feeding mechanism, clean oil and contaminants from the wire surface, replace the contact tip with one of appropriate diameter—ensuring the internal conductive section is not excessively long—thoroughly clean the groove, properly position the flux cup and rubber baffle, and ensure uniform flux particle size. The second common problem is excessive weld reinforcement. This occurs when the current is too high while the voltage is too low, the uphill welding angle is excessively steep, or the wire feed rate is too fast, leading to excessive wire melting. Solutions include adjusting the welding parameters, modifying the uphill welding angle, and fine-tuning the wire feed speed. The third frequent defect is undercut. It arises from improper wire positioning or angle, excessive current combined with low voltage, overly rapid welding speed, misalignment during forming, excessive buildup, uneven wire feeding, inadequate fixation of the welding torch, or torch oscillation during welding. Remedies involve adjusting the wire position or angle, optimizing process settings—avoiding excessive current—eliminating misalignment or excessive buildup, replacing the wire feed roller or bearings, inspecting and repairing the electrical system, and securely fixing the welding torch. The fourth common issue is lack of fusion. This typically results from misaligned wire placement,偏于坡口一侧 (biased toward one side of the groove), excessive local curvature of the weld, or insufficient welding current. Corrective measures include adjusting the wire position, focusing attention and executing precise operations, and fine-tuning the welding current. The fifth frequent problem is incomplete penetration. Causes include misaligned wire placement, significant deviation from the intended position, insufficient welding current or excessive voltage, overly rapid welding speed, excessively blunt groove edges or too small groove angles, inadequate cleaning of the weld root, and overly narrow forming gaps. Solutions involve restoring the wire to its proper position, adjusting both welding current and voltage, regulating welding speed, correcting the groove’s blunt angle and included angle, thoroughly cleaning the weld root, and optimizing forming gap dimensions. The sixth common defect is slag inclusion. This occurs when edge surfaces are not clean, interpass slag removal is incomplete in multi‑layer welding, welding current is too low, welding speed is too fast, wire positioning is improper, molten slag and metal fail to separate adequately, the weld bead’s width‑to‑depth ratio is too small, undercut is severe, groove angles are too shallow, or the flux is contaminated with foreign matter. Typical remedies include cleaning both edges of the strip steel, ensuring thorough interpass slag removal, adjusting welding current and voltage, repositioning the wire, increasing the weld bead’s width‑to‑depth ratio, enlarging the groove angle, and removing impurities from the flux.

The common defects in the welds of spiral steel pipes are mainly caused by the following factors. Let’s take a look at what they are and the corresponding countermeasures.

The first common issue is uneven or warped weld bead width. The causes include inconsistent welding speed, unstable welding voltage, and uneven wire feed speed.

, Poor conductivity of the welding wire; the surface of the welding wire is not clean.

Unreliable electrical contact at the contact tip, excessive oxide scale on the groove edges, an improperly fitted flux cup and rubber baffle, or excessively large flux particles or a high powder content. To address these issues, maintain stable welding parameters, troubleshoot and repair any malfunctions in the wire‑feeding mechanism, remove oil and contaminants from the wire surface, replace the contact tip (or block) with one of appropriate diameter, ensure that the conductive portion of the internal bore is not excessively long, thoroughly clean the groove, properly secure the flux cup and rubber baffle, and ensure uniform flux particle size.

The second common issue is excessive weld reinforcement. This occurs when the current is too high and the voltage is too low, the uphill welding angle is excessively steep, or the wire feed speed is too fast, leading to excessive wire melting. To address this, adjust the welding parameters, modify the uphill welding angle, and regulate the wire feed speed.

The third common issue is undercut. This defect arises from improper wire position or angle, excessive current, insufficient voltage, excessively fast welding speed, misalignment or excessive buildup during bead formation, uneven wire feed, inadequate weld‑torch fixation, or improper torch oscillation during welding. Remedial measures include adjusting the wire position and angle, optimizing process parameters—ensuring that the welding current is not too high—eliminating misalignment or excessive buildup, replacing the wire‑feed roller or bearings, servicing the electrical system, and securely fastening the welding torch.

The fourth common defect is lack of fusion. The causes include misalignment of the welding wire—offset toward one side of the groove—excessive local curvature of the weld, and insufficient welding current. Remedial measures involve adjusting the wire position, maintaining focused attention and meticulous operation, and optimizing the welding current.

The fifth common issue is incomplete penetration. The causes include misalignment of the welding wire—excessive deviation from the normal position—too low a welding current, excessive voltage, excessively fast welding speed, an overly large root face or too small a groove angle, insufficient cleaning of the weld root, and an excessively narrow bevel gap. Remedial measures involve adjusting the welding wire to the correct position, optimizing the welding current and voltage, fine-tuning the welding speed, correcting the root face and groove angle, thoroughly cleaning the weld root, and adjusting the bevel gap.

The sixth common defect is slag inclusion. The causes include dirty edges, inadequate interpass cleaning in multi-layer welding, insufficient welding current, excessive travel speed, improper wire positioning, poor separation between slag and molten metal, an excessively low weld bead width-to-depth ratio, excessive undercut, too small a groove angle, and contaminated flux containing foreign matter. Common remedies involve cleaning the edges on both sides of the strip steel, ensuring thorough interpass cleaning, adjusting the welding current and voltage, repositioning the welding wire, increasing the weld bead’s width-to-depth ratio, enlarging the groove angle, and removing contaminants from the flux.

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