STAINLESS STEEL TUBE & PIPE   

Typical composition ranges for grade 409 stainless steel are given in table 1.

Table 1. Composition ranges for 409 grade stainless steel

Typical mechanical properties for grade 409 stainless steel are given in table 2.

Table 2. Mechanical properties of 409 grade stainless steel

Typical physical properties for annealed grade 409 stainless steels are given in table 3.

Table 3. Physical properties of 409 grade stainless steel in the annealed condition

Grade Specification Comparison

Approximate grade comparisons for 409 stainless steel are given in table 4.

Table 4. Grade specifications for 409 grade stainless steel

Possible Alternative Grades

Possible alternative grades to grade 409 stainless steels are given in table 5.

Table 5. Possible alternative grades to 409 grade stainless steel

Corrosion Resistance

Grade 409 resists atmospheric and exhaust gas corrosion. A light surface rust will form in most atmospheres; this rust retards further corrosion but makes the surface undesirable for decorative applications. The corrosion resistance is about the same as that of 3CR12 and the 12% chromium martensitic grades such as 410, and inferior to the 17% chromium grade 430.

Heat Resistance

Generally 409 is classified as resistant to scaling in intermittent service up to 815°C and up to 675°C in continuous service, but these temperatures are dependent upon the exact service environment.

Heat Treatment

Annealing - heat to 790-900°C and air cool. This grade cannot be hardened by thermal treatment.

Welding

Readily welded but a pre-heat of 150-260°C is recommended. Grade 409 or Grade 430 electrode or filler rods can be used, but AS 1554.6 pre-qualifies welding of 409 with Grade 309 rods or electrodes. These austenitic fillers result in a more ductile weld.

Post-weld annealing at 760-815°C improves weld ductility.

Post-weld annealing is not required when welding thin sections. Automotive exhaust tubing is typically welded without filler metal (autogenously).

All welding must be carried out with minimum heat input to reduce grain growth effects.

Applications

Typical applications include:

•         Automotive exhaust systems

•         Catalytic converters

•         Mufflers

Density (lb / cu. in.)	0.278
Specific Gravity	7.68
Specific Heat (Btu/lb/Deg F - [32-212 Deg F])	0.11
Modulus of Elasticity Tension	29

Form	Sheet
Condition	Test Specimen Annealed
Temperature	70
Tensile Strength	68
Yield Strength	39
Elongation	30
Form	Sheet
Condition	Test Specimen Annealed
Temperature	200
Tensile Strength	58
Yield Strength	28
Elongation	28
Form	Sheet
Condition	Test Specimen Annealed
Temperature	400
Tensile Strength	53
Yield Strength	24
Elongation	21
Form	Sheet
Condition	Test Specimen Annealed
Temperature	600
Tensile Strength	50
Yield Strength	22
Elongation	20
Form	Sheet
Condition	Test Specimen Annealed
Temperature	800
Tensile Strength	46
Yield Strength	19
Elongation	22
Form	Sheet
Condition	Test Specimen Annealed
Temperature	1000
Tensile Strength	36
Yield Strength	16
Elongation	28
Form	Sheet
Condition	Test Specimen Annealed
Temperature	1200
Tensile Strength	23
Yield Strength	13
Elongation	34
Form	Sheet
Condition	Test Specimen Annealed
Temperature	1300
Form	Sheet
Condition	Test Specimen Annealed
Temperature	1400
Tensile Strength	8
Yield Strength	4
Elongation	68
Form	Sheet
Condition	Test Specimen Annealed
Temperature	1500
Form	Sheet
Condition	Test Specimen Annealed
Temperature	1600
Tensile Strength	4
Yield Strength	2
Elongation	79