A welding method for silver-steel composite plate

Abstract

The present invention discloses a welding method for a silver-steel composite plate, comprising: processing the weld groove of the silver-steel composite plate; welding the base layer of the silver-steel composite plate: aligning the grooves of the silver-steel composite plate to ensure that the silver layer side is flush, and leaving a gap of 2 to 4 mm between the silver-steel composite plate groove joint surfaces; sequentially welding the base layer, the filling layer, and the cap layer of the silver-steel composite plate; grinding the back of the base layer weld seam and performing non-destructive testing; welding the silver layer of the silver-steel composite plate; performing non-destructive testing on the silver layer of the silver-steel composite plate, and ensuring that the silver layer weld passes the 100% PT qualification level I test according to NB / T47013.5-2015. This method ensures that the base layer welding quality of the silver-steel composite plate meets the equipment design requirements, ensuring safe use of the equipment, and also solves the welding technical problem of the difficulty and poor welding quality of the silver layer of the silver-steel composite plate.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material welding and relates to a welding method for metal composite materials, in particular to a welding method for silver-steel composite plates, which is suitable for welding materials of pressure vessel equipment with a silver layer thickness of 0.5 to 3 mm and a base layer thickness of ≥6 mm. Background Art

[0002] In the polysilicon production industry, polysilicon production takes place in a reduction furnace, where raw materials undergo a high-temperature reaction to form silicon rods. The product quality of polysilicon is primarily related to the process performance of the reduction furnace, while the purity, quality, and energy cost of polysilicon are primarily affected by the materials used in the reduction furnace. Currently, domestic reduction furnaces are primarily made of stainless steel and nickel-steel composite plates, with silver-steel composite plates also being used. However, reduction furnaces using silver-steel composite plates are still in the experimental stage due to manufacturing difficulties and material costs.

[0003] Silver has high purity, excellent thermal conductivity, and high heat reflectivity. Silver-steel composite panels not only reduce equipment and material costs while retaining silver's excellent properties, making them an ideal material for reduction furnaces. Reduction furnaces made of silver-steel composite panels are used to produce electronic-grade polysilicon, increasing its purity and reducing energy consumption.

[0004] Due to the excellent thermal conductivity of silver, it is extremely difficult to weld silver, especially large-area silver-steel composite plates. It is almost impossible to weld silver to silver, the silver layer welds cannot pass non-destructive testing, and the welding quality cannot meet the use requirements of pressure vessel equipment.

[0005] Germany was an early adopter of silver-steel composite plate reduction furnaces. Their silver layer welding method involves melting silver using argon arc welding and then coating it on the substrate surface, without requiring the substrate to be melted. The silver weld is then hammered, leveraging the silver's ductility and formability to coat the substrate. However, as the equipment expands and contracts over time, delamination and shedding can occur at the silver weld. Summary of the Invention

[0006] The object of the present invention is to provide a method for welding silver-steel composite plates, which uses argon arc welding to weld silver-steel composite plates in an energy-saving and efficient manner, so that the welding quality meets the manufacturing requirements of pressure vessel equipment.

[0007] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0008] A method for welding a silver-steel composite plate comprises the following steps:

[0009] Step (1), processing of the welding groove of the silver steel composite plate;

[0010] Step (2), welding of the base layer of the silver-steel composite plate: align the grooves of the silver-steel composite plate to ensure that the silver layer side is flush and the gap between the groove joints of the silver-steel composite plate is 2 to 4 mm; sequentially perform the base layer welding of the silver-steel composite plate, the base layer filling layer welding of the silver-steel composite plate, and the base layer cover layer welding of the silver-steel composite plate;

[0011] Step (3), grinding and non-destructive testing of the back side of the weld seam of the base layer of the silver steel composite plate;

[0012] Step (4), welding the silver layer of the silver-steel composite plate: using GTAW welding, welding one weld, the thickness of the weld is not less than the surface of the silver base material; the shielding gas used by the welding gun is a mixed gas of helium and argon, and the volume fraction of helium is controlled at 70-75%;

[0013] Step (5): performing nondestructive testing of the silver layer of the silver-steel composite plate.

[0014] The thickness of the silver layer of the silver-steel composite plate is 0.5-3 mm, and the thickness of the base layer is ≥6 mm.

[0015] In step (1), the processing of the welding groove of the silver-steel composite plate is as follows: the welding end of the base layer of the silver-steel composite plate is processed into an outer groove, and the single-side groove angle is 25 to 30 degrees; the welding end of the silver layer of the silver-steel composite plate is processed into an outer groove, and the single-side groove angle is 15 to 20 degrees; the grooves of the base layer and the silver layer are processed to the bonding surface, and the blunt edge of the bonding surface is left with 0 to 1 mm.

