In recent years, nickel-titanium alloy (NiTi) has attracted much attention in thin-plate welding in aerospace, medical devices and other fields due to its unique shape memory effect and superelasticity. Recently, a study published by a Brazilian research team in 2018 revealed the effects of different heat treatments and welding processes on the electrothermal resistance (ERT) of NiTi materials, providing an important reference for understanding the performance differences of welding materials.
- Key findings: ERT correlation between heat treatment and welding process
The study compared NiTi substrates without heat treatment (BM-AR) and isothermal normalizing treatment (BM-PWHT) and found that the ERT change rate of both at 25°C was the same (Figure A). This phenomenon indicates that at room temperature, heat treatment may have limited effect on the basic electrothermal properties of the material. However, in the welded joint, the ERT curves of the two processes S11 (green solid line) and S12 (blue dotted line) also intersect at 25°C (Figure B), indicating that different welding methods may achieve performance convergence at a specific temperature, but the differences in high or low temperature ranges still need to be further verified.
- Material grade and applicability
According to industry standards, both ERTi-1 and ERTi-2 are commercially pure titanium welding wires, but their applicable scenarios are significantly different.
ERTi-1: Designed specifically for Grade 1 titanium, it is the welding wire with the lowest impurity content and the best ductility, suitable for scenarios with high requirements for formability and weldability but low strength requirements.
ERTi-2: Corresponding to Grade 2 titanium, it is compatible with both Grade 1 and Grade 2 welding requirements and has a wider range of applications. Its impurity content is slightly higher than ERTi-1, but its mechanical properties are better, making it the mainstream choice in the industrial field.
- Comparison of mechanical properties
From the perspective of mechanical properties, ERTi-2 has more advantages in strength:
Tensile strength: ERTi-2 is 50,000 psi, which is higher than the unspecified data of ERTi-1 (but based on the same level, ERTi-1 has lower strength).
Yield strength: ERTi-2 reaches 40,000 psi, further supporting its application in pressure-bearing equipment.
Elongation: Both maintain an elongation of 20%, ensuring the toughness of the welded joint.
- Differences in application scenarios
ERTi-1: Mostly used in low-stress environments, such as decorative welding, non-pressure pipelines, or shallow seawater equipment with high corrosion resistance requirements.
ERTi-2: With its excellent comprehensive performance, it is widely used in high-strength and corrosion-resistant scenarios such as seawater heat exchangers, chemical pressure vessels, and oil and gas pipeline systems.
