Construction method for controlling flange levelness in furnace top flange welding process

Abstract

The invention discloses a construction method for controlling flange levelness in a furnace top flange welding process, which comprises the following steps of: welding a plurality of rib plates between the lower end of a furnace top flange and the periphery of a furnace shell, and arranging dial indicators on the periphery of an intersection point of an orthogonal center line of the furnace top flange and the furnace shell when welding seams between the rib plates and the furnace top flange are welded, the device is used for detecting the levelness of the upper surface of a flange in the welding process, and the levelness deviation is corrected through reverse welding when the levelness is out of tolerance. Preheating the welding part of the furnace top flange and the furnace shell, firstly performing symmetrical spot welding and fixing on the furnace top flange and the furnace shell, and then performing symmetrical partition welding from each intersection point of an orthogonal center line of the furnace top flange and the furnace shell along the circumferential direction by taking the center of the furnace top flange until the welding process is finished, and each subarea is welded by adopting a step-by-step back welding method. The dial indicator is used for monitoring the position with large welding seam shrinkage, the welding amount is increased at the symmetrical position with large welding seam shrinkage in time, and the effect of shrinkage leveling in the opposite direction is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flanges, and in particular relates to a construction method for controlling the horizontality of a furnace top flange during welding. Background Art

[0002] Blast furnace top equipment is mounted on the blast furnace roof via a top flange. Prior to installing the top equipment, the top flange must be welded and installed on the blast furnace roof. The "Code for Acceptance and Installation of Ironmaking Machinery and Equipment" (GB50679-2011) stipulates that the top flange installation quality must meet the following requirements: an allowable elevation deviation of ±20mm; and a relative height difference of ≤1mm between any two points. The center of the top flange must align with the center of the furnace bottom, with a deviation of no more than 30mm.

[0003] The diameter of the blast furnace top flange is generally large, for example: a 1780m 3 The diameter of a blast furnace's top flange reaches 3020mm. For flanges with diameters exceeding 3000mm, maintaining installation accuracy within this range is difficult, not to mention the extensive welding required during installation. Therefore, the blast furnace top flange is a critical component in the installation of top equipment. Poor installation quality or improper sealing of the top flange will directly impact the service life of the top charging equipment, thereby reducing the lifespan of the blast furnace and impacting production efficiency.

[0004] During the installation of the furnace top flange, a lot of welding work must be done. It is difficult to ensure the horizontality of the furnace top flange during the welding process. According to a steel plant with a height of 1780m 3 Take the blast furnace top equipment as an example. The weight of the blast furnace top equipment is 220 tons, and the overall height of the top equipment is about 20 meters. The welding quality of the top flange directly affects the performance and life of the top equipment.

[0005] How to ensure that the thermal deformation of the furnace top flange during the welding process is controllable is the key to construction. However, the main feature of the current welding process is that the intermediate process is not monitored, and there is no effective method to prevent the deformation of the furnace top flange during welding. Therefore, it is necessary to improve the welding and installation method of the furnace top flange to improve its welding and installation quality. Summary of the Invention

[0006] To solve the above problems, this application prevents or reduces welding deformation by welding 8 evenly distributed ribs in advance, and uses a dial indicator to observe the deformation position of the furnace top flange during the welding process to adjust the welding position and welding sequence in time to correct the unevenness.

[0007] A construction method for controlling the horizontality of a furnace top flange during welding, comprising the following steps:

[0008] Step S3: After the furnace top flange is concentrically arranged on the furnace top and leveled, a plurality of ribs are evenly arranged along the circumferential direction between the lower end of the furnace top flange and the outer periphery of the furnace shell. The welds between the ribs and the furnace shell are first welded, and then the welds between the ribs and the furnace top flange are welded. When welding the welds between the ribs and the furnace top flange, a dial indicator is arranged around the intersection of the orthogonal center line of the furnace top flange and the furnace shell to detect the horizontality of the flange upper surface during the welding process. When the horizontality is out of tolerance, a reverse welding method is used to correct the horizontality deviation.

[0009] Step S4, preheating the welding part of the furnace top flange and the furnace shell, first symmetrically spot welding the furnace top flange and the furnace shell, and then starting from the intersection points of the orthogonal center line of the furnace top flange and the furnace shell, symmetrical partition welding is performed along the circumferential direction with the center of the furnace top flange until the welding process is completed, wherein each partition welding adopts the gradual back-welding method.

