Selection of solid core welding wire
1. Submerged arc welding wire
During submerged arc welding, the flux plays a role in protecting and metallurgical treatment of weld metal.
The welding wire is mainly used as filler metal.
At the same time, alloy elements are added to the weld and participate in the metallurgical reactions.
(1) Welding wires for low carbon steel and low alloy steel there are three types of commonly used welding wires for submerged arc welding of low carbon steel and low alloy steel.
- Low manganese welding wire (such as H08A): it is often used for welding low carbon steel and low alloy steel with high manganese flux.
- Medium manganese welding wire (such as H08MnA, H10MnS): it is mainly used for low alloy steel welding, and can also be used for low carbon steel welding with low manganese flux.
- High manganese welding wire (such as H10Mn2H08Mn2Si): used for welding low alloy steel
(2) High strength steel wire
This kind of welding wire contains more than 1% mn0 3% ~ 0.8%, such as H08MnMoA and H08Mn2MoA, which are used for welding low alloy high strength steel with high strength.
In addition, according to the composition and performance requirements of high-strength steel, Ni, Cr, V and re can be added to the welding wire to improve the weld performance.
MN-MO welding wire is mostly used for weld metal with tensile strength of 590MPa, such as H08MnMoA, etc.
(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, HoCr14, H1Cr13, H1Cr17 and other welding wires shall be used;
When welding chromium nickel stainless steel, H0Cr19Ni9 HoCr19Ni9 HoCr19Ni9Ti and other welding wires shall be used;
When welding ultra-low carbon stainless steel, corresponding ultra-low carbon welding wire shall be used, such as HOOCr19Ni9.
The flux can be smelting type or sintering type.
It is required that the oxidizability of the flux is small to reduce the burning loss of alloy elements. At present, sintered flux is mainly used to weld stainless steel abroad.
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.
Related reading: MIG vs TIG 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 for 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 metal.
Sometimes, filler wire is added. Because 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 weld.
Some also use the base metal composition as the welding wire composition to make the weld composition consistent with the base metal.
TIG welding has low welding energy, good weld strength, plasticity and toughness, and is easy to meet the performance requirements.
(2) MIG and MAG welding wires
MIG method is mainly used for welding high alloy steel such as stainless steel. In order to improve the arc characteristics, an appropriate amount of O2 or CO2 gas is added to Ar gas, which is called MAG method.
When welding alloy steel, Ar + 5% CO2 can improve the anti porosity of weld. However, when welding ultra-low carbon stainless steel, Ar + 5% CO2 mixed gas cannot be used, and only Ar + 2% O2 mixed gas can be used to prevent weld carburization.
At present, MIG welding of low alloy steel is gradually replaced by MAG welding of Ar + 20% CO2. During MAG welding, because the shielding gas has certain oxidation, the content of deoxidizing elements such as Si and Mn in the welding wire should be appropriately increased.
Other components can be consistent with or different from the base metal.
When welding high-strength steel, the content of C in the weld is usually lower than the base metal, and the content of Mn should be higher than the base metal, which is not only for deoxidation but also 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. Therefore, the welding wire used for CO2 welding must contain high deoxidizing elements such as Mn and Si.
- Mn-Si welding wire is usually used for CO2 welding, such as h08mnsia, H08Mn2SiA, h04mn2sia, etc. The diameter of CO2 welding wire is generally 0.89 1.0 1.2 1.6 2.0mm, etc.
- Wire diameter ≤ 2mm belongs to thin wire CO2 welding, and wire diameter ≥ 1.6mm belongs to thick wire CO2 welding.
H08Mn2SiA welding wire is a widely used CO2 welding wire. It has good process performance and is suitable for welding low alloy steel below 500MPa.
For the steel with higher strength grade requirements, H10MnSiMo and other brands of welding wire containing Mo in the welding wire composition shall be used.
