Views: 14 Author: Site Editor Publish Time: 2021-02-01 Origin: Site
The welding process performance and chemical metallurgical performance of the flux is one of the main factors that determine the chemical composition and performance of the weld metal. Using the same welding wire and the same welding parameters, but the matching flux is different, the performance of the resulting weld will be great The difference. One kind of welding wire can be reasonably combined with a variety of fluxes, whether it is on low-carbon steel or low-alloy steel.
1. Requirements for the process performance and quality of flux
(1) General requirements for flux
a. The flux should have good metallurgical properties. When welding, it should be equipped with appropriate welding wire and reasonable welding technology. The weld metal should be able to obtain suitable chemical composition and good mechanical properties (intensity compatible with the base metal and higher Plasticity, toughness) and strong resistance to cold cracks and hot cracks.
b. The flux should have good manufacturability, stable arc combustion, and the slag should have a suitable melting point, viscosity and surface tension. The weld bead and the weld bead and between the weld bead and the base metal are fully fused, the transition is smooth, there is no obvious undercut, the slag removal is easy, the weld surface is well formed, and the harmful gas generated during the welding process is small.
c. The flux must have a certain particle size and a certain particle strength to facilitate multiple recycling. The particle size of flux is divided into two types: the particle size of ordinary particle size flux is 2.5～0.45mm (8～40 mesh), which is used for ordinary submerged arc welding and electroslag welding; the particle size of fine particle size flux is 1.25～0.28mm ( 14～60 mesh), suitable for semi-automatic or fine wire submerged arc welding. Among them, the fine particles smaller than the specified particle size of 60 or less are not more than 5%, and the coarse particles above the specified particle size of 14 mesh are not more than 2%.
d. The flux should have low water content and good moisture resistance. The mass fraction of the factory flux should not be greater than 0.10%. The flux should be placed for 24h under the environmental conditions of 25℃ and 70% relative humidity, and it will absorb moisture. The rate should not be greater than 0.15%.
e. The content of mechanical inclusions (carbon particles, raw materials, ferroalloy beads and other impurities) in the flux shall not exceed 0.30% of the mass fraction of the flux;
f. The flux should have low S and P content, generally S≤0.06%, P≤0.08%.
(2) Requirements for fluxes for electroslag welding
For the flux for electroslag welding, in order to make the electroslag process stable and get a good welded joint, the following special requirements should also be met.
a. The electrical conductivity of the slag should be appropriate. If the conductivity is too low, welding cannot be performed; if the conductivity is too high, the resistance heat is too low, which will affect the smooth progress of the electroslag welding process.
b. The viscosity of molten slag should be appropriate. If the viscosity is too small and the fluidity is too large, it is easy to cause slag and metal loss and interrupt the welding process; if the viscosity is too large, the melting point is too high, and it is easy to form undercut and slag inclusion.
c. The initial evaporation temperature of molten slag should be appropriate.
The temperature at which the slag starts to evaporate depends on the most easily evaporable components in the slag. For example, the low boiling point of fluoride reduces the temperature at which the slag starts to evaporate, which is prone to arcing, which reduces the stability of the electroslag welding process and is easy to produce Splash. Under normal circumstances, when the SiO2 content in the flux increases, the conductivity decreases and the viscosity increases; when the fluoride and TiO2 increase, the conductivity increases and the viscosity decreases. In order to obtain high-quality welded joints, the flux must not only meet the above requirements, but also the appropriate brand of flux and matching wire for different steel grades.
Usually, the welding wire is selected mainly according to the type of steel to be welded and the requirements for the performance of the welded joint, and the appropriate flux is selected. In general, for welding low-carbon steel and low-alloy high-strength steel, the welding wire that matches the strength of the base material should be selected; for the welding of heat-resistant steel and stainless steel, the welding wire that matches the composition of the base metal should be selected; when surfacing welding According to the technical requirements of the surfacing layer, the alloy system and the welding wire of similar composition should be selected and the appropriate flux should be selected. According to the technical requirements of the products to be welded (such as groove and joint form, post-welding processing technology, etc.) and production conditions, select the appropriate combination of flux and welding wire. If necessary, perform welding process qualification and test the mechanics of the weld metal. Performance, corrosion resistance, crack resistance and the process performance of the flux to assess whether the selected welding material is suitable.
2. Selection of flux and wire for low carbon steel submerged arc welding
When selecting high-manganese, high-silicon and low-fluorine flux, it is combined with H08A or H08E. At present, the commonly used combination is H08A+HJ431 (HJ430, HJ433, HJ434). The MnO and SiO2 in the flux react with Fe at high temperature, and Mn and Si can be reduced and transferred to the welding pool. When cooled, it will act as a deoxidizer and alloying agent to ensure the mechanical properties of the weld metal. Compared with HJ430, HJ431 has improved arc stability, but reduced rust resistance and anti-porosity ability;
When selecting medium-manganese, low-manganese or manganese-free high-silicon and low-fluorine fluxes, a welding wire with higher manganese content should be selected to ensure that sufficient amounts of manganese and silicon are transferred to the molten pool during the welding process to ensure that the weld is deoxidized and deoxidized. Mechanical properties. The commonly used combinations of welding wire and flux are: (H08MnA, H08Mn2, H10Mn2Si, H10Mn2) + (HJ330, HJ230, HJ130).
In recent years, due to the rapid development and unique advantages of sintered flux, the application in welding production has gradually expanded. For example, SJ301, SJ401, etc. are used with welding wire H08A to weld low carbon steel. The weld quality is excellent, the welding efficiency is high, and the order can be realized. Surface welding is formed on both sides, and the weld seam is beautiful. It has been applied to products such as boilers and pressure vessels. The combination of commonly used sintered flux and welding wire is as follows.
① (H08A, H08E) + (SJ401, SJ402) SJ401 has strong anti-porous ability, SJ402 has strong anti-rust ability, suitable for welding thin and medium-thick plates; among them, SJ402 is more suitable for high-speed welding of thin plates.
② (H08A, H08E) + (SJ301, SJ302) welding process performance is good, the slag is "short slag" nature, does not drip down during welding, suitable for the welding of circular seams, of which SJ302 has slag removal, moisture absorption and Better crack resistance and low flux consumption.
National standard GB model H08A
American Standard AWS Model EL12
Description: H08A is a copper-plated carbon structural steel welding wire, with the corresponding flux HJ431 for automatic submerged arc welding, the weld metal has excellent mechanical properties.
Uses: Used with corresponding fluxes for submerged arc automatic welding of carbon steel (such as Q235, Q195) and low-strength alloy steels such as 09Mn2, 16Mn, 16MnCu, etc.
What flux, wire and electrode are used for L245 submerged arc welding
Welding wire: H08MnA /H08A Flux: HJ401/HJ431/SJ101 For details, see JB4709 (standard). If it is strict, the usual pressure vessel standards: 10MN2 submerged arc welding wire and J101 flux will be preferred.
Submerged arc welding welding wire and flux welding wire for 304 stainless steel cylinder. ER321 flux SJ601 welding wire can also use ER347. Our factory uses 347 to remove slag easier than 321. The welding wire adopts H0Cr20Ni10. Flux: HJ260. Baking temperature 350°, 2 hours.