A welding process for the upper beam of a large rolling mill
By optimizing the welding process of the crossbeams on large rolling mills and adopting step-by-step assembly and annealing stress relief technology, problems such as welding deformation and high stress were solved, ensuring weld quality and dimensional accuracy, and improving production efficiency and product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CITIC HEAVY INDUSTRIES CO LTD
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-05
AI Technical Summary
The welding process of the crossbeams of large rolling mills has problems such as deformation caused by uneven heating of the weld, high welding stress, weld cracking, and difficulty in ensuring dimensional accuracy after welding. In particular, welding operations are difficult in many confined spaces, making it difficult to meet the requirements of the drawings.
A step-by-step assembly and welding process is adopted, including pre-reserving welding shrinkage on the base plate, step-by-step assembly and stress relief by annealing, optimizing the welding sequence and bevel form, detecting weld quality by ultrasonic testing, and combining low-stress assembly and step-by-step correction technology to ensure weld quality and dimensional accuracy.
Effectively control welding deformation, reduce welding stress, avoid weld cracking, ensure the weld quality and dimensional accuracy of the upper crossbeam, and improve production efficiency and product quality.
Smart Images
Figure CN122142605A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a welding process for large structural components, specifically a welding process for a crossbeam on a large rolling mill. Background Technology
[0002] The upper crossbeam is a core load-bearing structural component in the stand of a large, thick plate rolling mill. It is a symmetrical structure assembled and welded from multiple thick plate parts made of Q355B material with thicknesses ranging from 50 to 120 mm, requiring all welds to be fully penetrated. During operation, the upper crossbeam bears enormous rolling forces and impact loads. Its dimensional accuracy, geometry, weld quality, and internal residual stress directly affect the rigidity of the rolling mill, the accuracy of the mill stand, and the final quality of the plate.
[0003] Due to the large number of components, complex structure, limited welding space, and relatively thick plates involved in the upper crossbeam, requiring complete penetration of the welds, the significant heat input during welding causes the weld and surrounding area to expand upon heating and contract upon cooling. Uneven heating of the weld and its surroundings leads to varying degrees of contraction, resulting in various welding deformations such as transverse shrinkage, longitudinal shrinkage, and angular deformation. This results in high internal welding stress, making subsequent corrections difficult and affecting product dimensional accuracy. The main challenges in manufacturing include: (1) Since the end caps welded to the intermediate vertical plate are all cut with a single V-shaped bevel, the height of the vertical plate is flush with the end cap, and the thickness direction of the vertical plate is cut with a 45° bevel, see [reference]. Figure 1 and Figure 2 Furthermore, the weld seam needs to be fully penetrated. Therefore, the thickness direction of the intermediate vertical plate is subjected to huge tensile stress during the welding process, which can easily lead to lamellar tearing of the intermediate vertical plate.
[0004] (2) There are many welds on the upper beam. After welding, the whole body is annealed to relieve stress. After welding and annealing, flame straightening is required to ensure dimensional accuracy. Welding, annealing and straightening processes will cause dimensional shrinkage, making it difficult to meet the dimensional accuracy requirements after welding.
[0005] (3) There are several semi-enclosed restricted spaces on the upper crossbeam. An unreasonable assembly sequence may prevent welders from entering the restricted space to perform welding, and may also fail to meet the requirement of full penetration of the weld as required by the drawings.
[0006] (4) All parts are assembled according to the drawing requirements before welding. After all parts are assembled and welded, they form a rigid whole, which is difficult to correct.
[0007] (5) Due to the large number of welds on the upper crossbeam, all of which are full penetration welds on thick plates, ultrasonic testing is required for all welds. Q355B is a low-alloy high-strength steel. Before welding, the area around the weld needs to be preheated to above 110°C. During the repeated local heating, welding, heat preservation and cooling process, the upper crossbeam is prone to generating large welding stress. After all welds are completed, large stress concentration will occur, causing structural deformation and weld cracking.
