Machining method for large-diameter first-and-second type flat welding flange with bushing ring

Abstract

The invention belongs to the technical field of pressure vessel manufacturing, and particularly relates to a machining method of a large-diameter first-and-second type flat welding flange with a bushing ring, which reduces the requirement on temperature control in the welding process through the adjustment of the steps of reserving the machining amount of the flange, not machining a bolt hole, applying an anti-deformation tool scheme, eliminating stress through local heat treatment, performing one-time machining and the like. The uncertainty caused by welding deformation is thoroughly shielded, and it is guaranteed that the deformation amount obtained after the flange and the cylinder are installed and welded reaches a perfect repairing result; meanwhile, the perpendicularity of flange bolt holes is guaranteed, smooth installation of bolt fasteners in the assembling process is guaranteed, and the problems that welding deformation cannot be thoroughly removed, and flange uncontrollable deformation is caused by the fact that flat welding flange welding is concentrated at the flange position (generally two positions) are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of pressure vessel manufacturing, in particular to a method for processing a large-diameter AB type flat welding flange with a liner ring. Background Art

[0002] Flat welding flange is a structure adopted by many pressure vessels (such as towers, storage tanks or heat exchangers), especially large diameter (generally 2800mm and above) flat welding flange, which can greatly reduce the purchase cost compared with butt welding flange. The diameter of forged flat welding flange is large. After being placed for a long time after processing, due to stress release, local dimensional deformation may also occur. This deformation is very small and has little effect on subsequent use. The manufacturing process of flat welding flange is easy to deform and the sealing difficulty is significantly increased compared to butt welding flange; especially for special material equipment, special material welding ring / lining ring will be installed on the basis of carbon steel or stainless steel flange to meet the corrosion resistance requirements of the equipment. After welding, the flange parts will be significantly deformed due to the large welding thermal stress and the internal stress, resulting in ripple-like fluctuations on the flange end face. This welding stress will continue to be released in subsequent use, and secondary deformation of the flange may occur.

[0003] For many years, for this type of large-diameter flat-weld flange structure, the manufacturing process has adopted the method of using finished flat-weld flanges, directly assembling welding rings and lining rings after welding with the cylinder, and then processing the sealing surface. This existing processing method causes serious deformation after welding, and cannot guarantee the flatness of the flat-weld flange after welding. Therefore, it is necessary to continuously increase the thickness of the lining ring / weld ring to meet the flatness of the sealing surface after processing, which requires the loss of a large amount of special metal. Not only is the cost high, but due to the release of welding stress during the welding process, secondary deformation after processing may occur, bolt hole deviation is prone to occur, and bolts cannot be inserted smoothly, the sealing surface flatness is poor, and the sealing cannot be performed, and the quality is very unstable. In addition, there may be a situation where the bolt hole is not parallel to the axis of the cylinder, and the subsequent assembly and installation of the bolts is difficult, and there is a possibility that it cannot be installed.

[0004] In short, this type of large-diameter Type AB flat-weld flange is the most difficult to manufacture. Since there is pressure inside the pressure vessel product when it is used, the deformation during welding and the subsequent deformation caused by stress release will cause the flange to fail to form a seal. If there are many special material products, on the basis of this large-diameter flange, it is necessary to weld welding rings of other precious materials or install non-weldable lining rings. Due to the unevenness of the flange after welding, the subsequent processing requirements for welding rings / lining rings are very large, which requires a lot of cost and has a high quality risk. Summary of the invention

[0005] In view of the above-mentioned problems existing in the processing of traditional flat welding flanges, the purpose of the present invention is to provide a processing method for large-diameter type AB flat welding flanges with lined rings. When the deformation caused by welding stress can only be reduced but not eliminated, by adjusting the manufacturing sequence and processing sequence and adding some process steps, the large-diameter flat welding flanges that need to form an effective seal can be manufactured stably with low cost and high quality.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The processing method of the present invention comprises the following steps:

[0008] Step A, purchasing a bare blank forging flange, which is a semi-finished flange with machining allowances in both the outer diameter and thickness directions and unmachined bolt holes;

[0009] Step B, welding a deformation-proof tooling reinforcement ring on the outer edge of the flange of the bare blank forging;

