A method of welding a cast steel piece having a box-like structure

Abstract

The present application belongs to the technical field of welding, and mainly relates to a welding method for a cast steel piece with a box body structure, which comprises the following steps: marking a wall thickness missing area of a box body structure part of the cast steel piece; dividing the missing area into a plurality of welding repair modules; cutting and separating the welding repair modules from the cast steel piece; welding the missing parts of the welding repair modules; shovel grinding and detecting the welding repair modules; and performing structural butt welding on the welding repair modules and the cast steel piece. By using the welding method, the size of the welding repair area can meet the standard requirements without deformation, and the welding quality of the cast steel piece is improved.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, and mainly relates to a welding method for cast steel parts with box-like structures. Background Technology

[0002] For cast steel parts with box-like structures, the limited space within the box structure makes it impossible to weld the missing parts in the internal cavity. Currently, the defect is repaired by overlaying the external cavity with welding. However, this method cannot guarantee that the absolute dimensions will meet the standard requirements. Therefore, it is urgent to solve the problem of how to weld defects in cast steel parts with box-like structures so that the repaired dimensions meet the standard requirements. Summary of the Invention

[0003] In view of the above description, the present invention provides a welding method for cast steel parts with box-like structures to solve the problem of difficult welding of defects in cast steel parts with box-like structures. The welding method specifically includes the following steps:

[0004] A welding method for cast steel parts with a box-like structure includes the following steps:

[0005] S01 indicates the area of ​​missing wall thickness in the box-like structural parts of cast steel parts, mainly marking the area of ​​missing wall thickness inside the cast steel parts on the surface of the cast steel parts.

[0006] S02, Divide the missing area into several welding modules, and mark the division according to the minimum cutting amount and the easiest welding operation;

[0007] S03, the welding repair module is cut and separated from the cast steel part by carbon arc gouging.

[0008] S04, Weld the missing parts of each welding module, and weld according to the missing part size value measured and marked by the wall thickness detection tool;

[0009] S05, grind and inspect each welding module, use non-destructive testing to measure whether the welding area of ​​the welding module is qualified. If each welding module is qualified, proceed to step S06.

[0010] S06, the welding repair module is structurally butt-welded to the cast steel part. After each welding is completed, the weld seam is cleaned and ground.

[0011] In one embodiment, in the step of identifying the missing wall thickness area of ​​the box-like structure of the cast steel part, ultrasonic testing is used to detect the wall thickness of the box-like structure of the cast steel part, and the missing area is marked by comparing it with the standard size.

[0012] In one embodiment, in the step of dividing the missing area into several welding repair modules, a wall thickness measuring instrument is used to measure the wall thickness of the missing area. Areas where the wall thickness does not meet the standard requirements are marked with the missing value. The welding repair module area is then divided and marked based on the marked point of the missing value. Preferably, when dividing the area, the area is divided outwards from the marked point with dimensions ranging from 80mm × 180mm to 120mm × 220mm.

[0013] In one embodiment, during the step of cutting and separating the weld repair module from the cast steel part, the weld repair module area is divided according to the marked point of the defect value, and the module is cut and separated from the cast steel part to obtain several weld repair modules. Preferably, carbon arc gouging is used to cut along the marked area. The diameter of the carbon rod is between φ13mm and φ15mm. This range means that the carbon rod generates less heat during gouging, which can avoid deformation due to the thickness of the box wall during gouging. Furthermore, if the diameter of the carbon rod is too large, the amount of gouging and welding will increase.

[0014] In one embodiment, in the step of welding the missing parts of each welding module, a segmented symmetrical welding method is adopted, that is, welding is performed in a skip-welding manner from both sides to the middle of the area to be welded according to a set grid range. Preferably, when using skip-welding, welding is performed from both sides to the middle according to a 100mm*100mm grid range. Since the wall thickness of the cast steel box-like structural parts is thin, a segmented symmetrical welding method is adopted to minimize welding deformation and avoid the severe deformation caused by sequential welding.

[0015] In one embodiment, in the step of welding the missing parts of each welding module, if gas metal arc welding is used, the diameter of the welding material is φ1.2mm to φ1.6mm and the welding current is 180A to 230A; if manual arc welding is used, the diameter of the welding material is φ4.0mm to φ5.0mm and the welding current is 130A to 180A.

[0016] In one embodiment, during the step of welding the missing parts of each welding module, when welding the area to be welded, the maximum swing width is less than or equal to 20mm, and the welding time is less than 5min.