[0008] Therefore, it is necessary to optimize the bevel form of the upper crossbeam, design a reasonable assembly and welding sequence, strictly control welding deformation and residual stress, avoid weld cracking, and ensure the quality and dimensional accuracy of the upper crossbeam weld. Summary of the Invention
[0009] To address the shortcomings of existing methods, this invention provides a welding process for the upper crossbeam of a large rolling mill, which can effectively control welding deformation of the upper crossbeam and ensure dimensional accuracy.
[0010] To achieve the above objectives, the present invention adopts the following technical solution: A welding process for the upper crossbeam of a large rolling mill, wherein the upper crossbeam comprises a symmetrical structure welded together from a bottom plate, vertical plates, stiffening plates, a cover plate, a sealing plate, and a blocking plate, and the vertical plates comprise two outer vertical plates and several middle vertical plates, comprising the following steps: S1. Allow for welding shrinkage when cutting the base plate; S2. Draw the position lines of the middle and outer vertical plates on the base plate, and assemble each vertical plate and each stiffening plate; S3. All welds between the base plate, each vertical plate, and each stiffening plate have passed ultrasonic testing. S4. Assemble the end caps and cover plates, weld the cover plates to each vertical plate, and pass ultrasonic testing. S5. Stress relief by furnace annealing, correction after annealing, sealing plates at both ends by welding, and ultrasonic testing to pass. S6. Assemble the end plates and weld them. After welding, correct the welds to ensure they are qualified, and then anneal the entire product in the furnace.
[0011] Preferably, in step S1, the base plate is cut to allow for welding shrinkage by a length of 1 / 1000-2 / 1000mm.
[0012] Preferably, the welding of all welds between the base plate, each vertical plate, and each stiffening plate in step S3 includes: first welding the main long weld between the outer vertical plate and the base plate, then welding the welds between the middle vertical plates and the middle vertical plates and the outer vertical plates and the base plate, and finally welding the welds between the stiffening plates and each vertical plate.
[0013] Preferably, the welding of the end caps in step S5 includes welding the welds between the end caps and the outer vertical plate, stiffening plate, cover plate / bottom plate, and middle vertical plate.
[0014] Preferably, the weld between the end sealing plates and the middle upright plate in step S5 includes: the two end sealing plates of the middle upright plate are provided with inclined surfaces on the side that are close to each other, and the inclined surfaces on the two end sealing plates together form a V-shaped bevel. The middle upright plate enters the smaller end of the V-shaped bevel and welds the end sealing plates to the upright plate, thereby sealing the thickness of the upright plate with the weld.
[0015] Preferably, the depth to which the intermediate upright plate enters the V-shaped bevel is less than half the thickness of the end caps.
[0016] Preferably, the two edges of the intermediate upright plate entering the V-shaped bevel are chamfered.
[0017] Preferably, the bevel angle is 30°.
[0018] The positive and beneficial effects of this invention are as follows: 1. During the welding process between the end plates of the upper crossbeam and the middle vertical plate, the middle vertical plate is subjected to huge tensile stress in the thickness direction, which can easily lead to lamellar tearing of the steel plate; the existing single V-shaped 45° bevel weld has a large filler volume, resulting in large welding deformation of the product, increased production costs, and long cycle time.
[0019] This invention optimizes the depth of the intermediate vertical plate entering the V-shaped groove to be flush with the sealing plate, so that the depth of the intermediate vertical plate entering the V-shaped groove is less than half the thickness of the sealing plate. The 45° V-shaped groove is optimized to a 30° groove. The weld is used to seal the thickness of the vertical plate, reducing the shrinkage stress in the thickness direction of the vertical plate and avoiding lamellar tearing of the intermediate vertical plate.
[0020] 2. The upper crossbeam has a large number of welds, all of which are full penetration welds on thick plates. All welds require ultrasonic testing. Q355B is a low-alloy high-strength steel. Before welding, the area around the weld needs to be preheated to above 110°C. During the repeated local heating, welding, heat preservation, and cooling process, the upper crossbeam is prone to generating large welding stress. After all welds are completed, there will be a large stress concentration, which may cause structural deformation and weld cracking.
