Yuhong Group Co.,Ltd
Yuhong Holding Group Co.,LTD
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Yuhong Special Steel has been engaged in seamless welded pipes and pipes of austenitic stainless steel and nickel alloy steel
(Hastelloy, Monel, Inconel, Inconel) for more than 25 years, with annual sales of more than 80,000 tons of steel pipes and pipes.
pipeline. Our customers are located in over 55 countries including USA, Canada, UK, Germany, Italy, Chile, Colombia,
Saudi Arabia, South Korea, Singapore, Australia, Poland and France.
Stainless Steel 321 is a basic austenitic 18/8 steel (grade 304) stabilized by the addition of titanium (321). SS 321 are used
because they are not susceptible to intergranular corrosion after heating in the carbide precipitation range of 425-850°C.
SS 321 is the grade of choice for applications in the temperature range up to about 900°C, combining high strength,
resistance to scaling and phase stability with subsequent resistance to water corrosion. SS 321H is an improved version
of SS 321 with a higher carbon content to provide higher high temperature strength.
| Stainless Steel SS 321 / 321H | |
|---|---|
| AISI | 321 / 321H |
| UNS | S32100 / S32109 |
| Werkstoff Nr. | 1.4541 / 1.4878 |
| Density | 8.0 g/cm3 |
| Melting Point | 1454 °C (2650 °F) |
| Tensile Strength | Psi – 75000 , MPa – 515 |
| Yield Strength (0.2%Offset) | Psi – 30000 , MPa – 205 |
| Elongation | 35 % |
| SS 321 | SS 321H | |
| Ni | 9 – 12 | 9 – 12 |
| Cr | 17 – 19 | 17 – 19 |
| C | 0.08 max | 0.04 – 0.10 |
| N | 0.10 max | |
| Fe | Balance | |
| Mn | 2 max | 2 max |
| Si | 0.75 max | 0.75 max |
| S | 0.03 max | 0.03 max |
| P | 0.045 max | 0.045 max |
| Ti | 5xC min 0.60% max | 4xC min 0.60% max |
Alloys 321 (S32100) and 347 (S34700) are stable stainless steels whose main advantage is their excellent resistance to
intergranular corrosion after exposure to the chromium carbide precipitation temperature range of 800 to 15000F (427 to 8160C).
Alloy 321 stabilizes chromium carbide formation by adding titanium. Alloy 347 is stabilized by the addition of niobium and tantalum.
While Alloys 321 and 347 continue to be used for long-term use in the 800 to 15000F (427 to 8160C) temperature range, Alloy 304L
has superseded these stable grades for applications involving only welding or short-term heating.
Alloy 321 and 347 stainless steels are also beneficial for high temperature applications because of their good mechanical properties.
Alloy 321 and 347 stainless steels offer higher creep and stress rupture properties than Alloy 304, especially Alloy 304L, which can also be
considered for exposures concerned with sensitization and intergranular corrosion. This results in higher high temperature allowable stresses
for these stable alloys used in ASME boiler and pressure vessel code applications. Alloys 321 and 347 have a maximum service temperature of
15000F (8160C) for code applications such as Alloy 304, while Alloy 304L is limited to 8000F (4260C).
High carbon versions of both alloys are available. These grades have UNS designations S32109 and S34709.
.
Resistance to Corrosion of 321 Stainless Steel Pipes and Tubes
general corrosion
Alloys 321 and 347 offer general bulk corrosion resistance similar to the unstable chromium-nickel alloy 304. Prolonged heating in the
chromiumcarbide precipitation range may affect the general resistance of alloys 321 and 347 in severely corrosive media.
In most environments, both alloys will exhibit similar corrosion resistance; however, Alloy 321 in the annealed condition is slightly less
resistant to general corrosion than annealed Alloy 347 in a strongly oxidizing environment. Therefore, Alloy 347 is more suitable for water
and other low temperature environments. The overall corrosion resistance of Alloy 321 is much more degraded than Alloy 347 when exposed
to the temperature range of 8000F to 15000F (4270C to 8160C). Alloy 347 is primarily used in high temperature applications where high
resistance to sensitization is required to prevent intergranular low temperature corrosion.
Physical Properties of 321 Stainless Steel Pipes and Tubes
The physical characteristics of the Models 321 and 347 are very similar and, for all practical purposes, can be considered the same.
The values given in the table can be used for both steels.
When properly annealed, Alloy 321 and 347 stainless steels consist primarily of austenite and carbides of titanium or niobium. Small amounts
of ferrite may or may not be present in the microstructure. A small amount of sigma phase may form during prolonged exposure in the temperature
range of 10000F to 15000F (5930C to 8160C).
Stable Alloy 321 and 347 stainless steels cannot be hardened by heat treatment.
The overall heat transfer coefficient of a metal depends on factors other than the thermal conductivity of the metal. In most cases, film coefficients,
fouling, and surface conditions make stainless steels that require no more than 10% to 15% surface area than other metals with higher thermal
conductivity. Stainless steel's ability to maintain a clean surface generally has better heat transfer than other metals with higher thermal conductivity.
