What Is a Flux Wire?

Flux-cored wire is also called powder-cored wire and tubular wire. It is divided into two categories: aerated protection and non-aerated protection. The surface of the flux-cored wire is the same as that of the solid-core wire, which is made of materials such as low-carbon steel or low-alloy steel with better plasticity. The manufacturing method is to first roll the steel strip into a U-shaped cross-sectional shape, then fill the U-shaped steel strip with the welding powder formulated according to the dosage, use a rolling mill to compact it, and finally draw it into different specifications. Cored wire. ^[1]

Back in the early 1950s

Flux-cored wire is divided into seam and seamless flux-cored wire according to production characteristics. The finished wire of seamless flux-cored wire can be copper-plated. The moisture-proof performance of the wire during storage and the conductivity during welding are better than those of the flux-cored wire.

There are different classification methods for flux-cored wires in different situations.

According to the protection situation, it can be divided into four types: gas protection (CO2, Ar-rich mixed gas), self-protection, submerged arc and open arc.

According to the wire diameter, it can be divided into fine diameter (less than 2.0mm) and thick diameter (more than 2.0mm).

According to the wire section, it can be divided into simple section and complex section.

According to the power used, it can be divided into AC steep drop power and DC flat power.

According to the filling material, it can be divided into slag-making flux-cored wire (titanium oxide type, titanium calcium type, calcium fluoride type) and metal powder cored flux cored wire.

Common gas shielded flux-cored wires are: AWS A5.29 / 5.28 E71T1-C (M), E81T1-K2, E81T1-NI1, E91T1-K2, E101-K3, E111T1-K3, E80C-G, E90C-G, E110C-G, etc. (General diameter 1.2mm-1.6mm)

Common self-protected flux-cored wire: general diameter: 1.6mm-3.2mm

Common submerged arc surfacing flux-cored wires are: AWS A5.23 F71A, F8A4, F9A4, F11-A8, etc. (General diameter: 2.4mm-4.0mm)

From the perspective of the development and application of flux-cored wire, it can be classified as follows:

Slagging type gas shielded flux-cored wire can be divided into CO2 gas shielded flux-cored wire. The main varieties are used for carbon steel, 50 kg low alloy structural steel (all-position welding), high strength steel (60-70 kg), low temperature Steel (-45 , -60 impact toughness), heat-resistant steel (1.25Cr-0.5Mo series, 2.25Cr-1Mo series), weathering steel (painted and non-painted), stainless steel (welded SUS304, 304L, 316 , 316L, 317, 317L, 321, 347, 309S stainless steel), wear-resistant surfacing (Hv250, Hv350, Hv450, Hv600).

Slagging type gas shielded flux-cored wire can be divided into Ar-rich mixed gas shielded flux-cored wire. The main varieties are used for carbon steel, 50 kg low alloy structural steel (all-position welding), and high-strength steel (60-70 kg). Low temperature steel (-45 , -60 impact toughness), wear-resistant surfacing (13Cr-2Ni series).

Metal powder cored flux-cored wires can be divided into CO2 gas shielded flux-cored wires. The main varieties are used for carbon steel, 50 kg-grade low-alloy structural steel, high-strength steel (60 kg-grade), and wear-resistant surfacing (high Cr-Fe series). , Hv800).

Metal powder cored flux-cored wires can be divided into Ar-rich mixed gas shielded flux-cored wires. The main varieties are used for carbon steel, 50kg-grade low-alloy structural steel, low-temperature steel (-60 ° C impact toughness), and stainless steel (13Cr-5Ni series). , 13Cr-4Ni-Mo series, 17Cr series), wear-resistant surfacing (13Mn series, 16Mn-16Cr series). Self-protected flux-cored wire is mainly used for carbon steel, low-alloy structural steel of 50 kg and wear-resistant surfacing welding.

The manufacturing process control of the flux-cored wire is very strict. Because the molten metal comes from the steel sheet skin and the components contained in the flux, the dimensions and chemical components before manufacturing need to be checked in detail to ensure quality.

Because the internal space of the welding material is limited, the size of the flux particles becomes more and more important. The particles form a bird's nest, and the flux composition elements are not uniform.

Most of the flux-cored wires are rolled into a U-shaped section by a flat metal sheet strip. The granular flux is filled in the U-shaped metal groove and then passed through the final sealing and rolling step to tightly roll the flux. Pressed into the tube wire

The wire wound into a tube shape is then subjected to a series of drawing actions to become the last required wire diameter. This drawing action can also make the filled flux uniformly fixed in the wire sheath material.

How to prevent some wires from forming hollow (without flux) in the welding wire due to poor control during the manufacturing / production process is the key to the quality of the flux-cored wire. In addition, the surface of the wire must be smooth and clean, otherwise it will affect the smoothness of wire feeding and the rapid transmission of welding current. The welding wire is packed into rolls or barrels to avoid entanglement or breakage of the wires. Usually, the coiled wires are wrapped with a plastic sleeve and a desiccant is placed to prevent the material from getting wet. The encapsulated material is put into a cardboard box and sent out.

