The commonly used stainless steels are 304 and 316, with extensions including 304L, 316L, and 316H. In addition, there are 440C, 2507, etc. So what are CF8M and CF3? How could I still see F316? What's going on with TP316L?
1、 To clarify this, let's first look at the form of materials. In the instrument valves and fittings industry, the materials used are mainly forgings, bar stock, castings, and pipes. What are the corresponding standards for these four forms of materials in our industry? Please take a look at this table:
|
|
304 |
304L |
316 |
316L |
|
Forging |
F304 |
F304L |
F316 |
F316L |
|
Bar Stock |
304 |
304L |
316 |
316L |
|
Casting |
CF8 |
CF3 |
CF8M |
CF3M |
|
Pipe |
TP304 |
TP304L |
TP316 |
TP316L |
The bar stock material adopts the basic grade, and F is added to the forging, where F represents forging; C has been added to the casting, where C represents casting; TP has been added to the pipe, which means pipe.
2、 What is the difference between 304 and 316? What does the L of 304L and 316L represent? What does the H of 316H mean? Let's take a look at the chemical composition table of different grades of ASTM A276, where 316H is the ASTM A182 standard (this grade is not included in the 276 standard):
|
Grade |
Chemical Composition，% |
||||||||
|
|
C |
Mn |
P |
S |
Si |
Cr |
Ni |
Mo |
Other |
|
304 |
0.08 |
2.00 |
0.045 |
0.030 |
1.00 |
18.0-20.0 |
8.0-11.0 |
… |
… |
|
304L |
0.030 |
2.00 |
0.045 |
0.030 |
1.00 |
18.0-20.0 |
8.0-12.0 |
… |
… |
|
316 |
0.08 |
2.00 |
0.045 |
0.030 |
1.00 |
18.0-20.0 |
10.0-14.0 |
2.00-3.00 |
… |
|
316L |
0.030 |
2.00 |
0.045 |
0.030 |
1.00 |
18.0-20.0 |
10.0-14.0 |
2.00-3.00 |
… |
|
316H |
0.04-0.10 |
2.00 |
0.045 |
0.030 |
1.00 |
16.0-18.0 |
10.0-14.0 |
2.00-3.00 |
… |
According to the table, it is clear that L means low carbon content, H means high carbon content, and the difference between 316 and 304 is the addition of a Mo element, which means CF3M has an additional Mo element compared to CF3.
3、 Besides these common 3-series stainless steels, what else are 2507, 440C and others? These common 3-head stainless steels are called austenitic stainless steels, while 2507 is a duplex steel (ferritic and austenitic), 440C belongs to martensitic stainless steel, and there are also ferritic stainless steels such as 430.
It can be seen that to clarify these common stainless steels, the first is to distinguish the form: bar stock pipes, etc., the second is the standards followed, and the third is the differences in composition. From this perspective, after familiarizing oneself with the meaning of letter codes, it is not difficult to understand the meaning of these grades.
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Post time: Feb-27-2025