1. Types and characteristics of flux-cored wires
According to the structure of the wire, flux-cored wire can be divided into two types of seamed wire and seamless wire. Seamless welding wire can be copper plated, good performance, low cost, has become the direction of future development.
According to whether there is a protective gas, flux-cored wire can be divided into gas-protected wire and self-protected wire; flux-cored wire core powder composition and welding electrodes similar to the flux, containing arc stabilizer, deoxidizer, slagging agent and alloying agent, according to the flux-cored wire inner filler powder with or without slagging agent, can be divided into "flux powder type" wire and "metal powder type" wire; according to the alkalinity of the slag, can be divided into titanium, titanium calcium and calcium type wire.
Titanium-type slag flux-cored wire welding channel forming beautiful, all-position welding into the process performance, arc stability, small spatter, but the weld metal toughness and anti-cracking properties are poor. In contrast, the calcium slag flux-cored wire has excellent weld toughness and crack resistance, but the weld channel formation and welding process performance is slightly worse. Titanium calcium slag system between the above two.
The welding process performance of "metal powder" flux-cored wire is similar to that of solid-cored wire, and its deposition efficiency and anti-cracking performance is better than that of "flux powder" wire. The majority of the powder core is metal powder (iron powder, deoxidizer, etc.), and a special arc stabilizer is added to ensure less slag, higher efficiency, less spatter and a stable arc during welding, as well as low diffusion hydrogen content and improved cracking 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 flux-cored wire can be divided into simple O-shaped and complex cross-sectional folding shape of two categories, folding shape can be divided into plum-shaped, T-shaped, E-shaped and intermediate filler wire shape.
The more complex and symmetrical the cross-sectional shape of the flux-cored wire, the more stable the arc and the more adequate the metallurgical reaction and protection of the flux-cored wire. But as the diameter of the wire decreases, this difference is gradually reduced, when the diameter of the wire is less than 2mm, cut into the shape of the impact is no longer obvious.
Flux cored wire has good welding process performance, good weld quality and strong adaptability to steel, and 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 overlays. The shielding gases used are CO2 and Ar+CO2, the former for general structures and the latter for important structures. Flux cored wire is suitable for automatic or semi-automatic welding, DC or AC arc are required.
2. Flux-cored wire for low carbon steel and high strength steel
Most of this type of wire is titanium type slag system, good welding technology, high welding productivity, mainly used in shipbuilding, bridges, construction, vehicle manufacturing, etc.. Low carbon steel and high strength steel flux cored wire varieties, from the weld strength level of 490MPa tensile strength and 590Mpa level of flux cored wire has been commonly used; from the performance point of view, some focus on process performance, some focus on the mechanical properties of the weld and crack resistance, some are suitable for all-position welding, including downward vertical welding, but also dedicated to the fillet weld.
3. Flux cored wire for stainless steel
Stainless steel flux-cored wire has more than 20 kinds of mouth, in addition to chromium-nickel stainless steel flux-cored wire, there are chromium stainless steel flux-cored wire. Wire diameter of 0.8, 1.2, 1.6mm, etc., can meet the stainless steel thin plate, plate and thick plate welding needs. Most of the shielding gas used is CO2, but also Ar + (20% to 50%) CO2 gas mixture can be used.
4. Flux cored wire for wear-resistant overlay welding
In order to increase the wear resistance or to make the metal surface obtain certain special properties, it is necessary to transition a certain amount of alloying elements from the wire, but the wire is difficult to process and manufacture because it contains more carbon and alloying elements. With the introduction of flux cored wire, these alloying elements can be added to the flux core, and processing and manufacturing is convenient, so the use of flux cored wire for submerged arc overlay wear-resistant surfaces is a common method, and has been widely used. In addition, the addition of alloying elements in the sintered flux, after overlay welding can also get the corresponding composition of the overlay layer, it and the solid core or flux cored wire with, can meet the different overlay welding requirements.
Commonly used flux cored wire CO2 overlay and flux cored wire submerged arc overlay welding methods are as follows.
Fine wire CO2 flux cored wire overlay welding The method of welding high efficiency, production efficiency for the hand arc welding 3 ~ 4 times; welding process performance is excellent, arc stability, small spatter, easy slagging, overlay welding forming beautiful. This method can only usually flux cored wire transition alloy elements, more for the alloy composition is not too high overlay layer.
Flux cored wire submerged arc overlay welding using large diameter (3.2, 4.0mm) flux cored wire, welding current, welding productivity increased significantly. When the use of burning flux, but also through the flux transition alloying elements, so that the overlay layer to get a higher alloy composition, the alloy content can vary between 14% to 20% to meet the different requirements of use. The method is mainly used for overlay welding rolling rolls, feeding rolls, continuous casting rolls and other wear-resistant and corrosion-resistant parts.
5. Self-protecting flux-cored wire
Self-protected flux-cored wire is not required to protect the gas or flux, you can arc welding, so as to obtain a qualified weld wire, self-protected flux-cored wire is used as slag, gas, deoxidation of the role of the powder and metal powder placed within the steel skin or coated on the surface of the wire, when welding the powder in the arc into slag and gas, slag and gas protection, without adding another gas protection.
Self-protected flux cored wire is significantly more efficient than electrodes, and the flexibility and wind resistance of field welding is better than gas shielded welding, usually under four levels of wind welding. Because it does not require shielding gas, it is suitable for field or high-altitude work, and is therefore mostly used on installation sites and construction sites.
Self-protected wire is generally less plastic and tough than flux cored wire with shielding gas. Self-protected welding wire is currently mainly used for low carbon steel welding structures, should not be used for welding high-strength steel and other important structures, in addition, self-protected welding wire welding fume is larger, in the narrow space operation should pay attention to strengthen the ventilation.