Definition
A high alloy steel that resists corrosion. Stainless steel has a beautiful surface and does not have to be treated with surface treatments such as color plating or paint. Many machinery manufacturers often do not apply any paint treatment to indicate that their products are stainless steel. However, normal steel is required to be rust-proofed.
Simplified classification
Stainless steel can be simply divided into three main categories: 200 series, 300 series and 400 series. Among them, the 300 series is the most commonly used, and the 200 series and 400 series are substitutes for the 300 series in a certain extent. Technically, the 400 series should be called stainless iron, because it is free of nickel, so it can be attracted with a magnet. The 200 and 300 series do have nickel in them, so they are non-magnetic and cannot be picked up by a magnet.
304 is the most common varieties in the 300 series, generally, from the price change of 304 we can judge the price trend of the whole stainless steel. The 200 series contains little nickel, while the 400 series contains no nickel, and the 300 series contains the most nickel, so the 300 series is the one that is most influenced by the nickel price.
The 300 series can be briefly divided into 304, 304L, 316, 316L, 321, 309S, 310S and more. The distinction is based on the different content of various metal elements, which leads to different properties of stainless steel. For example, the difference between 304 and 304L is that the carbon content is different, with L is to indicate low carbon content, also known as low carbon, the difference between 316 and 316L is the same.
Morphological classification
It can be divided into five categories: steel coil, flat product, profile, steel pipe and parts, the most important are steel coil and flat product.
Profiles are a variety of different shapes of materials made from plates, including angle steel, flat steel, I-beam steel and channel steel.
Steel pipe mainly refers to seamless steel pipe, and the opposite of seamless steel pipe is welded pipe, the difference is whether it is a one-time molding.
Parts are mostly elbows, flanges and other little stuff.
Steel coil and flat product are practically the same, just in different ex-factory forms. Generally, more than 16 millimeters cannot be rolled.
Stainless steel plate is divided into hot rolling and cold rolling according to the different rolling techniques of the rolling mill. Cold rolling from China is usually under 3 mm, and hot rolling is usually over 3 mm. Imported cold rolling plate thickness can reach 4 mm to 6 mm. Hot rolling thickness of 3 mm to 12 mm is called medium plate, more than 12 mm is called thick plate, and cold rolling is cold-rolled sheet.
Specific gravity (KG)
Different stainless steels have different specific gravity:
400 series: 7.75
304, 321, 304N, 201, 202, 304L, 301: 7.93
310S, 309S, 316, 316L: 7.98
Tolerance (allowed error)
Tolerance is a recognized permissible deviation in length or thickness. Due to various factors, in the production process of the plate, the actual thickness is often less than the theoretical thickness. For example, a 6 mm plate is produced at only 5.6 mm, and that is the tolerance. Different tolerance sizes result in different prices, with larger tolerances being cheaper.
Tolerance range of 304/2B (just for reference)
| Specification | Large tolerance | Normal | Small tolerance | No tolerance |
| 0.4MM | 0.3-0.32 | 0.33-0.37 | 0.37-0.39 | Above 0.39 |
| 0.5MM | 0.4-0.42 | 0.43-0.47 | 0.47-0.49 | Above 0.49 |
| 0.6MM | 0.5-0.52 | 0.53-0.57 | 0.57-0.59 | Above 0.59 |
| 0.7MM | 0.6-0.62 | 0.63-0.67 | 0.67-0.69 | Above 0.69 |
| 0.8MM | 0.7-0.72 | 0.73-0.77 | 0.77-0.79 | Above 0.79 |
| 0.9MM | 0.8-0.82 | 0.83-0.87 | 0.87-0.89 | Above 0.89 |
| 1.0MM | 0.89-0.91 | 0.91-0.94 | 0.94-0.99 | Above 0.99 |
| 1.2MM | 1.01-1.08 | 1.09-115 | 1.16-1.18 | Above 1.18 |
| 1.5MM | 1.32-1.38 | 1.39-1.45 | 1.46-1.48 | Above 1.48 |
| 2.0MM | 1.71-1.79 | 1.8-1.86 | 1.87-1.9 | Above 1.9 |
| 2.5MM | 2.23-2.38 | 2.39-2.42 | 2.42-2.47 | Above 2.47 |
| 3.0MM | 2.7-2.77 | 2.78-2.85 | 2.85-2.9 | Above 2.9 |
Tolerance range of hot rolled sheet (just for reference)
| Specification | Large tolerance | Normal | Small tolerance | No tolerance |
| 3.0MM | 2.6-2.75 | 2.75-2.85 | 2.86-2.9 | Above 2.9 |
| 4.0MM | 3.2-3.6 | 3.6-3.75 | 3.75-3.95 | Above 3.95 |
| 5.0MM | 4.2-4.6 | 4.6-4.75 | 4.75-4.95 | Above 4.95 |
| 6.0MM | 5.1-5.5 | 5.5-5.75 | 5.75-5.9 | Above 5.9 |
| 8.0MM | 7.2-7.5 | 7.5-7.75 | 7.75-7.95 | Above 7.9 |
| 10.0MM | 9.1-9.3 | 9.3-9.6 | 9.6-9.85 | Above 9.85 |
| 12.0MM | 11.1-11.2 | 11.2-11.6 | 11.6-11.85 | Above 11.85 |
| 14.0MM | 13.1-13.2 | 13.2-13.6 | 13.6-13.85 | Above 13.85 |
Characteristics and uses of the main types of stainless steel
304: As a widely used steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties. Good performance of hot metal working, such as stamping and bending. No hardening by heat treatment and no magnetic. Used in temperatures ranging from -193℃ to 800℃.
It can be used in the manufacture of tableware, kitchenware, water heaters, boilers, automobile parts, medical equipment, food machinery, wine storage containers, pressure vessels (chemical machinery, chemical equipment).
304L: Low carbon 304 steel. In the general state, the corrosion resistance is similar to 304, but it resists intergranular corrosion well after welding and stress relieving. It also maintains good corrosion resistance without heat treatment and is generally used below 400℃.
It can be used to manufacture petrochemical industries, building materials.
321: Ti is added to 304 steel to prevent intergranular corrosion. Suitable for temperatures from 430℃ to 900℃ and no magnetic. It can be used for automobile exhaust, heat exchangers, containers and other products that are not heat-treated after welding. Due to the addition of Ti element, it is not suitable for making food processing equipment.
316L: Due to the addition of molybdenum (Mo), it has particularly excellent corrosion resistance and high-temperature strength. Suitable for use below 900℃ and in harsh conditions and no magnetic.
It can be used in the manufacture of equipment for use in seawater and in coastal facilities. It can also be used in the production of chemicals, dyestuffs, papermaking, acetic acid, fertilizers and the food industry, which have special requirements for intergranular corrosion.
309S/310S: The higher content of nickel and chromium, as well as the increased content of silicon, make it resistant to high temperatures and corrosion. 309S can withstand repeated heating below 980℃. The use temperature of 310S reaches 1200℃, and the continuous use temperature is at 1150℃. Neither of them are magnetic.
They are mainly used for manufacturing the key parts of high-temperature electric furnace equipment and drying equipment.
200 Series: Similar to 304, it is cheap and economical. In addition, 201 is harder and less tough than 304.
It can be used in the manufacture of kitchen equipment, food processing equipment, filters, milk tanks, steel furniture, architectural decoration and more.
Summary
There is no one-size-fits-all solution for stainless steel, and CYCO will select the most appropriate material and machining method based on several factors, including your budget, production schedule, materials, tooling requirements, tolerances, quantities, and more.
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