A device and process for welding cracks in a U-shaped feeding trough in a preheating section of an electric furnace

Abstract

The present invention discloses a device and process for welding cracks in a U-shaped trough for feeding in the preheating section of an electric furnace, and belongs to the technical field of repairing U-shaped troughs. The present invention comprises a U-shaped trough, which is composed of a trough bottom wall, a trough side wall, and a trough upper edge. The surface of the trough side wall is provided with a heating plate, and the outer side surface of the heating plate is provided with a heating Z-shaped cover plate and heat-insulating cotton. The upper end of the heating Z-shaped cover plate is overlapped on the surface of the upper edge of the trough, and the lower end of the heating Z-shaped cover plate is also provided with a fixing screw and a Z-shaped pressing plate. The present invention is not only safe and easy to operate, with stable welding quality and low investment cost, which meets the actual needs on site and has high work efficiency, but also greatly reduces maintenance costs, reduces downtime losses, and provides a guarantee for reasonable production. The welding repair of cracks in the wear-resistant plate of the U-shaped trough for feeding in the preheating section of an electric furnace provides a scientific reference for the welding repair of other large wear-resistant plates.

Description

Technical Field

[0001] The present invention relates to the technical field of U-shaped trough repair, and more particularly to a device and process for welding cracks in a U-shaped trough body for feeding in a preheating section of an electric furnace. Background Art

[0002] The new ECS scrap preheating continuous charging electric arc furnace technology replaces the existing converter steelmaking equipment, achieving operational flexibility and allowing the choice of charge between scrap and molten iron, minimizing environmental impact. This energy-saving steelmaking equipment consists of two sections: a charging section and a preheating section. The feed end of the preheating section is connected to the waste heat recovery and dust removal system piping, and the discharge end is overlapped with the electric furnace port, forming a fully enclosed electric furnace steelmaking process that integrates scrap preheating, flue gas purification, and waste heat recovery, including continuous feeding, preheating, melting, and smelting. The preheating section features an arched upper section with a fume hood and a U-shaped water-cooled chute at the bottom. During operation, the scrap in the U-shaped chute is uniformly and continuously moved toward the furnace bath by vibration. The combined effects of flue gas waste heat and CO combustion heat gradually heat the scrap surface from room temperature to an average temperature of 400-650°C before rapidly melting in the furnace bath.

[0003] Because the U-shaped trough carries a large amount of scrap steel for a long time and is subjected to the adverse factors of thermal expansion and contraction caused by alternating hot and cold conditions, it directly leads to irregular cracking of the R corner in the U-shaped trough (such as Figure 1 As shown in the figure, since the outside of the U-shaped trough is water-cooled, if the R-angle inside the trough cracks irregularly, the cooling water on the outside will flow into the trough, which will not only reduce the temperature of the scrap steel entering the furnace in the preheating section, but also cause a large amount of water to enter the furnace, causing major equipment hazards. The existing problems are: if the trough is sent offline for repair or replacement, not only will the disassembly, lifting and transportation of the large U-shaped trough be difficult and the cycle will be long, but it will also fail to meet the needs of continuous production. Therefore, on-site welding repair is considered to ensure that the welds are free of cracks and porosity defects after UT and MT penetration testing, and the welds are manually ground for smooth transition before delivery. However, the material of this type of U-shaped trough is NM400, which has a large carbon equivalent, large thickness, and high tensile strength, resulting in poor weldability. The repair plan has the following difficulties:

[0004] 1. Cold cracks are easy to occur: According to the mechanical properties of the material, oxygen-acetylene flame can be used for preheating (100-130℃) before welding. The temperature between layers should not be less than 100℃ during multi-layer welding, which can effectively prevent cold cracks, reduce cooling speed and reduce welding stress.

[0005] 2. High requirements for welding groove and quality: In order to prevent cracks and other defects, clean the surface of the groove from water, paint, rust, oil, welding slag and other stains. Do not strike the arc directly on the groove surface. Use an arc-starting plate and design a single-sided U-shaped groove. Try to use a faster welding speed and short arc welding. Do not allow large lateral swings.