[0016] In step (2), the base layer of the silver-steel composite plate is welded by GTAW welding, and a total of 2 welds are welded. The welding process parameters of each weld are as follows: the welding current is 160-180A, the welding voltage is 12-14V, the welding speed is controlled to be 11-13cm / min, the shielding gas used by the welding gun is argon, and the flow rate of the shielding gas is 10-15L / min; when welding the first weld, the back of the weld is protected, the shielding gas is argon, and the flow rate of the shielding gas is 15-20L / min; when welding the second weld, the back of the weld does not need to be protected.

[0017] The argon gas is 99.99% argon gas.

[0018] When welding the base layer of the silver-steel composite plate, select the welding wire according to the material grade of the silver-steel composite plate. Specifically, when the material grade of the silver-steel composite plate base is 316L, choose ER316L welding wire; the specification of the welding wire is generally φ2.5mm.

[0019] If GTAW welding is not used for the base layer, back-ground cleaning is required after welding. Back-ground cleaning can contaminate or even damage the surface of the silver composite layer. Furthermore, back-ground cleaning widens the silver groove, increasing the amount of silver welded. This increases silver consumption and makes welding more difficult. Furthermore, the weld seam of this silver composite layer will not meet the quality requirements for long-term wear resistance. During base layer welding, due to the high thermal conductivity of silver, the weld solidifies quickly, resulting in a thin weld seam in the first layer. Using other welding methods for the second layer can burn through the first layer, compromising weld quality and necessitating new back-ground cleaning.

[0020] When the thickness of the base layer of the silver-steel composite plate is 6mm≤≤10mm, SMAW welding is selected for both the base layer, filling layer, and cover layer. When the thickness of the base layer of the silver-steel composite plate is greater than 10mm, SMAW welding or SAW welding is selected for the base layer, filling layer, and SAW welding is selected for the base layer and cover layer.

[0021] The welding of the base filling layer of the silver-steel composite plate adopts SMAW welding or SAW welding; the welding rod for SMAW welding is selected according to the grade of the base material of the silver-steel composite plate, the specification of the welding rod is φ4.0mm, and the process parameters of SMAW welding are: welding current is 145~170A, welding voltage is 22~25V, and the controlled welding speed is 12~14cm / min; the welding wire for SAW welding is selected according to the grade of the base material of the silver-steel composite plate, the specification of the welding wire is φ3.2mm, and the process parameters of SAW welding are: welding current is 450~550A, welding voltage is 26~32V, and the controlled welding speed is 40~45cm / min.

[0022] Specifically, when welding the base filler layer of a silver-steel composite plate, if the base material is 316L, the SMAW welding rod should be ER316L with a diameter of 4.0 mm; the SAW welding wire should be ER316L with a diameter of 3.2 mm. For SAW welding, the flux should be matched to the wire. Specifically, when using ER316L as the wire, the flux should be SJ601.

[0023] The base and cover layers of the silver-steel composite plate are welded by SMAW or SAW welding; the specification of the SMAW welding rod is φ4.0mm, and the process parameters of SMAW welding are: welding current is 130~160A, welding voltage is 22~25V, and the controlled welding speed is 14~16cm / min; the specification of the SAW welding wire is φ3.2mm, and the process parameters of SAW welding are: welding current is 380~450A, welding voltage is 28~35V, and the controlled welding speed is 35~40cm / min.

[0024] When welding the base and cover layers of a silver-steel composite plate, select the welding wire based on the base material grade of the silver-steel composite plate. Specifically, when the base material grade of the silver-steel composite plate is 316L, select ER316L as the SAW welding wire with a specification of φ3.2mm and use SJ601 as the flux.

[0025] In step (3), the back of the weld of the base layer of the silver-steel composite plate is ground as follows: the silver layer side of the back of the weld of the base layer of the silver-steel composite plate is ground using a grinding wheel grinder, the surface of the root weld is ground to completely remove the excess height, the weld is ground flat, and the grinding depth is controlled to be 0.1 to 0.2 mm lower than the silver layer of the bonding surface of the silver-steel composite plate, and the silver on the weld surface is completely removed.

[0026] The non-destructive testing is as follows: the back weld of the base layer weld of the silver steel composite plate is qualified according to NB / T47013.5-2015100% PT qualification level I test, the weld (referring to the weld of the base layer, filling layer and cover layer) is qualified according to NB / T47013.2-2015100% RT, qualification level II, technical level AB test, and the non-destructive testing of the base weld is in accordance with NB / T47013.2-2015RT, qualification level II, technical level AB test, which can ensure 100% qualification.

