How to control welding in sub-zero winter?

Entering winter, the environment temperature is low, if there is no protective measures to welding steel components, welding quality of steel components will have a significant impact.

For example, welding at low temperature will make the steel embrittlement, but also accelerate the cooling rate of the weld and the heat affected zone of the base metal, which is easy to produce the hardened structure and increase the brittleness, which is very harmful to the welding of low-alloy steel commonly used in building steel structure (such as Q345).

Therefore, winter welding construction must be implemented in strict accordance with the technical requirements, not blind welding.

Welding material requirements

1. Strict management of welding material library, welding rod must be dried according to the standard, drying times shall not exceed 2 times in the air exposure time shall not exceed 2 hours. If there is no oven on site, we must apply for it in time, and arrange someone to bake and distribute it.
2. The welder receives the electrode with the insulation barrel, and shall not use more than half a day at a time; The cover of the insulation barrel must be well covered during the welding process, and the insulation barrel must be kept energized; Positioning welding can only be used 1 at a time; No more than 3 pieces shall be taken at one time during welding. It is strictly prohibited to expose the welding material to moisture. If the welding material is found to be damp, it shall not be used again.
3. If the welding wire is not used up within four hours, it should be returned to the first class library of welding material for storage. It is not allowed to stay on the wire tray.
4 Gas protection welding of carbon dioxide, gas purity should not be less than 99.9%(volume ratio), water content should not exceed 0.005%(weight ratio).
When the new bottle of gas is used, it must be inverted 24 hours later and open the valve to drain all the water before use to prevent freezing. Stop using when the gas pressure in the bottle is lower than 1MPa. Before welding, check the indication on the gas pressure gauge, then check the gas flowmeter and adjust the gas flow. The mouth of the bottle must be connected with heating device when in use.
5. Gas cylinders must be stored in an environment above 0℃. Stop using bottled gas when the gas pressure in the bottle is lower than 1N/mm2. When used below zero temperature, check the bottle nozzle for freezing blockage.

General requirements before welding

1. Remove water, oxide skin, rust and oil stains from the steel surface to be welded.
2. The relative humidity of the welding operation area shall not be greater than 90%.
3. When the weldment surface is wet or covered with snow and ice, it should be heated to remove moisture and moisture.
4. Both ends of the main weld of T-joint, cross joint, Angle joint and butt joint must be equipped with arc plate and extraction plate, whose material should be the same as the base material to be welded, groove form should be the same as the weld, it is prohibited to use other materials as arc plate and extraction plate.
5. The leading length of manual arc welding and gas shielded arc welding shall be greater than 25mm. The width of the arc plate and the leading plate should be greater than 50mm, the length should be 1.5 times the thickness of the plate and not less than 30mm, the thickness should not be less than 6mm;
Non-manual arc welding weld outlet length should be greater than 80mm. The width of the arc plate and the leading plate should be greater than 80mm, the length should be 2 times the thickness of the plate and not less than 100mm, the thickness should not be less than 10mm.
6. After the completion of welding, the flame cutting is applied to remove the arc plate and the lead plate, and the grinding is smooth. Do not use a hammer to shoot down the arc and lead plate.

Winter welding measures (welding ambient temperature below -5 °C)

1. Set up protective shed:
In outdoor construction, when the ambient temperature is lower than -5 ° C, a protective shed must be installed in the welding area to increase the ambient temperature and prevent wind and rain.

2. Preheat before welding:
The weld should be preheated before welding, and the preheating area should be on both sides of the welding groove. If necessary, the accompanying preheating method should be adopted to ensure the preheating temperature and interlayer temperature.
The heating temperature is 80-150 ℃, and the preheating range is 1.5t of each side of the weld (t is the thickness of the plate), and not less than 100mm.
The temperature is measured by far infrared thermometer, and the temperature point is 75mm from the edge of the groove, parallel to the center of the weld on two straight lines.

2.1. Weld preheating temperature

Note: Refer to Q345 for preheating temperature of Q345GJ; Refer to Q460 for preheating temperature of Q390 and 420; When the plate thickness t=100~110mm, the lowest preheating temperature of Q420, Q460 and steel castings is 180℃.

2.2. Preheating temperature of positioning welding is 30~50 degrees higher than that of formal welding seam.

Welding speed and pass layout

The welding speed of manual arc welding is to specify the weld length of each electrode. The single pass welding seam is not allowed to swing, the thickness of the welding layer is controlled at 5-6mm, and the Angle between the electrode (torch) and the workpiece is not less than 30°. Maximum allowable swing width for vertical welding: 15mm ~ 20mm.

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About Us

Wuxi Zhouxiang complete set of welding equipment plant is a famous China manufacturer of H beam Welding equipment. Our factory is located in Wuxi city, China---was established in 1991. The company has fixed assets of more than 20 million US dollars, a factory area of 100,000 square meters, and annual sales of more than 40 million US dollars.We have full control of production from steel plate delivery, through to site installation and commissioning,design and manufacture highly sophisticated heavy engineering machinery, our research and development weld centre also more than 100 engineering. Zhouxiang Complete Set of Welding Equipment Co., Ltd is a national high-tech enterprise, with China's national CCC certification, CE, TüV, GS certification, ISO9001 international quality system certification, etc. Main products of Zhouxiang plant: 1)H beam productions line: CNC control Flame/ plasma cutting machine .H beam assembly machine.H Beam Welding Machine.H beam flange plate straightening machine. H beam shot blasting machine.H beam End Face Milling Machine.H beam assembly-welding-straightening machine.Horizontal H beam productions line etc. 2)BOX column production line: Steel plate groove milling machine.Box column assembly machine.Box column welding machine.Box column electroslag welding.Box beam shot blasting machine.Box beam end Face Milling Machine etc. 3)Welding Rotator: Portable pipe rotator.Conventional rotator.Self-aligned welding rotator.Wind tower productions line etc.Anti-creeping welding rotato etc. 4)Welding Manipulator: Column and Boom .Platform welding manipulator 5)Welding Positioner: Tilting positioner.L type welding positioner.Head and tail stock welding positioner etc.