【Chemical composition and characteristics of stainless steel sanitary pipe】
1. Purpose:
Stainless steel pipe has anti-corrosion properties because of its composition. This article discusses the composition of stainless steel sanitary pipe and understands the influence of the composition on the characteristics of stainless steel, to facilitate the public to understand the differences between various materials. The source of chemical composition data is based on the National Standards of the Republic of China (CNS).
2. Type and composition of stainless steel:
The main component of stainless steel is iron, and the rest are composed of different proportions of metals and carbon, among which chromium (Cr) is the largest. There are about 180 kinds of stainless steel in the market according to different proportions. This article focuses on Austenitic stainless steel, The discussion items are 304, 304L, 316, and 316L. This type of stainless steel is the most common in the market. The material is stable, non-toxic, acid and alkali resistant, non-magnetic, and most of the stainless steels recognized by the public are of this type.
| Types of symbols | C | Si | Mn | P | S | Ni | Cr | Mo |
| 304 TBS | 0.08↓ | 1.00↓ | 2.00↓ | 0.045↓ | 0.030↓ | 8.00-10.50 | 18.00-20.00 | - |
| 304L TBS | 0.030↓ | 1.00↓ | 2.00↓ | 0.045↓ | 0.030↓ | 9.00-13.00 | 18.00-20.00 | - |
| 316 TBS | 0.08↓ | 3.5L | 1.00↓ | 2.00↓ | 0.045↓ | 10.00-14.00 | 16.00-18.00 | 2.00-3.00 |
| 316L TBS | 0.030↓ | 1.00↓ | 2.00↓ | 0.045↓ | 0.030↓ | 12.00-15.00 | 16.00-18.00 | 2.00-3.00 |
| Type of metal | Characteristic | |||||||
| Chromium(Cr) | Significantly increases the potential of the steel-based electrode and improves the resistance to electrochemical corrosion, but it is not a linear relationship. Chromium must account for 12% to make the electrode potential change. The alloy composition of chromium and steel can form dense Cr2O3 in the outer layer to protect the interior from oxidation. At normal temperature, a sufficient amount of Cr-Ni matrix can make the steel obtain single-phase ferrite or single-phase austenite. | |||||||
| Nickel(Ni) | 304 contains 8% Ni, and 316 contains 10%. If stainless steel has more nickel, it will be more durable and corrosion-resistant. In places where pollution or chemicals are often contacted, 316L is used as the material of stainless steel. | |||||||
| Carbon(C) | Carbon can increase rigidity, but conversely makes mechanical strength worse. Low carbon can make stainless steel heat-treated, and can also make steel more corrosion-resistant. | |||||||
| Molybdenum(Mo) | The addition of molybdenum allows it to obtain a special structure that makes it resistant to chloride corrosion and can be used in highly corrosive environments such as high salt, seaside or chemical. | |||||||
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