Filler metals of alloy groups -B3 and higher are not prequalified due to differences in what factors?

Filler metals of alloy groups -B3 and higher are not prequalified primarily due to differences in tensile strength and ductility. These factors are crucial in determining how well a filler metal will perform when subjected to stress and strain during and after the welding process.

Tensile strength refers to the maximum amount of tensile (pulling or stretching) stress that a material can withstand before failure. In the context of welding, this means that the filler metal must have sufficient strength to ensure that the welded joint can handle the loads and forces it will encounter in service. Ductility, on the other hand, is the ability of the material to deform under tensile stress, which is important to prevent brittle failures. A filler metal with high ductility can absorb more energy before fracturing, making it more suitable for a wider range of applications.

Alloy groups -B3 and higher often include compositions and properties that change these mechanical characteristics significantly. Different filler metals can behave unpredictably during the welding process and later in service, making it necessary to ensure that they are thoroughly evaluated and validated for specific applications, hence the lack of prequalification.

In contrast, options related to weldability and hardness, thermal expansion and weight, or cost and availability impact different aspects