[0027] In step (4), the silver layer of the silver-steel composite plate is welded by GTAW welding, and one weld is welded. Considering that the performance of the weld cannot be lower than that of the base material, the silver layer will be worn during the use of the equipment. If the weld is lower than the base material, it will affect the service life of the equipment. Therefore, the thickness of the weld is not lower than the surface of the silver base material; GTAW welding uses silver welding wire, and the specification of the silver welding wire is φ2.4mm; the process parameters of GTAW welding are: welding current is 180-200A, welding voltage is 13-15V, and welding speed is controlled to be 11-13cm / min; the shielding gas used by the welding gun is a mixed gas of helium and argon, the volume fraction of helium is controlled to be 70-75%, and the flow rate of the shielding gas is 8-10 / min. The present invention uses a mixed gas of argon and helium as the shielding gas of the welding gun when welding the silver layer. If the proportion of helium in the shielding gas is less than 70%, the temperature of the argon arc welding arc will be too low, and the molten pool formed by the silver welding wire will cool rapidly, resulting in the molten pool formed by the silver being unable to fuse with the base material and the silver base material, forming a cold weld. At this point, the silver weld may peel or form a lack of fusion defect during nondestructive testing. Even if fusion is achieved, the bond strength between the weld and the base material will be weakened, leading to delamination during use. If the helium ratio in the shielding gas exceeds 75%, the heat of the TIG arc will be too high during welding. First, the tungsten electrode in the TIG arc weld will overheat and burn severely. The burned tungsten electrode will resolidify as vapor in the silver weld, resulting in a tungsten inclusion defect. This defect affects the performance of the silver weld and can also seep into the material during use, affecting its purity. Second, the base metal is subjected to high heat during welding, resulting in excessive base penetration, slow silver solidification, and excessive stirring when the base metal and silver wire are combined. This can cause the base weld metal to overflow onto the silver surface, damaging the silver weld and failing to meet the surface performance requirements.

[0028] The purity of the silver welding wire is 99.99%.

[0029] The non-destructive testing of the silver layer of the silver-steel composite plate requires that the silver layer weld pass the NB / T47013.5-2015 100% PT qualified level I test.

[0030] Beneficial effects of the present invention:

[0031] The present invention controls, processes and detects the welding process of the base layer of the silver-steel composite plate, thereby ensuring the mechanical properties of the weld of the silver-steel composite plate and the safety of the equipment; and also meets the technical requirements of silver layer welding.

[0032] Silver is extremely difficult to weld due to its excellent thermal conductivity, especially for large-area silver-steel composite plates. It is almost impossible to weld silver to silver, and the silver layer welds cannot pass non-destructive testing, and the welding quality cannot meet the requirements for use in pressure vessel equipment. The present invention utilizes the poor thermal conductivity of the base layer weld to maintain high-temperature characteristics for a short period of time. The silver layer welds can be formed in one step and meet the requirements of non-destructive testing. The silver layer welds can be 100% qualified according to the NB / T47013.5-2015PT Grade I test, ensuring that the silver layer welds will not fall off in later use. At the same time, the silver layer welding also avoids the need to heat the entire equipment to ensure the silver melts, thereby reducing energy and consumption.

[0033] When welding silver layers, a mixed gas with a specific ratio is used. On the one hand, it can increase the heat of the arc, which helps to melt the silver welding wire and silver base material during silver welding. On the other hand, the heat of the arc should be controlled not to be too high to avoid the tungsten electrode evaporating due to excessive arc heat, which will gather into small particles in the molten pool, resulting in tungsten inclusion defects in the silver weld, affecting the welding quality.

[0034] In summary, the welding method of the present invention is simple to implement, efficient and can effectively reduce costs and energy consumption. It can not only ensure the base welding quality of the silver-steel composite plate, meet the equipment design requirements, and meet the safe use of the equipment, but also solve the technical problems of difficulty in welding the silver layer of the silver-steel composite plate and the inability to guarantee welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of groove processing of silver-steel composite plate in Example 1.

[0036] Figure 2 This is a distribution diagram of the welding layer of the silver-steel composite plate in Example 1.

[0037] Figure 3 This is the structural diagram of the base layer of the silver-steel composite plate after welding in Example 1.

