High-strength thick plate large-section "eye" type beam welding method

Abstract

The application discloses a high-strength thick-plate large-section ''goal''-shaped beam welding method, which comprises the following steps: S1, node optimization: the flange plate of the bracket is designed as a stepped shape which is inwardly tapered from bottom to top; S2, welding seam design: the web of the steel beam adopts a ''K''-shaped groove, the lower flange of the steel beam adopts an ''X''-shaped groove, and the upper flange and the middle flange of the steel beam adopt single-side grooves; S3, steel beam installation: the steel beam is installed and corrected, and the web of the steel beam is connected with the web of the bracket by using a clamping code; S4, welding: the webs are symmetrically welded first, and then the lower flange plate, the internal partition plate and the upper cover plate are sequentially welded from bottom to top; and S5, post-welding treatment and detection. The application controls the stepped design of the bracket, the groove form of the web and the flange of the steel beam, the position of the code plate, the welding partition and the welding sequence and the like, guarantees the welding quality of the steel beam, solves the welding problem of complex structure, and realizes the purposes of zero rework, high efficiency and low cost of high-strength thick-plate steel structure construction site.

Description

Technical Field

[0001] The present invention relates to the technical field of steel structure construction, and particularly to a welding method for a high-strength thick-plate large-section "eye-shaped" beam. Background Art

[0002] As a relatively common component in modern architecture, steel structures have received extensive attention. The eye-shaped steel beam is one of the common components in steel structures, with the advantages of stable structure and strong load-bearing capacity, and is widely used in buildings. The cross-sectional dimensions of traditional steel structure steel beams are mainly within 600*800mm, and the plate thickness is mostly below 60mm. With the increasing development trend of steel structures as the main structure, the design application of high-strength thick-plate large-section "eye-shaped" steel beams in construction has gradually been recognized. The welding of eye-shaped steel beams has the characteristics of high strength, high restraint, and thick plates, and the welding operation space for internal diaphragms is narrow. On the premise of ensuring the safe operation of workers, preventing welding deformation, reducing welding stress, and ensuring structural safety are particularly important.

[0003] Currently, the joints of eye-shaped beams with ultra-large cross-sectional dimensions are all thick-plate welded joints, which have a high restraint degree and large rigidity. When welding under the conditions of large rigidity and high restraint degree, if the measures are improper, it is very easy to generate welding cracks. Especially when using Q390C high-strength steel, there is no possibility of rework; moreover, the special large-scale eye-shaped steel structure joints of high-strength thick plates are closed joints in a limited space, with narrow sites and extremely poor welding accessibility, and the welding quality cannot be guaranteed.

[0004] In addition, during the welding process of thick-plate components, generally, the internal diaphragms are welded first, and then the external webs are welded, which makes the webs form the restraint of circumferential welds, forming a strong tensile stress field of weld metal. Just like the "inclined Y test", the weld is very likely to crack during the welding process, affecting the welding quality. Summary of the Invention

[0005] The present invention provides a welding method for a high-strength thick-plate large-section "eye-shaped" beam, which can ensure welding quality, construction safety, and construction efficiency.

[0006] The technical problems to be solved are: welding cracks are likely to occur in the thick-plate welding of eye-shaped steel beams, the construction space is narrow, the welding accessibility is extremely poor, the welding quality cannot be guaranteed, and the existing thick-plate welding method is very likely to crack during the welding process, affecting the welding quality.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A welding method for a high-strength thick-plate large-section "eye-shaped" beam of the present invention includes the following steps:

[0009] S1: Node Optimization: Optimize the bracket structure connected to the steel beam. Design the flange plate of the bracket in a stepped shape that converges inward from bottom to top, and stagger the position of the weld between the steel beam and the steel column. Design a top cover plate connecting the steel beam and the bracket at the upper flange of the steel beam, and design an internal partition connecting the steel beam and the bracket at the middle flange of the steel beam.

[0010] S2: Weld Design: Connect the steel beam and the steel column by groove welding. Use "K" - shaped groove welding for the web of the steel beam, "X" - shaped groove welding for the lower flange of the steel beam, and single - bevel groove welding for the upper flange and middle flange of the steel beam.

