Fusion welding method of stainless steel pipe and brass pipe in medium pipeline of steel billet flame cleaning machine

Abstract

The present invention discloses a method for fusion welding of stainless steel pipes and brass pipes in a medium pipeline of a steel billet flame cleaning machine, belongs to the field of welding technology, and is suitable for welding and repairing dissimilar pipes. The method is: first clean each connection 3, then flame preheat the brass welding surface and apply silver brazing powder on the heated surface, then cool to about 100°C and weld the bottom layer, grind the bottom layer weld with an angle grinder and confirm that there are no defects, apply silver brazing powder on the bottom layer surface of the weld, cool to about 100°C, and then perform filling and cover layer welding in sequence, grind the weld with an angle grinder after the surfacing is completed and confirm that there are no defects, and then deliver it for use after passing the water pressure test. The present invention is not only safe and easy to operate, has stable welding quality, and has low investment costs, meets actual on-site needs, has high work efficiency, but also greatly reduces maintenance costs, reduces downtime losses, provides a guarantee for reasonable production, and provides a scientific reference basis for other dissimilar welding repairs.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and relates to a fusion welding method for a stainless steel pipe and a brass pipe in a medium pipeline of a steel billet flame cleaning machine, and is suitable for welding dissimilar pipelines. Background Art

[0002] The working principle of the billet flame cleaning machine is as follows: the burners arranged around the billet are closed and hold the four sides of the billet. The billet is moved to the cleaning position near the end for preheating through the control instructions of the flame cleaning machine. When the preheating is completed, the cleaning cycle is started, and the billet is transported according to the cleaning speed requirements. The burner is closed again to contact the billet surface. The oxygen and combustible gas in the medium pipe ejected from the burner melt a small fixed area of ​​the slab, and then this area is oxidized and cleaned at the set speed.

[0003] like Figure 1 and Figure 2 As shown, the oxygen and combustible gases in the media pipeline of the billet flame cleaning machine are transported through the connection of multiple stainless steel pipes 1 and brass pipes 2 within a closed box. The joints 3 of each stainless steel pipe 1 and brass pipe 2 are first tightened by threading and then brazed. If gas leaks from each joint 3 and accumulates to a certain concentration, an explosion will occur. Over the years, as the equipment has aged, the sealing of the entire connecting pipeline has gradually failed to meet the original design requirements. During the long-term high-temperature billet oxidation cleaning production process, a large amount of combustion products often appear inside the closed pipeline, causing fires. This directly melts the brazed joints with lower melting points, causing leaks and explosions, leading to production suspension. If the joints are repaired, the following problems often arise: 1. If all are dismantled and sent to the manufacturer to be sealed by brazing the original stainless steel and brass pipe joints, it will not only take a long time, but the overall equipment currently does not meet the original design sealing standards, and similar accidents may occur; 2. High-temperature glue is used to seal the stainless steel and brass pipe joints. Due to the sealing factors on the outside of the connecting pipes, long-term exposure to high-temperature production will cause the high-temperature glue at the pipe joints to melt and leak, and thus fail to achieve the desired effect. Therefore, it is necessary to design a fusion welding method for connecting stainless steel and brass pipes on a billet flame cleaning machine, and to ensure that the medium pipeline stainless steel pipes and brass pipes meet the following requirements after fusion welding: 1. It complies with the existing overall equipment status and can be exposed to high temperatures for long periods of production; 2. It has low investment costs, convenient on-site operation and maintenance, and short repair time; 3. It is safe and reliable for periodic use. Summary of the Invention

[0004] Aiming at the problem of gas leakage at the connection between the stainless steel pipe and the brass pipe in the medium pipeline of the steel billet flame scarfing machine in the background art, the present invention provides a fusion welding method for the stainless steel pipe and the brass pipe in the medium pipeline of the steel billet flame scarfing machine.

