Welding Wire

The main types of welding wire - solid wire, powder, activated.

Welding wire of solid section
Welding GMAW wire is used for semi-automatic and automatic welding, as well as for the manufacture of electrodes and filler rods.

The chemical composition and diameter of the wire for welding steels regulates GOST 2246-70. Welding wire manufactured according to GOST 10543-75, wires made of copper and alloys - according to GOST 16130-72, wire and aluminum alloys - according to GOST 7871-75. The most common is the steel wire. She released the following diameters (mm): 0.3, 0.5, 0.8, 1.0, 1.2, 1.4, 1.6, 2.0, 2.5, 3.0, 4, 0, 5.0, 6.0, 8.0, 10.0, 12.0.

Welding wire is denoted as follows (see figure below).

Designation of wire

1. Diameter.
2. Make of wire:
• appointment ( St - Welding, H - surfacing). 
• the carbon content in hundredths of a percent. For example, Sv08 - wire contains 0.08% carbon; 
• may specify the content of alloying elements, marked with the following letters: X - chrome H - Ni, C - Si, M - Mo, T - manganese, T - Ti: F - vanadium, D - copper, C - Zr, W - aluminum. In the letter, which indicates an alloying element, followed by a number indicating its contents as a percentage. If the alloying element contained in an amount of about 1%, the number is not assigned. For example, Sv08H21N5T interpreted as follows: welding wire, the carbon content of 0.08%, chromium 21% nickel 5%, 1% titanium; 
• may indicate increased demands on the purity of the wire on the harmful impurities - sulfur and phosphorus. They are found in the brand letters A and AA . For example, in the wire Sv08 allowed up to 0.04% sulfur and phosphorus, for CB08A - up to 0.03% of impurities, CB08A - up to 0.02%. 
3. The method of smelting: WA - vacuum-arc furnaces, WI - vacuum-induction furnaces; W - ESR.
4. If the wire is intended for the manufacture of electrodes, then, the letter e . 
5. If the wire comes with a copper plated surface, then put the letter on . 
6. Standard on the wire.

Example of designation: 3 Sv08HSMFA-VI-E GOST 2246-70.

The wire can be supplied in coils, on spools or in special packaging, for example, Marathon Pac company ESAB.

Cored welding wire
Cored welding wire is a tubular wire filled with powdered filler. The ratio of the powder mass to the mass of the metal shell ranges from 15 to 40%. The design of flux-cored wire can be different - a simple tube, with various bends shell, two-layer (see figure).

cored wire structures

Bends are used to impart stiffness of the wire and prevent sores for powder feed rollers squeezing her semiautomatic welding. Powder filler is a mixture of ores, minerals, ferro alloys, chemicals. It performs functions similar to those of the electrode coating - protect the metal from the air, stabilize the arc, deoxidation and alloying of the weld seam formation, regulation of the transfer of electrode metal, etc.

According to the composition of powder filler powder welding wires are divided into:

• rutile-organic,
• carbonate-fluorite,
• fluorite,
• rutile and
• rutile-fluorite.

By appointment cored wires are self-defense, designed for welding without additional gas protection, and wire for welding in carbon dioxide. Each of these groups, in turn, is divided into a wire of general purpose and special. The use of self-protecting wires simplifies the process of welding, because there is no need to use balloons with carbon dioxide. This extends the use of semiautomatic welding, in particular installation conditions. For the self-protecting wires used rutile powders, organic, carbonate-fluorite and fluorite types.

When welding wires rutile-organic type of weld metal chemical composition similar to that of mild steel poluspokoynoy. At high power current weld pool absorbs gases that lead to porosity. In this regard, the current strength is limited, which reduces the productivity of welding. A typical representative of the wires rutile-type organic can serve as a welding wire grade PP-AH1.

Wire carbonate-fluorite type is recommended for welding low carbon and low alloy steels critical structures. In this case the mechanical properties of weld is higher than for the rutile-organic wires. Welded joints more flexible and perform better at low temperatures. Representatives of this type are welding wire PP-AN11, AN17-PP.

Wire fluorite type of characteristics are intermediate between the wires rutile-organic and carbonate-fluorite type, for example, welding wire PP-2DSK.

The use of cored wires for welding in carbon dioxide can significantly improve the technological parameters of welding process and the mechanical properties of the weld compared to solid wire. Formation and improves the appearance of the weld spatter is reduced, increased mechanical properties of welded joints. For welding in carbon dioxide used wire rutile and rutile-fluorite type . Wire rutile type (PP-AN8, PP-AN10) are designed for welding a wide range of structures of low carbon and low alloy steel. Wire rutile-fluorite type (PP-AH4, PP-AN9, AN20-PP) provides high impact strength and are recommended for welding structures made ​​of alloy steel, working in difficult climatic conditions under dynamic loads.

Welding wire for special purposes are used for welding with a positive formation, under water, for welding cast iron, etc.

In addition to brand cored wire also has a symbol that contains four groups of alphanumeric indexes:

1. Purpose: PG - for gas-shielded welding, PS - self-protecting.
2. The strength of weld metal in MPa. Additional letter B or A means for welding cast iron or stainless steel. For low-carbon and low alloy steels letter is not assigned.
3. Designation of acceptable spatial positions: H - lower, in - the lower, horizontal, vertical, in tons - only horizontally, in the ^ - only vertical; T - all provisions, including the body of revolution.
4. The temperature of transition to brittle fracture: 0 - 20 ° C, 1 - 0 ° C, 2 - minus 20 ° C, 3 - minus 30 ° C, 4 - minus 40 ° C, 5 - minus 50 ° C, 6 - minus 60 ° C. The letter D - Requirements are not regulated.

Activated welding wire
Activated welding wire, as well as powder, is composed of powdered supplements. However, their number is significantly lower at 5-7% of the total weight of the wire. A small amount of powder additives can activate them in the Press in solid wire as thin wicks, using special technology. The most widely used wire to the introduction of activating additives in the central channel.

Activated wires are designed primarily for welding in carbon dioxide and its mixtures, so the metal base, as a rule, wire Sv08G2S.

As the activating additives used easily ionizable salts of alkali and alkaline earth metals: Cs 2 CO 3 , K 2 CO 3 , Na 2 C0 3 , ​​Vaso 3 , as well as slag-forming components: TiO 2 , SiO 2 , MgO, CaF 2 .

The introduction of salts of alkali and alkaline earth metals reduces the effective capacity of the arc and improves the stability of its combustion. Especially noticeable decrease in the ionization potential in the peripheral, relatively cold regions of the arc.

The thermal conductivity of alkali metals in the range 2500-4000 ° K for one or two orders of magnitude lower than that of carbon dioxide, which significantly reduces the selection of heat in the radial direction, ie promotes the expansion of the arc column and the active spots outside the drops. In turn, this reduces the electromagnetic force acting on the drop of the metal electrode, and reduces the size of the drop, which is its separation from the wire. The transition to the transfer of atomized, reduced spatter.

The presence of slag-forming components by reducing the surface tension of molten metal, and also facilitates the transfer of atomized, reduces spatter and improves formation of the joint.

A significant advantage of the activated wire as compared with powder is that you can use the same equipment as in the welding wire of solid section. In terms of mechanical properties of the activated wires close to the wire of solid section, allows multiple kinks in the process, secure the hoses fed semi-automatic, not flattened or crushed in the feed rollers. Welding technique is different from conventional welding in carbon dioxide.

See also:
Semi-automatic welding
MIG welding

Welding materials:

welding electrodes welding wire welding flux for arc welding carbon dioxide helium

argon protective gas mixture acetylene propane-butane IAF