[0006] 3. Conventional gas shielded welding cannot complete the welding repair of online cracks because there is draft on the outside and uncertain water and gas on the inside. In order to ensure the welding quality, arc welding is adopted for base-filling-covering.

[0007] 4. Post-weld insulation is difficult to control: reduce the hydrogen content in the weld and reduce cracking. Perform overall electric heating weld heat treatment after welding. Since all welds are at the R corners, the heating plate and insulation cotton cannot be fixed, so a fixed heating tool for the structural parts is designed.

[0008] 5. Due to the large size of the U-shaped trough and the complex location processing, the weld seam after welding is difficult to be machined online, so manual grinding is used to ensure a smooth transition on both sides of the weld seam. The overall effect meets the test of the sample and meets the operating size.

[0009] Therefore, it is necessary to design a device and process for welding cracked U-shaped troughs in the preheating section of electric furnaces. Furthermore, the welded repaired U-shaped troughs must: 1. be low-cost, easy to operate and maintain on-site, and require a short repair time; 2. have a metallurgically bonded weld layer that is durable enough for periodic use. Summary of the Invention

[0010] 1. Technical problem to be solved by the invention

[0011] In response to the defects and shortcomings of the existing technology, the present invention provides a device and process for welding cracks in the U-shaped feeding trough of the preheating section of an electric furnace. The present invention is not only safe and easy to operate, but also has stable welding quality and low investment cost, meets the actual needs on site, and has high work efficiency, but also greatly reduces maintenance costs, reduces downtime losses, and provides a guarantee for reasonable production organization. The welding repair of cracks in the wear-resistant plate of the U-shaped feeding trough of the preheating section of an electric furnace provides a scientific reference basis for the welding repair of other large wear-resistant plates.

[0012] 2. Technical solution

[0013] In order to achieve the above object, the technical solution provided by the present invention is:

[0014] The present invention provides a crack welding device for a U-shaped trough body for feeding a material in a preheating section of an electric furnace, comprising a U-shaped trough body, wherein the U-shaped trough body is composed of a trough body bottom wall, a trough body side wall, and a trough body upper edge, wherein a lower fillet is provided at the connection between the trough body side wall and the trough body bottom wall, and an upper fillet is provided at the connection between the trough body side wall and the trough body upper edge;

[0015] The surface of the side wall of the tank body is provided with a heating plate, and the outer side of the heating plate is provided with a heating Z-shaped cover plate and thermal insulation cotton, and the thermal insulation cotton is filled in the gap between the heating Z-shaped cover plate and the heating plate;

[0016] The upper end of the heated Z-shaped cover plate is overlapped on the surface of the upper edge of the trough body, and the lower end of the heated Z-shaped cover plate is close to the bottom wall of the trough body. The lower end of the heated Z-shaped cover plate is also provided with a fixing screw and a Z-shaped pressing plate, and the Z-shaped pressing plate is fixed to the heated Z-shaped cover plate by the fixing screw.

[0017] Furthermore, the lower end surface of the heating Z-shaped cover plate is fixed to the bottom wall of the trough body through a fixing screw and a Z-shaped pressing plate.

[0018] Furthermore, the heating Z-shaped cover is formed by mechanically pressing a 5mm steel plate. The heating Z-shaped cover is arranged on the outside of the thermal insulation cotton and covers the outer surface of the lower fillet and the upper fillet.

[0019] Furthermore, the cracks on the side walls of the tank body are repaired by welding at intervals to form welds.

[0020] Furthermore, the fixing screw is machined from a φ20mm round bar, and the Z-shaped cover is fixed and heated by the Z-shaped pressing plate in combination with the fixing screw.

[0021] Furthermore, after the Z-shaped pressing plate is pressed and fixed, the U-shaped trough body is welded to form a second weld.

