Views: 59 Author: Wang Publish Time: 2024-05-30 Origin: Site
Stainless steel 321 is a titanium-stabilized chromium-nickel austenitic stainless steel with corrosion resistance similar to 304/304L. This grade is typically used in the 800-1500˚F range. Titanium addition stabilizes it against chromium carbide precipitation, resulting in titanium carbide formation.
After exposure to 800-1500°F, Alloy 321 demonstrates excellent intergranular corrosion resistance. Additionally, it resists oxidation up to 1500°F and provides higher creep and stress rupture properties than 304/304L. It also possesses good low-temperature toughness and is non-magnetic in the annealed condition.
Grade 321 is the basic austenitic 18/8 steel stabilized by titanium or niobium additions. Because they are not vulnerable to intergranular corrosion following heating within the carbide precipitation range of 425-850°C. Grade 321 has excellent strength, scaling resistance, and phase stability with resistance.
321 stainless steel (UNS S32100) is a titanium stabilized austenitic stainless steel that features improved resistance to intergranular corrosion. This grade is suitable for high-temperature applications, where the titanium stabilizes the material against chromium carbide formation.
While corrosion resistance is similar to 304 and 304L in the annealed, it features higher creep and stress properties. These properties make it ideal for pressure vessels and boiler applications. 321 stainless steel is non-magnetic and heat resistant for continuous service at elevated temperatures.
321 stainless materials cannot be hardened through heat treatment, only cold working. It is easily welded by all standard methods, and post-weld annealing is not required. This product is ductile and can be formed with ease. While corrosion resistance is generally excellent, 321 SS is easy to pit and crevice.
Type 321 finds application in heavy welding components, along with dynamic environments that are subject to changes. However, the addition of titanium limits the application of 321 in terms of working. The metal is not recommended for certain welding techniques as it is not consumable.
Beyond this, stainless steel 321 has excellent forming characteristics and displays toughness in a range of temperatures. The metal shows strength even when exposed to cryogenic temperatures. Additionally, it is often chosen over Type 304 for its increased resistance to creep and rupture. Both metals may be susceptible to stress corrosion cracking.
321 stainless steel is manufactured with titanium but based on 304 stainless steel. The added titanium enhances its corrosion and heat resistance, among other properties. Stainless steel 321 is high-chromium, high-nickel stainless steel with the presence of titanium.
Titanium content is at least five times the carbon content. Chromium content is in the range of 17-19% with a nickel content of 9-12%.
Grade | C | Cr | Ni | Si | Mn | P | S | N | Ti | Fe |
321 | 0.08 max | 17-19% | 9-12% | 0.75 max | 2.0 max | 0.045 max | 0.03 max | 0.10 max | 5*(C+N) 0.70 max | balance |
Stainless steel Grade 321 attains a metric density of 0.29 g/cm3.
The modulus of elasticity is 193 Gpa.
Electrical resistivity is 72 Microhm-cm.
The melting point range is 1371- 1399°C
Thermal properties
Thermal expansion coefficient is 16.6 µm/m° at 1-100°C and
Thermal conductivity is 16.1 W/mK at 100°C and 22.2 W/mK at 500°C.
Mechanical properties
Stainless steel 321 attains a tensile strength of 515 Mpa and yield strength of 205 Mpa. Hardness is 70B. Elongation is 40% in 50mm.
The annealing temperature range for Type 321 is 1800 to 2000° F (928 to 1093° C). This steel allows safe stress-relief annealing at 800-1500°F, avoiding intergranular corrosion.
Short-term strain relief annealing (a few hours at 800-1500°F / 427-816°C) will not reduce general corrosion resistance. However, extended exposure within this temperature range may reduce it somewhat.
Annealing in the 800 to 1500°F temperature range does not result in sensitivity to intergranular attack. For maximum ductility, the higher annealing range of 1800 to 2000° F is recommended.
When maximum corrosion resistance is called for, it may be necessary with 321 to employ a stabilizing anneal. It consists of heating to 1550 to 1650° F (843 to 899° C) for up to 5 hours depending on thickness.
Furthermore, it is the temperature at which titanium combines with carbon to form harmless titanium carbides.
After heat treatment in an oxidizing environment, remove the oxide by annealing in a descaling solution. These acids should be thoroughly rinsed off the surface after cleaning.
