316 grade stainless steel is available from 0.4mm to 65mm in Engin Metal stocks. This grade is resistant to oxidation, and has good mechanical and strain characteristics up to 850°C. It’s used in vapor chambers of chemical, petro-chemical, and food industries, as well as for fruit juices, textile machines, and meat processing units. It’s also used against sea water.
PHYSICAL PROPERTIES / 316-316L-316Ti
| (At 20°C unless otherwise specified.) | ||
| Units | ||
| Density | 7,9 x 10 ³** | kg/m³ |
| Modulus of elasticity | 193 | GPa |
| Poisson’s ratio | 0,25 | |
| Specific heat capacity | 500 | J/kg K |
| Thermal Conductivity | ||
| At 100°C | 16,2 | W/mK |
| At 500°C | 21,5 | W/mK |
| Electrical resistivity | 74 | nWm |
| Mean co-efficient of thermal expansion between: | ||
| 0 – 100°C | 15,9 | µm/mK |
| 0 – 315°C | 16,2 | µm/mK |
| 0 – 540°C | 17,5 | µm/mK |
| 0 – 700°C | 18,5 | µm/mK |
| Melting range | 1375 – 1400 | C° |
| Realitive magnetic permeability | 1,02 |
* non-magnetic becoming slightly magnetic when cold worked.
** This figure is the true density of the material, for billing purposes the theoretical mass is calculated by using 8,07kg/m2/mm of thickness (this takes into account the effect of the various tolerances
MECHANICAL PROPERTIES
MECHANICAL PROPERTIES AT ROOM TEMPERATURE ACCORDING TO ASTMA240:
| 316 | 316L | 316Ti | Birimler | |
| Tensile Strength | 515 min | 485 min | 515 min | MPa |
| Proof Strength (0,2% strain) | 205 min | 170 min | 205 min | MPa |
| Elongation (in 50mm) | 40 min | 40 min | 40 min | % |
| Brinell Hardness | 217 max | 217 max | 217 max |
PROPERTIES AT ELEVATED TEMPERATURES
The values quoted below are for 316 and 316 Ti only as strength values for316 L fall rapidly at temperatures above 425°C. Values are for annealed material. These values are typical values only and should not be used for design purposes.
TYPICAL SHORT TIME ELEVATED TEMPERATURE TENSILE STRENGTH
| Temperature°C°C | 600 | 700 | 800 | 900 | 1000 |
| Tensile Strength MPa | 480 | 320 | 190 | 120 | 70 |
TYPICAL CREEP RUPTURE STRENGTH AFTER 10,000 HOURS
| Temperature°C°C | 540 | 600 | 650 | 700 | 800 | |
| Stress MPa | 316 | 296 | 182 | 111 | 66 | 29 |
| 316L | 268 | 162 | 98 | 59 | 24 |
TYPICAL AVERAGE STRESS TO PRODUCE 1% STRAIN IN 10,000 HOURS
Values quoted are for 316 and 316L only
| Temperature°C°C | 538 | 600 | 650 | 700 | 800 |
| Stress MPa | 172 | 120 | 80 | 52 | 36 |
MAXIMUM RECOMMENDED SERVICE TEMPERATURE
Values given for oxidising conditions (316 only)
| Continuous Service | 925°C |
| Intermitent Service | 870°C |
TYPICAL PROPERTIES AT SUB-ZERO TEMPERATURES
Values quoted for 316 only
| Temperature°C | -196 | -140 | -50 | -10 | 0 | 20 |
| Tensile Strenght (MPa) | 1360 | 1136 | 1105 | 830 | 680 | 584 |
| 0,2% Proof Stress (MPa) | 444 | 417 | 380 | 338 | 260 | 235 |
| Elongalion (%) | 58 | 61 | 65 | 69 | 70 | 61 |
| Charpy Darbe Mukavemeti (J) | 166 | 155 | 183 | 186 | 191 | 170 |
FATIGUE CONSIDERATIONS
When looking into the fatigue strength of satainless steels, it is important to note that design and fabrication-not material, are the major contriloutions to fatigue failure. Desion codes (e.g. ASME and BS 5500) are data form low- cycle fatigue tests carried out in machined specimens to produces conservative S-N curves used with stress concentration factors (Kl) or fatigue strength reduciton factors (Kt). In essence the fatigue strength of a welded joint should be used for design purposes as the inevitable flaws (even only those of cross – sectional change) within a weld will control the overall fatigue performance of the structure.
The curvers below show results of interesting actions of welded joints under variable loading for austenitic stainless steel 316Ti following Eurocode 3. When compared with the literature the fatigue properties of 316Ti appear to be similar for those mild steel.
CORROSION RESISTANCE
The 316 types have superior corrosion resistance to 304. The addition of molybdanium to the steel ensures that 316 has good resistance to localised corrosion such as pitting and crevice corrosion. 316 has good resistance to most complex sulphur compounds such as are found in the pulp and paper industry. 316 also has good resistance to pitting and phosphoric and acetic acids. 316 has excellent resistance to corrosion in marine environments under atmospheric conditions.
