Cold welding repair of cast iron cylinder block of

Cold welding repair of engine cast iron cylinder block

1. Basic essentials

(1) thoroughly inspect the area to be welded and the starting and ending points of cracks. The crack arrest holes with a diameter of 4~6mm shall be drilled at 2~3mm of the extension line at the beginning and end of the crack. For long cracks, the middle of the crack section shall not be 1 First, drill holes at the same part of the force sensor of the tension machine to reduce the welding stress

(2) prepare the corresponding groove by comprehensively considering the stress, deformation, operation difficulty, weldment thickness, welding position and electrode diameter. In this process, first, thoroughly remove the metal near the crack and remove the burr, impurities and oxide skin of the groove and its edge to ensure the exposure of metal luster; Second, the problem of avoiding parts from thermal shock should be considered. Generally speaking, the width of the upper groove should be 6~10mm, and the depth should be 2/3 or 3/5 of the thickness of the weldment. For workpieces with a thickness greater than 10mm, double-sided grooves can be opened and both sides can be welded

(3) barbecue both sides of the part to be welded with flame, so that all the oil penetrating into the matrix volatilizes until there is no smoke

(4) put the welding rod into a drying oven at 110~150 ℃ and dry it for 1H before standby

(5) adopt appropriate welding direction. When welding cracks, it is advisable to start welding from the crack end, so as to not only close the crack, but also eliminate the stress. If there are cracks at both ends of the crack, it should be welded from both ends to the middle. When welding in the middle, it is most likely to produce new cracks. At this time, pay more attention to pause, and the temperature of the weldment should be strictly controlled to slowly close the crater

(6) when welding, the arc should be low, the arc should be stopped quickly, and the arc should be suppressed to prevent the arc from leading. The arc should not jump left or right to narrow the weld formation and reduce the thermal stress zone

(7) at present, it has fallen to less than 20% using short arc and short weld welding, and the weld length generally should not exceed 60mm; Adopt intermittent segmented welding, weld one section at an interval, and then weld the next section; Adopt multi-layer welding, control the temperature between layers at 60~80 ℃, and try to make the weld center of the next layer on the fusion line of the weld of the previous layer; During welding, it is necessary to observe in time. If pores, slag inclusions, weld beading, etc. are found, it is necessary to immediately grind them with a hand grinding wheel, clean the weld, and then weld the next layer

(8) after welding a section or a layer, when the weld is in a red hot state, hit the weld with a small hammer until the weld darkens, so as to roll out the weld, relax the stress and squeeze the small pores, and refine the grain in the weld area at the same time

(9) if the place to be welded is massive and the area is small, the "small current + arc tempering" process can be used to ensure the welding quality. If the welding area is large after 23 years, it should be divided into several areas, and each area should be welded separately from the middle, and the joint between the periphery and the substrate should be finally welded

(10) welding repair area is too small (area