[0010] Step C, assembling and positioning the cylinder body and the flange of the bare blank forging, and then welding the two flanges of the bare blank forging together with a connecting rib plate to reduce deformation during the welding process;

[0011] Step D, welding the weld;

[0012] Step E, performing local heat treatment on the welded flange and weld by wrapping them with electric heating rope and insulation cotton to eliminate stress;

[0013] Step F, cutting and separating the two flange welds to prepare for processing;

[0014] Step G, cutting and removing the connecting ribs and tooling reinforcement ring outside the flange, processing the upper and lower end faces of the flange, measuring the thickness after flattening one side, ensuring that the thickness at the lowest point is not less than the set thickness, and then processing the other side; after the upper and lower end faces of the flange are processed, process the outer edge of the flange, and then process the bolt holes;

[0015] Step H, installing the liner ring on the flat end face of the flange that has been processed, and completing the weld between the liner ring and the connecting part as required;

[0016] Step I: secondary turning of the liner ring sealing surface.

[0017] Wherein: the diameter of the bare blank forging flange in step A is measured before use, and the maximum and minimum diameter deviations are one thousandth of the diameter.

[0018] In the step A, the weld seams of the flange of the bare blank forging are concentrated on the inner side surface close to the flange of the bare blank forging, so as to avoid weld seams on the upper surface of the flange of the bare blank forging.

[0019] In the step C, before the barrel and the flange of the bare blank forging are assembled and tack welded, the groove position required for assembling the flange of the bare blank forging and the barrel is first processed.

[0020] The temperature and time of the heat treatment in step E are 580° C. to 640° C. and the heat preservation time is 1 to 3 hours.

[0021] When the bushing ring installed in step H is a non-weldable bushing ring, in step G, while marking and drilling the corresponding bolt holes, it is necessary to drill the plug nail holes; when the bushing ring installed in step H is a weldable bushing ring, in step G, it is only necessary to mark and drill the corresponding bolt holes.

[0022] When the liner ring in step H is a non-weldable liner ring, the liner ring is tightened with a plug; when the liner ring in step H is a weldable liner ring, the liner ring is welded to the flat end face of the flange that has been processed.

[0023] When the liner ring in step H is a non-weldable liner ring, the connecting component is a liner sleeve, and the non-weldable liner ring is welded to the liner sleeve; when the liner ring in step H is a weldable liner ring, the connecting component is a flange, and the weldable liner ring is welded to the flange.

[0024] The advantages and positive effects of the present invention are:

[0025] Compared with the traditional flat welding flange processing technology, the present invention completely solves the deformation problem of large diameter A and B type flanges and the subsequent cost increase and unstable quality caused by deformation by adjusting the process sequence. The specific effects are as follows:

[0026] 1. The present invention solves the problem that welding deformation cannot be completely removed, and the flat welding flange welding is concentrated at the flange position (generally two places) causing uncontrollable deformation of the flange. By adjusting the steps of leaving processing allowance on the flange, not processing the bolt holes, applying anti-deformation tooling solutions, eliminating stress through local heat treatment, and one-time processing, the requirements for temperature control during the welding process are reduced, and the uncertainty caused by welding deformation is completely shielded, ensuring that the deformation amount after the flange and the cylinder are welded together reaches a perfect repair result; at the same time, the verticality of the flange bolt holes is guaranteed, ensuring the smooth installation of bolt fasteners during the assembly process.

[0027] 2. The present invention can make uncontrollable problems controllable only by properly adjusting and increasing the process sequence, and smoothly ensure the manufacturing accuracy of the flat welding flange components without significantly increasing the manufacturing difficulty; and eliminate stress through local heat treatment, thereby avoiding the risk of leakage during the service process due to uneven sealing surface after the stress is released due to aging effect during the service of the equipment.

[0028] 3. After ensuring the accuracy of the flange components, the present invention reduces the processing allowance of the liner ring to the greatest extent, greatly reduces the use of special materials, reduces direct costs, and has a very great reference significance for the processing of other large-diameter flat welding flanges.

