Low Carbon Ferritic Stainless Steel Tube Good Ductility Sensitisation Resistance

AMSE SA268 S44400 TP444 Ferritic Stainless Steel seamless Tube/Tubing/Pipe

TP444 is a low carbon, dual stabilised, molybdenum containing ferritic stainless steel with good ductility, toughness and resistance to sensitisation, even in the welds. With 18% chromium and 2% molybdenum, the steel has good pitting resistance and crevice corrosion resistance, similar to TP316 and good general corrosion resistance and oxidation resistance, similar to 316 in most environments. Being a ferritic stainless steel, TP444 is not susceptible to Stress Corrosion Cracking. Annealed TP444 is ductile and can be formed using a wide range of roll forming or mild stretch bending operations as well as the more common drawing and bending operations. TP444 does not harden excessively during cold working.

The steel has limited weldability and should not be used in the as-welded condition for dynamic or impact loaded structures. As with most ferritic stainless steels, TP444 can undergo grain growth in the heat affected zone of weldments, which may adversely affect the mechanical properties in these zones. Applications involving welded TP444 are thus generally limited to a thickness of 2.5mm.

TP444 has good pitting resistance and is thus suitable for roofing and cladding in marine environments, as well as hot water tanks and geysers, heat exchanger tubing and food processing equipment.

Ferritic stainless steel features high corrosion resistance and oxidation resistance due to its high chromium content, but its mechanical properties and machinability are poor. It is widely applied to acid-resistant structures with little stress and is used as anti-oxidation steel. This steel type can resist the corrosion of atmospheric, nitric acid and saline solution. It features high temperature oxidation resistance and small thermal expansion coefficient. It can be used in nitric acid and food factory equipment, and can also be used to produce parts working at high temperature, such as gas turbine parts.

Typical Manufacturing Specifications:
 

ASTM A268

ASME SA268

Typical applications for 430 grade include:

• Linings for dish washers
• Refrigerator cabinet panels
• Automotive trim
• Lashing Wire
• Element Supports
• Stove trim rings
• Fasteners
• Chimney Liners

Heat Treatment

• Solution Annealing – Heat to 815-845°C, hold for ½ hour per 25mm of thickness, slow furnace cool to 600°C and then quickly air cool. Slow cooling from 540-400°C will cause embrittlement.
• Sub-Critical anneal – Heat to 760-815°C and then air cool or water quench.
• This grade is not hardenable by thermal treatment.

Welding

• Pre-heat at 150-200°C if welding is necessary.
• Embrittlement in the weld metal and heat affected zone can be relieved by a post-weld anneal at 790-815°C
• Grain refinement will not occur.

Machining

• Easier to machine than the standard austenitic grades such as 304.
• Still a tendency for galling and pick-up on the cutting tool.
• Bars that have been lightly drawn are easier to machine than those in the annealed condition.
• Grade 430F, the free machining version of 430, is very much easier to machine.

Fabrication

• Lower work hardening rate makes bending and forming somewhat easier than for grade 304
• Lower ductility restricts very severe operations.
• Severe bends should be made with the bend axis at right angles to the rolling direction.
• Severe cold heading of 430 wire is possible.

Quality Assurance:

Spezilla's seamless bright annealed stainless steel tubes are produced acc. to the following process and inspection to assure our quality:

1. Chemical Composition Analysis Test With 100% PMI.

2. Solution Annealing / Bright Annealed.

3. 100% Hydrostatic Test and 100% Eddy Current Test

4. Mechanical Tests includes Tension Test, Flattening Test, Flaring Test, Hardness Test.

5. Impact Test subject to Standard request.

6. Grain Size Test and Intergranular Corrosion Test.

7. Visual Test and Endoscope Test for Surface Quality Test

ASTM A268 Tp410 tube composition: