Elements of Butt Welding of Titanium Steel Clad Plates

1. Abstract

Titanium clad plate / Steel clad plate is an advanced composite material, formed by layering titanium plate and steel plate. This material offers a unique combination of titanium's superior corrosion resistance and steel's high strength, coupled with its cost-effectiveness. Such properties make Titanium/Steel clad plates indispensable in various industries, including petrochemical, power generation, salt chemical production, transportation, desalination, and marine engineering.

As the application of these clad plates continues to expand, mastering the correct welding techniques becomes crucial to ensure the longevity and performance of equipment operating in harsh environments. This article discusses the essential elements involved in welding titanium steel clad plates, focusing on techniques that ensure durability and resistance to corrosion in complex working conditions.

2. Welding Method

Achieving high-quality welds in titanium steel clad plates requires a well-structured approach that includes the preparation of bevels, precise welding sequences, and adherence to safety precautions.

2.1 Bevel Form

The bevel design is critical to ensuring proper alignment and penetration during welding. The correct bevel form facilitates optimal fusion between the titanium and steel layers without causing contamination or separation at the weld interface.

2.2 Welding Sequence

A proper welding sequence ensures structural integrity and minimizes thermal stresses that can lead to defects. The recommended sequence includes:

• Surface Cleaning: Clean the weld seams and the surrounding area, extending approximately 200mm from the weld, to remove any potential contaminants that may affect weld quality.
• Positioning Welding: Begin with precise tack welding to ensure proper alignment of the plates.
• Base Layer Welding: Initiate the welding process by welding the steel base layer first. This reduces the thermal impact on the titanium layer, which is more sensitive to heat.
• Strip Welding: Following the base layer, proceed with the welding of the titanium strip. Ensuring even heat distribution in this stage is crucial to prevent uneven separation of the clad layers.

2.3 Welding Precautions

Titanium steel clad welding requires strict attention to environmental factors, materials preparation, and welding procedures to avoid defects that compromise the weld’s integrity.

2.3.1 Welding Environment

• Clean and Controlled Conditions: The welding environment should be kept clean, with no presence of moisture, grease, or any pollutants. Any contaminants can introduce flaws in the weld, such as porosity or contamination, particularly affecting the corrosion-resistant titanium layer.
• Humidity and Temperature Control: The relative humidity should not exceed 80%, and the temperature in the vicinity (100mm around the weld) should be maintained above 15℃ to prevent condensation. This ensures that moisture does not interfere with the welding process, which can otherwise lead to cracking or inclusions in the weld.

2.3.2 Low Current Base Welding

• Heat Control: When welding the steel base layer, a low current setting is crucial to avoid excessive heat. High heat can lead to oxidation of the titanium surface and cause uneven separation of the clad layers.
• Optimal Temperature Management: During the welding process, the interlayer temperature should be strictly controlled and kept below 150℃. This helps prevent overheating, which can adversely affect the mechanical and anti-corrosive properties of the titanium layer.

2.3.3 Surface Preparation and Assembly

• Thorough Cleaning: Both the welding wire and the groove surfaces, as well as the surrounding 20mm area, should be thoroughly cleaned to remove any dirt, oil, or oxide layers that could contaminate the weld. Any contamination can reduce the effectiveness of the weld and compromise the material's corrosion resistance.
• Assembly without Force: Forced assembly of the plates must be avoided, as it can cause misalignment and lead to defects in the weld. Precise alignment and fit-up are essential to avoid cracks, pores, and slag inclusions during welding.
• Weld Defects and Repair Limitations: In cases where welding defects occur, such as cracks or inclusions, the number of repairs on the same part should not exceed two times. After each repair, thorough penetration testing (PT) must be conducted to verify the integrity of the weld.

2.3.4 Certification of Welders

• Professional Training and Certification: Given the complexity and precision required for titanium steel clad plate welding, welders must undergo professional training. They should pass examinations and obtain proper certification before engaging in welding operations. The training requirements are specified in Appendix A of GB/T13149, which outlines the necessary competencies and qualifications for welders.

Conclusion: The Path to Optimal Welding of Titanium Steel Clad Plates

Titanium steel clad plates are a groundbreaking material that combines the best of titanium's corrosion resistance with steel's strength and cost-efficiency. However, realizing their full potential in industrial applications hinges on employing precise welding methods tailored to their unique properties. By meticulously following the recommended bevel designs, welding sequences, and environmental controls, industries can ensure durable, defect-free welds that withstand even the harshest operating conditions.

From maintaining cleanliness and controlling heat to ensuring proper alignment and using certified welders, every step in the welding process contributes to the structural integrity and performance of titanium steel clad plates. Adhering to these practices not only enhances the reliability of the equipment but also extends its service life, offering significant cost savings and operational efficiency.

As industries continue to innovate, the demand for advanced materials like titanium steel clad plates will grow, making expertise in their handling and welding an indispensable asset. Partnering with skilled professionals and leveraging cutting-edge techniques will ensure that this revolutionary material continues to drive progress across sectors such as petrochemicals, desalination, and marine engineering. Embrace these best practices, and unlock the immense potential of titanium steel clad plates for your next project.Contact us now!