A nuclear power high-carbon manganese steel rail welding anti-deformation tool and welding method

Abstract

The application discloses a kind of nuclear power high-carbon manganese steel track welding anti-deformation tool and welding method, tool includes base, several groups of support and portal, inclined shim and adjustable shim plate group with copper liner and steel liner, by adjusting shim plate group makes track joint arches up preset reverse deformation angle.Method includes: group preset arching angle and upper wide lower narrow gap when pairing, preheating to 300-400 DEG C and constant temperature, according to sequence multilayer multi-pass welding and according to shrinkage, shim plate and inclined shim are adjusted gradually, immediately after welding with preheating tool post-heat and use heat-insulating cotton cover, finally execute with not more than 73 DEG C / h to 600-650 DEG C, constant temperature 2h, not more than 83 DEG C / h cooling precise temperature control thermal cycle, thermocouple is distributed at the center of weld and at specified distance from weld edge.The application combines rigid portal, adjustable shim tool and whole-process temperature control process organically, effectively controls high-carbon manganese steel track welding deformation and crack, especially suitable for nuclear power plant bridge crane and ring crane and other high safety requirement occasions.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a welding fixture and welding method for preventing deformation during the installation and welding of high carbon manganese steel rails (especially QU120 section steel rails made of U71Mn material) for bridge cranes in nuclear power plants. Background Technology

[0002] Bridge cranes are widely used in the construction and maintenance of nuclear power plants, and their overhead rails must withstand heavy loads and operate frequently. Commonly used QU120 rails are made of U71Mn high-carbon manganese steel, which is hard and brittle with a large cross-section, making it highly susceptible to deformation and cold cracking during welding. Traditional processes using simple rigid fixing or simple reverse deformation methods are difficult to control deformation and cracking, and the welding quality often fails to meet the stringent requirements for safe operation of nuclear power plants. Summary of the Invention

[0003] The purpose of this invention is to solve the problems in the prior art by proposing a welding fixture and welding method for preventing deformation of high carbon manganese steel rails used in nuclear power plants. This invention can solve the problems of deformation and cracking in the welding of large-section high carbon manganese steel rails through the synergy of rigid adjustable fixtures and refined welding heat treatment processes.

[0004] To achieve the above objectives, the present invention proposes a welding anti-deformation fixture for high-carbon manganese steel rails used in nuclear power plants, comprising: a base; several sets of supports fixed to the base and spaced apart along the rail axis; a gantry mounted on the base, wherein the gantry and the supports form a space for accommodating the rail in a side view; inclined shims correspondingly disposed within each of the gantry for securing the rail within the gantry; and further comprising: an adjustable shim set located below the rail joint and below the rail outside the joint and supported on the supports, wherein the adjustable shim set below the rail joint includes at least one copper shim and multiple steel shims, and the adjustable shim set below the rail outside the joint includes multiple steel shims, wherein by adjusting the number and / or thickness of the steel shims, the rail axis is arched upward at a predetermined angle.

[0005] Preferably, the copper gasket is positioned directly below the weld seam of the track joint and is used as a backing for forming the back of the weld seam during welding.

[0006] Preferably, the base is made of a steel plate with a thickness of 20mm and a width of 400mm, the support is a No. 10 I-beam and welded to the base, and the gantry is a No. 10 channel steel with an inner net height of 330mm.

[0007] Preferably, the preset angle is an upward arch of 5 to 6 degrees in the direction of the track axis.

[0008] This invention also proposes a method for welding high-carbon manganese steel rails for nuclear power plants, using the tooling described in any of the above-mentioned claims, and comprising the following steps: Assembly steps: Hoist the rail onto the support of the tooling, support the adjustable pad assembly on the support and place it below the rail joint and below the rail, adjust the adjustable pad assembly to arch the rail axis upward by 5 to 6 degrees, and adjust the gap between the two rail joints to be wider at the top and narrower at the bottom, and control the rail bottom gap to 12mm to 14mm. Then use the inclined shims to tighten the rail into each gantry. Preheating steps: Use a flexible ceramic resistance heater to heat the track to 300℃-400℃, maintain the temperature for more than 0.5 hours, and ensure that the temperature difference between any two temperature measuring points does not exceed 30℃; Welding steps: Perform multi-layer, multi-pass welding in the order of rail base, rail web, and rail top. During the welding process, check the deformation and shrinkage of the rail at any time, and adjust the shims in the adjustable shim group one by one according to the shrinkage to adjust the rail level. After welding, immediately use the preheating heating device for post-heating and cover the rail with insulation cotton. Post-weld heat treatment steps: Use a track-type flexible ceramic resistance heater to fit around the track, heat up to 600℃-650℃ at a rate not exceeding 73℃ / hour, hold at the temperature for 2 hours, then cool down to 300℃ at a rate not exceeding 83℃ / hour, and then allow to cool naturally to room temperature within the insulation layer.