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 represent non-ferrous metal and cast iron welding wires; The first digit in the brand indicates the academic composition type of 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 cemented carbide welding wires for surfacing: high chromium alloy cast iron (solmait) and cobalt based (Stellite) alloy.
High chromium alloy cast iron has good oxidation resistance and cavitation resistance, high hardness and good wear resistance.
Cobalt based alloys can maintain high hardness and good corrosion resistance at a high temperature of 650 degrees.
The toughness of low carbon and low tungsten is good;
High carbon and high tungsten have high hardness, but poor impact resistance.
Hard alloy surfacing welding wire can be overlaid by oxygen acetylene, gas electric welding and other methods.
Although the production efficiency of oxygen acetylene surfacing is low, the equipment is simple, the welding depth is shallow, the melting amount of base metal is small, and the surfacing quality is high, because it is widely used.
(2) Copper and copper alloy welding wire
Copper and copper alloy welding wires are commonly used for welding copper and copper alloys, and brass welding wires are also widely used for brazing carbon steel, cast iron and cemented carbide tools.
A variety of welding methods can be used for the welding of copper and copper alloys.
The correct selection of filler metal is a necessary condition for obtaining high-quality welds. When oxygen acetylene gas welding is used, it shall be used together with gas welding flux.
(3) Aluminum and aluminum alloy welding wire
Aluminum and aluminum alloy welding wires are used as filler materials for aluminum alloy argon arc welding and oxygen acetylene gas welding.
The selection of welding wire is mainly based on the type of base metal, crack resistance, mechanical properties and corrosion resistance of the butt joint.
In general, welding wires with the same or similar brand as the base metal are used for welding aluminum and aluminum alloy, so as to obtain better corrosion resistance;
However, when welding heat treatment strengthening aluminum alloy with large tendency of hot cracking, the selection of welding wire mainly starts from solving the crack resistance.
At this time, the composition of welding wire is very different from that of base metal.
(4) Cast iron welding wire
It is mainly used for repairing cast iron by gas welding.
Because the oxygen acetylene flame temperature (less than 3400 ℃) is much lower than the arc temperature (6000 ℃), and the hot spots are not concentrated, it is more suitable for welding repair of gray cast iron thin-walled castings.
In addition, when the flame temperature of gas welding is lower than, the evaporation of spheroidizing agent can be reduced, which is conducive to ensuring the microstructure of nodular cast iron in the weld.
At present, there are two kinds of nodular iron welding wires for gas welding: rare earth magnesium alloy and yttrium-based heavy rare earth.
Because yttrium has a high boiling point and has stronger resistance to spheroidization decline than magnesium, it is more conducive to ensure weld spheroidization, 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 welding wire, flux cored wire can be divided into seam welding wire and seamless welding wire.
Seamless welding wire can be plated with copper, with good performance and low cost. It has become the direction of development in the future.
According to whether there is shielding gas, flux cored wire can be divided into gas shielded wire and self shielded wire;
The composition of flux cored wire core powder is similar to that of electrode coating, including arc stabilizer, deoxidizer, slag forming agent and alloy agent.
According to whether there is slag forming agent in the filler powder in the inner layer of flux cored wire, it can be divided into “flux type” welding wire and “metal powder type” welding wire; According to the basicity of slag, it can be divided into titanium type, titanium calcium type and calcium type welding wires.
Titanium slag flux cored wire has beautiful weld bead forming, good all position welding process performance, stable arc and small spatter, but the toughness and crack resistance of weld metal are poor.
On the contrary, the weld toughness and crack resistance of calcium slag flux cored wire are excellent, but the weld bead forming and welding process performance are slightly poor. 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 cored 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 stabilizer is added to ensure less slag formation, high efficiency, small spatter, stable arc, low content of diffusible hydrogen in the weld and improved crack resistance.
The section shape of flux cored wire has a great influence on the welding process and metallurgical properties.
According to the section shape of flux-cored wire, it can be divided into simple O-shape and complex section folding shape.
