Properties This article has property data, click to view

Stainless Steel - Grade 409 (UNS S40900)

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

Topics Covered

Introduction
Key Properties
    Composition
    Mechanical Properties
    Physical Properties
    Grade Specification Comparison
    Possible Alternative Grades
Corrosion Resistance
Heat Resistance
Heat Treatment
Welding
Applications

Introduction

Grade 409 stainless steel is a Ferritic steel that offers good mechanical properties and high-temperature corrosion resistance. It is commonly considered as a chromium stainless steel, with applications in exhaust systems of automobiles and applications that demand weldability.

Grade 409 steels are also available in highly stabilized forms, such as grades S40930, S40920 and S40910. The stability of these grades is provided by the presence of niobium, titanium, or both, in the composition of steels.

Key Properties

The properties given below relate to annealed tubing of ASTM A268. The specified properties may not be similar to other products such as bar and coil.

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.

Heat Treatment

Annealing of grade 409 steels is carried out at temperatures ranging from 790 to 900°C, followed by air-cooling. Thermal treatment does not harden grade 409 steels.

Welding

Grade 409 steels must be pre-heated to temperatures of 150 to 260°C before welding. Although grade 430 and 409 filler rods or electrodes can be used during welding of grade 409 steels, grade 309 electrodes or filler rods are strongly recommended by AS 1554.6. Care should be taken to weld grade 409 steels with minimum heat, in order to mitigate grain growth.

Ductility of the welded products can be improved by annealing post-welding at temperatures of 760 to 815°C. However, this is not required for thin welded products. Welding of exhaust tubing of automobiles is carried out without filler rods.

Applications

The typical applications of grade 409 stainless steels are listed below:

  • Automotive exhaust tubing
  • Catalytic converter systems
  • Mufflers

 

Date Added: Oct 23, 2001 | Updated: Apr 25, 2014
Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit