Identify some common stainless steel grade

1. Content and application of some common stainless steel grade:

This table as below show the application of stainless steel correspondened to each grade of them.

Stainless steel grade	Main component, %	Applications
Martensite Stainless steel
403	C ≤ 0.15, Si ≤ 0.5, Mn ≤ 1	Jewelry, screw, heating details ≤  450oC
	Cr : 11.5 ~ 13
410	C ≤ 0.15, Si ≤ 0.5, Mn ≤ 1
	Cr : 11.5 ~ 13, Ni ≤ 0.75
420	C ≥ 0.15, Si ≤ 1, Mn ≤ 1
	Cr : 13 ~ 14.0
440B	C ≤ 0.75 ~ 0.95, Si ≤ 1, Mn ≤ 1	Stainless steel spring, measuring tools, surgical tools, exhausted valve
	Cr : 16 ~ 18, Mo ≤ 0.75
Ferrite Stainless steel
405	C ≤ 0.8, Si ≤ 1, Mn ≤ 1	Oil industrial, HNO3 acid tank, food box or food container
	Cr : 11.5 ~ 14.5, Al 0.1 ~ 0.3
4430	C ≤ 0.12, Si ≤ 1, Mn ≤ 1
	Cr : 16 ~ 18
446	C ≤ 0.2, Si ≤ 1, Mn ≤ 1.5	Details which anti-oxygen in high temperature
	Cr : 23 ~ 27, N ≤ 0.25
Austenite Stainless steel
201	C ≤ 0.15, Si ≤ 1, Mn 5.5 ~ 7.5	Acid manufacture industrial Oil-chemical industrial Food processing industrial Cookingware stainless steel
	Cr : 16 ~ 18, Ni 3.5 ~ 5.5, N ≤ 0.25
202	C ≤ 0.15, Si ≤ 1, Mn 7.5 ~ 10.5
	Cr : 17 ~ 19, Ni 4 ~ 6, N ≤ 0.25
301	C ≤ 0.15, Si ≤ 1, Mn ≤ 2
	Cr : 16 ~ 18, NI 6 ~ 8
	Mo ≤ 0.75, Cu ≤ 0.75
304	C ≤ 0.08, Si ≤ 0.12, Mn ≤ 2
	Cr : 18 ~ 20, Ni 8 ~ 12
	Mo ≤ 0.75, cu ≤ 0.75
304L	C ≤ 0.03, Si ≤ 1, Mn ≤ 2
	Cr : 18 ~ 20, Ni 8 ~ 10
	Mo ≤ 1, Cu ≤ 1
316	C ≤ 0.08, Si ≤ 1, Mn 1.25 ~ 2
	Cr : 16 ~ 18, Ni 10 ~ 14
	Mo 2 ~ 2, Cu ≤ 0.75
316L	C ≤ 0.03, Si ≤ 1, Mn 1.25 ~ 2
	Cr : 16 ~ 18, Ni 10 ~ 14
	Mo 2 ~ 3, Cu ≤ 1

2. Identify stainless steel 2xx, 3xx, and 4xx:

We can see at the Table No.1,  the 4xx stainless steel grade is belongs to Martensite and Ferrite, the stainless steel grade of 2xx and 3xx belong to Austenite stainless steel. In theory, the original austenite stainless steel group completely from magnification. And with this theory, the austenite stainless steel group transfer strongly hard when has a cold plastic deformation. This reason because of the transformation from austenite to deformation martensite (and martensite phase which is magnetic). So, in fact, if we used a magnet to separate the stainless steel grades, especially to distinguish the marks 2xx and 3xx, then I can say is impossible. For the most accurate distinction, we can only use the chemical composition analysis methods (but high cost) or based on the experience method known as grinding sparks (depends much on experience).

• Stainless steel 4xx group: Because in their component contains many Cr and almost have no Ni, so when grinding it will make a ray and fire-flower with color of dark orange, end bloom in to flowers. This group has stronger magnetic more than 2xx and 3xx.
• Stainless steel 2xx group: Because of a amount of Ni is replaced by Mn, so if the same thickness with 3xx grade, when we break or bend it, we will feel stiffer. When grinding, it makes a yellow-orange beam light, fire sparks is thicker, and fire flowers have more wings (compared to 3xx)
• Stainless steel 3xx group: When we grind, it makes a yellow-orange beam, fewer fire flowers, and along the fire sparks have flashing spots.

3. How to storage stainless steel for the best condition of using:

With the explain of the corrosion resistance of stainless steels above, we can be found in common that most of stainless steel is not corrode in normal atmospheric conditions. So, especially with the stainless steel appliances for storage, food processing, the best way to preserve stainless steel appliances after using is we have to wash, dry and storage in well-ventilated place.


Reference:

* Vật liệu học. Chủ biên: Lê Công Dưỡng. NXB KHKT - 1996.
* Ăn mòn và bảo vệ kim loại. Alain Galerie, Nguyễn Văn Tư. NXB KHKT - 2002.
* http://en.wikipedia.org/wiki/Stainless_steel
* http://meslab.org/mes/threads/2951-C...en-dung-