[0021] This invention adds a furnace annealing stress relief step after the cover plate is welded and before the end plates are welded. This timely eliminates the welding stress of most of the welded seams in the welded parts, and corrects the product dimensions step by step to ensure product quality.
[0022] 3. Existing technology requires assembling all parts according to the drawings before welding. The upper crossbeam has a large number of parts, and the welding stress and shrinkage are large. After all parts are assembled and welded, the rigidity is strong, which makes it difficult to straighten and ensure dimensional tolerances. In addition, there are multiple welding confined spaces after assembly, making it difficult to guarantee the quality of the weld.
[0023] This invention employs a low-stress assembly and welding technology that "divides the whole into parts and integrates the parts into a whole." By reserving welding shrinkage in the length direction of the base plate, reserving sufficient operating space for step-by-step assembly and welding, and using step-by-step correction methods, product quality is guaranteed. Attached Figure Description
[0024] Figure 1 This is one of the schematic diagrams of the welding structure of the sealing plate and the upright plate in the existing technology; Figure 2 This is the second schematic diagram of the welding structure of the sealing plate and the upright plate in the existing technology; Figure 3 This is a schematic diagram of the base plate structure of the present invention; Figure 4 This is a schematic diagram of the assembly structure of the base plate, each vertical plate, and each stiffening plate of the present invention. Figure 5 This is a schematic diagram of the sealing plate assembly structure of the present invention; Figure 6 This is a schematic diagram of the cover plate assembly structure of the present invention; Figure 7 This is a schematic diagram of the assembly structure of the blocking plate of the present invention; Figure 8 This is one of the schematic diagrams of the four-welded structure of the sealing plate and the upright plate of the present invention; Figure 9 This is the second schematic diagram of the four-welded structure of the sealing plate and the upright plate of the present invention; In the diagram: 1-Upright plate one, 2-Upright plate two, 3-Upright plate three, 4-Upright plate four, 5-Upright plate five, 6-Triangular rib plate, 7-Square rib plate, 8-Bottom plate, 9-Cover plate, 10-Sealing plate, 11-Blocking plate, 12-Weight reduction hole, 13-Mounting hole. Detailed Implementation
[0025] The present invention will be further described below with reference to some specific embodiments. Example 1
[0026] See Figure 3-7 A large rolling mill upper crossbeam includes a bottom plate 8 and a cover plate 9. Two parallel vertical plates 1 are welded between the bottom plate 8 and the cover plate 9. The two vertical plates 1 are the outer vertical plates. There is an installation space between the two vertical plates 1. Two parallel vertical plates 2 are arranged in the middle of the installation space. The vertical plates 2 are welded perpendicularly to the vertical plates 1, the bottom plate 8, and the cover plate 9. The two vertical plates 2 divide the installation space into a middle space and side spaces located on both sides of the middle space. A vertical plate 3 is set in the central space. The vertical plate 3 is vertically welded to the vertical plate 1, the bottom plate 8, and the cover plate 9. Several triangular ribs 6 are also welded to the vertical plate 3. The triangular ribs 6 are parallel to each other and are also vertically welded to the vertical plate 2 and the vertical plate 1. Reinforcing components are installed in both side spaces. These components include a fourth vertical plate (4), one end of which is vertically welded to a second vertical plate (2). The fourth vertical plate (4) is parallel to a first vertical plate (1) and vertically welded to a base plate (8) and a cover plate (9). A fifth vertical plate (5) is installed between the fourth vertical plate (4) and the two first vertical plates (1). The fifth vertical plate (5) is vertically welded to a first vertical plate (1), a fourth vertical plate (4), a base plate (8), and a cover plate (9). The fifth vertical plate (5) is parallel to a second vertical plate (2). The second vertical plate (2), the third vertical plate (3), the fourth vertical plate (4), and the fifth vertical plate (5) form intermediate vertical plates. The fourth vertical plate (4) and the fifth vertical plate (5) divide the side spaces into four parts. Each part has a square stiffening plate 7 welded to its center, which is parallel to the bottom plate 8. Two sets of sealing plates are provided in each of the two side spaces. Each set includes two sealing plates 10 symmetrically arranged on both sides of the vertical plate 4. Each side space has four sealing plates. The sealing plates 10 are welded perpendicularly to the vertical plate 1, the square stiffening plate 7, the bottom plate 8 / cover plate 9, and the middle vertical plate 4. The ends of the square stiffening plates 7 are also welded with blocking plates 11, which are also welded to the vertical plate 1, the bottom plate 8, and the cover plate 9. The two side spaces and the reinforcing components in the side spaces are symmetrically arranged. Weight reduction holes 12 are provided on vertical plate 1, vertical plate 4, triangular stiffener 6, and square stiffener 7. The weight reduction holes on vertical plate 1, vertical plate 4, and square stiffener 7 also facilitate the entry and exit of operators for welding. Weight reduction holes 12 are provided on bottom plate 8. Mounting holes 13 are provided on bottom plate 8 and cover plate 9. The mounting holes are used to install hydraulic cylinders during the use of the crossbeam.