[0011] S3: Steel Beam Installation: Install and align the steel beam. Connect the web of the steel beam and the web of the bracket using clamping codes to restrain the entire steel beam.

[0012] S4: Welding: First, symmetrically weld the web. After the web welding is completed, weld the lower flange plate, internal partition, and upper cover plate in sequence from bottom to top.

[0013] S5: Post - welding Treatment and Inspection: Adopt post - heating, heat preservation, and slow cooling, clean the weld, and use VT and UT technologies for weld inspection.

[0014] For a welding method of a high - strength thick - plate large - section "eye" - shaped beam in the present invention, further, in step S3 specifically, clamping codes are symmetrically arranged on both sides of the steel beam. Set one end of the steel beam as area A and the other end as area B. Adopt a symmetric welding method to weld the clamping codes in area A and area B simultaneously. After the clamping code welding is completed, start welding from the single - side joint of the steel beam.

[0015] For a welding method of a high - strength thick - plate large - section "eye" - shaped beam in the present invention, further, in step S4, before welding, grind and preheat the welding area.

[0016] For a welding method of a high - strength thick - plate large - section "eye" - shaped beam in the present invention, further, in step S4, monitor the following during the welding process: inter - layer temperature, welding technique, welding specification, and air quality monitoring.

[0017] For a welding method of a high - strength thick - plate large - section "eye" - shaped beam in the present invention, further, in step S4, adopt a multi - pass and multi - layer staggered welding technique for welding.

[0018] For a welding method of a high - strength thick - plate large - section "eye" - shaped beam in the present invention, further, the weld staggering length is more than 50 mm.

[0019] For a welding method of a high - strength thick - plate large - section "eye" - shaped beam in the present invention, further, in step S5, for post - heating, heat preservation, and slow cooling specifically, re - heat the welding area to 200 - 250 °C after welding, keep warm, and slow - cool to make the weld slowly cool to room temperature.

[0020] A welding method for a high-strength thick plate large-section "eye" - shaped beam of the present invention. Further, the heat preservation time depends on the thickness of the component plate, increasing by 0.5 h for every 25 mm of plate thickness, and the heat preservation time is not less than 1 h.

[0021] A welding method for a high-strength thick plate large-section "eye" - shaped beam of the present invention. Further, in step S2, a small groove welding technique is adopted, and the welding groove angle is 30°.

[0022] A welding method for a high-strength thick plate large-section "eye" - shaped beam of the present invention. Further, the lower flange of the steel beam adopts an "X" - shaped groove, the backhand welding is t / 3, and the flat welding is 2t / 3, where t is the thickness of the lower flange of the steel beam.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Based on two - dimensional drawings and three - dimensional models, this application controls various aspects such as the stepped design of the steel column bracket, the groove form of the steel beam web and flange, the position of the steel beam detail part code plate, the welding zone and the welding sequence, etc., to ensure the welding quality of the steel beam, solve the complex welding problem of the joint structure, and achieve the purpose of zero rework, high efficiency and low cost in the construction site of high - strength thick - plate steel structures, which has great guiding significance for the construction of similar steel structure joints; especially applicable to the butt welding of "eye" - shaped beams and box - shaped beams with Q355, Q390, Q420, Q460 high - strength steel, plate thickness above 40 mm, face width greater than 400 mm, and height greater than 500 mm with steel columns;

[0025] 2. Through the stepped design of the bracket, the weld positions are staggered, so that the HAZ (heat - affected zone) is not in the same stress plane, minimizing the harm of welding to the structure; and the stepped design of the bracket is also more conducive to the implementation of the welding work at the structure connection.

[0026] 3. Through the design of the groove form of the steel beam web and flange, the welding residual stress and deformation at the welding joint can be made uniform, improving the reliability of the connection node, which is particularly important for thick - wall nodes with very high stiffness and high restraint.

[0027] 4. By adopting the method of symmetric welding code plates, the welding deformation is effectively controlled.

[0028] 5. Adopting the multi - layer and multi - pass staggered welding technology reduces the influence of the welding HAZ on the base metal and ensures the welding quality of the welding joint.