[0022] A process for welding a cracked U-shaped trough body in a preheating section of an electric furnace, comprising the following steps:

[0023] Step 1: First, repair the cracks in the U-shaped trough and complete the weld;

[0024] Step 2: Install heating plates and insulation cotton on the outer surfaces of the lower and upper fillets;

[0025] Step 3: After the heating plate completely covers the weld seam, install the heating Z-shaped cover on the outside of the insulation cotton so that the heating Z-shaped cover completely covers the lower and upper fillets;

[0026] Step 4: After heating the Z-shaped cover plate and fixing its position, make its bottom surface contact horizontally with the bottom wall of the U-shaped trough body;

[0027] Step 5: Install the Z-shaped pressing plate at the lower end of the heating Z-shaped cover, and use fixing screws to fix the Z-shaped pressing plate and the heating Z-shaped cover to prevent the heating plate and the insulation cotton from deviating from their positions during the heating process;

[0028] Step 6: Finally, fix the connection between the Z-shaped pressure plate and the bottom wall of the trough body by welding to form a second weld.

[0029] Furthermore, the welding process route is: determine the cracking position of the U-shaped trough body - cut the single-sided U groove - preheat - weld the bottom layer with low-strength welding materials - hammer the weld surface - confirm the defect - control the interlayer temperature - weld the filling layer with low-strength welding materials - hammer the weld surface - confirm the defect - weld the cover with high-strength welding rods - confirm the defect - post-weld heat treatment - manual grinding - inspection and acceptance - delivery for use.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0032] The present invention is not only safe and easy to operate, with stable welding quality and low investment cost, it meets the actual needs on site and has high work efficiency, but also greatly reduces maintenance costs, reduces downtime losses, and provides a guarantee for reasonable production. The welding repair of cracked wear-resistant plates on the U-shaped trough body of the preheating section feed of the electric furnace provides a scientific reference basis for the welding repair of other large wear-resistant plates.

[0033] The present invention is applicable to the field of repairing parts of various electric furnace equipment production. It has a novel structure, compact and reasonable configuration, low investment, small site occupation, low operation and maintenance costs, easy operation, and reliable operation. All relevant connections of the structural parts production tooling are welded and machined, with a simple structure, easy production and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the overall structural diagram of the present invention;

[0035] Figure 2 It is the front view of the present invention;

[0036] Figure 3 It is a schematic diagram of the groove and welding layer of the present invention.

[0037] In the figure: 1. U-shaped trough; 101. trough bottom wall; 102. trough side wall; 103. trough top edge; 104. lower fillet; 105. upper fillet; 2. weld; 3. heating Z-shaped cover; 4. fixing screw; 5. Z-shaped pressure plate; 6. second weld; 7. thermal insulation cotton; 8. heating plate. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0039] Example 1

[0040] from Figure 1-3It can be seen that the present embodiment of the present invention is a U-shaped trough body crack welding device for feeding the preheating section of an electric furnace, comprising a U-shaped trough body 1. The U-shaped trough body 1 is composed of a trough body bottom wall 101, a trough body side wall 102, and a trough body upper edge 103. A lower fillet 104 is provided at the connection between the trough body side wall 102 and the trough body bottom wall 101, and an upper fillet 105 is provided at the connection between the trough body side wall 102 and the trough body upper edge 103.

[0041] The surface of the tank side wall 102 is provided with a heating plate 8, and the outer side of the heating plate 8 is provided with a heating Z-shaped cover plate 3 and thermal insulation cotton 7, and the thermal insulation cotton 7 is filled in the gap between the heating Z-shaped cover plate 3 and the heating plate 8;

[0042] The heating plate 8 has two functions: 1. Preheating before welding. After the preheating temperature is reached, the heating plate is removed and normal welding is carried out. 2. After the overall welding is completed, the heating plate 8 is covered on the weld to heat it for post-weld heat treatment.

[0043] The upper end of the heating Z-shaped cover plate 3 overlaps the surface of the upper edge 103 of the trough body, and the lower end of the heating Z-shaped cover plate 3 is close to the bottom wall 101 of the trough body. The lower end of the heating Z-shaped cover plate 3 is also provided with a fixing screw 4 and a Z-shaped pressing plate 5. The Z-shaped pressing plate 5 is fixed to the heating Z-shaped cover plate 3 by the fixing screw 4.

[0044] The lower end surface of the heating Z-shaped cover plate 3 is fixed to the bottom wall 101 of the tank body through the fixing screw 4 and the Z-shaped pressing plate 5.

