Grade 446 is a high chromium, ferritic, heat resistant, stainless steel grade. It is known for its excellent resistance to oxidation, corrosion, and sulfidation. Grade 446 stainless steel pipes are most commonly used in applications with elevated temperatures between 1500 to 2100 °F. These are the only heat resistant stainless steel pipes that can tolerate molten copper, lead, tin, and brass. Likewise, other high chromium ferritic stainless grades, 446 also possess an embrittlement temperature of 885 °F. Hence, it is recommended not to use it in this temperature range of 700-1000° F.
446 Stainless Steel Pipe Properties
The following properties of 446 stainless steel pipes make them suitable for high temperature applications:
Corrosion and Oxidation Resistance
- Excellent corrosion resistance in many industrial environments.
- Excellent oxidation resistance at elevated temperatures (up to 2000° F).
- Fair Sulfidation resistance.
- Good resistance to chlorides, organic acids, and molten copper.
446 steel pipes have a high ductile-to-brittle impact transition temperature.
It is recommended to work on 446 steel pipes at slow speeds with positive feeds with rigid mounts and sharp tooling surfaces.
- Suggested preheating to 250-400° F.
Most conventional welding methods can be successfully employed with 406 stainless steel pipes.
Preheating and postheating to 300-600° F is suggested.
Austenitic weld fillers, like AWS E310 or E312 are generally used to maximize weld deposit ductility.
- Oxyacetylene welding is not recommended.
Forging recommended to begin at 2100° F, and finish at 1600° F.
Grain refinement and room temperature embrittlement can be achieved by performing final 10% of work below 1600° F.
- Hot working for 446 steel pipes is recommended between 2000 – 2150° F.
When cold working, 446 is more difficult to bend, draw, spin, and weld than other stainless steel grades.
- This is due to its elevated chromium content.
- Annealing, should be performed at 1550-1650° F followed by rapid cool.
- Recommended to soak and water quench at 1500° F.
- Do not exceed 1650° F at any time.
- Slow cooling below 1200° F will result in the loss of ductility.
- Stainless steel pipes of 446 grade do not respond to heat treatment.
|Typical Chemical Composition % (max values, unless noted)|
|446||0.12 max||1.50 max||0.75 max||0.04 max||0.03 max||min: 23.0 max: 30.0||0.50 max||Balance||min: 0.10 max: 0.25|
|Typical Room Temperature Mechanical Properties|
|Grade||Tensile StrengthKSI (MPA)||Yield Strength 0.2% KSI offset KSI (MPA)||Elongation (% in 2ʺ(50.8 mm)||Hardness (Brinell) MAX||Hardness (Rockwell B) MAX|
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