[0029] 6. After welding, reheating to 250 °C and then heat - preserving and slow - cooling can not only extend t100, but also does not affect t8 / 5 and t8 / 3, and can also make the diffusible hydrogen escape fully, thus eliminating the generation of hydrogen - induced cracks.

[0030] The present invention will be further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the process flow chart of the present invention;

[0032] Figure 2 is the schematic diagram of the installation structure of the present invention;

[0033] Figure 3 is the schematic diagram of the connection between the steel beam and the bracket of the present invention;

[0034] Figure 4 is the schematic diagram of the connection between the web and the bracket of the present invention;

[0035] Figure 5 is the schematic diagram of the "K" - shaped groove structure of the present invention;

[0036] Figure 6 is the schematic diagram of the "X" - shaped groove structure of the present invention;

[0037] Figure 7 is the schematic diagram of the single - bevel groove structure of the present invention.

[0038] Reference numerals:

[0039] The steel beam; 1.1 The upper flange; 1.2 The middle flange; 1.3 The lower flange; 1.4 The web; 2 The bracket; 3 The steel column; 4 The top cover plate; 5 The internal partition; 6 The "K" - shaped groove; 7 The "X" - shaped groove; 8 The single - bevel groove; 9 The clamp. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] As Figures 1-7 shown, the present invention discloses a welding method for a high - strength thick - plate large - cross - section "eye" - shaped beam, including the following steps:

[0041] S1: Node optimization: Optimize the bracket structure connected to the steel beam. Design the flange plate of the bracket as a stepped shape that converges inward from bottom to top, and stagger the position of the weld between the steel beam and the steel column; Design a top cover plate for connecting the steel beam and the bracket at the upper flange of the steel beam, and design an internal partition for connecting the steel beam and the bracket at the middle flange of the steel beam; By designing the bracket in a stepped shape and staggering the weld positions, the HAZ (heat - affected zone) is not in the same stress - bearing plane, minimizing the harm of welding to the structure; Moreover, the stepped design of the bracket is also more conducive to the implementation of the welding work at the structure connection.

[0042] S2: Weld design: In order to reduce welding stress and strain, design a groove form that is conducive to controlling welding quality, and adopt a small - groove welding technique to reduce the cross - sectional area of the weld.

[0043] Specifically, the steel beams and steel columns are connected by bevel welding. The web of the steel beam uses a "K" shaped bevel; the lower flange of the steel beam uses an "X" shaped bevel; and the upper and middle flanges of the steel beam use single-sided bevels. The bevel angles of the "K" shaped bevel, "X" shaped bevel, and single-sided bevel are 30°, with a gap of 8mm. The "X" shaped bevel is used for overhead welding at t / 3 and for flat welding at 2t / 3, where t is the thickness of the lower flange of the steel beam. Through the above bevel design, the residual welding stress and deformation at the weld joint can be made uniform, improving the reliability of the connection node, which is especially important for thick joints with high stiffness and high restraint.

[0044] The above-mentioned bevel design adopts full penetration (CJP) bevel weld forming coefficient control. The bevel design breaks through the original standard drawing set's erroneous design of unequal width on both sides, that is, regardless of the plate thickness, the bevel design with 45° on the large side and 64° on the small side with different widths on both sides is adopted. Instead, the projection and ruler measurement method is used to ensure that the bevel width on both sides of the plate is consistent.

[0045] S3: Steel Beam Installation: Install and align the steel beams. Symmetrically install clamps on both sides of the beam to connect the web of the beam and the corbel, thus constraining the entire beam while keeping the weld tensile strength relatively free. This prevents cracks caused by tensile stress from simultaneous welding on both sides. Specifically, designate one end of the beam as welding zone A and the other as welding zone B. Assign one welding team to each zone, ensuring that the number of welding machines and welders, current, voltage, and welding speed are consistent across all teams. Use symmetrical welding, simultaneously welding zones A and B. After clamp welding is completed, begin welding from one side of the beam joint. Symmetrical welding means, for example, welding the upper edge of zone A while welding the lower edge of zone B, ensuring symmetrical welding of zones A and B both vertically and horizontally. To effectively control welding deformation, ten clamping plates can be installed at each end of the beam: two at the lower flange and four on each side of the web. These clamps increase the constraint of the weld area and prevent welding deformation.

