Đặc điểm: Là loại thép có khả năng hàn và khả năng tạo hình nổi trội nhờ có chứa thêm thành phần Ti.
Các loại sản phẩm hiện có: Thép cuộn cán nóng, thép cuộn cán nguội
Ứng dụng: Các bộ phận của hệ thống xả tự động của xe hơi (óng dẫn trước, bộ phận chuyển đổi khí thải, ống dẫn gữa, phần cuối ống dẫn) thiết bị trao đổi nhiệt, container.
Các thiết bị chịu nhiệt.
Chemical Formula
Fe, <0.08% C, 10.5-11.75% Cr, <0.5% Ni, <1.0% Mn, <1.0% Si, <0.045% P, <0.03% S, 6x%C-0.75% Ti
Composition
The typical chemical compositional ranges of grade 409 stainless steels are given below:
Table 1 - Composition ranges of grade 409 stainless steels
Grade
|
C
|
Mn
|
Si
|
P
|
S
|
Cr
|
Ni
|
Ti
| |
409
|
min.
max.
|
-
0.08
|
-
1.00
|
-
1.00
|
-
0.045
|
-
0.045
|
10.5
11.75
|
-
0.5
|
6x C
0.75
|
Mechanical Properties
The table below provides the mechanical properties of grade 409 stainless steels:
Table 2 - Mechanical properties of grade 409 stainless steels
Grade
|
Tensile Strength (MPa) min
|
Yield Strength 0.2% Proof (MPa) min
|
Elongation (% in 50mm) min
|
Hardness
| |
Rockwell B (HR B) max
|
Brinell (HB) max
| ||||
409
|
450
|
240
|
25
|
75
|
131
|
Physical Properties
The physical properties of annealed grade 409 stainless steels are tabulated below:
Table 3 - Physical properties of annealed grade 409 stainless steels
Grade
|
Density (kg/m3)
|
Elastic Modulus (GPa)
|
Mean Coefficient of Thermal Expansion (μm/m/°C)
|
Thermal Conductivity (W/m.K)
|
Specific Heat 0-100°C (J/kg.K)
|
Electrical Resistivity (nΩ.m)
| |||
0-100°C
|
0-315°C
|
0-538°C
|
at 100°C
|
at 500°C
| |||||
409
|
7800
|
200
|
11.0
|
11.7
|
12.4
|
25.8
|
27.5
|
460
|
600
|
Grade Specification Comparison
Table 4 provides approximate grade comparisons of 409 stainless steels:
Table 4 - Grade specifications for 409 grade stainless steel
Grade
|
UNS No
|
Old British
|
Euronorm
|
Swedish SS
|
Japanese JIS
| ||
BS
|
En
|
No
|
Name
| ||||
409
|
S40900
|
409S19
|
-
|
1.4512
|
X6CrTi12
|
-
|
SUH 409
|
Possible Alternative Grades
The following table gives possible alternative grades of 409 stainless steels:
Table 5 - Possible alternative grades of 409 stainless steels
Grade
|
Properties
|
3CR12
|
Easy to weld and good corrosion resistance. Heavy sections are more easily available when compared to 409.
|
304
|
High heat resistance and corrosion resistance. Grade 304 is expensive.
|
321
|
Better heat resistance when compared to 304 or 409.
|
Aluminized steel
|
Cheaper than grade 409 stainless steel, but less resistant to exhaust gases.
|
Corrosion Resistance
Grade 409 stainless steels have excellent resistance to exhaust gas and atmospheric corrosion, superior to that of 410 martensitic grades with 12% chromium and 3CR12. However, the corrosion resistance is lower than that of grade 430 steels containing 17% chromium. The surface of grade 409 steels is liable to mild corrosion, which limits the usage of steels for decorative purposes.
Heat Resistance
Grade 409 stainless steels offer scaling resistance at temperatures up to 675°C during continuous operation, and up to 815°C under intermittent conditions. These temperatures pertain to specific service environments.
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