[0038] In the figure, 1-silver layer of silver-steel composite plate, 2-silver-steel composite plate base layer, 3-silver-steel composite plate base layer, 4-silver-steel composite plate base layer filling layer, 5-silver-steel composite plate base layer cover layer, 6-silver-steel composite plate silver layer welding layer. DETAILED DESCRIPTION

[0039] In order to make the technical solution of the present invention more clear and specific to those skilled in the art, the present invention is further described in detail below with reference to embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0040] Example 1

[0041] A silver-steel composite plate, wherein the silver layer is made of silver (brand: Ag1), the base layer is made of stainless steel plate (brand: 316L), the silver layer of the silver-steel composite plate has a thickness of 2mm, and the base layer has a thickness of 20mm.

[0042] according to Figure 1 、 Figure 2 As shown, welding the silver-steel composite plate includes the following steps:

[0043] Step (1) machining the welding groove of the silver-steel composite plate by mechanical processing, processing the base layer of the silver-steel composite plate into an outer groove with a single-side groove angle of 25°, and processing the silver layer of the silver-steel composite plate into an outer groove with a single-side groove angle of 20°; the grooves on both sides are processed to the bonding surface, and no blunt edge is left on the bonding surface;

[0044] Step (2), base welding of silver steel composite plate material:

[0045] Assemble the grooves of the silver-steel composite plate to ensure that the silver layer side is flush and leave a gap of 3mm between the joint surfaces of the grooves. Then weld the base layer, filler layer and cover layer of the silver-steel composite plate in sequence.

[0046] The base layer of the silver steel composite plate was welded using GTAW welding with ER316L wire of φ2.5mm. Two welds were welded in total. The welding process parameters for each weld were set as follows: welding current 180A, welding voltage 13V, controlled welding speed 11cm / min, and the shielding gas used by the welding gun was 99.99% argon at a gas flow rate of 15L / min. The back of the weld needed to be protected when welding the first weld, with the shielding gas being 99.99% argon at a shielding gas flow rate of 20L / min. The back of the weld did not need to be protected when welding the second weld.

[0047] The base filling layer of the silver steel composite plate is welded by SAW welding, the welding wire is ER316L, the specification is φ3.2mm, the flux is SJ601, the welding process parameters are set as follows: welding current 480A, welding voltage 30V, and controlled welding speed 40cm / min;

[0048] The base and cover layers of the silver steel composite plate are welded by SAW welding, with the welding wire ER316L, specification φ3.2mm, and flux SJ601. The welding process parameters are set as follows: welding current 400A, welding voltage 35V, and controlled welding speed 40cm / min.

[0049] Step (3), the structure after welding of the silver steel composite plate base is as follows Figure 3 As shown in the figure, the back of the weld of the base layer of the Yingang composite plate was ground and non-destructively tested:

[0050] The silver layer on the back of the weld seam of the base layer of the silver-steel composite plate was ground using a grinding wheel grinder. The root weld surface was ground to completely remove the excess height and smooth the surface. The grinding depth was controlled to be 0.2mm below the bonding surface, and the silver on the weld surface was completely removed. The back weld of the base layer of the silver-steel composite plate passed the NB / T47013.5-2015 100% PT qualification level I test, and the overall weld passed the NB / T47013.2-2015 100% RT, qualification level II, technical level AB test.

[0051] Step (4), welding of the silver layer of the silver-steel composite plate material:

[0052] The silver layer of the silver-steel composite plate is welded using GTAW welding, with only one weld seam being welded to ensure a weld seam thickness of 2.5 mm (i.e., the silver layer weld layer). The welding process parameters are set as follows: welding current 180 A, welding voltage 14 V, welding speed control 13 cm / min, and the shielding gas used in the welding gun is a mixture of helium and argon (the volume fraction of helium is controlled at 70%), with a gas flow rate of 8 L / min.

[0053] Step (5), nondestructive testing of the silver layer weld of the silver-steel composite plate: the silver layer weld is tested and qualified according to NB / T47013.5-2015 100% PT qualified level I.

[0054] Welding silver-steel composite plates using the method of this embodiment ensures that the base welds of the silver-steel composite plates pass the NB / T47013.2-2015 100% RT, Qualification Level II, Technical Level AB test with 100% compliance, ensuring that the mechanical properties of the base welds of the equipment meet the requirements and the safe use of the equipment. It also ensures that the silver layer welds pass the NB / T47013.5-2015 100% PT Qualification Level I test with 100% compliance, ensuring that the silver layer welds achieve the surface properties of the base material and that the process performance of the equipment meets the design requirements.

