“Composition AS PER ASTM A312/312M”
Composition
      Typical compositional ranges for grade 310 stainless steels are given in table 1.
Table 1. Composition ranges for 310 grade stainless steel

（310S AS PER ASTM A312/312M）
Mechanical Properties
      Typical mechanical properties for grade 310S stainless steels are given in table 2.
Table 2. Mechanical properties of 310S grade stainless steel

Physical Properties
      Typical physical properties for annealed grade 310 stainless steels are given in table 3.
Table 3. Physical properties of 310 grade stainless steel in the annealed condition

Grade Specification Comparison
      Approximate grade comparisons for 310 stainless steels are given in table 4.
Table 4. Grade specifications for 310 grade stainless steel

Possible Alternative Grades
      Possible alternative grades to grade 310 stainless steels are given in table 5.
Table 5. Possible alternative grades to 310 grade stainless steel

Corrosion Resistance
      The high chromium content - intended to increase high temperature properties - also gives these grades good aqueous corrosion resistance. The PRE is approximately 25, and seawater resistance about 22°C, similar to that of Grade 316. Excellent resistance at normal temperatures, and when in high temperature service exhibits good resistance to oxidising and carburising atmospheres. Resists fuming nitric acid at room temperature and fused nitrates up to 425°C.
Subject to stress corrosion cracking but more resistant than Grades 304 or 316.
Aqueous Corrosion Resistance
      Alloys 310/310S is primarily used at elevated temperature to take advantage of their oxidation resistance. However, both of these stainless grades are resistant to aqueous corrosion due to their high chromium and nickel contents.
      Although their higher nickel content provides marginal improvement with respect to chloride stress corrosion cracking (SCC) compared to the 18-8 stainless steels, Alloys 309/309S and 310/310S austenitic stainless steels remain susceptible to this form of attack.
      Certain applications specify the use of Alloy 310/310S stainless steel where increased resistance to aqueous corrosion is needed. An example is service in concentrated nitric acid, where preferential attack of grain boundaries may occur.

Heat Resistance
      Good resistance to oxidation in intermittent service in air at temperatures up to 1040°C and 1150°C in continuous service. Good resistance to thermal fatigue and cyclic heating. Widely used where sulphur dioxide gas is encountered at elevated temperatures. Continuous use in 425-860°C range not recommended due to carbide precipitation, if subsequent aqueous corrosion resistance is needed, but often performs well in temperatures fluctuating above and below this range.
      Grade 310 is generally used at temperatures starting from about 800 or 900°C - above the temperatures at which 304H and 321 are effective.
Elevated Temperature Oxidation Resistance
      Metallic alloys will react with their surroundings to some degree under most conditions. The most common reaction is oxidation – metallic elements combining with oxygen to form oxides. Stainless steels are resistant to oxidation through selective oxidation of chromium, which forms a slow-growing, very stable oxide (Cr2O3 or chromia). Given enough chromium in the underlying alloy, a compact and adherent surface layer of chromium oxide is established which prevents the formation of other, faster growing oxides and serves as a barrier to further degradation. The rate of oxidation is controlled by transport of charged species through the external chromia scale. As the surface scale thickens, the rate of oxidation decreases dramatically because the charged species have to travel farther. This process, the high temperature analogue of passivation during corrosion at low temperatures, is known as protective scale formation.
      The oxidation resistance of austenitic stainless steels can be approximated by the chromium content of the alloy. True heat resistant alloys generally contain at least 20% (by weight) chromium. Replacing iron with nickel also generally improves an alloy's high temperature behavior. Alloys 309/309S and 310/310S are highly alloyed materials and are, therefore, very resistant to oxidation.
      An oxidized metal sample will increase in weight corresponding to the amount of oxygen incorporated into the scale and any internal oxidation. Measuring the change in weight of a sample which has been exposed at high temperatures for a set period of time is one way to determine the oxidation resistance of an alloy. Greater weight gains typically indicate more severe oxidation.
Oxidation is more complex than simple scale thickening. Spallation, or the detachment of the surface oxide scale, is the most common problem encountered during the oxidation of stainless steels. Spallation is typically manifested by rapidly accelerating weight loss. A number of factors can cause spallation, chief among them thermal cycling, mechanical damage, and excessive oxide thickness.
      During oxidation, chromium is tied up in the scale in the form of chromium oxide. When the oxide scale spalls off, fresh metal is exposed and the local rate of oxidation temporarily increases as new chromium oxide forms. Given sufficient scale spallation, enough chromium may be lost to cause the underlying alloy to lose its heat resistant properties. The result is the formation of rapidly growing oxides of iron and nickel, known as breakaway oxidation.
      Very high temperature oxidation can lead to scale volatilization. The surface chromium oxide scale formed on heat resistant stainless steels is primarily Cr2O3. At higher temperatures, the tendency is for further oxidation to CrO3, which has a very high vapor pressure. The rate of oxidation is then split into two parts – scale thickening by formation of Cr2O3 and the thinning effect of CrO3 evaporation. The tendency is for eventual balance between growth and thinning with the scale remaining at a constant thickness. The result is continuous recession of the surface and consumption of the metal beneath. The effect of scale volatilization becomes a significant problem at temperatures above approximately 2000°F (1093°C) and is exacerbated by rapidly flowing gases.