[0045] The heating Z-shaped cover plate 3 is mechanically pressed from a 5mm steel plate. The heating Z-shaped cover plate 3 is arranged on the outside of the thermal insulation cotton 7 and covers the outer surface of the lower fillet 104 and the upper fillet 105. The bottom surface of the heating Z-shaped cover plate 3 forms a plug-in fit with the Z-shaped pressing plate 5.

[0046] The U-shaped trough body 1 is formed by mechanical pressing of a whole plate. The cracks in the U-shaped trough body 1 are irregular. The trough body sidewalls 102 are repaired by welding at intervals along the surface cracks to form weld seams 2.

[0047] The fixing screw 4 is machined from a φ20 mm round bar, and the Z-shaped pressing plate 5 cooperates with the fixing screw 4 to press and fix the heating Z-shaped cover 3 .

[0048] After the Z-shaped pressing plate 5 is pressed and fixed, the U-shaped trough body 1 is welded to form a second weld 6 .

[0049] A process for welding a cracked U-shaped trough body in a preheating section of an electric furnace, comprising the following steps:

[0050] Step 1: First, repair the cracks in the U-shaped trough 1 and complete the weld 2;

[0051] Step 2: Install the heating plate 8 and the insulation cotton 7 on the outer surface of the lower fillet 104 and the upper fillet 105;

[0052] Step 3: After the heating plate 8 completely covers the weld 2, install the heating Z-shaped cover plate 3 on the outside of the insulation cotton 7 so that the heating Z-shaped cover plate 3 completely covers the lower fillet 104 and the upper fillet 105;

[0053] Step 4: After heating and fixing the Z-shaped cover plate 3, its bottom surface is in horizontal contact with the bottom wall 101 of the U-shaped trough body 1;

[0054] Step 5: Install the Z-shaped pressing plate 5 at the lower end of the heating Z-shaped cover 3, and use the fixing screw 4 to fix the Z-shaped pressing plate 5 to the heating Z-shaped cover 3 to prevent the heating plate 8 and the insulation cotton 7 from deviating from their positions during the heating process;

[0055] Step 6: Finally, the connection between the Z-shaped pressing plate 5 and the bottom wall 101 of the tank body is fixed by welding to form a second weld 6.

[0056] The welding process route is: determine the cracking position of the U-shaped trough body - cut the single-sided U groove - preheat - weld the bottom layer with low-strength welding materials - hammer the weld surface - confirm the defect - control the interlayer temperature - weld the filling layer with low-strength welding materials - hammer the weld surface - confirm the defect - weld the cover with high-strength welding rods - confirm the defect - post-weld heat treatment - manual grinding - inspection and acceptance - delivery for use.

[0057] Figure 3 A refers to the groove type; B refers to welding layers 1, 2, and 3;

[0058] The welding process for cracking the U-shaped trough in the preheating section of the electric furnace also includes:

[0059] Preparation before welding:

[0060] 1) Welding equipment: HT400D digitally controlled inverter manual (argon arc welding machine) combined with DC welding machine, overall NM400 wear-resistant plate welding layer: welding rod φ3.2mm, φ4.0mm, welding materials: E5015 and J857Cr

[0061] 2) Heating device: Preheating: Oxygen-acetylene flame preheating, post-weld heat treatment: electric heating

[0062] 3) Auxiliary facilities: angle grinder, file, hammer, flat shovel, mask, sample, thermometer, magnifying glass, thermal insulation cotton

[0063] 4) Welding material: NM400 wear-resistant plate

[0064] 5) Requirements for surfacing welding before welding: Clean the surface of the groove, such as water, paint, rust, oil, welding slag, etc. Do not strike the arc directly on the groove surface. Use an arc striker plate. Preheat the oxyacetylene flame to 100-130℃ before welding.

