Gearbox body crack welding repair method

Abstract

The invention relates to a gearbox body crack welding repair method which comprises the following steps: S1, heating a welding rod to 145-155 DEG C and preserving heat; s2, a welding groove is machined in the crack; s3, the groove is preheated, and the preheating temperature ranges from 300 DEG C to 350 DEG C; s4, multi-layer and multi-pass welding is adopted for welding in the welding groove; s5, knocking the welded surface of the welding seam of the gearbox body, and releasing stress; s6, the surface of the welded gearbox body weld joint is heated to 600-650 DEG C, and asbestos is used for wrapping and slow cooling; and S7, after the gearbox body is cooled, primary penetrant flaw detection is carried out, and after a weld joint is ground to be flat, secondary penetrant flaw detection is carried out. During welding, a multi-layer and multi-pass welding process is adopted, through preheating and postweld heat treatment, welding stress is reduced, welding cracks are avoided, the problems of welding center change, stress concentration, postweld delayed cracks and the like can be effectively avoided, the gearbox body crack welding repair efficiency is high, and the repair effect is good.

Description

Technical Field

[0001] The invention relates to the field of locomotive maintenance, and in particular to a method for welding and repairing cracks in a gearbox case. Background Art

[0002] The starter gearbox is an auxiliary transmission system on a diesel locomotive. The input shaft of the starter gearbox is connected to the diesel engine crankshaft through a universal shaft, an elastic coupling, and the armature shaft extension of the traction generator. The starter gearbox has two output shafts, divided into four output ends: one end of the starter shaft drives the starter motor through an elastic sleeve pin coupling, and the other end drives the tachometer generator through a V-belt; one end of the exciter shaft drives the front air fan through a nylon rope coupling, and the other end drives the exciter through an elastic sleeve pin coupling.

[0003] During operation, the gearbox body is subjected to cyclic impact loads, which often cause cracks and oil leakage in the gearbox body. The traditional welding repair method is to directly repair the cracks or grind and remove the cracks before welding. The gearbox body is made of gray cast iron, which has low strength and poor plasticity. It is very sensitive to cooling speed and has poor weldability. Delayed cracks or crack area expansion often occur after welding, which brings great distress to the staff. After multiple repairs, it is still unqualified, and the gearbox body has to be updated to meet the maintenance requirements, which greatly increases the maintenance cost and maintenance cycle. To this end, the present invention proposes a gearbox body crack welding repair method. Summary of the invention

[0004] Aiming at the problem that the existing gearbox case crack welding repair has poor weldability and is easy to cause the crack to expand, the present invention proposes a gearbox case crack welding repair method, and the specific technical scheme is as follows: A method for welding and repairing cracks in a gearbox housing comprises the following steps: S1. Heat the electrode to 145-155℃ and keep it warm; S2. Processing welding groove at the crack; S3, preheating the groove, the preheating temperature is 300 ~ 350 ℃; S4. To reduce the influence of welding stress on the weld, multi-layer and multi-pass welding is adopted within the welding groove; S5. Tap the weld surface of the gearbox housing after welding to release stress; S6. Heat the weld surface of the gearbox housing to 600-650°C and wrap it with asbestos to slow down cooling; S7. After the gearbox case has cooled, a first penetrant inspection is conducted, and after the weld is smoothed, a second penetrant inspection is conducted.

[0005] Specifically, in S1, the welding rod is heated to 150°C and kept warm.

[0006] Specifically, in S2, a first U-shaped groove is formed for the non-penetrating crack.

[0007] Specifically, in S2, for the through crack, a second U-shaped groove with a depth of one third of the plate thickness is opened on one side of the box body, and a third U-shaped groove with a depth of two thirds of the plate thickness is opened on the other side of the box body.

[0008] Specifically, in S4, firstly, a second U-shaped groove having a welding depth of one third of the plate thickness is welded by multi-layer multi-pass welding, and then a third U-shaped groove having a welding depth of two thirds of the plate thickness is welded by multi-layer multi-pass welding.

[0009] Specifically, in S7, after the gearbox case is cooled to room temperature and left for one day, a first penetrant flaw detection is performed, and after the weld is ground flat, a second penetrant flaw detection is performed.

[0010] The beneficial effects of the present invention are: Different welding grooves are used depending on whether the cracks penetrate the gearbox case. Multi-layer and multi-pass welding processes are used during welding. Preheating and post-weld heat treatment are performed to reduce welding stress and avoid the occurrence of welding cracks. Problems such as welding deflection, stress concentration, and delayed cracking after welding can be effectively avoided, making the gearbox case crack welding repair efficient and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0012] Figure 1 is a schematic diagram of a welding groove in Embodiment 1 of the present invention; Figure 2 is a schematic diagram of a welding groove in the second embodiment of the present invention; Figure 3 It is a schematic diagram of welding of the second U-shaped groove in the second embodiment of the present invention.

[0013] In the figure: 1, first welding layer; 2, second welding layer; 3, third welding layer; 4, fourth welding layer; 5, first U-shaped groove; 6, second U-shaped groove; 7, third U-shaped groove. DETAILED DESCRIPTION

[0014] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0015] Embodiment 1: Taking a non-penetrating crack on a gearbox housing as an example, the present invention provides a gearbox housing crack welding repair method, comprising the following steps: S1. Select welding rods according to the material of the gearbox housing and heat them to 145-155°C and put them in a heat preservation bucket for use. In this embodiment, the gearbox housing is made of gray cast iron (HT15-33), and Z308 pure nickel core welding rods with diameters of φ2.5 (base) and φ3.2 (cover) are selected.