[0005] The technical solution of the present invention to solve the technical problem is as follows:

[0006] The present invention provides a method for fusion welding stainless steel pipes and brass pipes in a medium pipeline of a steel billet flame scarfing machine. The medium pipeline includes a plurality of stainless steel pipe fittings and brass pipe fittings that are threadedly connected to each other. The method is characterized in that the connection between the stainless steel pipe fittings and the brass pipe fittings is fusion welded and sealed. The specific steps are as follows:

[0007] Step 1: Preparation before welding;

[0008] 1.1) Welding equipment: DC welding machine with digital control inverter manual welding and argon arc welding, welding materials are T1 pure copper wire and silver brazing powder;

[0009] 1.2) Heating device: heating gun;

[0010] 1.3) Auxiliary facilities: angle grinder, file, hammer, flat shovel, mask, sample, thermometer, magnifying glass and thermal insulation cotton;

[0011] 1.4) Welding materials: stainless steel pipe fittings, brass pipe fittings;

[0012] 1.5) Requirements for surfacing before welding: Use a manual angle grinder to clean the worn surface to remove rust, grease and moisture;

[0013] 1.6) Welding position: vertical fillet weld;

[0014] 1.7) Welding requirements: All weld layers must be free of any welding defects and fused to the parent material;

[0015] 1.8) Welding process parameters: Welding parameters are determined based on welding equipment, welding materials, weldment materials and welding requirements;

[0016] Step 2: Welding implementation;

[0017] First, after the stainless steel pipes and brass pipes are threaded and fixed, the joints of the stainless steel pipes and brass pipes are cleaned with a manual angle grinder. Then, digitally controlled inverter manual welding and argon arc welding are combined with a DC welding machine for welding. The brass pipes to be welded at each joint are preheated to the first set temperature with an oxygen-acetylene flame, coated with silver brazing powder, and then cooled to the second set temperature. Then, manual argon arc welding is used to weld the bottom layer of each joint with T1 pure copper wire. The bottom layer is welded quickly with narrow channels. The gun is tilted toward the side of the brass pipe; after the bottom layer welding is completed, the weld is ground with an angle grinder and confirmed to be free of welding defects, and then the interlayer temperature is controlled before filling and covering layer welding is performed. Silver brazing powder is applied to the surface of the bottom layer weld at each connection and cooled to the second set temperature. Then, manual argon arc welding is used with T1 pure copper welding wire for narrow channel rapid welding. During welding, the welding gun is also tilted toward the side of the brass pipe. After the filling and covering layer welding is completed, the weld is ground with an angle grinder and confirmed to be free of defects. Then, a water pressure test is performed and qualified, and the tolerance size is restored.

[0018] Furthermore, the welding equipment is a DC welding machine of model HT400D or HT500D that combines digitally controlled inverter-type manual welding and argon arc welding.

[0019] Furthermore, the heating device is a H01-20 heating gun.

[0020] Furthermore, the range of the first set temperature is 200±5°C, the range of the second set temperature is 100±5°C, and the range of the interlayer temperature is 100±5°C.

[0021] Furthermore, when welding the bottom layer, a Φ2.0mm T1 pure copper welding wire is used, the welding current is 70-90A, the arc voltage is 21±1V, and the welding speed is 15±1cm / min; when welding the filling layer, a Φ2.0mm T1 pure copper welding wire is used, the welding current is 80-100A, the arc voltage is 22±1V, and the welding speed is 15±1cm / min; when welding the cover layer, a Φ3.0mm T1 pure copper welding wire is used, the welding current is 90-120A, the arc voltage is 24±1V, and the welding speed is 17±1cm / min.

[0022] Compared with the prior art, the fusion welding method for stainless steel pipes and brass pipes in the medium pipeline of a steel billet flame scraping machine described in the present invention is not only safe and easy to operate, has stable welding quality, and has low investment costs, but also meets actual on-site needs and has high work efficiency. It also greatly reduces maintenance costs and reduces downtime losses, providing a guarantee for reasonable production organization. In addition, the fusion welding method for connecting stainless steel pipes and brass pipes on a steel billet flame scraping machine also provides a scientific reference basis for other dissimilar welding repairs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the medium pipeline of the billet flame cleaning machine;

[0024] Figure 2 This is a schematic photo showing the wear of the medium pipe in the billet flame scarfing machine;

[0025] In the figure: 1. Stainless steel pipe fittings; 2. Brass pipe fittings; 3. Connections. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present disclosure belongs. The terms "upper", "lower", "left", "right", "front", "back", etc. used in the patent application specification and claims of this disclosure are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship also changes accordingly; "connected" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The parts not described in detail in the present invention are all common knowledge to those skilled in the art.

