Examination and Discussion of Issues in Composite and Laminated Steel Pipe Development Part II

Literature Overview

This 2017 publication in the journal "Steel Pipes" represents the second instathe writing systement of a comprehensive technical series by He Defu and Wang Jingying from Shanghai Jiuli Industry and Trade Development Co., Ltd. and Zhejiang Dechuan Pipe Industry Co., Ltd. The series addresses practical challenges, quality control issues, and development bottlenecks in the manufacturing of composite and laminated steel pipes — a field that directly relates to the broader cladding and bimetal product industry.

Core Technical Content

Part II of this series focuses on advanced topics including process optimization, defect analysis, and quality assurance methodologies for composite steel pipes. The authors draw upon extensive industrial experience to identify and address the most common problems encountered in production environments.

Classification of Composite Pipe Manufacturing Methods

Method	Applicable Materials	Typical Bond Strength	Production Speed
Explosion cladding	Dissimilar metals (Ti/steel, Ni/steel)	Metallurgical bond	Batch process
Roll bonding	Similar CTE materials	Metallurgical bond	Continuous
Weld overlay (SAW/ESW)	Carbon steel/stainless/Ni-alloy	Fusion bond	Semi-continuous
Laser cladding	Wide material range	Fusion/diffusion bond	Flexible
Extrusion bonding	Soft metal combinations	Solid-state bond	Continuous

Common Defects and Countermeasures

The study systematically catalogs defects observed in composite pipe production:

Delamination — caused by insufficient bonding pressure, surface contamination, or thermal mismatch

Countermeasure: Improve surface preparation (pickling + passivation), increase bonding temperature/pressure

Cracking — occurs at the interface or in the clad layer under residual stress

Countermeasure: Optimize cooling rate, implement post-weld heat treatment (PWHT)

Inclusions — entrapped oxide or slag particles at the interface

Countermeasure: Enhanced flux protection, clean welding environment, proper wire feed speed

Uneven thickness — due to material flow inconsistency during rolling or welding

Countermeasure: Real-time thickness monitoring, process parameter feedback control

Hydrogen-induced cracking (HIC) — particularly in high-strength steels with overlay layers

Countermeasure: Low-hydrogen consumables, preheating, post-weld bake-out

Process Parameter Optimization

The authors emphasize the critical nature of process parameter control, particularly for weld-overlay composite pipes:

Parameter	Optimal Range	Effect on Quality
Welding current	350–550 A (SAW)	Penetration depth, dilution rate
Travel speed	200–400 mm/min	Bead width, heat input
Preheat temperature	100–250 °C	Residual stress, HIC prevention
Interpass temperature	≤250 °C	Microstructure control
Flux coverage	Continuous, ≥50 mm	Protection against oxidation
Wire diameter	2.0–3.2 mm	Deposition rate, penetration

The dilution rate — the percentage of base metal mixed into the overlay layer — is a critical quality indicator. For stainless steel overlay on carbon steel, dilution should be controlled below 30% to maintain the required corrosion resistance. This is directly analogous to the dilution control requirements in PTA cladding and laser cladding processes.

Quality Assurance and Inspection

The study recommends a multi-level inspection protocol:

Inspection Stage	Method	Acceptance Criteria
Pre-weld	Visual + PT	No cracks, clean surface
During welding	Visual + process monitoring	Stable arc, proper bead profile
Post-weld	UT + MT	No delamination, no surface cracks
Final	Hydrostatic test + dimensional check	Pressure hold, thickness tolerance

The emphasis on process monitoring during welding reflects the PDCA (Plan-Do-Check-Act) quality management philosophy. Real-time monitoring of parameters such as arc voltage, wire feed speed, and travel speed enables immediate corrective action, preventing defect propagation.

Study Insights and Implications

This publication provides invaluable practical wisdom for engineers involved in composite pipe manufacturing. The systematic approach to defect identification and countermeasure development mirrors the FMEA (Failure Mode and Effects Analysis) methodology widely used in pressure vessel fabrication. The emphasis on surface preparation quality — often underestimated in industrial settings — is particularly noteworthy, as it parallels the critical importance of surface cleanliness in weld-overlay cladding where even trace contamination can lead to bonding failure.

The industrial perspective offered by this research complements the more academic literature available on cladding and bimetal products. For practitioners, the key takeaway is that process discipline and parameter control are more important than any single technological innovation. The consistent application of documented procedures, combined with rigorous inspection protocols, remains the most reliable path to producing high-quality composite pipes that meet demanding service requirements.