When the skin is thicker, the section is mostly the butt (BUTT) method and the amount of welding is small. Most carbon steels and low-alloy steels with wire diameters of 2.8mm and below all have this shape, such as stainless steel. When the alloy and the wire diameter are large, the wire needs a large space to contain the cross-section shape of the flux and the alloy element, which are mostly overlapped or heart-shaped (LAP and HEART SHAPED) joints ^[1]

As mentioned earlier, flux-cored wires highlight many

Flux-cored wire originated in the 1950s and developed in the 1960s and 1970s. Flux-cored wires are mainly thick-diameter (3.2mm, 2.4mm) using AC power. Gas-shielded flux-cored wires are used for welding steel pipes. Self-protection Flux-cored wire is used in building structures. In the 1980s, a small-diameter flux-cored wire ( 1.2 to 1.6 mm) was developed using a DC power source. Among them, all-position flux-cored wires with a diameter of 1.2 to 1.6 mm were widely used in ship manufacturing and developed rapidly, greatly improving The degree of semi-automation of shipbuilding welding. During this period, various flux-cored wires for stainless steel, low-temperature steel, and 590N / mm2 strength grade steel were developed. Fine-diameter self-protected flux-cored wires with a diameter of 1.2 to 1.6 mm can be used for welding steel pipe piles. Since the late 1980s, the manufacture and use of a variety of 1.2 1.6mm gas-shielded flux-cored wires have been rapidly promoted, and they have been used and expanded in the non-shipbuilding industry. Subsequently, metal powder cored flux-cored wires and seamless flux-cored wires were developed.

From the perspective of the total output of flux-cored wire and the total output of welding materials, in 1983 the output of flux-cored wires in the United States accounted for 15% of the total output of welding materials. The total output of flux-cored wires was about 42,000 tons. The annual output of cored wire reaches 76,000 tons. Mainly used for flat welding and fillet welding, used to weld construction machinery, heavy machinery, steel frames, bridges, etc. In 1995, the annual output of the British flux-cored wire surpassed the electrode for the first time. Japan mainly produces fine-diameter flux-cored wires. Flux-cored wires accounted for 3.8% of the total output of welding materials in 1983, 13% of the total output of welding materials in 1988, 20% of the total output of welding materials in 1992, and welding materials in 1994 23% of the total output. The production ratio of flux-cored wire in Japan has increased year by year, while the production of solid cored wire in 1984 accounted for 32% of the total production of welding materials, and gradually increased to 50% in 1991. Since 1992, solid cored wire has been decreasing year by year, and by 1994, the proportion of solid cored wire was 42%. According to the latest information, the total production of flux-cored wire in Japan in 1997 was about 100,000 tons, which was 27% of the total output of welding materials. From this point of view, Japan is the country with the fastest development of flux-cored wire. In China, the development of flux-cored welding wire is in the original stage of development: a large number of foreign production lines have not been fully applied, hoping to increase production capacity and technical level without mutual communication, attach importance to hardware investment and neglect software development, and suffer from insufficient funds. limits.

Fortunately, after the unremitting efforts of our country's scientific researchers, the first production line of flux-cored wire with independent intellectual property rights was completed in the mid-1990s. The overall level of flux-cored wires has also made a qualitative leap. Core welding wire has occupied more than half of the Chinese market, and not only has basically eliminated imported products from the country, but has gradually gained the upper hand in competition with foreign brands. Through the transfer of key equipment, a group of high-tech flux-cored welding wire enterprises has fostered a large number of flux-cored welding wire enterprises, which has promoted the development of domestic flux-cored welding wire enterprises. The inherent quality of flux-cored welding wires has not changed much, and its output has ranked first in the world. One person ^[1]

Generally speaking, flux-cored wire is mainly divided into self-shielded flux-cored wire and gas-shielded flux-cored wire. Gas-shielded flux-cored wire is usually divided into two types of slag systems, namely, acid and alkaline (T1 and T5). Acid slag-based flux-cored wire has good process performance and can be used for all-position welding. This type of slag-based flux-cored wire is a typical and efficient welding material most widely used in the shipbuilding industry. Weld metal of alkaline flux-cored wire has better purification effect. Through proper formula adjustment, excellent process performance can be obtained, which is suitable for flat welding and fillet welding.

The filling factor of the all-position flux-cored wire powder is 13-16%, and rutile with a TiO2 content of 92% or more is mainly selected, which accounts for 35-55% of the powder weight, and iron powder accounts for 15-30% of the powder weight. In addition, an appropriate amount of SiO2, ZrO2, Al2O3, and MgO is added to form an appropriate slag, which is suitable for the basic conditions of all-position welding. An appropriate amount of K and Na-containing arc stabilizers are used to improve the stability of the arc. It is best to pre-process sintering Powder. Add appropriate amount of aluminum powder, aluminum magnesium powder to improve the anti-porosity of the weld, add appropriate amount of Si, Mn iron alloy to obtain the corresponding chemical composition and mechanical properties. The main characteristics of this slag welding wire are stable arc, small spatter and easy slag removal. The thin diameter flux cored wire is suitable for all-position welding. However, the slag itself is relatively oxidative, and the low-temperature toughness of the weld metal is low. It is generally used for welding of carbon steel and some low-alloy steels. The shipbuilding industry uses this type of flux-cored welding wire in large quantities, and it is also the largest variety.

The filling factor of basic flux-cored wire powder is 24 to 28%. CaF, CaCO3, a part of SiO2, or an appropriate amount of TiO2 is used as the basic slag system. The slag series has high alkalinity, low oxidation, strong S and P removal ability, and excellent metallurgical properties. Such a slag system creates conditions for the development of high-toughness flux-cored welding wires, which requires good process performance and excellent low-temperature toughness of the weld to be used for the welding of important steel structures. The development prospect of this type of flux-cored wire is good, which is suitable for the development of flux-cored wire for welding high strength steels with different strength levels and different toughness requirements. All-position alkaline flux-cored wire will broaden new welding fields and have broad development prospects ^[1] .