Vickers hardness (HV) test is also an indentation test method. It presses a square pyramidal diamond indenter with an included angle of 1360 degrees into the test surface at a selected test force (F). After the holding time, remove the test force and measure the length of the two diagonals of the indentation. Vickers hardness value is the quotient obtained by dividing the test force by the indentation surface area. Its calculation formula is HV--Vickers hardness symbol, N/mm2 (MPa); F--test force, d--indentation two Arithmetic mean of diagonals, mm. The test force F used in Vickers hardness is 5 (49.03), 10 (98.07), 20 (196.1), 30 (294.2), 50 (490.3), 100 (980.7) Kgf (N) and other six levels. The hardness value can be measured The range is 5~1000HV. During construction, you should check whether groundwater and rainwater have come into contact with the pipe. If water comes into contact with the pipe, the pipe jacket should be dried. When installing pipes, you should handle them with care and avoid collisions and falls. The insulation layer of the insulation pipe must not collide with the burning fire to prevent the insulation layer from being burned. Pipes and fittings should be stored on relatively flat ground, stacked neatly, and the stacking height should not exceed 1.5 meters.

The influence of several main chemical elements in spiral steel pipes on performance:

Phosphorus (P): Increasing the phosphorus content will increase the strength and hardness of spiral steel pipes, but significantly reduce the plasticity and corrosion resistance.

Silicon (Si): When the content is less than 1%, silicon can improve the strength of spiral steel pipes, but has little effect on plasticity and corrosion resistance.

Carbon (C): Carbon is the most important element that determines the performance of spiral steel pipes. As the carbon content increases, the strength and hardness of spiral steel pipes increase, but the plasticity and corrosion resistance decrease.

Oxygen (O): Oxygen is a harmful element that will reduce the mechanical properties of spiral steel pipes, especially the corrosion resistance. The presence of oxides worsens welding performance.

Sulfur (S): Sulfur is a harmful element. The sulfide generated by it lowers the melting point of spiral steel pipes and easily causes hot cracks and hot brittleness, thus reducing weldability, impact toughness, fatigue, and corrosion resistance.

Manganese (Mn): Manganese can reduce the effects of sulfur and oxygen on spiral steel pipes and improve their hot processing properties.

Nitrogen (N): The effect of nitrogen is similar to that of carbon and phosphorus, which will increase the strength of spiral steel pipes, but the plasticity and corrosion resistance will be significantly reduced.