[0027] The welding process for the upper crossbeam of the aforementioned large rolling mill includes the following steps: S1. The base plate 8 is cut to allow for welding shrinkage at 1 / 1000 of its length. S2. Draw the position lines of the middle and outer vertical plates on the base plate 8, and assemble each vertical plate and each stiffening plate. S3. Weld all welds between the base plate 8, each vertical plate, and each stiffening plate, including: first welding the main long weld between the outer vertical plate 1 and the base plate 8, then welding the weld between the middle vertical plate 2, vertical plate 5 and vertical plate 4, as well as the weld between the middle vertical plate 2, vertical plate 3, vertical plate 5 and the two outer long vertical plates 1, and the weld between the middle vertical plate 2, vertical plate 3, vertical plate 4 and vertical plate 5 and the base plate 8, then welding the square stiffening plate 7 with the weld between vertical plate 1, vertical plate 2, vertical plate 4 and vertical plate 5, and finally welding the triangular stiffening plate 6 with the weld between vertical plate 1, vertical plate 2, vertical plate 3, and vertical plate 3. The welds are qualified by ultrasonic flaw detection. S4. Assemble the end caps 10 and cover plates 9, weld the cover plates 9 to the vertical plates 1, 2, 3, 4, and 5, and test the welds with ultrasonic flaw detection. S5. After annealing in the furnace to relieve stress, the straightening is qualified after annealing. The weld between the end sealing plate 10 and the outer vertical plate 1, square stiffening plate 7, cover plate 9 / bottom plate 8, and middle vertical plate 4 is qualified by ultrasonic flaw detection. S6. Assemble the end plates 11 and weld the end plates 11 to the bottom plate 8, cover plate 9, vertical plate 1, and square stiffener 7. After welding, correct the defects and anneal the whole in the furnace.
[0028] In this embodiment, the present invention adds a furnace annealing stress relief step after the cover plate is welded and before the end plates are welded, which promptly eliminates the welding stress of most of the welded seams in the welded parts, and corrects the product dimensions step by step to ensure product quality. Moreover, the present invention adopts a low-stress assembly and welding technology of "breaking down the whole into parts and integrating the parts into a whole", which ensures product quality by reserving welding shrinkage in the length direction of the base plate, reserving sufficient operating space for step-by-step assembly and welding, and correcting step by step.
[0029] Further, see Figure 8 and Figure 9 The weld between the end sealing plates 10 and the middle vertical plate 4 in step S5 includes: the two sealing plates of the middle vertical plate 4 are provided with inclined surfaces on the side that are close to each other, and the inclined surfaces on the two sealing plates 10 together form a V-shaped groove. The width of the V-shaped groove gradually increases in the direction away from the vertical plate 2. The side of the vertical plate 4 away from the vertical plate 2 enters the smaller end of the V-shaped groove and performs welding between the end sealing plates 10 and the vertical plate 4, and uses the weld to seal the thickness of the vertical plate.
