Selection of solid welding wire

(1) Submerged arc welding wire

When submerged arc welding, the flux plays a role in protecting and metallurgical treatment of the weld metal. The welding wire is mainly used as a filler metal, and at the same time, alloying elements are added to the weld and participate in the metallurgical reaction.

1) Low carbon steel and low alloy steel welding wire for low carbon steel and low alloy steel submerged arc welding wire commonly used in the following three categories.

A, low manganese welding wire (such as H08A): often with high manganese flux for low carbon steel and low strength low alloy steel welding.

B, manganese welding wire (such as H08MnA,H10MnS): mainly used for low alloy steel welding, but also with low manganese flux for low carbon steel welding.

C, high manganese welding wire (such as H10Mn2 H08Mn2Si): for low alloy steel welding

2) High strength steel wire

This kind of welding wire containing more than Mn1%, containing Mo0.3%~ 0.8%, such as H08MnMoA, H08Mn2MoA, used for high strength low alloy high strength steel welding. In addition, according to the composition and performance requirements of high-strength steel, elements such as NI, CR, V and Re can be added to the welding wire to improve the weld performance. The weld metal with tensile strength of 590Mpa is mostly MN-MO welding wire, such as H08MNMOA wire.

3) Welding wire for stainless steel

The composition of the welding wire used shall be basically the same as that of the stainless steel to be welded. When welding chromium stainless steel, welding wires such as HoCr14 H1Cr13 H1Cr17 shall be used. When welding chromium-nickel stainless steel, welding wires such as H0Cr19Ni9 HoCr19Ni9 HoCr19Ni9Ti shall be used. When welding ultra-low carbon stainless steel, corresponding ultra-low carbon welding wires such as HOOCr19Ni9 shall be used. The flux shall be of melting type or sintering type. At present, sintered flux is mainly used in foreign countries to weld stainless steel, while smelting flux is still the main method in China, but sintered flux is being developed and popularized.

(2) Welding wire for gas shielded welding

Gas shielded welding is divided into inert gas shielded welding (TIG welding and MIG welding), active gas shielded welding (MAG welding) and self-shielded welding. Pure Ar is used for TIG welding, and Ar + 2% O2 or Ar + 5% CO2 is generally used for MIG welding. CO2 gas is mainly used in MAG welding. In order to improve the process performance of CO2 welding, CO2 + Ar or CO2 + Ar + O2 mixed gas or flux-cored wire can also be used.

1)TIG welding wire

TIG welding sometimes does not add filler wire, which is directly connected after being heated and melted by the welding base material, and sometimes filler wire is added. Since the shielding gas is pure Ar and has no oxidation, the composition of the welding wire basically does not change after melting, so the composition of the welding wire is the composition of the welding seam. Some also use the base metal composition as the welding wire composition, so that the weld composition is consistent with the base metal. TIG welding welding energy is small, weld strength and plastic, good toughness, easy to meet the performance requirements.

2)MIG and MAG welding wire

MIG method is mainly used for welding stainless steel and other high alloy steel. In order to improve the arc characteristics, an appropriate amount of O2 or CO2 gas is added to the Ar gas, that is, the MAG method. When welding alloy steel, the use of Ar + 5% CO2 can improve the anti-porosity ability of the weld. However, when welding ultra-low carbon stainless steel, Ar + 5% CO2 mixed gas cannot be used, only Ar + 2% O2 mixed gas can be used to prevent the weld from increasing carbon. At present, MIG welding of low alloy steel is gradually replaced by MAG welding of Ar + 20% CO2. MAG welding due to the shielding gas has a certain oxidation, should be appropriate to increase the content of Si, Mn and other deoxidizing elements in the wire, other components can be consistent with the base metal, can also be different. When welding high strength steel, the content of C in the weld is usually lower than that of the base metal, and the content of Mn should be higher than that of the base metal, which is not only for deoxidation, but also for the requirement of weld alloy composition. In order to improve the low temperature toughness, the content of Si in the weld should not be too high,

3)CO2 welding wire

CO2 is an active gas with strong oxidation, so the welding wire used in CO2 welding must contain high Mn, Si and other deoxidizing elements. CO2 welding usually uses C- Mn-Si welding wire, such as H08MnSiA, H08Mn2SiA, H04Mn2SiA, etc. CO2 welding wire diameter is generally 0.89 1.0 1.2 1.6 2.0mm. Wire diameter ≤ 1.2mm belongs to fine wire CO2 welding, and wire diameter ≥ 1.6mm belongs to coarse wire CO2 welding.

H08Mn2SiA welding wire is a widely used CO2 welding wire, which has good process performance and is suitable for welding low alloy steel below 500Mpa.