[0046] S4: Welding: Before welding, the welding area is ground, preheated, a windproof protective shed is erected, and ventilation equipment is installed. The web plates are welded symmetrically first. After the web plates are welded, the lower flange plates, internal partitions, and upper cover plates are welded sequentially from bottom to top. During welding, the following should be monitored: interpass temperature, welding technique, welding specifications, and air quality. Interpass temperature monitoring refers to detecting the temperature between each layer of weld, which is used to prevent cold cracking caused by temperature differences in the weld.

[0047] In this application, carbon equivalent is used to estimate the welding preheating temperature. We recommend using the technique proposed by welding expert Mr. Zeng Le, which uses carbon equivalent to calculate the preheating temperature. In addition to the chemical composition of the steel, the influence of the steel thickness on weldability is also considered.

[0048] Due to the confined space, the flat welding of the lower flange plates of the steel beams and the welding of the internal partitions were all carried out inside the box, which was very difficult. CO2 shielded welding was used, but during the welding process, insufficient oxygen and excessive CO levels occurred inside the box. Therefore, to ensure the safety of the workers, an exhaust fan was used at the end of each steel beam in the confined space, and a fixed person was assigned to each node to monitor the work. The air inside the box was tested every half hour to ensure that the oxygen content and carbon monoxide levels were within acceptable limits.

[0049] To ensure welding quality while reducing the HAZ dwell time in high-strength steel welding, the operation method is to adopt "multi-layer multi-pass staggered welding technology". Multi-layer multi-pass staggered welding technology is developed from multi-layer welding technology. Multi-layer welding technology does not form in one step, but in multiple layers. The welding rod movement is allowed to swing, and the welding thickness is generally not controlled. It is suitable for welding thick plates of low carbon steel.

[0050] Multi-layer, multi-pass staggered welding is based on multi-layer welding, but the welding thickness must be clearly specified to limit the heat input of the weld. Generally, GMAW is semi-automatic solid wire gas shielded welding, FCAW-G is semi-automatic flux-cored wire gas shielded welding, and SMAW is shielded metal arc welding.

[0051] For GMAW and FCAW-G, each pass should not exceed 5mm, typically between 3 and 5mm. SMAW uses the AV value to determine the thickness of each pass: AV = length of weld seam welded by one electrode / length of one electrode excluding the electrode tip, usually AV ≥ 0.6mm. Oscillation is allowed in vertical welding positions, but the amplitude is limited. SMAW allows a width of three times the electrode diameter; GMAW and FCAW-G allow oscillation of 15-20mm. Multi-layer, multi-pass staggered welding technology adds staggered connections between each pass of the weld joint, meaning the joint is not in the same plane, typically staggered by more than 50mm. This technology is particularly suitable for welding thick high-strength steel plates.

[0052] S5: Post-weld treatment and inspection: After each weld is completed, post-heat insulation and slow cooling are performed, followed by weld cleaning and weld inspection using VT and UT techniques. Post-heat insulation and slow cooling refers to heating and insulating the weldment as a whole or in parts after welding to reduce residual welding stress and improve the microstructure and properties of the weld and heat-affected zone.

[0053] VT—Visual Inspection of Welds

[0054] UT—Ultrasonic non-destructive testing of welds.

[0055] Specifically, post-heat insulation and slow cooling are crucial for Q390C steel, which has a hardening tendency and is one of the risk factors for cold cracking. Cold cracking has three main characteristics: 1. Highly concealed and delayed development, easily leading to large-scale outbreaks; 2. Lowering the brittle transition temperature of welded joints, making them prone to brittle fracture at low temperatures; 3. Reducing the cross-sectional dimensions of components and decreasing load-bearing capacity after crack propagation. For Q390C steel with a high hardening tendency, due to its low plastic deformation capacity and the tendency for stress concentration at defects, the critical stress required to induce delayed cracking is low, and the critical hydrogen content is also low, resulting in a high tendency for cracking. Therefore, heat insulation and hydrogen removal treatment should be performed after welding.