[0030] Furthermore, the sealing plate 10 has a bisecting surface (middle surface) between the two sides of the sealing plate 10 that are close to the vertical plate 2 and away from the vertical plate 2. The vertical plate 4 is located on the side of the bisecting surface that is close to the vertical plate 2. The depth of the vertical plate 4 entering the V-shaped bevel is less than half the thickness of the sealing plate 10.
[0031] Furthermore, the two edges of the vertical plate 4 entering the V-shaped bevel are chamfered to reduce lamellar tearing in the thickness direction of the vertical plate 4.
[0032] Furthermore, the bevel angle is 30°.
[0033] In this embodiment, the present invention optimizes the existing technology so that the depth of the intermediate vertical plate entering the V-shaped groove is flush with the sealing plate, so that the depth of the intermediate vertical plate entering the V-shaped groove is less than half the thickness of the sealing plate, and optimizes the 45° V-shaped groove to a 30° groove. The weld is used to seal the thickness of the vertical plate, reduce the shrinkage stress in the thickness direction of the vertical plate, and avoid the layered tearing of the intermediate vertical plate.
[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.
Claims
1. A welding process for an upper crossbeam of a large rolling mill, wherein the upper crossbeam comprises a symmetrical structure welded together from a bottom plate, vertical plates, stiffening plates, a cover plate, a sealing plate, and a blocking plate, and the vertical plates comprise two outer vertical plates and several middle vertical plates, characterized in that, Includes the following steps: S1. Allow for welding shrinkage when cutting the base plate; S2. Draw the position lines of the middle and outer vertical plates on the base plate, and assemble each vertical plate and each stiffening plate; S3. All welds between the base plate, each vertical plate, and each stiffening plate have passed ultrasonic testing. S4. Assemble the end caps and cover plates, weld the cover plates to each vertical plate, and pass ultrasonic testing. S5. Stress relief by furnace annealing, correction after annealing, sealing plates at both ends by welding, and ultrasonic testing to pass. S6. Assemble the end plates and weld them. After welding, correct the welds to ensure they are qualified, and then anneal the entire product in the furnace.
2. The welding process for the upper crossbeam of a large rolling mill according to claim 1, characterized in that, In step S1, the base plate is cut to allow for welding shrinkage by reserving a length of 1 / 1000-2 / 1000mm.
3. The welding process for the upper crossbeam of a large rolling mill according to claim 1, characterized in that, Step S3 involves welding all the welds between the base plate, each vertical plate, and each stiffening plate, including: first welding the main long weld between the outer vertical plate and the base plate, then welding the welds between the middle vertical plates and between the middle vertical plates and the outer vertical plates and the base plate, and finally welding the welds between the stiffening plates and each vertical plate.
4. The welding process for the upper crossbeam of a large rolling mill according to claim 1, characterized in that, Step S5 involves welding the end caps, including welding the welds between the end caps and the outer vertical plate, stiffening plate, cover plate / bottom plate, and middle vertical plate.
5. The welding process for the upper crossbeam of a large rolling mill according to claim 4, characterized in that, The weld between the end sealing plates and the middle upright plate in step S5 includes: the two end sealing plates of the middle upright plate are provided with inclined surfaces on the side that are close to each other, and the inclined surfaces on the two end sealing plates together form a V-shaped bevel. The middle upright plate enters the smaller end of the V-shaped bevel and welds the end sealing plates to the upright plate, and uses the weld to seal the thickness of the upright plate.
6. The welding process for the upper crossbeam of a large rolling mill according to claim 5, characterized in that, The depth to which the intermediate vertical plate enters the V-shaped bevel is less than half the thickness of the end caps.
7. The welding process for the upper crossbeam of a large rolling mill according to claim 5, characterized in that, The two edges of the middle vertical plate entering the V-shaped bevel are chamfered.
8. The welding process for the upper crossbeam of a large rolling mill according to claim 5, characterized in that, The bevel angle is 30°.