(3) Electroslag welding wire

Electroslag welding is suitable for medium plate and thick plate welding. Electroslag welding wire mainly plays the role of filler metal and alloying.

(4) Non-ferrous metal and cast iron welding wire

The first two letters "HS" of the brand indicate non-ferrous metals and cast iron welding wires. The first digit in the brand indicates the type of the meridian composition of the welding wire, and the second and third digits in the brand indicate different brands of the same type of welding wire.

1) Surfacing welding wire

At present, there are two main types of hard alloy welding wire for surfacing: high chromium alloy cast iron (Solmaite) and cobalt-based (Stellite) alloy. High chromium alloy cast iron has good oxidation resistance and cavitation corrosion resistance, high hardness and good wear resistance. The cobalt-based alloy can maintain high hardness and good corrosion resistance at a high temperature of 650 degrees. Among them, low carbon and low tungsten have good toughness; high carbon and high tungsten have high hardness, but poor impact resistance.

Cemented carbide surfacing welding wire can be used oxygen-acetylene, gas welding and other methods of surfacing welding, including oxygen-acetylene surfacing although low production efficiency, but the equipment is simple, surfacing welding penetration depth, less base metal melting, surfacing welding quality is high, because the application is more extensive.

2) Copper and copper alloy welding wire

Copper and copper alloy welding wire is commonly used for welding copper and copper alloy, in which brass wire is also widely used for brazing carbon steel, cast iron and carbide tools. Copper and copper alloy welding, can use a variety of welding methods, the correct choice of filler metal is a necessary condition to obtain high quality weld. Oxygen-acetylene gas welding shall be used together with gas welding flux.

3) Aluminum and aluminum alloy welding wire

Aluminum and aluminum alloy welding wire for aluminum alloy argon arc welding and oxygen-acetylene gas welding as filler material. The selection of welding wire is mainly based on the type of base metal, the crack resistance, mechanical properties and corrosion resistance of butt joints. Under normal circumstances, welding aluminum and aluminum alloy are used with the base metal composition of the same or similar brand of welding wire, so that better corrosion resistance can be obtained; but welding hot cracking tendency of heat treatment to strengthen the aluminum alloy, the choice of welding wire is mainly from the crack resistance to solve the problem, then the composition of the welding wire and the base metal is very different.

4) Cast iron welding wire

Mainly used for gas welding welding repair cast iron. Because the oxygen-acetylene flame temperature (less than 3400 ℃) is much lower than the arc temperature (6000 ℃), and the hot spot is not concentrated, it is more suitable for welding of gray cast iron thin-walled castings. In addition, the gas welding flame temperature is lower than that can reduce the evaporation of the spheroidizing agent, which is conducive to ensuring the weld to obtain the ductile iron structure. At present, the ductile iron welding wire for gas welding mainly has two kinds of rare earth magnesium alloy and yttrium-based heavy rare earth. Due to the high boiling point of yttrium, the ability to resist spheroidization recession is stronger than that of magnesium, which is more conducive to ensuring the spheroidization of weld, so it has been widely used in recent years.

Selection of flux-cored wire

(1) Types and characteristics of flux-cored wire

According to the structure of the welding wire, the flux cored wire can be divided into two kinds of seamed welding wire and seamless welding wire. Seamless welding wire can be plated with copper, good performance, low cost, has become the direction of future development.

According to whether there is shielding gas, flux-cored wire can be divided into gas-shielded wire and self-shielded wire. The composition of the flux-cored wire core powder is similar to that of the electrode coating, including arc stabilizing agent, deoxidizer, slag forming agent and alloy agent. According to whether there is slag forming agent in the inner filler powder of flux-cored wire, it can be divided into "flux powder type" wire and "metal powder type wire. According to basicity, can be divided into titanium type, titanium calcium type and calcium type welding wire.

Titanium-type slag-based flux-cored wire has a beautiful formation of the weld bead, good all-position welding process performance, arc stability, small spatter, but the toughness and crack resistance of the weld metal is poor. On the contrary, the calcium-type slag-based flux-cored wire has excellent weld toughness and crack resistance, but the weld bead forming and welding process performance are slightly worse. The titanium-calcium slag system is between the above two.

The welding process performance of "metal powder type" flux cored wire is similar to that of solid wire, and its deposition efficiency and crack resistance are better than that of "powder type" wire. Most of the powder core is metal powder (iron powder, deoxidizer, etc.), and special arc stabilizing agent is also added to ensure less slag, high efficiency, small splash, stable arc, low diffusion hydrogen content and improved crack resistance.

The cross-sectional shape of the flux-cored wire has a great influence on the welding process performance and metallurgical properties. According to the cross-sectional shape of the flux-cored wire, it can be divided into simple O-shape and complex section folding shape. The folding shape can be divided into plum blossom shape, T-shape, E-shape and intermediate filling wire shape.

