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Centered cardan shaft: eight defects in the welding process

Views: 0     Author: Site Editor     Publish Time: 2022-07-25      Origin: Site

The quality defects in welding engineering mainly include the following aspects: And who or low power magnifying glass to the naked eye can see on the surface of the weld defects, such as biting edge (bit), flash, arc pit, surface porosity, slag inclusion, surface crack, called external defects such as weld position is unreasonable and must have special NDT methods with destructive test or to find internal cracks, porosity, slag inclusion, incomplete fusion, not together referred to as the internal defects, etc. But it is common to do not clean the welding slag and spatter after welding and do not clean the welding scar.

Single double cardan shaft: weld size does not meet the specification requirements

Phenomenon: Weld in the inspection of the weld height is too large or too small; Or the width of the weld is too wide or too narrow, and the transition part between the weld and the base metal is not smooth, the surface is rough, the longitudinal and transverse weld is not neat, and the amount of concave weld in the fillet weld is too large.

Reason: Weld groove processing flatness is poor, groove Angle is improper or assembly gap size is not equal and caused by. Welding current flow is large, so that the electrode melting too fast, control the weld forming difficulties, the current is too small, in the welding arc will make the electrode produce "adhesion phenomenon", resulting in welding penetration or welding tumor. The welder's operation is not proficient enough, the method of running the rod is improper, such as too fast or too slow, and the Angle of the electrode is not correct.

Prevention and control measures: according to the design requirements and welding specifications of the weld groove centered u joint shaft - xinsanmingprocessing, as far as possible to choose mechanical processing to make the groove Angle and the straightness of the groove edge and the straightness of the groove edge to meet the requirements, avoid manual gas cutting, manual shovel cutting processing groove. In pairing, ensure the uniformity of weld gap, to ensure the quality of welding to lay a foundation. Through welding process evaluation, select appropriate welding process parameters. Welders should be licensed to work, and the trained welders have certain theoretical basis and operational skills. The last layer of multi-layer welding seam on the welding surface should be welded by a electrode with a small diameter (φ2.0mm~3.0mm), which is smaller than the welding current between the layers under the condition of ensuring the fusion with the bottom layer. When welding, it is required that the speed of the strip is uniform, rhythmically pushed to the longitudinal direction, and the lateral swing of a certain width can make the weld surface neat and beautiful.

Biting the edge (biting the meat)

Phenomenon: Welding arc will weld edge molten depression or groove did not get molten metal supplement and left a notch. Too deep edge bite will weaken the strength of the welded joint, resulting in local stress concentration, and crack will occur at the edge bite after load bearing.

Reason: the main welding current is too large, arc is too long, the electrode Angle is not appropriate and the speed of the rod is not appropriate, and the end of the welding rod retention length is too short and so on. It is a common defect in vertical welding, horizontal welding and vertical welding.

Prevention and control measures: welding current should not be too large, the arc should not be too long or too short, as far as possible to use short arc welding. Grasp THE PROPER Angle OF THE electrode AND skilled HANDLING OF the rod, the electrode swing to the edge should be slightly slower, so that the molten electrode metal filled the edge, and in the middle of the slightly faster. The depth of the weld edge bite shall be less than 0.5mm, the length shall be less than 10% of the total weld length, and the continuous length shall be less than 10mm. Once THE DEPTH OR yield exceeds the above allowance, the defect should be cleaned up, the electrode with smaller diameter and the same grade, the welding current is slightly larger than the normal, and the welding is filled.

Crack

Phenomenon: IN the welding process or after welding, metal cracking occurs in the welding area, which occurs inside or outside the weld, and may also occur in the heat affected zone. According to the parts produced, it can be divided into longitudinal cracks, transverse cracks, arc pit cracks, root cracks, etc., and can be divided into hot cracks, cold cracks and reheat cracks.

Reason: The heat affected zone of welding seam produces large stress after shrinkage. The base metal contains more quenched tissue and is prone to crack after cooling. There is a fairly high concentration of hydrogen in the weld. And other harmful element impurities, easy to produce cold, hot crack.

Prevention and control measures: mainly from the elimination of stress and correct use of welding materials and perfect operation process. Pay attention to the groove form of welded joints to eliminate cracks caused by thermal stress caused by uneven heating and cooling of welds. If the steel plate of different thickness is welded, the thick steel plate should be thinned. The SELECTION of materials must MEET the requirements of the design drawing, strictly control the source of hydrogen, welding electrode should be dried before use, and carefully clean up the groove of oil, water and other impurities. During welding, select reasonable welding parameters to control the input heat between 800 ℃ and 3000℃ cooling temperature, so as to improve the microstructure of weld and heat affected zone. In the welding environment temperature is low, the material is thin, in addition to increasing the operating environment temperature, should also be preheated before welding. At the end of welding, we should try to keep warm and slow cooling and post-welding heat treatment to eliminate the delayed crack caused by residual stress in the welding seam during cooling.

Arc pit

Phenomenon: Arc pit is a sliding phenomenon at the end of the weld, which not only weakens the weld strength, but also produces cracks in the cooling process.

Reason: The main reason is that the arc extinguishing time is too short at the end of welding, or the current used in welding sheet is too large.

Prevention and control measures: at the end of the weld, make the electrode stay for a short time or do a few annular strips, do not stop arc suddenly so that there is enough metal to fill the pool. Ensure proper current during welding, main components can be added arc plate to lead the arc pit out of the weldment.

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  : The Innovation Industrial Park, No.36, Jingwei Road ,Xi'an Economic and Technological Development Zone,Xi'an City,Shaanxi Province,China
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