Böhler Union S 2 Si EM12K Submerged Arc Wire

The standard C-Mn SAW wire for general structural steel

Böhler Union S 2 Si is a copper-coated solid wire for submerged arc welding of general structural steel grades up to S235-S420. It is classified AWS A5.17 / SFA-5.17 EM12K and EN ISO 14171-A S2Si, which makes it the workhorse wire for plate girders, pressure-vessel shells, tank walls, pipe seams and heavy fabrication where the weld metal has to match mild and normalised structural steel. Its manganese level of about 1.10 % and silicon of about 0.30 % give a deoxidised weld that is forgiving of mill scale and moderate surface condition.

Technical specifications

Parameter	Specification
Product type	SAW wire, unalloyed, copper coated, solid
AWS classification	A5.17 / SFA-5.17 EM12K
EN ISO classification	14171-A S2Si
Typical wire analysis, wt %	C 0.10; Si 0.30; Mn 1.10
Base materials	General structural steels up to S235 to S420
Diameters, mm (global data sheet)	2.0; 2.4; 3.0; 3.2; 4.0
Diameters, inch (US data sheet)	5/64; 3/32; 1/8; 5/32
Recommended SAW fluxes (Böhler)	UV 305, UV 306, UV 310 P, UV 400, UV 418 TT, UV 419 TT-W, UV 420 TTR
Approvals on data sheet	None listed

Flux choice and where the wire fits

The mechanical properties of a submerged arc weld come from the wire and flux together, not from the wire alone. Böhler lists seven fluxes for this wire on its data sheet. Within the Böhler flux range on this site, is a general aluminate-basic choice, while

UV 418 TT.

is a high-basicity flux for tougher, fine-grained steels. If the weld must reach higher strength, move up to . For creep-resistant steels a Cr-Mo wire is needed, not a C-Mn wire.

Related Böhler SAW wire	AWS / EN ISO class	Typical steel
Union S 3 Si	EH12K / S3Si	C-Mn structural steel up to S460
Union S 2 CrMo	EB2R / S S CrMo1	1.25Cr-0.5Mo boiler and vessel steel
Union S 3 NiMo 1	EF3 / S3Ni1Mo	Fine-grained steels, Ni-Mo wire

Storage and wire handling

Copper-coated SAW wire protects itself from rust only while it stays dry and clean. Keep spools and coils in their original packing until use, store them off the floor in a dry room, and do not leave an opened spool on the machine overnight in humid conditions. Surface rust and dust shorten contact tip life, disturb feeding and add hydrogen to the weld. Before ordering, confirm the diameter, spool or coil type and the certificate level (for example EN 10204 type 3.1) that your project requires.

Documents and quotation

The Böhler Welding data sheet for Union S 2 Si (global edition, 06/2021) is attached. Browse the SAW Wire category for other wire grades. For a quotation, send diameter, packaging, quantity and certificate requirements, and name the flux you plan to use.