[0065] 6) Welding position: single-sided U-groove, vertical welding

[0066] 7) Welding requirements: All welding layers must be free of any welding defects and fused to the base material

[0067] Welding process parameters

[0068]

[0069] The specific operation process is as follows:

[0070] a) By Figure 1 The U-shaped trough shown in the figure has a cracked weld. In order to ensure the welding quality, especially the online welding of NM400 wear-resistant plate, reduce the heat input and adopt a faster welding speed, short arc welding, and no large lateral swing, a single-sided U-shaped groove is designed and cut at the crack of the whole plate by a manual angle grinder (such as Figure 3 As shown in A), in order to prevent cracks and other defects, clean the surface of the groove, including water, paint, rust, oil, welding slag, etc., and preheat with an oxygen-acetylene flame to 100-130°C 50-100mm on both sides of the groove. Since the U-shaped trough body is made of NM400 with a large carbon equivalent, large thickness, and high tensile strength, a temperature gun must be used to verify the temperature on both sides of the weld. After the temperature is reached, the HT400D digitally controlled inverter manual (argon arc welding machine) combined with the DC welding machine is used, and the E5015 electrode φ3.2mm is used to start the bottom welding with an arc starter plate.

[0071] b) If Figure 3 As shown in the figure, the bottom layer 1 is welded in a vertical welding operation, with a vertical angle of 60 to 75 degrees. The welding rod is moved in a slightly smaller crescent shape and in a short arc operation. When welding, the two sides pause slowly and the middle welding rod transitions quickly, which is conducive to the fusion of the parent material. After the bottom layer weld is completed, hammering is performed on the surface immediately to eliminate welding stress and control the interlayer temperature to be not less than 100 degrees. After confirming that there are no welding defects, the same process is carried out as shown in the figure. Figure 3 The welding of the filling layer 2 shown in the figure is changed to a regular triangle. Figure 3 The cover layer 3 shown is welded with high-strength steel electrode J857Cr. After ensuring sufficient interlayer temperature, a small crescent-shaped electrode movement method is adopted, and the vertical angle of the electrode is 85 to 90 degrees. The cover layer must be higher than the base material to facilitate manual grinding and smooth transition with the base material.

[0072] c) After the high-temperature weld is completed, a local heating furnace at 500-600°C is used to eliminate stress in the fixed heating fixture of the designed structural component. After 1 hour of horizontal temperature, the component is slowly cooled at 150-170°C and wrapped with insulation cotton before cooling to room temperature. The weld is then tested by UT and MT penetrant testing to ensure there are no cracks or pores. The weld is then precisely ground with a manual angle grinder to achieve a smooth transition between the weld and the U-shaped trough base material. The component is then compared with a previously produced sample to restore the tolerance size and put into use. After a period of operation, the mechanical performance effect is achieved.

[0073] 1) The present invention adopts arc welding in combination with working conditions, selects low-strength E5015 welding rods for transition and filling and high-strength steel welding rods J857Cr for covering, realizes on-site heating, and the temperature control and insulation capabilities meet the requirements of the welding process;

[0074] 2) The present invention adopts a simple structural member to fix the heating fixture and adopts a rigid fixing method to effectively prevent the local heat treatment process after welding.

[0075] 3) The present invention has low investment cost, convenient on-site operation and maintenance, and short repair time. The key is that after welding and repair, the large preheating section feeding U-shaped trough body and the metallurgically bonded welding layer are suitable for periodic use.

[0076] The present invention is not only safe and easy to operate, with stable welding quality and low investment cost, it meets the actual needs on site and has high work efficiency, but also greatly reduces maintenance costs, reduces downtime losses, and provides a guarantee for reasonable production. The welding repair of cracked wear-resistant plates on the U-shaped trough body of the preheating section feed of the electric furnace provides a scientific reference basis for the welding repair of other large wear-resistant plates.

[0077] The present invention is applicable to the field of repairing parts of various electric furnace equipment production. It has a novel structure, compact and reasonable configuration, low investment, small site occupation, low operation and maintenance costs, easy operation, and reliable operation. All relevant connections of the structural parts production tooling are welded and machined, with a simple structure, easy production and good stability.