[0009] Preferably, in the welding step, shielded metal arc welding is used, the welding material is E5015 with a diameter of Φ3.2mm, and DC reverse polarity is used; the welding current for the root pass is 104A-150A, and the welding current for the remaining passes is 133A-177A; the weld width is not greater than 4 times the diameter of the welding rod, and the weld thickness is not greater than the diameter of the welding rod plus 2mm.

[0010] Preferably, in the welding step, after the rail bottom welding is completed, the arc-starting plate and the arc-extinguishing plate are removed by mechanical cutting, and the copper pad is removed.

[0011] Preferably, in the welding step, the welding directions of the front and rear layers are opposite, and the weld joints are staggered.

[0012] Preferably, in the post-weld heat treatment step, a thermocouple is arranged at the center of the weld at the bottom of the rail, the web of the rail, and the top of the rail, as well as at 50mm from the edge of the weld. The thermocouple located at the center of the weld is used to control the heating, while the thermocouple at 50mm from the edge of the weld is used for monitoring. Each control thermocouple controls a heater separately.

[0013] Preferably, in the post-weld heat treatment step, the heating width is not less than 600 mm, and the insulation layer wrapping width is not less than 450 mm on each side from the center of the weld.

[0014] The beneficial effects of this invention are: 1. The adjustable pad assembly provides precise preset anti-deformation, which, together with the successive adjustment operations during the welding process, enables dynamic release of shrinkage stress, significantly reducing deformation and cracks.

[0015] 2. The copper backing serves as both a backing plate and a weld backing, simplifying the tooling and ensuring thorough fusion and forming of the rail bottom.

[0016] 3. Strict temperature control throughout the entire process (preheating, interpass heating, postheating, and heat treatment heating and cooling rates) effectively avoids the hardening and cold cracking problems of high carbon manganese steel.

[0017] 4. The tooling structure is simple, the operation method is clear, the position of the gantry can be flexibly adjusted according to the site conditions, it is highly adaptable and suitable for the on-site installation environment, especially suitable for nuclear power lifting equipment with extremely high safety and reliability requirements.

[0018] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the rail welding joint assembly of the tooling of the present invention; Figure 2 This is a schematic diagram of the heat treatment of the track welding joint of the present invention; Figure 3 yes Figure 2 A schematic diagram of the cross-section where the thermal insulation cotton meets the track.

[0020] In the diagram: 1-base, 2-support, 3-gantry, 4-sloping shim, 5-adjustable shim assembly with copper pad, 6-adjustable shim assembly, 7-track, 8-thermocouple, 9-heater, 10-insulation cotton. Detailed Implementation

[0021] See Figure 1 , Figure 2 and Figure 3 This invention proposes a rail welding anti-deformation tooling, including a base, a support, a gantry, inclined shims, and an adjustable shim assembly. The base consists of a base plate and a support. The base plate is made of a 20mm thick and 400mm wide steel plate. The support is made of No. 10 I-beams welded and fixed to the base plate. The gantry is made of No. 10 channel steel, and the net height of the gantry is 330mm.

[0022] The specific process steps are as follows: 1. Pre-welding inspection 1) The bevel of the rail weld is "I" type. Before welding, the rail welding surface and the surrounding 30mm surface area are ground clean until the metal luster is exposed.

[0023] 2) Perform PT testing on the surface to be welded and the surrounding 30mm surface area to ensure that the base material is free of inclusions, cracks and other defects.

[0024] 3) Hoist the rail onto the fixture base, and elevate the rail joint using copper shims (180-190mm long, 60-80mm wide, 10mm thick) and steel shims (5-15mm thick). Figure 1 The number of shims should be adjusted according to the actual site conditions, with the track axis angle arched upwards by 5-6 degrees as a counter-deformation angle. Steel pads should be used for support under the track outside the joint. Simultaneously adjust the gap at the joint of the two tracks, ensuring the gap is wider at the top and narrower at the bottom. The rail bottom gap is generally controlled between 12mm and 14mm, and should not be less than 12mm. Align the ends of the two rails, ensuring their center lines are in a straight line without any twisting or misalignment. After adjustment, use wedge shims to tightly secure the track within the gantry. The installation position of the gantry fixture can be adjusted along the track axis direction according to the track length and joint location.

[0025] 4) Place the arc-starting and arc-extinguishing plates on both sides of the copper backing plate to ensure the welding quality of the joint. Remove the arc-starting and arc-extinguishing plates after welding is completed.