Claims

1. A method for welding a silver-steel composite plate, characterized in that: The steps include: Step (1), processing the welding groove of the silver-steel composite plate: processing the welding end of the base layer of the silver-steel composite plate into an outer groove, with a single-side groove angle of 25 to 30 degrees; processing the welding end of the silver layer of the silver-steel composite plate into an outer groove, with a single-side groove angle of 15 to 20 degrees; the grooves of the base layer and the silver layer are processed to the bonding surface, and the blunt edge of the bonding surface is left at 0 to 1 mm; Step (2), welding of the silver-steel composite plate base: aligning the grooves of the silver-steel composite plate to ensure that the silver layer side is flush, and leaving a gap of 2 to 4 mm between the groove joint surfaces of the silver-steel composite plate; sequentially performing the base layer welding of the silver-steel composite plate base, the base filling layer welding of the silver-steel composite plate base, and the base cover layer welding of the silver-steel composite plate base; the base layer welding of the silver-steel composite plate base is performed by GTAW welding, and a total of 2 welds are welded. The welding process parameters of each weld are as follows: the welding current is 160 to 180 A, the welding voltage is 12 to 14 V, the welding speed is controlled to be 11 to 13 cm / min, the shielding gas used by the welding gun is argon, and the flow rate of the shielding gas is 10 to 15 L / min; when welding the first weld, the back of the weld is protected, the shielding gas is argon, and the flow rate of the shielding gas is 15 to 20 L / min; when welding the second weld, the back of the weld does not need to be protected; Step (3), grinding and non-destructive testing of the back side of the weld seam of the base layer of the silver steel composite plate; Step (4), welding of the silver layer of the silver-steel composite plate: GTAW welding is adopted, silver welding wire is used for GTAW welding, and one weld is welded, and the thickness of the weld is not less than the surface of the silver base material; the shielding gas used by the welding gun is a mixed gas of helium and argon, and the volume fraction of helium is controlled at 70-75%; the process parameters of GTAW welding are: welding current of 180-200A, welding voltage of 13-15V, welding speed controlled at 11-13cm / min; the flow rate of shielding gas is 8-10L / min; Step (5): performing nondestructive testing of the silver layer of the silver-steel composite plate.

2. The welding method of silver-steel composite plate according to claim 1, characterized in that: The thickness of the silver layer of the silver-steel composite plate is 0.5-3 mm, and the thickness of the base layer is ≥6 mm.

3. The welding method of silver-steel composite plate according to claim 1, characterized in that: In step (2), when the thickness of the base layer of the silver-steel composite plate is 6 mm ≤ thickness ≤ 10 mm, SMAW welding is selected for the welding of the base filling layer and the cover layer of the silver-steel composite plate; when the thickness of the base layer of the silver-steel composite plate is greater than 10 mm, SMAW welding or SAW welding is selected for the welding of the base filling layer of the silver-steel composite plate, and SAW welding is selected for the welding of the base cover layer of the silver-steel composite plate.

4. The welding method of silver-steel composite plate according to claim 1 or 3, characterized in that: In step (2), the silver-steel composite plate base filling layer is welded by SMAW welding or SAW welding; The specification of the SMAW welding electrode is φ4.0mm. The process parameters of SMAW welding are: welding current is 145~170A, welding voltage is 22~25V, and welding speed is controlled at 12~14cm / min; The specification of the SAW welding wire is φ3.2mm, and the process parameters of SAW welding are: welding current is 450~550A, welding voltage is 26~32V, and the controlled welding speed is 40~45cm / min.

5. The welding method of silver-steel composite plate according to claim 1 or 3, characterized in that: In step (2), the base layer and cover layer of the silver-steel composite plate are welded by SMAW or SAW welding; The specification of the SMAW welding electrode is φ4.0mm. The process parameters of SMAW welding are: welding current is 130~160A, welding voltage is 22~25V, and welding speed is controlled at 14~16cm / min; The specification of the SAW welding wire is φ3.2mm, and the process parameters of SAW welding are: welding current is 380~450A, welding voltage is 28~35V, and the controlled welding speed is 35~40cm / min.

6. The method for welding silver-steel composite plates according to claim 1, wherein: In step (3), the back of the weld of the base layer of the silver-steel composite plate is ground as follows: the silver layer side of the back of the weld of the base layer of the silver-steel composite plate is ground using a grinding wheel grinder, the surface of the root weld is ground to completely remove the excess height, the weld is ground flat, and the grinding depth is controlled to be 0.1 to 0.2 mm lower than the silver layer of the bonding surface of the silver-steel composite plate, and the silver on the weld surface is completely removed.

7. The welding method of silver-steel composite plate according to claim 1, characterized in that: In step (4), the specification of the silver solder wire is φ2.4 mm.

8. The method for welding silver-steel composite plates according to claim 1, wherein: In step (4), the non-destructive testing of the silver layer of the silver-steel composite plate requires that the silver layer weld pass the NB / T47013.5-2015 100% PT qualification level I test.

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