[0010] Optionally, in step S4, during the welding process, the horizontality change of the furnace top flange is monitored according to the dial indicator. If the horizontality is out of tolerance, the welding speed is accelerated in the symmetrical area of ​​the out-of-tolerance area to correct the horizontality deviation.

[0011] Optionally, during the welding process of the furnace top flange and the furnace shell, after completing one layer of welds, the horizontality change of the furnace top flange is monitored by a dial indicator. If the horizontality is out of tolerance, a welding position sequence different from that of the previous layer of welds is used when welding the next layer of welds to correct the horizontality deviation.

[0012] Optionally, in step S4, carbon dioxide gas shielded welding is used for welding.

[0013] Optionally, before step S3, step S2 is further included: before welding and installing the furnace top flange, water, rust and oil stains within a range of 15-20 mm around the groove are removed.

[0014] Optionally, before step S2, step S1 is further included, in which, before welding and installing the furnace top flange, the opening and welding operations on the furnace shell cover are completed. The furnace shell cover is the uppermost section of the furnace shell.

[0015] Optionally, step S0 is further included before step S1, in which the horizontality of the furnace top flange is checked. If the horizontality is out of tolerance, it should be repaired before welding and installation.

[0016] Optionally, 8 ribs are provided in step S3. Before welding the welds between the ribs and the furnace shell and between the ribs and the furnace top flange, first adjust the horizontality of 4 symmetrical points of the furnace top flange, spot weld the horizontal welds between the ribs and the lower end face of the flange, and use a dial indicator to monitor the horizontality of the furnace top flange on the upper surface of the furnace top flange. Then, select the remaining 4 symmetrical points to adjust the horizontality of the furnace top flange, spot weld the horizontal welds between the ribs and the lower end face of the flange, and use a dial indicator to monitor the horizontality of the furnace top flange on the upper surface of the furnace top flange.

[0017] Optionally, before welding the furnace top flange and the furnace shell, a windproof enclosure is set around the furnace to prevent wind during the welding process.

[0018] Optionally, the furnace top flange and the furnace shell are welded by multi-layer and multi-pass welding with low current, and there is a time interval between each weld.

[0019] Compared with the prior art, this application has the following beneficial effects:

[0020] (1) Before welding the furnace top flange, the present application installs 8 auxiliary ribs to limit the deformation of the furnace top flange during the welding process and reduce the deformation amount.

[0021] (2) In the past, during the welding process of the furnace top flange, there was no accurate monitoring of the welding deformation using a dial indicator. The welding deformation was often controlled by the construction workers’ experience. The uneven shrinkage caused by the uneven welding heat was not controlled by adjusting the welding position during the welding process. This inevitably led to rework, resulting in a waste of manpower, material, and financial resources. In the present application, four dial indicators are used to monitor the deformation of the furnace top flange during the welding process. Based on the monitoring results, the areas where the welds have shrunk the most are found. In this way, the welding amount is increased in the symmetrical areas where the welds have shrunk the most, thereby achieving the effect of leveling the shrinkage in the opposite direction.

[0022] (3) After completing one layer of welds, the present application uses a dial indicator to observe the levelness change of the furnace top flange. If the levelness is out of tolerance, a welding position sequence different from that of the previous layer is used when welding the next layer of welds to correct the levelness deviation.

[0023] (4) Before welding and installing the furnace top flange, the present application first completes the opening and welding of the inspection hole of the furnace shell cover, the gas outlet pipe and the probe to eliminate the influence of the opening welding on the flange installation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a front view of the furnace top flange installation according to an embodiment of the present invention.

[0025] Figure 2 This is a top view of the furnace top flange installation according to an embodiment of the present invention.

[0026] Figure 3Schematic diagram of the rib weld according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of symmetrical partition welding according to an embodiment of the present invention.

[0028] Reference numerals

[0029] Furnace top flange 1, furnace shell 2, rib plate 3, bracket 4, dial indicator base 5, dial indicator 6, weld 33, first weld 331, second weld 332, third weld 333, fourth weld 334, fifth weld 335, sixth weld 336 DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] The installation levelness of the blast furnace top flange is highly demanding. Due to limited conditions, it is difficult to maintain a relatively balanced welding temperature in the welding area during on-site welding. The top flange is prone to uneven shrinkage and deformation during welding, resulting in excessive levelness. This embodiment ensures heat balance and the levelness of the tuyere flange during welding by monitoring the uneven shrinkage trend of the weld seam and adjusting the welding position in a timely manner. A supplementary welding connection plate is added between the top flange and the furnace shell to reduce welding deformation of the top flange. This method ensures the levelness of the top flange during welding and installation.

