Winter construction measures for welding production of steel structure installation in Dongguan
First, the basic requirements:
(1) When installing the steel structure at a negative temperature, pay attention to the deviation of the outer dimensions of the steel structure caused by the temperature change. If the steel structure is installed at a normal temperature and installed at a negative temperature, measures should be taken to adjust the deviation.
(2) Steels that are to be started at negative temperatures should be accepted in open furnace or oxygen converter Q235 steel, 16Mn, 15MnV, 16Mnq and 15MnVq steel. Steel should be included to combat toughness. Q235 steel should have -20°D, and other should have -40°D qualified tube.
(3) Selecting the welding rod and welding wire for steel structure welding under negative temperature, under the premise of the preset strength requirement of the foot, the low-hydrogen type electrode with lower yield strength and better toughness should be selected, and the important structure can be accepted high. Toughness ultra low hydrogen electrode.
(4) Alkaline welding rods must be baked in accordance with the product's factory certificate before use. After baking, it is stored in the 80~100°D oven. When it is used, it is taken out and placed in the heat preservation tube. If the electrode is exposed for more than 2 hours at a negative temperature, it should be re-baked. The number of baking of the electrode should not exceed 3 times.
(5) The flux must be baked according to the regulations of the factory certificate before use. The water content should not exceed 0.1%. When welding at a negative temperature, the interval between repeated use of the flux shall not exceed 2 hours, otherwise it is necessary to re-bake.
(6) The carbon dioxide used for gas shield welding should not be less than 99.5% (volume ratio), and the water content should not exceed 0.005% (weight ratio). When using bottled gas, stop using when the pressure inside the bottle is lower than 1N/mm2. When using at negative temperature, check the bottle mouth for freezing blockage.
(7) High-strength bolts and ordinary bolts shall have product certification. High-strength bolts shall be subjected to re-inspection of torque coefficient and axial force at negative temperature, and shall be used after meeting the requirements.
(8) The coating used in the steel structure should meet the functional requirements of painting under negative temperature. It is forbidden to use water-based paint.
Second, Dongguan steel structure construction:
(1) When the steel structure is staked at a negative temperature, the size of the cutting and milling should consider the effect of shrinkage of the steel at a negative temperature.
(2) When the end is the material of the welded joint, the shrinkage of the weld should be reserved according to the process requirements. The multi-section frame and the multi-section column of the high-rise steel structure should also reserve the load to make the column produce compression deformation. the amount.
(3), ordinary carbon structural steel working place temperature is lower than -20 & # 176; D, low alloy steel working place temperature is lower than -15 & # 176; D can not be cut, punched, ordinary carbon structural steel work place When the temperature is lower than -16°D, the low alloy structural steel working place temperature is lower than -12°D, cold correction and cold bending are not allowed.
(4) The assembly of the components must be carried out according to the number of times specified in the process, and the group should be expanded from the inside to the outside. When the welded structure is assembled at a negative temperature, the reserved weld shrinkage value should be determined by testing. The number and length of spot welds are determined by calculation.
(5), the assembly of parts must be cleaned and cleaned of rust, burrs, dirt, oil, ice and snow within 50mm on both sides of the joint, and keep the joints dry, no residual moisture.
(6) The preheating temperature of the medium-thick steel plate, the thick steel plate and the thick steel pipe welded at a negative temperature can be determined by testing.
(7) When the assembly of the component is under the negative temperature, the welding process should be carried out in strict accordance with the welding process. Since the starting point and the finishing point of the welding are more likely to be infiltrated than the normal temperature, the various defects are not welded and accumulated. The arcing plate and the arc extinguishing plate must be arranged at both ends of a single weld. The material of the arc striking plate and the arc extinguishing plate should be consistent with the base material. It is strictly forbidden to lead the arc on the base metal.
(8) Steel plates with a thickness greater than 9 mm at a negative temperature shall be super-layered and welded, and the welds shall be welded from bottom to top. In order to prevent the temperature from falling too low, in principle, a welded joint should be welded once and must not be interrupted. When re-welding, it should be disposed of first to remove the welding defects. After passing the welding, it can be welded according to the welding process. .
(9) When the steel structure is welded in the open air at a negative temperature, a temporary protective shed should be set up. Rainwater and snowflakes are strictly prohibited from falling on the hot weld.
(10) Before applying the anti-corrosion coating on the steel members below 0#176;D, the painting process shall be tested. When painting, it is necessary to remove the rust, oil stains, and flash burrs of the edges of the components, and keep the components dry. In order to accelerate the drying speed of the coating, it can be dried by hot air or infrared rays. Drying temperature and time are determined by testing. Do not perform painting work during rain or snow or when there is thin ice on the components.
Third, Dongguan steel structure installation
(1) When transporting steel structures in winter, it is necessary to take anti-slip measures. The piled up yards must be flat and solid, with no water pits or no ice on the ground. When the unified model components are stacked, it is necessary to ensure the level of the components, and the spacers must be on the uniform lead line to prevent the components from slipping.
(2) Before the installation of the steel structure in Dongguan, in addition to the general inspection, the quality of the components must be re-inspected according to the negative temperature conditions. In the case of structural deformation caused by missing inspection and transport stacking during construction, if the deviation is greater than the specified impact on the installation quality, it must be repaired and corrected on the ground. It is necessary to lift the installation after the standard is specified.
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