[0026] 2. Preheating Before welding, the track is preheated with a flexible ceramic resistance heater to 300℃-400℃ and kept at that temperature for more than 0.5 hours to ensure that the track temperature is uniform before welding. The temperature difference between any two temperature measuring points is no more than 30℃. The interpass temperature is maintained at 300-400℃. During the welding process, the interpass temperature is not lower than the minimum preheating temperature.

[0027] 3. Welding 1) Rail welding can only be carried out after the specified preheating requirements are met. Weld the rail bottom first, then the rail web, then the rail top, and finally repair the surrounding area. Weld strictly according to the welding process requirements. The weld width should not be greater than 4 times the diameter of the welding rod, and the weld thickness should not be greater than the diameter of the welding rod plus 2mm. The welding process parameters are shown in the table below.

[0028]

[0029] 2) During welding, start welding from one end of the arc-starting plate and continue welding until the end. Then, fill the crater on the arc-extinguishing plate using spot welding. After the rail bottom welding is completed, remove the arc-starting plate and arc-extinguishing plate using mechanical cutting and remove the copper backing plate to avoid premature removal of the weld, which could cause cracks or other defects due to stress.

[0030] 3) Use multi-layer, multi-pass welding. For each layer, weld the two sides of the bevel first and then the middle. The two sides of the bevel should be left for a slightly longer time to ensure complete fusion of the weld.

[0031] 4) The weld beads extend more than 5mm beyond the outer surface of the track at both ends. After the heat treatment is completed, they should be removed by mechanical grinding. Apply appropriate grinding force to avoid excessive force and generating large cutting stress.

[0032] 5) Avoid ending the arc at the end during welding and minimize the number of weld joints. Stagger the arc ending and starting points of the two layers as much as possible to avoid arc crater cracks. Clean each layer with a saw blade and wire brush after welding. Minimize grinding while ensuring weld quality to avoid grinding stress and hardening of the weld due to air cooling. Proceed to the next layer after confirming there are no defects.

[0033] 6) Minimize the number of times the arc is extinguished. The welding directions for the front and rear layers should be opposite, and the joints should be staggered. The number of steel plates can be adjusted during welding to meet the heat treatment requirements.

[0034] 7) During the welding process, check the deformation and shrinkage of the rails at any time, and adjust the shims and wedges one by one according to the deformation and shrinkage, and adjust the level of the rails to ensure that the center lines of the two rails are on a straight line after welding.

[0035] 8) Weld continuously as much as possible. If welding is stopped for a long time, the preheating temperature should be maintained and the weld quality should be checked before welding is resumed. Welding can only be carried out according to the process after confirming that there are no quality defects.

[0036] 9) After welding, clean the surface with a saw blade and wire brush, and repair the surface by welding to avoid surface defects after grinding.

[0037] 10) After welding is completed, use the preheating fixture to immediately perform post-heating. After cooling, wrap and heat treat. During the post-heating process, cover the entire track with insulation cotton to avoid excessive temperature difference and thermal stress.

[0038] 4. Post-weld heat treatment 1) Use a tracked flexible ceramic resistance heater for local heating heat treatment. Heat the temperature to 600-650℃ at ≤73℃ / h, hold it at 2h, then cool it down to 300℃ at ≤83℃ / h, and then let it cool naturally to room temperature within the insulation layer. During the insulation process, the temperature difference between any two points within the heating range should not exceed 50℃.

[0039] 2) Three thermocouples are placed at the center of the weld seams at the rail bottom, rail web, and rail top for temperature control. Each thermocouple controls a separate heater to ensure uniform weld temperature. Three thermocouples are placed at the rail bottom, rail web, and rail top, 50mm from the weld edge, for monitoring. They are fixed using a capacitor discharge welding method.

[0040] 3) Three flexible ceramic resistance heaters for tracks are attached to the perimeter of the track to ensure close contact with the track surface, and to ensure that the heating center is in the center of the weld, with a heating width of not less than 600mm.

[0041] 4) Use dry aluminum silicate insulation cotton for wrapping, and the heating width should be no less than 450mm on each side from the center of the weld.

[0042] 5) The heat treatment area should be fenced off and marked with warning signs.

[0043] 5. Visual inspection After the heat treatment of the rail weld joint is completed and cooled to room temperature, the weld is ground to be flush with the top of the rail using an electric grinder. Finally, the surface is polished with a file or fine sandpaper, and a visual quality inspection is carried out to confirm that there are no surface defects such as undercut, cracks, slag inclusions, or porosity.

[0044] 6. Non-destructive testing Once the appearance quality inspection is passed, 100% MT or 100% PT inspection is required. Non-destructive testing shall be carried out in accordance with NB / T47013.4-2015 or NB / T 47013.5-2015 standards, and the evaluation standard shall be Level I qualified.