[0032] This embodiment provides a construction method for controlling the horizontality of a furnace top flange during welding, comprising the following steps:

[0033] Step S0, check the horizontality of the furnace top flange to see if it is deformed during transportation. If deformed, it should be repaired before welding and installation.

[0034] Step S1: Before welding and installing the furnace top flange, complete the drilling and welding of the furnace shell cover's manhole, gas outlet pipe, and probe to eliminate the impact of drilling welding on flange installation accuracy. The drilling operations include cutting holes in the furnace shell cover and welding the connecting structure around the edges of the holes.

[0035] The furnace shell enclosure is part of the blast furnace shell, located on top of the blast furnace shell. It caps the entire blast furnace structure. Multiple holes are required in the shell, such as gas outlet pipe connection holes, chute inspection holes, manholes, and detection holes. Connection structures, such as pipe connections, are welded to these openings to meet the process requirements of blast furnace ironmaking.

[0036] At present, when welding the furnace top flange, there is no restriction on whether to perform the hole-opening related operations first or to weld the furnace top flange first. According to the observation of the inventor of the present application, it is believed that after the furnace top flange is welded and installed, the hole-opening related operations are performed on the furnace shell cover. In the hole-opening related operations, whether it is cutting or welding, high temperature will be generated. The heat is transferred to the furnace top flange, thereby affecting the welding quality of the furnace top flange. Therefore, before the furnace top flange is welded and installed, the hole-opening related operations on the furnace shell cover are completed first, thereby avoiding the influence of the hole-opening related operations on the welding and installation quality of the furnace top flange.

[0037] Step S2: Before welding the furnace top flange, clean the water, rust and oil within 15-20 mm around the groove to reveal the metallic luster.

[0038] Step S3, after concentrically arranging the furnace top flange 1 on the furnace top and leveling it, a plurality of ribs 3 are arranged circumferentially between the lower end of the furnace top flange and the outer periphery of the furnace shell 2 to prevent and reduce shrinkage deformation during welding of the furnace shell and the flange. The ribs 3 can be evenly arranged in the circumferential direction, and 8 ribs 3 are more suitable in the circumferential direction. First, weld the weld 33 between the rib 3 and the furnace shell 2, and then weld the weld 33 between the rib 3 and the furnace top flange 1. In addition, when welding the weld between the rib and the flange, a dial indicator 6 is arranged around the intersection of the orthogonal center line of the flange and the furnace shell to detect whether the levelness of the upper surface of the flange exceeds the tolerance due to uneven shrinkage of the weld during the welding process. When the levelness exceeds the tolerance, reverse welding is used to correct the uneven shrinkage of the weld. The so-called reverse welding is to increase the welding amount at the symmetrical position. The increase in heat at the symmetrical position will offset the deformation at that position.

[0039] The dial indicator 6 is mounted on the furnace shell 2 via the dial indicator base 5 and the bracket 4 , wherein the bottom of the bracket 4 may be magnetic and can be arranged on the furnace shell 2 by magnetic attraction.

[0040] Specifically, after the flange is initially leveled and aligned, the weld between the rib plate and the furnace shell is welded first. At this time, the weld mainly produces shrinkage deformation in the lateral direction. At this time, the shrinkage deformation of the weld of the welded rib plate will not affect the furnace top flange. Then fine-tune the flange levelness. When fine-tuning, first adjust the four symmetrical points, spot-weld the horizontal weld between the rib plate and the lower end face of the flange, and use four dial indicators at 90° positions to align with the upper surface of the furnace top flange to monitor the deformation of the furnace top flange. Then select the remaining four symmetrical points to fine-tune the flange levelness, spot-weld the horizontal weld between the rib plate and the lower end face of the flange, and use four dial indicators at 90° positions to align with the upper surface of the furnace top flange to monitor the deformation of the furnace top flange. The furnace top flange and the rib plate are only spot-welded and fixed without welding, which basically will not affect the levelness of the furnace top flange.

