FAQ steel welding process

FAQ steel welding disposal

(B) the cold crack
Generally refers to weld cold cracking during cooling down to the temperature changes in the temperature of martensite size (300-200 ℃ below) occurs, can be presented immediately after welding, and can only occur after the welding in a long time, it is also known as delayed cracking. The basic conditions for its formation are three: the formation of hardened weld joint arrangements; presence of hydrogen dispersion and concentration; there is a large welding tensile stress. Its preventive measures are:
(A) a reasonable choice of welding standards and lines can improve the weld and heat affected zone arrangement states, such as preheating before welding, handling interlayer temperature, slow cooling after welding or hot, etc. in order to accelerate the escape of hydrogen molecules. (2) electrode or an alkaline flux to reduce the dispersion of the oxygen content in the weld. (3) Before applying electrodes and flux should be strictly in accordance with the requirements of the rule for drying (low hydrogen electrodes 300 ℃ ~ 3 50 ℃ insulation lh; acid electrode l 00 ℃ ~ l50 ℃ insulation lh; 200 ℃ ~ 250.C heat flux 2h), carefully clean the groove and wire, so in addition to oil, water and dirt and rust, etc., in order to reduce the source of hydrogen. (4) timely post-weld heat treatment. First, annealed disposal to eliminate stress, make arrangements for quenching and tempering to improve their toughness; two: eliminate hydrogen disposal is carried out so that the abundant hydrogen to escape from the welded joints. (5) advances the quality of steel, reducing the steel lamellar inclusions. (6) can be taken to reduce the stress of all kinds of welding technical measures.
Third, Foshan steel welding inspection of the relevant issues
(A) weld grades, inspection levels, assessment
Level difference and connection requirements for internal quality testing of welds, according to quality grade points a and two, called a weld seam and two, that is, for the weld grades. The accuracy of the inspection rating means checking to see achievable accuracy, that view contact instruments and viewing methods view the results obtained. Ultrasonic flaw detection using GB / T ll 34 5 l 9 89 standards by viewing rating from low to high is divided into A, B, C three grades, ray detection using GB / T 3 3 2 3 a l 9 8 7 Press to view the rating standard from low to high is divided into a, AB, B three levels, which are the rules of the craft of view ultrasonic testing method, exploration side, view the size and allowable defect equivalent (dB values​​) and ray detection sensitivity to be achieved (through the thickness IQI's relationship with).
Rating refers to the testing personnel in the detection of defects according to the standard measurement of the defect and then determine the internal weld quality grade. Specifically, ultrasonic flaw detection refers to the wave height is measured between long-term and rejection line (Ⅱ area) defect length measurement, according to the standard GB / Tl1345 l989 Table 6 for defect classification; ray detection refers to the measurement of the length of the film defect indication and size, according to the standard GB / T3 3 2 3 a l987 table 6 table 7, Table 9, Table l0 and comprehensive rating (see the standard l 6.1 ~ l 6.4), this one is every person has the necessary proficiency testing of .
(B) the disposal and reuse of excessive defect detection, expanding exploration GB 50205 steel construction quality acceptance criteria "only rule viewing methods. View share and pass grade for defects does not explicitly require disposal.
Referring JG l 8 l construction steel welding procedures "and other industry standard welding inspection standards, for ten detected defects can be disposed of as follows: (1) does not allow viewing of the need to repair the defect, repair and press the same kinds of ways to view a qualified rear view that qualified the weld. (2) ask to see the inspection of weld defects found are not allowed, it should be viewed in the whole area two each weld length l 0% and not less than 00inin (the length of time allowed) regional expansion inspection. a) If the defect is not found excessive expansion inspection area, should that qualified the weld. b) If it is found defective in excessive expansion of inspection area, which welds all seized. (3) requirements for on-site installation inspection of welds view, does not allow discovery of the defect, according to the following criteria expanded inspection; a) to add the same type of two welders weld view, if this is not tested weld two expansion found that excessive defects, should be thought qualified batch of welds. b) If this check welds found excessive expansion of two defects, each containing a weld defects exceeding the criteria described by Bu then each sampling two welds. C) If the re-sampling found no excessive weld defects should be thought qualified batch weld. d) If the re-sampling of weld defects are still found to have exceeded, then the type of weld welder welding the full inspection. Together,