[0017] In one embodiment, in the step of structurally butt welding the welding repair module to the cast steel part, before butt welding, bevels are made at the welding positions of the cast steel part and several welding repair modules. The bevel angle ranges from 30° to 50°, and the bevel width is 0.7 to 0.9 times the corresponding wall thickness. This can reduce the amount of welding, prevent deformation during welding, reduce the generation of welding defects, and improve the welding qualification rate.

[0018] In one embodiment, during the structural butt welding step of the welding repair module to the cast steel part, the welding module to be welded to the cast steel part is welded first, followed by the welding of the remaining welding modules in sequence. The welding sequence is followed according to the principle of facilitating the cleaning of the joint after each welding is completed; the welding parameters are set reasonably according to the material.

[0019] In one embodiment, during the structural butt welding step of the welding module and the cast steel part, the welding module and the area to be welded on the cast steel part are preheated before welding. The preheating temperature is determined according to the material of the cast steel part. If the material of the cast steel part is carbon steel or martensitic stainless steel, the preheating temperature is 100°C to 120°C; if the material of the cast steel part is high alloy steel, the preheating temperature is 200°C to 250°C; if the material of the cast steel part is low alloy steel, the preheating temperature is 150°C to 200°C; if the material of the cast steel part is austenitic stainless steel, preheating is not required. Selecting an appropriate preheating temperature according to the material can reduce the cooling rate of the casting, reduce the hardness value, and prevent cracks.

[0020] The welding method for cast steel parts with box-like structures provided by this invention can effectively solve the problem of insufficient material in box-like structures of cast steel parts, which cannot be welded. The method involves rationally dividing the area according to the structure of the cast steel part and the indication of insufficient material, while strictly controlling the welding parameters at each stage during the welding process. This ensures that the welded area does not deform and that the dimensions of the welded area meet standard requirements. The welding module and the cast steel part body are welded in a set sequence, which facilitates the cleaning operation of the welded area and improves the welding quality of the cast steel parts. Attached image description:

[0021] Figure 1 This is a schematic diagram of the welding sequence for a skip welding method;

[0022] Figure 2 This is a partial schematic diagram of a box-type structure made of cast steel. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0024] This embodiment mainly relates to a welding method for cast steel parts with box-like structures. After casting, the box-like casting structure has a missing part defect in its internal cavity. Since the missing part is internal, it cannot be welded externally. Therefore, it is necessary to cut and weld the defect, and then weld it to the main body of the cast steel part in a predetermined sequence to form a complete casting. The specific steps include:

[0025] S01, marking the areas of missing wall thickness in the box-like structural parts of cast steel parts; using ultrasonic testing to detect the wall thickness of the box-like structure of cast steel parts, and comparing it with standard dimensions to mark the areas of missing wall thickness; mainly marking the areas of missing wall thickness inside the cast steel parts on the surface of the cast steel parts.

[0026] S02, the missing area is divided into several welding repair modules, and the division is carried out by marking lines according to the minimum cutting amount and the easiest welding operation; specifically, the wall thickness of the missing area is measured using a wall thickness measuring instrument, and the missing value is marked for the parts whose wall thickness does not meet the standard requirements. The area range of the welding repair module is divided with the marked point of the missing value as the center, and marked accordingly. When dividing the area range, the area is divided to both sides with the outer range of 80mm×180mm to 120mm×220mm centered on the marked point.

[0027] S03, the welding repair module is cut and separated from the cast steel part using carbon arc gouging. Specifically, the welding repair module area is divided into sections centered on the marked defect value, and the modules are cut and separated from the cast steel part to obtain several welding repair modules. Carbon arc gouging is used to cut along the marked sections. The carbon rod diameter ranges from φ13mm to φ15mm. This range minimizes the heat generated by the carbon rod during gouging, preventing deformation due to variations in the box wall thickness. Furthermore, a larger carbon rod diameter would increase the amount of gouging and welding required.

[0028] S04, Welding repairs are performed on the missing parts of each welding module, based on the missing part dimensions measured and marked by the wall thickness measuring tool. Specifically, a segmented symmetrical welding method is used, i.e., welding is done in a skip-and-go manner from both sides to the middle of the area to be welded, according to the set grid range. See Appendix for details. Figure 1 As shown, welding is performed in the order of 1-2-3-4-5. Due to the thin wall thickness of the cast steel box-type structural parts, a segmented symmetrical welding method is adopted to minimize welding deformation and avoid the severe deformation caused by sequential welding. When using skip welding, welding is performed from both sides to the middle within a 100mm*100mm grid range, with a maximum swing width of less than or equal to 20mm and a welding time of less than 5 minutes.

