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| Grade ASTM | C | Si | Mn | S | P | Cr | Ni |
| 201 | ≤0.15 | ≤0.75 | 5.50-7.50 | ≤0.030 | ≤0.060 | 16.00-18.00 | 3.50-5.50 |
| 304 | ≤0.07 | ≤1.00 | ≤2.00 | ≤0.030 | ≤0.035 | 17.00-19.00 | 8.00-11.00 |
| 304L | ≤0.03 | ≤1.00 | ≤2.00 | ≤0.030 | ≤0.035 | 18.00-20.00 | 8.00-12.00 |
| 309S | ≤0.08 | ≤1.00 | ≤2.00 | ≤0.030 | ≤0.035 | 22.00-24.00 | 12.00-15.00 |
| 310S | ≤0.08 | ≤1.00 | ≤2.00 | ≤0.030 | ≤0.035 | 24.00-26.00 | 19.00-22.00 |
| 316 | ≤0.08 | ≤1.00 | ≤2.00 | ≤0.030 | ≤0.045 | 16.00-18.00 | 10.00-14.00 |
| 316L | ≤0.03 | ≤1.00 | ≤2.00 | ≤0.030 | ≤0.035 | 16.00-18.00 | 12.00-15.00 |
The reason why the stainless steel precision tube is called a precision tube is because of its high precision, better tolerance control range, uniform wall thickness, smooth inner wall, no texture and smoother surface roughness than ordinary pipes.
Effect of surface roughness on pipe
(1) Affecting wear resistance. The rougher the surface, the smaller the effective contact area between the mating surfaces, the greater the pressure, the greater the friction resistance, the faster the wear.
(2) Affect the fatigue strength. There are large troughs on the surface of rough stainless steel tubes, which, like sharp notches and cracks, are sensitive to stress concentration and thus affect fatigue strength.
(3) Affect the corrosion resistance. Rough surface, easy to make corrosive gas or liquid through the surface of the microscopic concave valley into the metal inner layer, resulting in surface corrosion.
(4) Affect the sealing. Rough surfaces do not fit tightly together, and gas or liquid leaks through gaps between contact surfaces.
(5) Affect the measurement accuracy. The surface roughness of the measured surface and the measured surface of the measuring tool will directly affect the measurement precision, especially in the precise measurement.
