1 set reducer output shaft diameter of 80 mm, material is quenched after 45 gauge steel. Since the construction of illegal operations, the axis appears as shown in drawings of breakage. We use field repair process, the implementation of the restoration of the shaft.
Because carbon steel 45 when a large amount of heat affected zone during welding hardened tend to be larger, prone to cold cracking, and the axis welding larger, inevitably there is a large welding deformation and welding stresses. To reduce the welding deformation, improve weld quality, preheat take measures before machining the parts and then make the appropriate heat treatment to slow the cooling rate to facilitate the diffusion of hydrogen to escape and prevent cold cracking, eliminate welding stress. After heat treatment in accordance with the requirements of the welding parts turning, you can reach the shaft size requirements.
1 welding preparation
(1) Select equipment and materials
In view of the construction site conditions, the axis SMAW welding methods. Welding equipment used BX1-330 AC arc welding machine. Power DC power supply, reverse polarity connection (electrode connected to the positive level). To improve crack resistance and strength of the weld, welding materials with low hydrogen type J507 (E5015) basic electrode for welding, welding electrodes prior to baking for 1 ~ 2 h, so that the temperature reaches 350 ℃, and then stored at 100 ~ 150 ℃ incubator, the use of time out on the drying cylinder. Ⅰ, Ⅱ layer weld rod with a diameter of 3.2 mm to reduce welding stresses. After the weld rod with a diameter of 4 mm, in order to improve work efficiency.
( 2 ) design and welding groove gap
Before welding the parts machining shaft fracture formation , as well as reduce the residual stresses in the weld groove designed to take some measures . First, according to the circumstances and parts breakage diameter designed U-shaped groove, the groove width of 20 mm, a depth of 37 mm. To enable consistent groove shape , the broken parts of the flat end face machining , the use of molding tools for beveling. In order to avoid stress concentration, each part of the groove should be rounded to reduce the base metal melt into the weld metal ratio , to prevent weld cracking. Welding gap on weld quality also have important implications , the gap is too small easy to produce incomplete penetration or excessive accumulation of defects in welds , the gap is too large, easy to burn . Selected as the axis welding gap 2 mm.
( 3 ) clean before welding
Before welding the shaft groove welds and blunt edge surface rust , oil, water and descaling , the first flame baking Clear water, oil , and then use emery cloth or hand grinder grinding, rust treatment. Oxide grinding wheel machine can be directly used to clear , for some more difficult to clean the oil is cleaned with acetone or ethanol .
Welding , to prevent distortion, the mouth should be added in the slope of the positioning block in order to ensure that the weld gap equal. In order to avoid the welding deformation of the shaft , positioning welding position selected in the positioning block sides. Since 45 steel weldability general , the acetylene flame before welding the weld about 50 ~ 80 mm on both sides of the part preheated to 150 ~ 200 ℃, in order to reduce the cooling rate of the weld region , to prevent cracks.
Welding Ⅰ, Ⅱ layer welds , try using a small current, low voltage , slow welding speed , ie, small energy welding and weld layer should be thinner ( less than 2 mm), but penetration, short arc does not swing . Welding should be uniform rotation with the shaft welding , each weld seam finish a level , the appearance of visual inspection of welds deal , if pores, slag and cracks , etc., should be used to clear the carbon arc gouging weld defects , as supplemented by welding the rear can continue welding. When welding to the positioning block height, until the weld cooling temperature not lower than 200 ℃, destroyed positioning block, continue welding. Surfacing height should exceed the original shaft diameter , leaving enough machining allowance . The welds process parameters such as shown in the table .
3 treated after welding and machining
After welding is covered with asbestos insulation, to reduce the degree of hardening , to avoid embrittlement. In order to eliminate welding stress , can be used acetylene flame will weld zone is heated to 350 ~ 550 ℃, buried in hot sand or lime slowly cooled until it cools to room temperature . Weld appearance requirements neat appearance , weld uniform, no pores, slag , lack of fusion , spatter and undercut . Check the appearance of compliance , will be re- welded parts car output shaft cylindrical and end to the required size can be.
The repair method is simple and practical, low cost repair . Proven repaired output shaft strength , precision, speed reducer fully meet the requirements .