Among austenitic stainless steels, SS 316 is the standard titanium alloy grade and is second only to grade 304 in importance. In general, Grade 316 has stronger corrosion resistance than Grade 304 thanks to molybdenum, and it is especially resistant to corrosive environments in chloride conditions. Excellent molding and welding properties are present. It is easily shaped into various elements for use in the transportation, architectural, and industrial sectors. Additionally, grade 316 offers excellent weldability qualities. When welding narrow parts, post-weld softening is not necessary.

Key properties:

In their individual requirements, other goods like pipes and bars are offered to equal but not identical standards.

Corrosion resistance:

316 is excellent in numerous corrosive media and various climatic conditions; typically more durable than 304. In warm chloride settings, subject to etching and crevice corrosion and stress rusting breaking above 60 °C. Potable water is thought to be resistant to chlorides up to around 1000 mg/L at room temperature, which drops to around 5mg at 60 °C.

Although 316 is frequently referred to as the industry standard for “marine grade stainless steel,” it is not heat resistant. In addition, 316 does experience surface corrosion in various marine settings, typically seen as brown staining. This is especially related to crevices and an uneven surface finish.

Welding:

Excellent weldability with or without filler metals using all common fusion techniques. Welding of 316 using Category 316 & 316L with Grade 316L rods or wires is pre-qualified by AS 1554.6. Heavy welded sections made of Grade 316 need to be post-annealed to get the highest level of corrosion resistance. For 316L, this is not required. For heavy section welding, grade 316Ti can also be utilized as a substitute for grade 316.

Heat treatment:

Heat the solution between 1010 and 1120 °C and then quickly let it cool. Thermal treatment cannot be used to harden these grades. Grade 316L can be used in the abovementioned temperature range and is more susceptible to carbide precipitation. At temperatures over around 500 °C, grade 316H is occasionally utilized for structure and pressure-containing applications due to its increased strength at these temperatures.

Machining:

Round and cylindrical bar items made of grade 316 are offered in a “Ugima” increased machinability form. With higher machining speeds and less tool wear in various processes, this machine is much better than the conventional 316 or 316L.

Heat Resistance:

Excellent oxidation resistance in continuous service at 925 °C and intermittent service at 870 °C. If aqua corrosion resistance is crucial, using 316 continuously in the 425-860 °C range is not advised.

Dual and Certification:

The “Dual Certified” type of 316 and 316L is frequently available, mostly found in sheets and pipes. These products meet both 316 and 316L requirements regarding their chemical and mechanical qualities. However, such a dual-certified product might not be suitable for high heat resistance because it does not fulfill 316H specifications.

Applications:

Application examples include:

  • Tools for food processing, especially in chloride conditions.
  • Equipment and benches for laboratories
  • Architectural paneling, railings, and trim along the coast.
  • Vessel fittings.
  • Containers for chemical storage and transportation.
  • Exchangers of heat.
  • For use in mining, quarrying, and water filtration, woven or welded screens.
  • Fastening with threads.
  • Springs.

SS 321:

With more carbon added, Grade 321H is a variation of SS 321 that offers better high-temperature strength.

Titanium does not transmit well over a high-temperature arc, a drawback of 321 and is not suggested as a consumable for welding. Grade 347 is chosen in this situation because it can travel over a welding arc while still performing the same carbide stabilizing function. As a result, the preferred flux for welding 321 is grade 347. Rarely is Grade 347 utilized as master plate material.

Like other austenitic stainless steel, 321 and 347 are easily brake or roll-formed, have good welding capabilities, and have excellent forming properties. Therefore, annealing after welding is not necessary. Additionally, they are extremely tough, even at cryogenic temperatures. Neither does Grade 321.

It works poorly for decorative purposes because it polishes nicely.

If the need is just resistance to corrosion damage after welding, grade 304L is usually preferred over 321 since it is more easily accessible in most product forms. However, 304L is not the ideal option if the need is durability for a working environment exceeding roughly 500 °C because it has less hot toughness than 321.

Key properties:

These characteristics are listed in ASTM A240/A240M for flat-rolled materials (plates, sheets, and coils). Other goods like pipes and bars have requirements that call for similar but not automatically equal qualities.

Corrosion resistance:

Comparable to tool steel in the annealing state, and higher if a joint made of these categories has not undergone post-weld annealing or if it will be subjected to service at temperatures between 425 and 900 °C. In warm chloride settings, prone to cracking and crevice corrosion and to strain corrosion cracking above 60 °C. Potable water is thought to be resistant to chlorides up to 200 mg/L at room temperature, which drops to 150 mg/L above 60 °C.

Heat Resistance:

Excellent oxidation resistance in continuous service at 925 °C and intermittent service at 900 °C. These grades work well between 425 and 900 °C, especially when subsequent aqueous corrosive conditions occur.Because of its greater hot strength, 321H is especially well suited for structural uses involving high temperatures.

Heat Treatment:

For best corrosion resistance, solution treatment (annealing) should be heated to 950–1200 °C and then quickly cooled.

Stabilizing: heat to 870–900 °C for one hour per 25 mm of thickness, then allow to cool in the air. Stabilization is advised for materials exposed to the harshest service conditions (over 425 °C), especially for materials annealing at the higher end of the processing temperature range.

Preheat to 750 °C for one to two hours, then let the air cool.

Thermal treatment cannot be used to harden these grades.

Welding:

Excellent weldability with or without filler metals using all common fusion techniques. With Category 347 rods or electrodes, AS 1554.6 pre-qualifies for the welding of 321 and 347; a high lead form of 347 too, which was before for welding of 321.

Applications:

Application examples include:

  • Exhaust manifolds for aircraft
  • Joints for expansion
  • Section of a furnace
  • Tubes for heating elements
  • Exchangers of heat
  • For use in high-temperature mineral processing, woven or welded screens
  • Spiral Furnace pipes and flues are made of the welded tube.