[0029] When using gas metal arc welding, the diameter of the welding material is φ1.2mm to φ1.6mm, and the welding current is 180A to 230A; when using manual arc welding, the diameter of the welding material is φ4.0mm to φ5.0mm, and the welding current is 130A to 180A.

[0030] S05, grind and inspect each welding repair module, use non-destructive testing to measure whether the welding repair area of ​​the welding repair module is qualified. If the inspection fails, continue welding repair; if each welding module is qualified, proceed to step S06.

[0031] S06. Before butt welding, bevel the casting steel parts and several welding repair modules at the welding locations. The bevel angle ranges from 30° to 50°, and the bevel width is 0.7 to 0.9 times the corresponding wall thickness. Then, perform structural butt welding between the welding repair modules and the casting steel parts. After each butt welding is completed, clean and grind the weld seam. See appendix for details. Figure 2 As shown, the welding repair module specifically consists of a first welding repair module 1, a second welding repair module 2, and a third welding repair module 3. First, the first welding repair module 1 is welded to the cast steel part 4. Then, the third welding repair module 3 is welded to the cast steel part 4. Subsequently, the second welding repair module 2 is butt-welded to the first welding repair module 1 and the third welding repair module 3 to complete the overall casting steel part. Specifically, during the butt welding, the welding module that is butt-welded to the casting steel part is welded first, and then the remaining welding modules are welded in sequence. The welding sequence follows the principle of cleaning the joint after each weld is completed for ease of welding. Welding parameters are set appropriately based on the material. Before butt welding, the welding module and the areas to be welded on the cast steel parts are preheated. The preheating temperature is determined based on the material of the cast steel parts: if the cast steel parts are made of carbon steel or martensitic stainless steel, the preheating temperature is 100℃ to 120℃; if the cast steel parts are made of high-alloy steel, the preheating temperature is 200℃ to 250℃; if the cast steel parts are made of low-alloy steel, the preheating temperature is 150℃ to 200℃; if the cast steel parts are made of austenitic stainless steel, preheating is not required.

[0032] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0033] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A welding method for cast steel parts with a box-like structure, characterized in that, Includes the following steps: Identify areas of missing wall thickness in box-like structures of cast steel parts; use ultrasonic testing to measure the wall thickness of box-like structures of cast steel parts, and mark the areas of missing wall thickness by comparing with standard dimensions. The missing area is divided into several welding repair modules; the wall thickness of the missing area is measured using a wall thickness measuring instrument, and the missing value is marked for the parts whose wall thickness does not meet the standard requirements. The area range of the welding repair module is divided with the missing value as the center and marked accordingly. The welding repair module is cut and separated from the cast steel part; the area of ​​the welding repair module is divided into marked areas based on the missing value, and the module is cut and separated from the cast steel part to obtain several welding repair modules. Weld the missing parts of each welding module; adopt a segmented symmetrical welding method, and weld in a skipping manner from both sides to the middle of the area to be welded according to the set grid range; Grind and inspect each weld repair module; The welding repair module is structurally butt-welded to the cast steel part.

2. The welding method for cast steel parts with box-like structures according to claim 1, characterized in that, In the step of welding the missing parts of each welding module, when welding the area to be welded, the maximum swing width is less than or equal to 20mm, and the welding time is less than 5min.

3. The welding method for cast steel parts with box-like structures according to claim 1, characterized in that, In the step of structurally butt welding the welding repair module to the cast steel part, before butt welding, bevels are made at the welding positions of the cast steel part and several welding repair modules. The bevel angle ranges from 30° to 50°, and the bevel width is 0.7 to 0.9 times the corresponding wall thickness.

4. The welding method for cast steel parts with box-like structures according to claim 1, characterized in that, In the step of structurally butt welding the welding repair module to the cast steel part, the welding module that is butt welded to the cast steel part is welded first, and then the remaining welding modules are welded in sequence.

5. The welding method for cast steel parts with box-like structures according to claim 1, characterized in that, In the step of structurally butt welding the welding module to the cast steel part, the welding module and the part to be welded are preheated before butt welding. The preheating temperature is determined according to the material of the cast steel part.

Images