[0041] like Figure 1 As shown, there is a certain angle between the lower end of the furnace top flange and the outer periphery of the furnace shell. A rib plate can be set according to the shape of the angle. For example, the rib plate is a triangle, and the angle of one of its corners is the same as the angle between the lower end of the furnace top flange and the outer periphery of the furnace shell. The angle of the triangle equal to the angle is inserted into the angle, so that the rib plate can well support the furnace top flange.

[0042] Step S4, welding of the furnace top flange and furnace shell: Before welding, set up enclosures around the furnace to prevent wind during the welding process, preheat the welding parts of the flange and furnace shell, first symmetrically spot weld the furnace top flange and furnace shell, and then symmetrically partition the welds 33 along the circumferential direction starting from the intersection points of the orthogonal center line and the furnace shell until the welding process is completed.

[0043] Among them, each zone welding is welded by the step-by-step back-welding method. Four welders can be arranged to perform symmetrical zone welding along the circumferential direction starting from the intersection of the orthogonal center line and the furnace shell. The step-by-step back-welding method is an advanced technology widely used in welding processes, especially suitable for processing long welds or occasions where welding deformation and stress need to be strictly controlled. This method is a welding process that subdivides the full length of the weld into several shorter welds, and the welding direction of each section is opposite to the growth direction of the entire weld. This welding method significantly improves the uneven heating and cooling phenomenon during the welding process, thereby effectively reducing the stress and deformation after welding. Four welders can perform symmetrical intermittent welding to complete the first layer of backing welding between the furnace top flange and the furnace shell after repeated welding for two rounds. During the welding process, the horizontality change of the flange is monitored according to 4 dial indicators. If the change is large, the welding speed is accelerated at the symmetrical part of the center of the furnace top flange, or the welding amount is increased to correct the shrinkage deformation of the weld. For example Figure 4There are two symmetrical zones, each of which is further divided into three welds 33: a first weld 331 and a sixth weld 336 are welded symmetrically, a second weld 332 and a fifth weld 335 are welded symmetrically, and a third weld 333 and a fourth weld 334 are welded symmetrically. If the horizontality of the furnace top flange in the area where the first weld 331 is located is out of tolerance, the welding speed at the sixth weld 336 is increased, or the welding load is increased. The horizontality of the furnace top flange at the first weld 331 is corrected by the deformation of the furnace top flange at the sixth weld 336.

[0044] The welding adopts multi-layer and multi-pass welding with small current. There is a certain time interval between each weld to reduce the large welding shrinkage deformation caused by heat accumulation in the weld. The high current and low current in welding technology are relative to the current selection range of a welding wire. This is a conventional technical means and will not be explained in detail here. After the completion of the first layer of base welding, observe the horizontality change of the furnace top flange through the dial indicator after a period of interruption. If the horizontality is out of tolerance, when welding the second layer of welds, the construction can correct some of the horizontality deviation by adopting a welding position sequence different from the previous layer. The same method can be used to weld the second and third layers of welds. For example Figure 4 In the figure, the first layer is the welding position sequence of the first weld 331 and the sixth weld 336, the second weld 332 and the fifth weld 335, the third weld 333 and the fourth weld 334. In the second layer of welds, the welding position sequence can be changed to the second weld 332 and the fifth weld 335, the first weld 331 and the sixth weld 336, the third weld 333 and the fourth weld 334.

[0045] The furnace roof flange and shell are welded using CO2 gas shielded welding, using, for example, ER50-6 flux-cored wire. Compared to conventional arc welding, this type of welding produces less heat and deformation. Multi-pass welding is performed in multiple layers and at low currents to minimize heat and deformation.

[0046] For example, before welding, the furnace top flange is surrounded with colored cloth to provide draft protection during the welding process. The welded portion of the furnace top flange and the furnace shell is preheated using specialized gas or four hot torches to a temperature of 180°C to 200°C. A far-infrared thermometer is used to monitor the heating temperature, and preheating must be continued throughout the welding process. For the overhaul welding, four welding machines are used to weld symmetrically along the circumference, starting at the intersection of the orthogonal centerline and the furnace shell, until the overhaul welding process is complete. Welding is performed in multiple layers and passes, with direction reversed during the welding process. Four dial indicators are used to monitor deformation throughout the welding process. Reverse welding is performed symmetrically at locations with significant deformation to adjust for uneven weld shrinkage. Specifically, reverse welding is performed symmetrically around the center of the flange. After welding is completed, a spray penetrant inspection is performed on the outside of the weld to detect cracks or other defects. The final inspection elevation difference is ≤1mm.