PITTING CORROSION
Pitting resistance is important, mainly in applications invotving contact with chloride solutions, particulary in the presence of oxidising media. These conditions may be conduive to localised penalration of the passive surface lilm on the steel and a single deep pit may well be more damaging than a much greater number of relatively shallow pits. Where pitting corrosion is anticipated steels containing molybdenum additions such as 316 have a superior performance over the other grades.
ATMOSPHERIC CORROSION
The atmospheric corrosion resistance of austenitic stainless steels is unaqualled by virtually all other uncoated engineering materials. Stainless steel develops maximum resistance to staining and pitting with the addition of molybdenum. For this reason, is it common practice to use the 316 molybdenum bearing grade in areas where the atmosphere is higly poliuted with chlorides, sulphur compounds and solids either singly or in combination. However in urban and rual areas 304 grade is generaly perfectly satisfoctory
INTERGRANULAR CORROSION
Sensitisation may occur when some austenitic stainless steels are welded or otherwise heated in the sensitising temperature range 450-850°C, when acompositional change may occur at the grain boundaries. İf a sensitised material is then subjected to a corrosive environment, some intergranular attack may be experienced.
When associated with welding, corrosion takes place preferentially in the heat affected zone on the parent material parallel to weld. Susceptibility to this from of attack, often termed “weid decay”, may be assessed by the following standard tests:
a) boiling copper sulphate/sulphuric acid test as specified in ASTM A262-70, Practice E.
b) boiling nitric acid test specified in ASTM A262-66 Practice C.
316 has reasonable resistance to carbide precipitation. The low carbon “L” grades should in any case be specified for welded structures unless the higher carbon types are required for their increased strength at elevated temperatures. In tis case 316 Ti should be specified..
STRESS CORROSION
Stress corrosion can ocour in austenitic stainless steels when they are stressed in tension in chloride environments at temperatures şb excess of about 60°C. The stress may be applied, as in a pressure system or it may be residual aristing from cold working operations or welding. Additionally, the chloride ion concentration need not be very high initialy, il locations exits in which concentrations of salt can accumulate. Assessment of these parameters and accurate prediction of the protability of stress corrosion occuring in service is therefore diffucult.
Where there is a likellhood of stress corrosion occuring, a benaficial increase in life can be easily obtained by a reduction in operating stress and temperature. Alternatively, specially designed alloys, such as duplex stainless steels, will have to be used where s.c.c. is likely to occur.
HEAT RESISTANCE
316 has good oxidation resistance in intermitent service to 870°C and in continuos service to 925°C. Continuous use 316 in the 425°C/850°C temperature range is not recommended due tı carbide precipitation but often pereforms well in temperatures fluctuating above and below this range.
THERMAL PROCESSING & FABRICATION
ANNEALING
Heat from 1010-1120°C and cool rapidly in air or water. The best corrosion resistance is achieved when the final annealing temperature is above 1070°C. Controlled atmospheres are recommended in order to avoid excessive oxidatioın of the surface.
STRESS RELIEVING
316 L can be stress relievedet at 450 – 600°C for one hour with little danger of sensitisation. Alower stress relieving temperature of 400°C maximum must be used with 316 with longer soaking times. If however, stress relieving is to be carried out above 600°C, there is a serious theal lf grain boundary sensitisation occuring with a conoomitant loss in corrosion resistance In this instance, a stabilised grade such as 316 Ti should be used.
HOT WORKING
The steel can be readily forget, upset and hot headed Uniform heating of the steel in the range of 1150 to 1250°C. The finishing temperature should not be below 900°C. Upsetting operations and forgings require a finishing temperature between 930 and 980°C Forgings should be air cooled. All hot working operations should be followed by annealing.
COLD WORKING
316 types, being extremaly tough and ductile, can be readily deep drawn, stamped, headed and upset without difficultly. Since this steel work hardnes, severe cold forming operations should be followed by annealing.
MACHINING
Like all the austenitic steels, this alloy machines with a tough and stringy swart. Rigidly supported tools with as heavy a cut possible should be used to prevent glazing. In turning operations speeds of 12 – 18 rpm should be used./div>
WELDING
316 types have good welding charahteristics and are suited to all standard welding methods. Either matching or slightly over-alloyed filter wires (e.g. ERW 309 Mo) should be used. For maximum corrosion resistance, the higher carbon type 316 should be annealed after welding to dissolve any chromium carbides which may have precipated.
All operations involving high temperatures (e.g. thermal processing and welding) must be followed by pickling and passivating of the affacted areas to restore full corrosion resistance. Fresh surfaces which have been produced bye mechanical means (e.g. machining, grinding) are best passivarted in order to restore maximum corrosin resistance..