[0029] 4. After the application of the present invention, during the product pressure test, workers do not need to waste a lot of time and physical strength on bolting work, and do not need to make up for the problem of insufficient flatness of the cover by excessive bolt tightening, which reduces the labor intensity of workers, ensures the smooth completion of the pressure test, and greatly improves the manufacturing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the bare blank flange and the tooling reinforcement ring of the present invention;

[0031] Figure 2 This is a schematic diagram of welding two flanges together according to the present invention;

[0032] Figure 3 This is a schematic diagram of the flange of the present invention after one-time processing;

[0033] Figure 4 This is a schematic diagram of the present invention after the liner ring is installed;

[0034] Figure 5 This is a schematic diagram of a finished component after the liner ring sealing surface is finally processed in the present invention;

[0035] Among them: 1 is the blank flange, 2 is the tooling reinforcement ring, 3 is the cylinder, 4 is the connecting rib plate, 5 is the bolt hole, 6 is the flange, 7 is the plug hole, and 8 is the liner ring. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings.

[0037] The processing method of the large-diameter AB type flat welding flange with liner ring of the present invention comprises the following steps:

[0038] Step A, adjusting the incoming material situation, purchasing the bare blank forging flange 1 that needs secondary processing according to the drawings, the bare blank forging flange 1 is a semi-finished flange with processing allowances in both the outer diameter and thickness directions and unprocessed bolt holes; the welds of the bare blank forging flange are concentrated on the inner side surface close to the bare blank forging flange 1, which can ensure that the welds on the upper surface of the bare blank forging flange 1 are not damaged after processing, ensure the strength of welding, and avoid having welds on the upper surface of the bare blank forging flange 1, because the upper surface of the bare blank forging flange 1 needs to be processed first after welding, and the processing may cause the welds to be removed, affecting the strength; the diameter of the bare blank forging flange 1 is measured before use, and the maximum and minimum diameter deviations are one thousandth of the diameter (7 mm in this embodiment);

[0039] Step B, when the blank forging flange 1 is inspected and qualified and put into production, a circle of anti-deformation tooling reinforcement ring 2 is first welded on the outer edge of the blank forging flange 1, such as Figure 1 As shown, the subsequent welding and heat treatment process of the bare blank forging flange 1 itself will continue to deform, and the roundness of the bare blank forging flange 1 body can be controlled as much as possible;

[0040] Step C, such as Figure 2 As shown, the groove position required for the assembly of the bare blank forging flange 1 and the cylinder 3 is first processed, the cylinder 3 and the bare blank forging flange 1 are assembled and position welded, and then the two bare blank forging flanges 1 are welded together with the connecting rib plate 4, which plays a role in welding deformation prevention and reduces the deformation during the welding process; after completing the above work, welding can be directly carried out according to the process requirements without excessive consideration of factors such as interlayer temperature, thereby ensuring the product manufacturing cycle;

[0041] Step D, welding the weld according to the drawings and process requirements. The welding can be performed according to the welding process requirements without paying special attention to the workpiece temperature;

[0042] Step E, the welded flange 6 and the weld are locally heat treated by wrapping with electric heating rope and insulation cotton to eliminate stress. The heat treatment temperature and time are 580°C to 640°C and the insulation time is 1 to 3 hours. The insulation time can be adjusted according to the thickness of the flange. After the insulation is completed, the insulation cotton is not removed to avoid rapid cooling.

[0043] Step F, cutting and separating the two flanges 6 at the welding point, and preparing for processing;

[0044] Step G, cut and remove the connecting rib plate 4 and the tooling reinforcement ring 2 outside the flange 6; process the upper and lower end faces of the flange 6, measure the thickness after flattening one side, ensure that the thickness at the lowest point is not less than the set thickness, and then process the other side; after the upper and lower end faces of the flange are processed, process the outer edge of the flange, and then process the bolt holes 5; after processing Figure 3 As shown;

[0045] Step H, install (weld or tighten with a setter) the liner ring 8 on the flat end surface of the flange 6 that has been processed, and complete the weld between the liner ring 8 and the connecting part according to the drawing and welding process (the welding amount is small at this time and no deformation will occur again);

[0046] Step I, secondary machining of the sealing surface of the liner ring 8. At this time, due to the effective control in the early stage and the one-time machining, the unevenness will be very small, generally controlled below 2mm, and the machining cycle and the amount of special material removed are very small; after the machining is completed, the sealing surface will not be deformed again, and the sealing effect can be fully guaranteed; the machining is completed as shown in the following figure. Figure 5 shown.

