What GR12 Is
GR12 is titanium Grade 12, UNS R53400, an alloy containing molybdenum 0.2 to 0.4 percent and nickel 0.6 to 0.9 percent. The additions give the alloy roughly 40 percent higher strength than Grade 2 and markedly better resistance to reducing acids and crevice corrosion. In welded tube form it brings these properties to heat exchangers and process lines.
How Welded Tube Is Made
Welded tube starts as strip that is roll-formed into a cylinder and welded by tungsten arc or plasma methods under full argon shielding. The welded tube is then drawn over a mandrel and annealed, which refines the weld zone and the grain structure and restores ductility. The welded and drawn route produces thin-wall tube with the tight tolerances that exchanger bundles require.
Properties of GR12 Tube
Under ASTM B338, GR12 tube must meet a minimum tensile strength of 483 MPa and a minimum yield strength of 345 MPa with 18 percent elongation. The alloy keeps useful strength at elevated temperature and welds with standard titanium practice. Density is 4.51 g per cubic centimetre.
Corrosion Performance
GR12 resists hot brines, seawater and dilute reducing acids where CP grades pit or crevice corrode, and it performs well in both oxidizing and reducing media. The welded and drawn tube carries the same corrosion resistance as the parent strip because the weld is produced under inert shielding. This makes GR12 a dependable material for aggressive exchanger service.
Standards and Testing
Welded GR12 tubing is supplied to ASTM B338 and ASME SB338 for heat exchangers, with ASTM B862 for welded pipe. Each tube is dimensionally verified and pressure tested, and the certificate reports composition and mechanical results. The weld is examined by the flattening and flaring checks required by the specification.
Applications
Chemical process heat exchangers.
Brine and seawater coolers.
Process piping for dilute acid streams.
Geothermal and desalination plant tubing.
Frequently Asked Questions
Q: What is GR12 welded tube?
A: It is tube manufactured from titanium Grade 12, UNS R53400 strip, formed, welded and drawn to close tolerances.
Q: Why is Grade 12 used for tube?
A: It combines higher strength than CP grades with resistance to reducing acids and crevice corrosion.
Q: Which standard covers GR12 tube?
A: ASTM B338 and ASME SB338 cover GR12 heat exchanger tubing, with B862 for welded pipe.
Q: What are the strength minimums?
A: 483 MPa minimum tensile strength and 345 MPa minimum yield strength with 18 percent elongation.
Q: Does welding reduce corrosion resistance?
A: No, the weld is produced under argon shielding and the tube keeps the corrosion performance of the parent strip.
Q: Where is GR12 welded tube used?
A> In chemical exchangers, brine coolers, dilute-acid piping and geothermal tubing.