Heat Treatment
      The primary reason for annealing these alloys is to produce a recrystalized microstructure with a uniform grain size and for dissolving detrimental chromium carbide precipitates. To ensure complete annealing, pieces should be held in the range 2050-2150°F (1120-1175°C) for approximately 30 minutes (time at temperature) per inch of section thickness. This is a general recommendation only – specific cases may require further investigation. When properly annealed, these grades are primarily austenitic at room temperature. Some small quantities of ferrite may be present.
      Oxide scale formation is inevitable during air annealing of Alloys 309/309S and 310/310S. The scale that forms is generally rich in chromium and relatively adherent. The annealing scale generally must be removed prior to further processing or service. There are two typical methods for removing scale – mechanical and chemical. A combination of surface blasting prior to chemical scale removal is generally effective at removing all but the most tightly adherent scale. Silica sand or glass beads are a good choice for the blasting media. Iron or steel shot can also be used but will lead to embedded free iron in the surface which may then result in surface rusting or discoloration unless the surface is subsequently pickled.
      Chemical removal of scale is generally performed with mixed nitric-hydrofluoric acids. The proper bath makeup and process temperature combination depends on the situation. A typical pickling bath used consists of 5-15% HNO3 (65% initial strength) and 1/2 -3% HF (60% initial strength) in aqueous solution. Higher concentrations of hydrofluoric acid lead to more aggressive scale removal. Bath temperatures generally range from ambient to about 140°F (50°C). Higher temperatures result in faster descaling but may attack grain boundaries aggressively, resulting in surface grooving. Acid pickling must be followed with a thorough water wash to remove all traces of pickling acids. Drying should then be used to avoid spotting and staining.
      As noted, Alloys 309/309S and 310/310S consist solely of austenite at room temperature – they cannot be hardened through heat treatment. Higher mechanical strengths are attainable via cold or warm working, but these grades are generally not available in such conditions. The higher tensile and yield strengths obtainable through cold working not followed by full annealing are not stable at the higher temperatures at which these alloys are often used. Creep properties in particular may be adversely affected by the use of cold worked material at elevated temperatures.
These grades cannot be hardened by thermal treatment.

Welding
      The austenitic grades are generally considered to be the most weldable of the stainless steels. They can be welded using all of the common processes. This is generally true of Alloys 309/309S and 310/310S. When filler metal is required, matching compositions are generally used. The elevated alloy contents of this grade can make the weld pool sluggish. If weld pool fluidity is a problem, filler metal containing silicon can help (e.g., ER309Si, ER309LSi).
      Alloys 309/309S and 310/310S exhibit a relatively high coefficient of thermal expansion and low thermal conductivity and form low levels of ferrite in the solidifying weld metal. These factors can lead to hot cracking. The problem can be more severe for restrained and/or wide joints. Filler metal with a lower alloy content (e.g., ER308) will increase the amount of ferrite in the weld deposit and reduce the tendency for hot cracking. The subsequent dilution of the base metal may decrease the corrosion/heat resistance of the weld.
      The "S" grades are relatively low in carbon. With proper weld practices, intergranular corrosion of the heat affected zone is unlikely. Heat tint or scale should be removed to ensure complete restoration of corrosion resistance near the weld. Grinding or brushing with a stainless steel brush can be used to remove the heat tint scale. Acid pickling will also remove heat intent. Small pieces can be treated in a bath, and larger pieces can be locally pickled using a special paste consisting of a mixture of nitric acid and HF or hydrochloric acid suspended in an inert filler. A thorough water wash should immediately follow, taking care to completely remove all traces of pickling paste.

“Dual Certification”
      310 and 310S are sometimes stocked in "Dual Certified" form - mainly in plate and pipe. These items have chemical and mechanical properties complying with both 310 and 310S specifications.

Applications
       Higher alloyed stainless steels generally exhibit excellent elevated temperature strength along with resistance to creep deformation and environmental attack. As such, they are used widely in the heat treatment industry for furnace parts such as conveyor belts, rollers, burner parts, refractory supports, retorts and oven linings, fans, tube hangers, and baskets and trays to hold small parts. These grades are also used in the chemical process industry to contain hot concentrated acids, ammonia, and sulfur dioxide. In the food processing industry, they are used in contact with hot acetic and citric acid.
Typical applications include:
·        boiler, radiant tubes, burners, combustion tubes,, furnace components and other high temperature containers ,Used as materiale for furnace and exhaust gas cleaning systems of automobiles.     
         Heat Treatment baskets and jigs
         Heat Exchangers
        Welding filler wire and electrodes