Welding preparation: 4mm thickness of about not break open, direct welding wire, a single penetration. 4 - 6 mm thickness of butt weld joints can be no open break-sided welding. 6 mm or more, generally open V or U, X-shaped groove.
Second: welding pieces of filler wire for degreasing and descaling. To ensure the welding quality.
Welding parameters: including the welding current, tungsten diameter, arc length, arc voltage, welding speed, protect air, the nozzle diameter.
1, weld welding current is a key factor in the decision. Usually based on welding consumable , thickness, and the groove shape to decide.
2, welding pole diameter according to the size of the welding current decisions, current increases, the greater the diameter.
3, the welding arc and electric arc movies, arc length range of about 0.5 to 3mm, the corresponding arc voltage is 8 ~ 10V.
4, the welding speed: Choose to take into account the current size of the sensitivity of weldment material, welding position and method of operation and other factors.
Development of welding procedure qualification rules for the purpose: to prevent leakage assessment; minimize unnecessary evaluation. The steel pressure vessel, for example, the standard provides for the following: I. Review of the required provisions of the weld steel pressure vessel weld must be assessed in five: 1, the weld pressure components; pressure parts include: head (or cover), barrel, manhole covers, manholes, flanges, manhole to take over, opening reinforcement ring, spherical tank shell plate. 2, compared with the pressure parts welding seam; 3, melting into a permanent position within the weld seam 4, the surface of the base material of pressure parts welding, repair welding; 5, the weld repair weld. Second, substitution between the base material in accordance with the provisions of the relationship between chemical composition, mechanical properties and mig welding wiresof the similar degree of group classification, comparison of similar classified as a class, the more similar are grouped together. 1, groups of similar rules in the same group assessed the base metal, as long as one of the assessment of compliance, the process is suitable for groups of numbers with the other parent material. At the same classification number, the higher the assessment of the base metal group number applicable to the group number group number and the low base metal base metal consisting of welded joints. Group No. VI-2 assessment of the base metal group number for the base material II-1. 2, No. classification rule class II (or group number is VI-1, VI-2) of the steel base metal with the assessment applicable to that type of number (or the group number) base metal and the type of number I composed of base metal of welded joints. Third, the effective thickness of the specimen provided the scope of application 1. Sample base material for the IV-2 group and the lower limit of vegetation is greater than 540MPa grade σb low-alloy steel, welded specimen thickness for the thickness range 2. Other base metal, weld specimen thickness for the effective range of the thickness (transverse bending) Table 3-5 welding specimen thickness tested in the thickness of the effective range (vertical bending) Fourth, the classification of the welding process and analysis of factors 1, the welding process factors, classification (1) important factors: the tensile strength of welded joints and bending properties of the welding process factors, such as welding wire , welding materials. (2) additional factors: the impact toughness of welded joints of welding technology factors, such as heat input, the current type and so on. (3) Secondary factors: the determination of the requirements had no effect on the mechanical properties of the welding process factors, such as the groove, groove root gap and so on. 2, the analysis of various technological factors (1) changing the welding method of welding method to be re-assessed; when used with a seam welding method of two or more (or welding), the combination can be assessed and were assessed in two ways. For example, there is a weldment made of 16MnR, impact toughness of welded joints are required, welded with three welding methods, how to assess? The first method: combined evaluation method and Table 3-6 for the thickness of the effective range of welding the second method: Assessment method, respectively, see below: Table 3-7 for the thickness of the effective range of welding (2) the form of welded joints in the form of welds: butt joint, T-shaped joint, cross joint, lap joint, corner joint, lock the end of joints, terminations and other joints. Weld form: butt weld, fillet weld, such as weld termination. T-joint butt joint locking corner joint bottom corner joints joints joints Lap T-butt joint butt weld joints are due to any connected together by welding, the weld can be connected with a different connector, so when the welding process evaluation study aimed at the "seam" rather than welded joints. States: assessment of butt weld specimen technique is also applicable to a qualified welding pieces of fillet weld; plate butt weld specimen evaluation process is also applicable to qualified pipe butt weld, and vice versa. Fillet weld pipe and plate technology assessment also apply to qualified fillet weld plate, and vice versa. Groove, groove root gap and other general as the second plate butt weld butt weld pipe specimen specimen specimen plate fillet weld pipe and plate weld specimen angle photo shows the butt weld specimen photo corner weld specimen (3) Fill materials include: welding, welding wire, flux and filler metal added. Are important factors. (4) Welding positions include: welding, horizontal welding, vertical welding, overhead position welding, etc., usually are secondary factors. Only change the location when the upward vertical position welding, as additional factors. (5) Preheat include: warm-up and do not warm up. Preheated by the warm-up does not change, or the preheating temperature by 50 degrees Celsius, the need to re-assess. (6) gas, including: combustible gases (eg acetylene, propane, etc.) and protection of the gas (such as CO2, argon, etc.) are important factors (7) post-weld heat treatment include: no heat treatment and post-weld heat treatment (such as normalizing, tempering, solution treatment, etc.), or to not change the heat treatment heat treatment, need to re-assess. (8) Electrical features include: heat input, power type, polarity, type or diameter tungsten. Heat input E = 36UgIg / V (J / CM) heat input, power supply type and polar properties of the toughness of welded joints, and therefore additional factors; Tungsten type or diameter of a secondary factor. (9) Technical measures include: wire swings, multi-pass welding with single-pass welding, welding direction, layer cleaning methods, and more generally for the additional factors or secondary factors.