What are the testing methods for the mechanical properties of spiral welded steel pipes

The testing methods for the mechanical properties of spiral welded steel pipes mainly fall into two categories: tensile testing and hardness testing.

1. Tensile testing involves preparing a specimen from the spiral welded steel pipe and stretching it to fracture on a tensile testing machine. One or more mechanical properties are then measured, typically only tensile strength, yield strength, elongation after fracture, and reduction of area. Tensile testing is a fundamental mechanical property testing method for metallic materials; almost all metallic materials with mechanical property requirements are subject to tensile testing. Especially for materials whose shape is inconvenient for hardness testing, tensile testing becomes the sole means of mechanical property testing for spiral welded steel pipes.

2. Hardness testing involves slowly pressing a hard indenter into the surface of the spiral welded steel pipe specimen under specified conditions, then measuring the indentation depth or size to determine the material’s hardness. Hardness testing of spiral welded steel pipes is a relatively simple, rapid, and easy-to-implement method among material mechanical property tests. The hardness test for spiral welded steel pipes is non-destructive, and there is an approximate conversion relationship between material hardness and tensile strength. The ability to convert material hardness to tensile strength is of great practical significance, and this method is currently widely used.

In contrast, tensile testing is less convenient, and converting hardness to strength is much easier. Therefore, people increasingly test only the hardness of materials and less frequently their strength. Especially due to continuous advancements and innovations in hardness tester manufacturing technology, some materials that were previously impossible to test directly for hardness, such as spiral welded steel pipes, stainless steel plates, and stainless steel strips, can now be directly tested for hardness. Therefore, there is a trend of hardness testing gradually replacing tensile testing.