[0047] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications shall fall within the scope of protection of the claims of the present invention.

Claims

1. A construction method for controlling the horizontality of a furnace top flange during welding, characterized in that: The steps include: Step S3: After the furnace top flange is concentrically arranged on the furnace top and leveled, a plurality of ribs are evenly arranged along the circumferential direction between the lower end of the furnace top flange and the outer periphery of the furnace shell. The welds between the ribs and the furnace shell are welded first, and then the welds between the ribs and the furnace top flange are welded. When welding the welds between the ribs and the furnace top flange, a dial indicator is arranged around the intersection of the orthogonal center line of the furnace top flange and the furnace shell to detect the horizontality of the upper surface of the furnace top flange during the welding process. When the horizontality is out of tolerance, a reverse welding method is used to correct the horizontality deviation. Step S4, preheating the welding part of the furnace top flange and the furnace shell, first symmetrically spot welding the furnace top flange and the furnace shell, and then starting from the intersection points of the orthogonal center line of the furnace top flange and the furnace shell, symmetrical partition welding is performed along the circumferential direction with the center of the furnace top flange until the welding process is completed, wherein each partition welding adopts the gradual back-welding method.

2. The construction method for controlling the horizontality of the flange during the furnace top flange welding process according to claim 1, characterized in that: In step S4, during the welding process, the horizontality change of the furnace top flange is monitored according to the dial indicator. If the horizontality is out of tolerance, the welding speed is accelerated in the symmetrical area of ​​the out-of-tolerance area to correct the horizontality deviation.

3. The construction method for controlling the horizontality of the flange during the furnace top flange welding process according to claim 2, characterized in that: During the welding process of the furnace top flange and the furnace shell, after completing one layer of welds, the horizontality change of the furnace top flange is monitored by a dial indicator. If the horizontality is out of tolerance, a different welding position sequence is used when welding the next layer of welds than the previous layer to correct the horizontality deviation.

4. The construction method for controlling the horizontality of the flange during the furnace top flange welding process according to claim 1 is characterized in that: In step S4, carbon dioxide gas shielded welding is used for welding.

5. The construction method for controlling the horizontality of the flange during the furnace top flange welding process according to claim 1, characterized in that: Before step S3, the method further includes step S2: before welding and installing the furnace top flange, clearing water, rust and oil stains within a range of 15-20 mm around the groove.

6. The construction method for controlling the horizontality of the flange during the furnace top flange welding process according to claim 5, characterized in that: Before step S2, step S1 is also included, in which, before welding and installing the furnace top flange, the opening and welding operations on the furnace shell cover are completed. The furnace shell cover is the uppermost section of the furnace shell.

7. The construction method for controlling the horizontality of the flange during the furnace top flange welding process according to claim 6, characterized in that: Before step S1, step S0 is also included, in which the horizontality of the furnace top flange is checked. If the horizontality is out of tolerance, it should be repaired before welding and installation.

8. The construction method for controlling flange horizontality during furnace top flange welding according to claim 1, characterized in that: In step S3, 8 ribs are provided. Before welding the welds between the ribs and the furnace shell and the ribs and the furnace top flange, first adjust the levelness of the 4 symmetrical points of the furnace top flange, spot weld the horizontal welds between the ribs and the lower end face of the flange, and use a dial indicator to monitor the levelness of the furnace top flange on the upper surface of the furnace top flange. Then, select the remaining 4 symmetrical points to adjust the levelness of the furnace top flange, spot weld the horizontal welds between the ribs and the lower end face of the flange, and use a dial indicator to monitor the levelness of the furnace top flange on the upper surface of the furnace top flange.

9. The construction method for controlling flange horizontality during furnace top flange welding according to claim 1, characterized in that: Before welding the furnace top flange and furnace shell, set up enclosures around them to protect against wind during the welding process.

10. The construction method for controlling flange horizontality during furnace top flange welding according to claim 1, characterized in that: The welding between the furnace top flange and the furnace shell adopts low current multi-layer and multi-pass welding, and there is a time interval between each weld.

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