The folding shape can be divided into quincunx shape, T-shape, E-shape and intermediate wire filling shape.
The more complex and symmetrical the section shape of flux-cored wire is, the more stable the arc is, and the more sufficient the metallurgical reaction and protection of flux-cored wire are. However, with the decrease of wire diameter, this difference gradually decreases. When the wire diameter is less than 2mm, the influence of the cutting 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 shielding gases used include 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.
2. Flux cored wire for low carbon steel and high strength steel
Most of these welding wires are titanium slag system, with good welding processability and high welding productivity.
They are mainly used in shipbuilding, bridge, construction, vehicle manufacturing, etc. There are many kinds of flux-cored wires for low carbon steel and high strength steel.
From the perspective of weld strength, flux-cored wires with a tensile strength of 490MPa and 590MPa have been widely used;
In terms of performance, 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 dedicated to fillet welds.
3. Stainless steel flux cored wire
There are more than 20 kinds of stainless steel flux cored wire, including chromium nickel stainless steel flux cored wire and chromium stainless steel flux-cored wire.
The diameter of welding wire is 0.8, 1.2 and 1.6mm, which can meet the welding needs of stainless steel thin plate, medium plate and thick plate.
Most of the shielding gas used is CO2, and the mixed gas of Ar + (20% ~ 50%) CO2 can also be used.
4. Hardfacing flux cored wire
In order to increase wear resistance or obtain some special properties on the metal surface, a certain amount of alloy elements need to be transferred from the welding wire, but the welding wire is difficult to manufacture because of its high carbon content and alloy elements.
With the advent of flux cored wire, these alloy elements can be added to the flux core, and the processing and manufacturing is convenient.
Therefore, submerged arc surfacing of wear-resistant surface with flux cored wire is a common method and has been widely used.
In addition, by adding alloy elements to the sintered flux, the surfacing layer with corresponding components can also be obtained after surfacing.
It can meet different surfacing requirements when combined with solid core or flux cored wire.
The common methods of flux cored wire CO2 surfacing and flux-cored wire submerged arc surfacing are as follows.
This method has high welding efficiency, and the production efficiency is 3 ~ 4 times that of manual arc welding;
Excellent welding process performance, stable arc, small splash, easy slag removal and beautiful surfacing.
This method can only be used for the transition alloy elements of flux-cored wire, and is mostly used for the surfacing layer with low alloy composition.
Flux-cored wire submerged arc surfacing adopts flux-cored wire with large diameter (3.2, 4.0mm). The welding current is large and the welding productivity is significantly improved.
When the flux is used, the alloy elements can also be transferred through the flux to make the surfacing layer obtain higher alloy composition, and the alloy content can vary from 14% to 20% to meet different application requirements.
This method is mainly used for surfacing wear-resistant and corrosion-resistant parts such as rolling roll, feed roll and continuous casting roll.
5. Self-protective flux cored wire
Self-shielded welding wire refers to the welding wire that can conduct arc welding without shielding gas or flux, so as to obtain qualified welds.
Self-shielded flux cored welding wire places the powder and metal powder as slag making, gas making and deoxidation in the steel sheet or coated on the surface of welding wire.
During welding, the powder becomes slag and gas under the action of arc, which plays the role of slag making and gas making protection without additional gas protection.
The deposition efficiency of self-shielded flux cored wire is obviously higher than that of electrode.
The flexibility and wind resistance of field welding are better than that of gas shielded welding. It can usually be welded under four levels of wind.
Because it does not need protective gas and is suitable for field or high-altitude operation, it is mostly used in installation site and construction site.
The weld metal plasticity and toughness of self shielded welding wire are generally lower than that of flux-cored welding wire with shielding gas.
At present, the self protective welding wire is mainly used for welding low-carbon steel structures, and is not suitable for welding important structures such as high-strength steel.
In addition, the self protective welding wire has large smoke and dust during welding, so it is necessary to strengthen ventilation when working in narrow space.