Stainless steel welding rod should be used with the following questions:
1, chromium stainless steel with a certain degree of corrosion (oxidizing acids, organic acids, cavitation), heat and wear resistance. Commonly used in power plants, chemical, oil and other equipment and materials. Chromium stainless steel is poor, should pay attention to welding, heat treatment conditions and appropriate choice of electrodes.
2, chromium stainless steel after welding, hardening of 13 large, easy to crack. If using the same type of chromium Stainless Steel Electrode (G202, G207) welding, must be more than 300 â„ƒ 700 â„ƒ preheating and after welding so slow cooling treatment. If the weldment after welding can not be heat treated chrome-nickel stainless steel welding rod should be used.
3, 17 Cr stainless steel, to improve corrosion resistance and increase the amount of welding stability and appropriate elements of Ti, Nb, Mo, etc., welding of stainless steel better than the chrome 13. Using the same type of chromium stainless steel electrode (G302, G307) should be carried out more than 200 â„ƒ 800 â„ƒ preheating and post weld tempering about. If the weldment can not be heat treated chrome-nickel stainless steel welding rod should be chosen
4, Cr-Ni stainless steel electrode has good corrosion resistance and oxidation resistance, widely used in chemical, fertilizer, petroleum, medical equipment manufacturing.
5, Cr-Ni stainless steel welding, carbide precipitation by repeated heating and reduce the corrosion resistance and mechanical properties.
6, chrome-nickel stainless steel with titanium calcium type coating and low-hydrogen type. Titanium calcium type can be used for AC and DC, but the exchange of shallow penetration welding, and easy to redness, so as far as possible with DC power supply. Diameter of 4.0 and below can be used for all position welding parts, and above 5.0 for a flat butt and fillet weld.
7, the electrode should be used to keep dry, titanium calcium type should be dried at 150 â„ƒ for 1 hour, low-hydrogen type should be dried by 200-250 â„ƒ for 1 hour (can not be repeated drying, easy to crack or flake coating), to prevent the electrode Sticky coating of oil and other dirt, so resulting in increased carbon content, and weld pieces of welding quality.
8, in order to prevent corrosion of heat generated between the eyes, welding current is not too large, less than about 20% of Carbon Steel Welding Electrode, the arc should not be too long, rapid cooling between layers in order to narrow bead suitable.
Aluminum is widely used, divided into cold hardening and heat treatment to strengthen two broad categories. Spot welding of aluminum is poor, especially the heat treatment to strengthen aluminum alloys. Its causes and the process should take the following measures:
(1) high electrical conductivity and thermal conductivity must be higher current and shorter time to achieve sufficient heat to form both the nugget; can reduce the surface overheating, to avoid
(2) Plastic narrow temperature range, linear expansion coefficient must be greater pressure on the electrode, the electrode is good with the move to avoid nugget solidification, because the content is too large cracks caused by tensile stress. Tendency of large aluminum alloy on the crack, such as LF6, LY12, LC4, but also in forging force must be used to increase the ways in which a sufficient nugget solidification of the plastic deformation and reduce the tensile stress in order to avoid cracks. Bending the electrode in the set bear a large forging force, they can add in the slow cooling after welding pulse pulse method avoids cracks. For large thickness of the aluminum electrode and can be used two ways.
(3) surface oxide film is easily produced to strict clean-up before welding, otherwise easily lead to undesirable splash and nugget shaped (tear checks, irregular nugget shape, convex sets and the hole is not rounded), so that joint strength reduced. Clean-up will lead to uneven solder joint strength stable.