[0056] t100 is the time for diffusing hydrogen to escape from the weld. Theoretically, the longer the better. If the welding heat input (line energy) is increased to extend t100, then t8 / 5 and t8 / 3 will also be extended simultaneously, resulting in coarser weld and HAZ grains, worsening the overall performance of the welded joint, reducing quality indicators, and ultimately harming the fundamental structure, which is counterproductive. However, after welding, reheating to 250℃ and then holding at that temperature for slow cooling can extend t100 without affecting t8 / 5 and t8 / 3, and also allow diffusing hydrogen to escape sufficiently, thereby eliminating the formation of hydrogen-induced cracks.

[0057] The heating temperature for hydrogen removal heat treatment should reach 200-250℃. The holding time at this temperature depends on the thickness of the component plate, and should be 0.5h for every 25mm plate thickness, but not less than 1h. Then, allow it to cool slowly to room temperature.

[0058] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A welding method for a large-section "eye" - shaped beam made of high-strength thick plate, characterized in that, Includes the following steps: S1: Node optimization: Optimize the corbel structure connected to the steel beam by designing the flange plate of the corbel to be a stepped shape that tapers inward from bottom to top, and stagger the position of the weld connecting the steel beam and the steel column. A top cover plate is designed at the upper flange of the steel beam to connect the steel beam and the corbel, and an internal partition plate is designed at the middle flange of the steel beam to connect the steel beam and the corbel. S2: Weld Design: The steel beams and columns are connected by bevel welding, specifically using small bevel welding technology with a bevel angle of 30°; the web of the steel beam is welded with a "K" shaped bevel, and the lower flange of the steel beam is welded with an "X" shaped bevel. The thickness of the weld is t / 3 for overhead welding and 2t / 3 for flat welding, where t is the thickness of the lower flange of the steel beam; the upper and middle flanges of the steel beam are welded with a single-sided bevel. S3: Steel beam installation: Install and align the steel beams, and use clamps to connect the web of the steel beams to the web of the corbels to constrain the entire steel beam; S4: Welding: First, weld the web plate symmetrically. After the web plate welding is completed, weld the lower flange plate, internal partition plate, and upper cover plate from bottom to top in sequence. S5: Post-weld treatment and inspection: Post-heat insulation and slow cooling are adopted for weld cleaning, and VT and UT technologies are used for weld inspection.

2. A welding method for a high-strength thick plate large-section "eye" - shaped beam according to claim 1, characterized in that: Specifically, in step S3, symmetrical clamps are set on both sides of the steel beam, one end of the steel beam is designated as area A and the other end as area B. The clamps in areas A and B are welded simultaneously using a symmetrical welding method. After the clamp welding is completed, welding begins from the joint on one side of the steel beam.

3. A welding method for a high-strength thick plate large-section "eye" - shaped beam according to claim 1, characterized in that: In step S4, before welding, the welding area is ground and preheated.

4. A welding method for a high-strength thick plate large-section "eye" - shaped beam according to claim 1, characterized in that: In step S4, the following are monitored during the welding process: interpass temperature, welding technique, welding specifications, and air quality.

5. A welding method for a high-strength thick plate large-section "eye" - shaped beam according to claim 1, characterized in that: In step S4, multi-pass, multi-layer staggered welding technology is used for welding.

6. A welding method for a high-strength thick plate large-section "eye" shaped beam according to claim 5, characterized in that: The weld misalignment length is more than 50mm.

7. A welding method for a high-strength thick plate large-section "eye" shaped beam according to claim 1, characterized in that: In step S5, the post-heating and slow cooling process involves reheating the weld to 200-250℃ after welding, maintaining the temperature, and then slowly cooling the weld to room temperature.

8. A welding method for a high-strength thick plate large-section "eye" - shaped beam according to claim 7, characterized in that: The insulation time depends on the thickness of the component plate, with an additional 0.5 hours for every 25mm of plate thickness, and the insulation time shall not be less than 1 hour.

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