[0016] S2, such as Figure 1 As shown, a first U-shaped groove 5 is processed at the crack. When processing the groove, the surface of the gearbox housing is polished until the metallic luster is exposed. The polishing range is equidistantly expanded by 25 mm in the groove range, and the edge of the groove is chamfered.

[0017] S3. Preheat the groove at a temperature of 300-350°C to reduce the white structure. The preheating range is 100mm equidistantly expanded within the groove range. During the heating process, an infrared temperature gun is used to detect the preheating temperature.

[0018] S4. In order to reduce the influence of welding stress on the weld, multi-layer and multi-pass welding is adopted in the welding groove, slag is removed between layers during welding, small welding specifications and small serrated oscillating welding gun are used to reduce welding heat input.

[0019] S5. Tap the weld surface of the gearbox case after welding to release stress.

[0020] S6. Heat the weld surface of the gearbox case to 600-650℃, and use asbestos to wrap the cracks and slowly cool them to eliminate the stress in the weld. The heating range is 100mm equidistantly expanded from the groove range. S7. After the gearbox case cools down to room temperature and is left for one day, a penetrant inspection is performed. After the inspection is qualified, the weld is ground flat, and then a second penetrant inspection is performed to ensure that there are no cracks.

[0021] Specifically, in S1, the welding rod is heated to 150°C and kept warm.

[0022] Embodiment 2: Taking a through crack on a gearbox housing as an example, the present invention provides a gearbox housing crack welding repair method, comprising the following steps: S1. Select welding rods according to the material of the gearbox housing and heat them to 145-155°C and put them in a heat preservation bucket for use. In this embodiment, the gearbox housing is made of gray cast iron (HT15-33), and Z308 pure nickel core welding rods with diameters of φ2.5 (base) and φ3.2 (cover) are selected.

[0023] S2, such as Figure 2 As shown, a second U-shaped groove 6 with a depth of one third of the plate thickness is opened on one side of the gearbox housing, and a third U-shaped groove 7 with a depth of two thirds of the plate thickness is opened on the other side of the housing.

[0024] S3. Preheat the groove at a temperature of 300-350°C to reduce the white structure. The preheating range is 100mm equidistantly expanded within the groove range. During the heating process, an infrared temperature gun is used to detect the preheating temperature.

[0025] S4. In order to reduce the influence of welding stress on the weld, multi-layer and multi-pass welding is adopted. First, the second U-shaped groove 6 with a depth of one-third of the plate thickness is welded. Figure 3 As shown, the groove is layered in the depth direction, and the first welding layer 1, the second welding layer 2, the third welding layer 3 and the fourth welding layer 4 are welded layer by layer in the order from deep to shallow, and the slag is removed between the welding layers; then the third U-shaped groove 7 with a depth of two-thirds of the plate thickness is welded, and the root cleaning is first performed at this time, and the slag is removed between the layers, and the weld stress is eliminated at the same time. Small welding specifications and small sawtooth oscillating welding guns are used during welding to reduce welding heat input.

[0026] S5. Tap the weld surface of the gearbox case after welding to release stress.

[0027] S6. Heat the weld surface of the gearbox case to 600-650℃, and use asbestos to wrap the cracks and slowly cool them to eliminate the stress in the weld. The heating range is 100mm equidistantly expanded within the groove range.

[0028] S7. After the gearbox case cools down to room temperature and is left for one day, a penetrant inspection is performed. After the inspection is qualified, the weld is ground flat, and then a second penetrant inspection is performed to ensure that there are no cracks.

[0029] Specifically, in S1, the welding rod is heated to 150°C and kept warm.

[0030] Different welding grooves are used depending on whether the cracks penetrate the gearbox case. Multi-layer and multi-pass welding processes are used during welding. Preheating and post-weld heat treatment are performed to reduce welding stress and avoid the occurrence of welding cracks. Problems such as welding deflection, stress concentration, and delayed cracking after welding can be effectively avoided, making the gearbox case crack welding repair efficient and effective.

[0031] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A gearbox case crack welding repair method, characterized in that: The following steps are included: S1. Heat the electrode to 145-155℃ and keep it warm; S2. Processing welding groove at the crack; S3, preheating the groove, the preheating temperature is 300 ~ 350 ℃; S4, adopt multi-layer and multi-pass welding to weld in the welding groove; S5. Tap the weld surface of the gearbox housing after welding to release stress; S6. Heat the weld surface of the gearbox housing to 600-650°C and wrap it with asbestos to slow down cooling; S7. After the gearbox case has cooled, a first penetrant inspection is conducted, and after the weld is smoothed, a second penetrant inspection is conducted.

2. A gearbox case crack welding repair method according to claim 1, characterized in that: In S1, the electrode is heated to 150°C and kept at this temperature.

3. A gearbox case crack welding repair method according to claim 1, characterized in that: In S2, a first U-shaped groove (5) is formed for the non-penetrating crack.

4. A gearbox case crack welding repair method according to claim 1, characterized in that: In S2, for penetrating cracks, a second U-shaped groove (6) with a depth of one third of the plate thickness is opened on one side of the box body, and a third U-shaped groove (7) with a depth of two thirds of the plate thickness is opened on the other side of the box body.

5. A gearbox case crack welding repair method according to claim 4, characterized in that: In S4, firstly, a second U-shaped groove (6) is welded with multi-layer multi-pass welding to a depth of one third of the plate thickness, and then a third U-shaped groove (7) is welded with multi-layer multi-pass welding to a depth of two thirds of the plate thickness.

6. A gearbox case crack welding repair method according to claim 1, characterized in that: In S7, a first penetrant inspection is performed after the gearbox case has cooled to room temperature and has been left for one day, and a second penetrant inspection is performed after the weld is ground flat.

Images