[0078] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A crack welding device for a U-shaped trough body for feeding a preheating section of an electric furnace, comprising a U-shaped trough body (1), characterized in that: The U-shaped trough body (1) is composed of a trough body bottom wall (101), a trough body side wall (102), and a trough body upper edge (103); a lower fillet (104) is provided at the connection between the trough body side wall (102) and the trough body bottom wall (101); and an upper fillet (105) is provided at the connection between the trough body side wall (102) and the trough body upper edge (103); The surface of the trough side wall (102) is provided with a heating plate (8), and the outer side of the heating plate (8) is provided with a heating Z-shaped cover plate (3) and thermal insulation cotton (7), and the thermal insulation cotton (7) is filled in the gap between the heating Z-shaped cover plate (3) and the heating plate (8); The upper end of the heating Z-shaped cover plate (3) is overlapped on the surface of the upper edge (103) of the trough body, and the lower end of the heating Z-shaped cover plate (3) is closely attached to the bottom wall (101) of the trough body. The lower end of the heating Z-shaped cover plate (3) is also provided with a fixing screw (4) and a Z-shaped pressing plate (5), and the Z-shaped pressing plate (5) is fixed to the heating Z-shaped cover plate (3) by the fixing screw (4); The heating Z-shaped cover plate (3) is formed by mechanically pressing a 5 mm steel plate. The heating Z-shaped cover plate (3) is arranged on the outside of the thermal insulation cotton (7) and covers the outer surface of the lower fillet (104) and the upper fillet (105); The trough sidewall (102) is repaired by welding at intervals along the surface cracks to form weld seams (2).

2. The device for welding cracks in a U-shaped feeding trough in the upper preheating section of an electric furnace according to claim 1, characterized in that: The lower end surface of the heating Z-shaped cover plate (3) is fixed to the bottom wall (101) of the tank body via a fixing screw (4) and a Z-shaped pressing plate (5).

3. The device for welding cracks in a U-shaped feeding trough in the upper preheating section of an electric furnace according to claim 1, characterized in that: The fixing screw (4) is machined from a φ20 mm round bar, and the Z-shaped pressing plate (5) cooperates with the fixing screw (4) to press and fix the heated Z-shaped cover (3).

4. The device for welding cracks in a U-shaped feeding trough in the upper preheating section of an electric furnace according to claim 1, characterized in that: After the Z-shaped pressing plate (5) is pressed and fixed, the U-shaped trough body (1) is welded to form a second weld seam (6).

5. The process for welding cracks in a U-shaped feeding trough in a preheating section of an electric furnace according to claim 4, characterized in that: The steps are: Step 1: First, repair the cracks of the U-shaped trough (1) and complete the weld (2); Step 2: Install a heating plate (8) and thermal insulation cotton (7) on the outer surface of the lower fillet (104) and the upper fillet (105); Step 3: After the heating plate (8) completely covers the weld (2), a heating Z-shaped cover plate (3) is installed on the outside of the thermal insulation cotton (7) so that the heating Z-shaped cover plate (3) completely covers the lower fillet (104) and the upper fillet (105); Step 4: After heating the Z-shaped cover plate (3) and fixing its position, make its bottom surface contact horizontally with the bottom wall (101) of the U-shaped trough body (1); Step 5: Install the Z-shaped pressing plate (5) at the lower end of the heating Z-shaped cover (3), and use the fixing screw (4) to fix the Z-shaped pressing plate (5) and the heating Z-shaped cover (3) to prevent the heating plate (8) and the insulation cotton (7) from deviating from their positions during the heating process; Step 6: Finally, the connection between the Z-shaped pressing plate (5) and the bottom wall of the tank body (101) is fixed by welding to form a second weld (6).

6. The process for welding cracks in a U-shaped feeding trough in a preheating section of an electric furnace according to claim 5, characterized in that: The welding process route is: determine the cracking position of the U-shaped trough body - cut the single-sided U groove - preheat - weld the bottom layer with low-strength welding materials - hammer the weld surface - confirm the defect - control the interlayer temperature - weld the filling layer with low-strength welding materials - hammer the weld surface - confirm the defect - weld the cover with high-strength welding rods - confirm the defect - post-weld heat treatment - manual grinding - inspection and acceptance - delivery for use.

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