[0027] like Figure 1-2 As shown, the present invention discloses a method for welding stainless steel and brass pipes in a steel billet flame scrapping machine medium pipeline. The medium pipeline comprises a plurality of stainless steel pipe fittings 1 and brass pipe fittings 2 that are threadedly connected to each other. If a leak occurs at the connection 3 between each stainless steel pipe fitting 1 and brass pipe fitting 2, an explosion may occur. The present invention completes the repair of the medium pipeline by welding and sealing the connection 3 between the stainless steel pipe fitting 1 and the brass pipe fitting 2. The specific steps are as follows:

[0028] Step 1: Preparation before welding;

[0029] 1.1) Welding equipment: Model HT400D or HT500D digitally controlled inverter DC welding machine for combined manual welding and argon arc welding, welding materials are T1 pure copper wire and silver brazing powder;

[0030] 1.2) Heating device: H01-20 heating gun preheating;

[0031] 1.3) Auxiliary facilities: angle grinder, file, hammer, flat shovel, mask, sample, thermometer, magnifying glass and thermal insulation cotton;

[0032] 1.4) Welding materials: stainless steel pipe fittings, brass pipe fittings;

[0033] 1.5) Requirements for surfacing before welding: Use a manual angle grinder to clean the worn surface to remove rust, grease and moisture;

[0034] 1.6) Welding position: vertical fillet weld;

[0035] 1.7) Welding requirements: All weld layers must be free of any welding defects and fused to the parent material;

[0036] 1.8) Welding process parameters: Welding parameters are determined based on welding equipment, welding materials, weldment materials and welding requirements;

[0037] Welding process parameters

[0038]

[0039] Step 2: Welding implementation;

[0040] Welding process route: Clean each joint 3 times - Preheat the brass welding surface with a flame - Apply silver brazing powder to the heated surface - Cool to about 100° - Weld the base layer - Grind the weld with an angle grinder and confirm any defects - Apply silver brazing powder to the base surface of the weld - Cool to about 100° - Fill and cover the surface - Grind the weld with an angle grinder and confirm any defects - Hydrostatic test - Delivery for use. Details are as follows:

[0041] First, after the stainless steel pipe fittings 1 and the brass pipe fittings 2 are threaded and fixed, the joints 3 of the stainless steel pipe fittings 1 and the brass pipe fittings 2 are cleaned with a manual angle grinder to remove rust, grease and moisture on the worn surface. Then, the bottom layer, the filling layer and the cover layer are welded respectively by combining digitally controlled inverter manual welding and argon arc welding with a DC welding machine. The surface of the brass pipe fitting 2 to be welded at each joint 3 is preheated to a first set temperature of about 200°C using an H01-20 heating gun oxygen·acetylene flame, then coated with silver brazing powder and cooled to a second set temperature of about 100°C. Then, the bottom layer of each joint 3 is welded using a Φ2.0mm T1 pure copper wire using a narrow channel and fast Speed ​​welding, during welding, the manual argon arc welding torch is biased towards the brass pipe fitting 2 side to prevent the stainless steel side from overburning and causing intergranular corrosion to damage the internal structure performance and produce crack defects; after the bottom layer welding is completed, the weld is ground with an angle grinder and confirmed to be free of welding defects, and the interlayer temperature is controlled at about 100°C before filling and covering layer welding is carried out, and silver brazing powder is applied to the surface of the bottom weld of each connection 3 and cooled to a second set temperature of about 100°C, and then narrow and fast welding is carried out using T1 pure copper wire using manual argon arc welding. During welding, the welding torch is also biased towards the brass pipe fitting 2 side, and after the filling and covering layer welding is completed, the weld is ground with an angle grinder and confirmed to be free of defects, and then a water pressure test is carried out and qualified before the use of tolerance size is restored.

