SS 446

SS 446 is a high chromium ferritic heat-resistant alloy with excellent resistance to oxidation, sulfidation and other forms of hot corrosion. This grade is most commonly used between 1500 - 2100°F, although its elevated temperature strength is quite low. 446 is the only heat-resistant alloy that will tolerate molten copper and brass. As with other high chromium ferritic stainless, 446 embrittles severely in the 700-1000°F temperature range (885°F embrittlement). 446 should not be used in this temperature range unless nearly complete loss of room temperature ductility may be tolerated. Sigma phase embrittlement occurs upon long-time exposure in the 1000-1300°F range 446 has a high ductile-to-brittle impact transition temperature. Therefore, successful forming and bending is aided by low forming speeds, edge preparation and preheating to 250-400°F. Annealing, when necessary should be performed at 1550-1650°F followed by rapid cool. Conventional methods may accomplish welding. Preheating and postheating to 300-600°F is helpful. Austenitic weld fillers, such as AWS E310 or E312 are generally suggested to maximize weld deposit ductility.

Specification

• UNS: S44600
• W. Nr./EN: 1.4763 Similar
• ASTM: A 276, A 240 Chemical

Equivalent materials to grade 446 stainless steel are:

• AISI 446
• ASTM A176
• ASTM A268
• ASTM A276
• ASTM A314
• ASTM A473
• ASTM A511
• ASTM A815
• DIN 1.4762
• QQ S763
• QQ S766
• ASME SA268
• ASTM A580
• FED QQ-S-763
• FED QQ-S-766
• MIL-SPEC MIL-S-862
• SAE J405 (51446)

 Chemical Composition, %

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Applications of Stainless Steel 446

The Grade 446 stainless steel can be used in the following products:

• X-ray tube bases
• Boiler baffles
• Oil burner components
• Annealing boxes
• Industrial mufflers
• Kiln linings
• Glass molds
• Furnace parts

  Physical Properties

• Density:  7.80 g/cm³ at 20 °C (0.282 lb/in³)
• Melting Point: 1448-1487 ^oC
• Modulus of Elasticity:  199.9 KN/mm2 at 20 ^oC
  
• Electrical Resistivity: 402 μΩ.cm room
  
• Thermal Conductivity: 21.6 W/m.K at 20 ^oC (150 BTU in/hr.ft².°F)
  
• Thermal Expansion: 20-100°C - 10.4 μm/m °C (5.78 μin/in°F)
  
• Specific Heat: 500 J/kg-K at 0 - 100 ^oC
  

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Coefficient of linear thermal expansion 10^-6 K^-1 between 20°C and

  Heat Resistance of Stainless Steel 446

Ferritic heat resistant steel JIS SUH446, UNS S44600, 25Cr-0.2N-0.2C ( 4C54 Grade Strong against high-temperature corrosion and no generation of scales easily peeled off up to 1,082℃. Excellent at sulfur resistance

 Hot Working of Stainless Steel 446

The hot working of grade 446 stainless steel is performed in between the ranges 1093- 1177°C (2000-2150° F). The last 10% of hot working has to be performed below 871°C (1600°F) to gain grain refinement

Heat Treatment of Stainless Steel 446

The Grade 446 stainless steel is more difficult to cold work than other stainless steels due to the high level of chromium content.

Fabrication of Stainless Steel 446

Machinability of the grade 446 stainless steel is possible at slow speeds with positive feeds, rigid mounts and sharp tooling surfaces.

Mechanical Properties of Stainless Steel 446

The mechanical properties of grade 446 stainless steel are displayed in the following table. For more details click the PDF here with all regulations here

Corrosion Resistance of Stainless Steel 446

AISI 446 offers good corrosion & oxidation resistance at elevated temperatures. Although a ferritic Stainless Steel, AISI 446 offers considerable corrosion resistance as compared to other 400 series Alloys.

Machinability

Slow speeds and positive feeds combined with rigid mounts and sharp tooling surfaces optimize machining 446.

 Welding of Stainless Steel 446

Most common welding methods can be successfully employed with this alloy. Type 308 welding material may be used, but will not display scaling resistance equal to the base metal. Consideration must be given to the differences in the coefficient of thermal expansion of base and weld metal. Oxyacetylene welding is not recommended.