[0045] Application Examples Using the tooling and welding method of this invention, welding operations for a total of 40 weld joints on the rails of two bridge cranes have been completed in a nuclear power project. After welding, 100% visual inspection and 100% physical testing were conducted, and all welds passed the inspection on the first attempt, with no surface defects such as undercut, cracks, slag inclusions, or porosity found. In the rail length direction, the deviation of curvature in both the horizontal and vertical planes was no greater than 0.5 mm per 2m of tested length, and the deformation was far less than the limit specified in Article 3.0.5 of GB50278-2010 "Code for Construction and Acceptance of Lifting Equipment Installation Engineering".

[0046] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A welding fixture for preventing deformation of high-carbon manganese steel rails used in nuclear power plants, comprising: Base (1); Several sets of supports (2) are fixed on the base (1) and spaced apart along the track axis; The gantry (3) installed on the base (1) forms a space for accommodating the track in the side view between the gantry (3) and the support (2); The inclined shims (4) are correspondingly installed in each of the gantry (3) to secure the rails within the gantry (3); Its characteristic is that it further includes: An adjustable pad assembly located below the track joint and supported on the support (2), wherein the adjustable pad assembly located below the track joint includes at least one copper pad and multiple steel pads, and the adjustable pad assembly located below the track outside the joint includes multiple steel pads, and the track axis direction is arched upward at a preset angle by adjusting the number and / or thickness of the steel pads.

2. The tooling according to claim 1, characterized in that, The copper gasket is placed directly below the weld seam of the track joint and is used as a backing for forming the back of the weld seam during welding.

3. The tooling according to claim 1 or 2, characterized in that, The base (1) is made of a steel plate with a thickness of 20mm and a width of 400mm. The support (2) is a No. 10 I-beam and is welded and fixed on the base (1). The gantry (3) is a No. 10 channel steel and has an inner net height of 330mm.

4. The tooling according to claim 1, characterized in that, The preset angle is an upward arch of 5 to 6 degrees along the track axis.

5. A method for welding high-carbon manganese steel rails for nuclear power plants, using the tooling described in any one of claims 1 to 4, characterized in that, Includes the following steps: Assembly steps: Hoist the rail onto the support (2) of the tooling, support the adjustable pad group on the support (2) and place it below the rail joint and below the rail, adjust the adjustable pad group to make the rail axis arch upward by 5 to 6 degrees, and adjust the gap between the two rail joints to be wider at the top and narrower at the bottom, and control the gap between the rail bottoms to 12mm to 14mm. Then use the inclined shims (4) to tighten the rail into each gantry (3); Preheating steps: Use a flexible ceramic resistance heater to heat the track to 300℃-400℃, maintain the temperature for more than 0.5 hours, and ensure that the temperature difference between any two temperature measuring points does not exceed 30℃; Welding steps: Perform multi-layer and multi-pass welding in the order of rail bottom, rail web and rail top. During the welding process, check the deformation and shrinkage of the rail at any time. Adjust the pads in the adjustable pad group one by one according to the shrinkage to adjust the rail level. After welding, use the preheating heating device for post-heating and cover the rail with insulation cotton (10). Post-weld heat treatment steps: Use a track-type flexible ceramic resistance heater to fit around the track, heat up to 600℃-650℃ at a rate not exceeding 73℃ / hour, hold at the temperature for 2 hours, then cool down to 300℃ at a rate not exceeding 83℃ / hour, and then allow to cool naturally to room temperature within the insulation layer.

6. The method according to claim 5, characterized in that, In the welding process, shielded metal arc welding is used with E5015 welding material, diameter Φ3.2mm, and DC reverse polarity. The welding current for the root pass is 104A-150A, and the welding current for the remaining passes is 133A-177A. The weld width is no more than 4 times the diameter of the welding rod, and the weld thickness is no more than the diameter of the welding rod plus 2mm.

7. The method according to claim 5, characterized in that, In the welding process, after the rail bottom welding is completed, the arc-starting plate and arc-extinguishing plate are removed by mechanical cutting, and the copper pad is removed.

8. The method according to claim 5, characterized in that, In the welding process, the welding directions of the front and rear layers are opposite, and the weld joints are staggered.

9. The method according to claim 5, characterized in that, In the post-weld heat treatment step, a thermocouple (8) is arranged at the center of the weld at the bottom of the rail, the web of the rail, the top of the rail, and 50 mm from the edge of the weld. The thermocouple (8) located at the center of the weld is used to control the heating, and the thermocouple (8) located 50 mm from the edge of the weld is used for monitoring. Each control thermocouple (8) controls a heater (9) separately.

10. The method according to claim 5, characterized in that, In the post-weld heat treatment step, the heating width is not less than 600mm, and the insulation layer wrapping width is not less than 450mm on each side from the center of the weld.

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