Austenitic stainless steels are the most weldable steels and can be welded by all fusion and resistance welding. It is important to maintain the level of stabilizing element present in Alloy 321 during welding. 321 is more prone to loss of titanium.
Care needs to be exercised to avoid pickup of carbon from oils and other sources and nitrogen from air. Metal welded with a fully austenitic structure is more susceptible to cracking during the welding operation. For this reason, Grade 321 is designed to resolidify with a small amount of ferrite to minimize cracking susceptibility.
Columbiu-stabilizedd stainless steels are more prone to hot cracking than titaniu-stabilizedd stainless steels. Matching filler metals are available for welding Type 321 stabilized stainless steel. Stabilized alloys may be joined to other stainless steels or carbon steels.
321 stainless steel is used in so many different applications because of its resistance to corrosion. Below, we outline a few key applications of 321 stainless steel.
Aerospace industry: To manufacture exhaust systems and heat exchangers.
Automotive industry: In catalytic converters and exhaust systems.
Chemical processing industry: For pipes, tanks and valves in chemical handling.
Food processing industry: To manufacture food processing equipment.
Medical industry: In medical equipment like dental tools and surgical implants.
Petrochemical industry: In boilers, heat exchangers, and pipes.
321 vs. 304: Superior resistance to sensitization and IGC after welding/high-temp exposure. Better high-temperature strength. Similar general corrosion resistance and cost.
321 vs. 304L: Alloy 304L has very low carbon (0.03% max), reducing but not eliminating sensitization risk. SS 321 offers higher strength, especially at elevated temperatures. 321 is generally preferred for high-temp structural components.
321 vs. 316L: 316L adds molybdenum for better pitting/crevice corrosion resistance, especially against chlorides. SS 321 has better high-temperature strength and stabilization against IGC. Choose 316L for marine/chloride environments and 321 for high-temp/corrosion environments where IGC is the primary concern.
321 vs. 347: Stabilized with Niobium (Nb) instead of Titanium. Properties are very similar. 347 generally has slightly better hot workability and weld hot cracking resistance, often making ER347 filler preferred for welding.
Product | Standard | Show |
Pipe SMLS & Welded | ASTM A312 |  |
Tube SMLS & Welded | ASTM A269/A213 |  |
Sheet / Plate | ASTM A240 |  |
Bar / Rod | ASTM A276/A479 |  |
Forging / Flange | ASTM A182 |  |
BW Fittings | ASTM A403 |  |
Both 304 and 321 are austenitic stainless steels with good corrosion resistance, formability, and weldability. The key difference is 321's addition of titanium.
304 vs 321 Stainless Steel: Chemical Composition
304 stainless steel has an iron-chromium-nickel alloy. It contains carbon, which is essential for strength but problematic at high temperatures.
321 stainless steel has a very similar base composition to 304. Its defining feature is the intentional addition of titanium, usually at a minimum of 5 times the carbon content.
304 vs 321 Stainless Steel: Performance Differences
Resistance to Sensitization and Intergranular Corrosion: In welding or long-term exposure to 800–1500°F, 321 resists sensitization and intergranular corrosion better than 304. 304 is prone to intergranular corrosion here unless replaced by ultra-low-carbon 304L with strict thermal controls.
High-Temperature Oxidation Resistance: 321 generally exhibits better resistance to scaling and retains higher strength at elevated temperatures compared to standard 304. For very high continuous service, grades 309 or 310 are often better suited.
General Corrosion Resistance: In most common corrosive environments, 304 and 321 offer similar corrosion resistance if kept below sensitizing temperatures. Neither is suitable for highly corrosive environments like marine chloride exposure, where 316 is preferred.
Mechanical Properties and Fabrication: At room temperature, their mechanical properties are virtually identical. Both are formable and weldable using common austenitic stainless techniques. Post-weld annealing is less critical for 321 due to its stabilization.
304 vs. 321 Stainless Steel: Typical Applications
304: For a vast range of applications not involving sustained high temperatures or severe welding thermal cycles. Examples: Food processing equipment, kitchen appliances, architectural trim, chemical containers, fasteners, tubing, tanks, cryogenic vessels.
321: Specifically chosen for parts subjected to intermittent high temperatures or requiring welding without subsequent annealing. Examples: High-temperature applications like aircraft exhausts, furnace parts, heat exchangers, flue gas systems, expansion joints, and welded assemblies.