[0042] After the fusion welding method of the stainless steel pipe and the brass pipe in the medium pipeline of the steel billet flame scarfing machine described in the present invention was implemented, the welding was not only very successful, but also passed the high-temperature resistance inspection and acceptance, fully meeting the current existing operating requirements of the overall steel billet flame scarfing machine assembly. After delivery and use, the mechanical performance effect can be achieved through periodic operation.

Claims

1. A method for fusion welding a stainless steel pipe and a brass pipe in a medium pipeline of a steel billet flame cleaning machine, wherein the medium pipeline comprises a plurality of stainless steel pipe fittings (1) and brass pipe fittings (2) threadedly connected to each other, characterized in that: The connection (3) between the stainless steel pipe fitting (1) and the brass pipe fitting (2) is sealed by welding. The specific steps are as follows: Step 1: Preparation before welding; 1.1) Welding equipment: DC welding machine with digitally controlled inverter manual welding and argon arc welding, welding materials are T1 pure copper wire and silver brazing powder; 1.2) Heating device: heating gun; 1.3) Auxiliary facilities: angle grinder, file, hammer, flat shovel, mask, sample, thermometer, magnifying glass and thermal insulation cotton; 1.4) Welding materials: stainless steel pipe fittings, brass pipe fittings; 1.5) Requirements for surfacing before welding: Use a manual angle grinder to clean the worn surface to remove rust, grease and moisture; 1.6) Welding position: vertical fillet weld; 1.7) Welding requirements: All weld layers must be free of any welding defects and fused to the parent material; 1.8) Welding process parameters: Welding parameters are determined based on welding equipment, welding materials, weldment materials and welding requirements; Step 2: Welding implementation; First, after the stainless steel pipe fittings (1) and the brass pipe fittings (2) are threaded and fixed, the joints (3) of the stainless steel pipe fittings (1) and the brass pipe fittings (2) are cleaned by a manual angle grinder, and then the welding is carried out by combining digitally controlled inverter manual welding and argon arc welding with a DC welding machine; the brass pipe fittings (2) to be welded at each joint (3) are preheated to a first set temperature by an oxygen-acetylene flame, and then silver brazing powder is applied and cooled to a second set temperature, and then the bottom layer of each joint (3) is welded by manual argon arc welding using T1 pure copper wire, and the bottom layer is welded by a narrow channel fast welding. Welding, when welding, the welding gun is tilted toward the brass pipe (2) side; after the bottom layer welding is completed, the weld is ground with an angle grinder and confirmed to be free of welding defects, and then the temperature between layers is controlled before welding the filling layer and the cover layer. Silver brazing powder is applied to the surface of the bottom layer weld at each joint (3) and cooled to the second set temperature. Then, manual argon arc welding is used to perform narrow channel fast welding using T1 pure copper wire. When welding, the welding gun is also tilted toward the brass pipe (2) side. After the filling layer and the cover layer are welded, the weld is ground with an angle grinder and confirmed to be free of defects. Then, a water pressure test is performed and qualified, and the tolerance size is restored; The range of the first set temperature is 200±5°C, the range of the second set temperature is 100±5°C, and the range of the interlayer temperature is 100±5°C.

2. The method for fusion welding a stainless steel tube and a brass tube in a medium pipeline of a steel billet scarfing machine according to claim 1, characterized in that: The welding equipment is a DC welding machine of model HT400D or HT500D that combines digitally controlled inverter-type manual welding and argon arc welding.

3. The method for fusion welding a stainless steel tube and a brass tube in a medium pipeline of a steel billet scarfing machine according to claim 1, characterized in that: The heating device is a H01-20 heating gun.

4. The method for fusion welding a stainless steel tube and a brass tube in a medium pipeline of a steel billet scarfing machine according to claim 1, characterized in that: When welding the bottom layer, a Φ2.0mm T1 pure copper welding wire is used, the welding current is 70-90A, the arc voltage is 21±1V, and the welding speed is 15±1 cm / min; when welding the filling layer, a Φ2.0mm T1 pure copper welding wire is used, the welding current is 80-100A, the arc voltage is 22±1V, and the welding speed is 15±1cm / min; when welding the cover layer, a Φ3.0mm T1 pure copper welding wire is used, the welding current is 90-120A, the arc voltage is 24±1V, and the welding speed is 17±1cm / min.

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