ASTM A213 TP316Ti Seamless Tubes

ASTM A213 TP316Ti seamless tubes are primarily used for pressure piping in accordance with ASME B31.1 – Power Piping and ASME B31.3 – Process Piping. It has the nominal composition of 16Cr-12Ni-2Mo-Ti, with UNS designation S31635 and P-No. 8. Titanium is added to the molybdenum-bearing stainless steel to tie up the carbon content so that the damaging chromium carbide precipitation (chromium depletion) can be avoided. Thus, TP316Ti tubing can be applied to services with long exposure to temperatures in sensitization range. The tubing sizes and thicknesses usually are 1/8″ in inside diameter to 5″ in outside diameter, and 0.015″ to 0.500″, inclusive, in minimum wall thickness or average wall thickness. The permissible variations (tolerances) of outside diameter, length, and wall thickness (minimum or average) wall thickness shall be in accordance with ASTM A1016.

Chemical Composition Requirements

Element	Composition, %
C	≤0.08
Mn	≤2.00
P	≤0.045
S	≤0.030
Si	≤0.75
Cr	16.0-18.0
Ni	10.0-14.0
Mo	2.00-3.00
N	≤0.10
Ti	*Note

*Composition requirements for ASTM A213 TP316Ti seamless tubes.
*Note: 5x(C+N)≤Ti≤0.70%; All values shall be determined by product analysis.

Mechanical Properties

Mechanical Tests	Requirements
Tensile Strength min. MPa [ksi]	515 [75]
Yield Strength min. MPa [ksi]	205 [30]
Elongation in 2", min. %	35
Brinell Hardness max. HBW	192
Vickers Hardness max. HV	200
Rockwell Hardness max. HRB	90

*Tensile & hardness requirements for ASTM A213 TP316Ti seamless tubes at room temperature.

Manufacture, Heat Treatment & Welding

The ASTM A213 TP316Ti tubing shall be made by the seamless process and shall be either hot finished or cold finished. Usually, the 316Ti stainless steel shall be made by electric-arc furnace (EAF) melting, with subsequent argon-oxygen decarburization (AOD) and ladle furnace refining. The cast tube ingot passes through the roughing mill for preliminary rolling and is ground on the billet grinder. The tube billet (ingot) is then forged on the radial forging mill to attain desired diameter for further processing. The seamless tube is then made by combined processes of hot-piercing/ hot extrusion, and cold drawing & cold rolling. The tubing will be marked and packaged after heat treatment and straightening on a leveller.

ASTM A213 TP316Ti seamless tubing shall be furnished with solution annealing treatment, in which the tubing is soaked at a temperature no less than 1900°F [1040°C] for full austenization and it is quenched in water after leaving the furnace. A subsequent stabilizing heat treatment may be applied at a temperature lower than that used for the initial solution annealing heat treatment. The holding temperature of stabilizing heat treatment shall be between 1550-1650°F [845-900°C] for TP316Ti.

ASTM A213 TP316Ti tubes are primarily used for the construction of boilers, superheaters, and heat exchangers. When inserted in a boiler or tube sheet, the tubing shall stand expanding and beading without showing cracks or flaws. When applied to superheaters, it stand all forging, welding, and bending operations necessary for application without developing defects. TP316Ti tubes are often welded autogenously. Care must be taken to avoid solidification cracking and to preserve corrosion resistance of the weld and heat affected zones. If filler metal must be used for welding TP316Ti tubing, it is advisable to utilize the low carbon types 316L or E318 filler metals. The weld region must be cleaned thoroughly to avoid any residual copper or zinc, which may create weld cracking.

Inspection & Tests

Tensile test, hardness test, chemical analysis, flattening test, flaring test, visual examination, dimensional inspection, eddy current test/ hydrostatic test are required for ASTM A213 TP316Ti seamless tubing. When specified, the tubing shall pass intergranular corrosion tests conducted in accordance with ASTM A262 Practice E.

Design Temperature Limits & Allowable Stresses

The minimum and maximum design temperature limits for ASTM A213 TP316Ti in power piping of ASME B31.1 are 100°F and 1200°F, respectively. The minimum & maximum design temperature limits for ASTM A213 TP316Ti tubing in process piping are -325°F and 1500°F, respectively.

Temp. °F	S, ksi	S', ksi
100	20.0	20.0
200	17.7	20.0
300	15.8	20.0
400	14.3	19.4
500	13.2	17.8
600	12.4	16.8
650	12.2	16.5
700	12.0	16.2
750	11.9	16.0
800	11.8	15.9
850	11.7	15.8
900	11.6	15.7
950	11.5	15.5
1000	11.4	15.3
1050	11.2	15.1
1100	11.0	12.3
1150	9.8	9.8
1200	7.4	7.4

*Maximum allowable stress values in tension, S & S’, for ASTM A213 TP316Ti at metal temperatures, not exceeding. S’ only applies when slightly greater deformation (permanent strain) is acceptable. All values are extracted from ASME B31.1 Table A-3.

Temp. °F	S, ksi
100	20.0
200	20.0
300	20.0
400	19.3
500	17.8
600	16.8
650	16.5
700	16.2
750	16.1
800	15.9
850	15.8
900	15.7
950	15.5
1000	15.3
1050	15.1
1100	12.3
1150	9.8
1200	7.4
1250	5.5
1300	4.1
1350	3.1
1400	2.3
1450	1.7
1500	1.3

*Basic allowable stress values in tension, S, for ASTM A213 TP316Ti at metal temperatures, not exceeding. All values are extracted from ASME B31.3 Table A-1.