[0047] When the liner ring 8 installed in step H is a non-weldable liner ring, in step G, while marking and drilling the corresponding bolt holes 5, it is necessary to drill the plug nail holes 7. After assembly, the situation is as follows: Figure 4 As shown; when the liner ring 8 installed in step H is a weldable liner ring, in step G, only the corresponding bolt holes 5 need to be marked and drilled.

[0048] When the liner ring in step H is a non-weldable liner ring, the liner ring 8 is tightened with a plug; when the liner ring in step H is a weldable liner ring, the liner ring 8 is welded to the flat end face of the flange 6 that has been processed.

[0049] When the liner ring 8 in step H is a non-weldable liner ring, the connecting component is a liner sleeve, and the non-weldable liner ring is welded to the liner sleeve; when the liner ring in step H is a weldable liner ring, the connecting component is a flange 6, and the weldable liner ring is welded to the flange 6.

Claims

1. A method for processing a large diameter AB type flat welding flange with liner, characterized in that: The following steps are included Step A, purchasing a bare blank forging flange, which is a semi-finished flange with machining allowances in both the outer diameter and thickness directions and unmachined bolt holes; Step B, welding a deformation-proof tooling reinforcement ring on the outer edge of the flange of the bare blank forging; Step C, assembling and positioning the cylinder body and the flange of the bare blank forging, and then welding the two flanges of the bare blank forging together with a connecting rib plate to reduce deformation during the welding process; Step D, welding the weld; Step E, performing local heat treatment on the welded flange and weld by wrapping them with electric heating rope and insulation cotton to eliminate stress; Step F, cutting and separating the two flange welds to prepare for processing; Step G, cutting and removing the connecting ribs and tooling reinforcement ring outside the flange, processing the upper and lower end faces of the flange, measuring the thickness after flattening one side, ensuring that the thickness at the lowest point is not less than the set thickness, and then processing the other side; after the upper and lower end faces of the flange are processed, process the outer edge of the flange, and then process the bolt holes; Step H, installing the liner ring on the flat end face of the flange that has been processed, and completing the weld between the liner ring and the connecting part as required; Step I: secondary turning of the liner ring sealing surface.

2. The processing method of the large diameter liner ring AB flat welding flange according to claim 1 is characterized in that: The diameter of the bare blank forging flange in step A is measured before use, and the maximum and minimum diameter deviations are one thousandth of the diameter.

3. The processing method of the large diameter liner ring AB flat welding flange according to claim 1 is characterized in that: In the step A, the weld seams of the flange of the bare blank forging are concentrated on the inner side surface close to the flange of the bare blank forging, so as to avoid weld seams on the upper surface of the flange of the bare blank forging.

4. The processing method of the large diameter AB type flat welding flange with liner according to claim 1 is characterized in that: In the step C, before the barrel and the flange of the bare blank forging are assembled and tack welded, the groove position required for assembling the flange of the bare blank forging and the barrel is first processed.

5. The processing method of the large diameter AB type flat welding flange with liner according to claim 1 is characterized in that: The temperature and time of the heat treatment in step E are 580° C. to 640° C. and the heat preservation time is 1 to 3 hours.

6. The processing method of the large diameter liner ring AB flat welding flange according to claim 1 is characterized in that: When the bushing ring installed in step H is a non-weldable bushing ring, in step G, while marking and drilling the corresponding bolt holes, it is necessary to drill the plug nail holes; when the bushing ring installed in step H is a weldable bushing ring, in step G, it is only necessary to mark and drill the corresponding bolt holes.

7. The processing method of the large diameter liner ring type AB flat welding flange according to claim 6 is characterized in that: When the liner ring in step H is a non-weldable liner ring, the liner ring is tightened with a plug; when the liner ring in step H is a weldable liner ring, the liner ring is welded to the flat end face of the flange that has been processed.

8. The method for processing a large diameter AB type flat welding flange with liner according to claim 6 is characterized in that: When the liner ring in step H is a non-weldable liner ring, the connecting component is a liner sleeve, and the non-weldable liner ring is welded to the liner sleeve; when the liner ring in step H is a weldable liner ring, the connecting component is a flange, and the weldable liner ring is welded to the flange.

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