The more complex and symmetrical the cross-sectional shape of the flux-cored wire is, the more stable the arc is, and the more sufficient the metallurgical reaction and protection of the flux-cored wire are. However, with the decrease of the diameter of the welding wire, this difference is gradually reduced. When the diameter of the welding wire is less than 2mm, the influence of the cut shape is not obvious.

Flux-cored wire has good welding process performance, good weld quality and strong adaptability to steel. It can be used to weld various types of steel structures, including low carbon steel, low alloy high strength steel, low temperature steel, heat-resistant steel, stainless steel and wear-resistant surfacing. The protective gases used are CO2 and Ar CO2, the former is used for ordinary structures, and the latter is used for important structures. Flux-cored wire is suitable for automatic or semi-automatic welding, DC or AC arc.

1) Flux-cored wire for low carbon steel and high strength steel

Most of this kind of welding wire is titanium type slag system, welding process is good, welding productivity is high, mainly used for shipbuilding, bridges, construction, vehicle manufacturing, etc. There are many kinds of flux-cored wires for low carbon steel and high strength steel. From the weld strength level, flux-cored wires with tensile strength of 490MPa and 590Mpa have been widely used. From the performance point of view, some focus on process performance, some focus on weld mechanical properties and crack resistance, some are suitable for all-position welding including downward vertical welding, and some are specially used for fillet welds.

2) Flux-cored wire for stainless steel

There are more than 20 kinds of stainless steel flux-cored wire. In addition to chromium-nickel series stainless steel flux-cored wire, there are chromium series stainless steel flux-cored wire. The diameter of the welding wire is 0.8mm, 1.2mm, 1.6mm, etc., which can meet the welding needs of stainless steel sheet, medium plate and thick plate. Most of the protective gas used is CO2, and a mixed gas of Ar +(20% ~ 50%)CO2 can also be used.

3) Flux-cored wire for hardfacing

In order to increase the wear resistance or to obtain some special properties of the metal surface, it is necessary to transfer a certain amount of alloying elements from the welding wire, but the welding wire is difficult to process and manufacture because of the large amount of carbon and alloying elements. With the advent of flux-cored wire, these alloying elements can be added to the flux-cored wire, and the processing and manufacturing are convenient, so the use of flux-cored wire for submerged arc surfacing wear-resistant surface is a common method, and has been widely used. In addition, alloy elements are added to the sintered flux, and the surfacing layer with corresponding components can be obtained after surfacing. It can be matched with solid core or flux-cored wire to meet different surfacing requirements.

Common flux-cored wire CO2 surfacing and flux-cored wire submerged arc surfacing methods are as follows.

Filament CO2 flux-cored wire surfacing welding This method has high welding efficiency, and the production efficiency is 3 to 4 times that of hand arc welding; the welding process has excellent performance, stable arc, small spatter, easy slag removal, and beautiful surfacing welding. This method can only usually flux-cored wire transition alloy elements, and is mostly used for surfacing layers with low alloy composition.

Flux-cored wire submerged arc surfacing adopts large diameter (3.2mm, 4.0mm) flux-cored wire, the welding current is large, and the welding productivity is obviously improved. When using burning flux, but also through the flux transition alloy elements, so that the surfacing layer to get a higher alloy composition, the alloy content can be changed between 14% to 20%, to meet different requirements. This method is mainly used for surfacing rolling rolls, feeding rolls, continuous casting rolls and other wear-resistant and corrosion-resistant parts.

(2) Self-shielded flux-cored wire

Self-shielded welding wire refers to a welding wire that can be arc welded without shielding gas or flux to obtain a qualified weld. Self-shielded flux-cored welding wire is to place powder and metal powder as slagging, gassing and deoxidizing in the steel skin or coat the surface of the welding wire. During welding, the powder becomes slag and gas under the action of arc, thus playing the role of slagging and gassing protection without additional gas protection.

The deposition efficiency of self-shielded flux-cored wire is obviously higher than that of welding rod, and the flexibility and wind resistance of field welding are better than that of gas shielded welding, which can usually be welded under four-level wind. Because it does not require protective gas, it is suitable for field or high-altitude operations, so it is mostly used for installation sites and construction sites.

The weld metal plasticity and toughness of the self-shielded welding wire are generally lower than that of the flux-cored wire using shielding gas. Self-shielded welding wire is currently mainly used for low-carbon steel welding structure, should not be used for welding high-strength steel and other important structures, in addition, self-shielded welding wire welding when the smoke is larger, in the narrow space operation should pay attention to strengthen ventilation.