Welding method for rotor-grade titanium sponge circular reaction device

Abstract

The invention discloses a rotor-grade sponge titanium circular reaction device welding method in the technical field of titanium-containing stainless steel medium-thickness plate welding, which comprises the following steps: a welding material selection stage: matching welding materials and adjusting the carbon content and ferrite content according to high-temperature and high-pressure chlorine-containing working conditions; in the welding process evaluation stage, the X-shaped groove is determined as a target groove through finite element analysis, different heat inputs are set for welding, furnace tests are carried out, it is found that a fine grain zone is formed at a fusion line after circulation of an X-shaped groove test plate with moderate heat inputs, and therefore optimal process parameters are determined; in the product production and manufacturing stage, a welding material is customized, a target groove is formed, and welding is accurately controlled through a dynamic supervision system; and in a product use cycle verification stage, tracking service performance. Welding materials, grooves and heat input are optimized, the problem that key welding seams are prone to cracking is solved, the creep resistance and corrosion resistance of the welding seams are improved, and the service life of the device is prolonged.

Description

Technical Field

[0001] This invention relates to the field of welding technology for titanium-containing stainless steel medium-thick plates, and particularly to a welding method for a rotor-level sponge titanium circulating reactor. Background Technology

[0002] Rotor-type titanium sponge reactors operate under high-temperature, high-pressure cyclic conditions in environments with high chloride ion concentrations. These extreme operating environments demand that the weld metal in critical welds possess high-temperature resistance, creep resistance, and corrosion resistance. Currently operating reactors commonly exhibit a problem where, after several cyclic cycles, longitudinal and circumferential welds extend in width, and the corrosion rate of the weld metal is significantly higher than that of the base material, leading to regular cracks along the fusion line. This causes the titanium sponge reactor to enter its maintenance period prematurely, shortening the effective cycle time, impacting normal production line operations, wasting materials, and increasing production costs. Therefore, a welding process that can improve the quality and service life of reactor welds is urgently needed. Summary of the Invention

[0003] The technical task to be solved by the present invention is to provide a welding method for a rotor-level sponge titanium circulating reactor, so as to solve the problems of premature failure of key welds in the reactor and difficulty in maintenance in the prior art, and to provide equipment guarantee for the stable and orderly operation of the sponge titanium production line.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A welding method for a rotor-level titanium sponge circulating reactor includes the following steps: Step 1, Welding Material Selection Stage: The chemical composition of the titanium-containing stainless steel medium-thick plate base material used for the main body of the reaction device is retested, and the welding material model is matched according to the characteristics of the base material; In view of the high temperature, high pressure and chloride ion-containing service conditions of the reaction device, the chemical composition of the matched welding material is adjusted so that the adjusted welding material meets the chemical composition requirements of the target deposited metal. Step 2, Welding Procedure Qualification Stage: A finite element analysis model of the reaction device structure is established based on different bevel types to simulate the stress on the weld during use. The target bevel type is determined through comparison. Based on the determined target bevel type, product test plates are fabricated, and at least two sets of welding process parameters with different welding heat inputs are set for welding as the test group. The mechanical properties and metallographic structure of the welded test plates are tested, and the remaining material is fed into the furnace along with the reaction device materials for in-furnace testing. After several process cycles, the remaining material is removed and its mechanical properties and metallographic structure are re-examined. The optimal welding process parameters are determined by comprehensively comparing the changes in mechanical properties and metallographic structure. Step 3, Product Manufacturing Stage: Based on the chemical composition of the welding materials determined in Step 1, customize the welding materials; based on the target groove type determined in Step 2, cut grooves for the longitudinal and circumferential welds of the reaction device, and inspect the groove deviation value; input the optimal welding process parameters determined in Step 2 into the dynamic monitoring and control system of the welding equipment, weld the longitudinal and circumferential welds, and complete the manufacturing of the reaction device. Step 4, Product Use Cycle Verification Phase: Put the manufactured reaction device into production and use, track its periodic operation, until the reaction device is scrapped and eliminated.

[0006] Furthermore, in step one, the base material is a titanium-containing stainless steel medium-thick plate. Its chemical composition is retested according to GB / T713.7-2023 "Steel Plates and Strips for Pressure Equipment - Part 7: Stainless Steel and Heat-Resistant Steel", requiring a C content not exceeding 0.08%, Si not exceeding 0.75%, P content ≤0.035%, S content ≤0.015%, Cr content ranging from 17.00% to 19.00%, Ni content ranging from 9.00% to 12.00%, and Ti content ≥5C~0.70%. The welding materials matched according to the material characteristics are E347-15 welding rods and ER347 welding wires, both with a diameter of 3.2mm. For extreme high-temperature, high-pressure environments rich in chloride ions, the key components carbon (C) and ferrite content (FN) in the welding material's chemical composition are adjusted. After adjustment, a welding surfacing test is conducted to verify whether the FN and C content in the deposited metal meets the target requirements, and the target welding material chemical composition is output.

[0007] Furthermore, in step two, the establishment of finite element analysis models based on different bevel types specifically includes: establishing three-dimensional geometric models of V-grooves and X-grooves, setting the chemical composition of the weld metal and the base material, meshing, setting boundary conditions and applying various loads, solving the model, and outputting the stress-strain numerical calculation results; by comparing the tensile stress of the optimal solution for the V-grooved and X-grooved weld formations, the optimal bevel type is determined. Numerical simulation results show that the optimal solution for the V-grooved weld formation experiences tensile stress F... max =2.0598MPa, the tensile stress F of the optimal solution for the X-groove forming weld is... max =1.3364MPa. The stress on the V-groove weld is 1.54 times that of the X-groove weld. Therefore, the X-groove is determined as the target groove type for the product.

[0008] Furthermore, in step two, setting at least two sets of welding process parameters with different welding heat inputs specifically involves: fabricating the product bevel based on the optimal bevel type, setting the welding process parameters according to the welding heat input, and setting three sets of welding process parameters for small, moderate, and large welding heat inputs. Specifically, the welding heat input for parameters 1 and 2 (small and moderate heat inputs) does not exceed 25 kJ / cm, and the welding heat input for parameter 3 (large heat input) ranges from 25 to 32 kJ / cm. Three X-shaped bevel product test plates are welded as the test group, and three V-shaped bevel product test plates are welded while keeping the three sets of welding process parameters unchanged as the control group.

[0009] Furthermore, in step two, the determination of optimal welding process parameters by comprehensively comparing changes in mechanical properties and metallographic structure includes: after welding, mechanical property and metallographic samples are taken from each test plate and sent for testing. Residual material is fed into the furnace along with the raw material for in-furnace testing. After several cycles, the mechanical properties and metallographic structure of each sample are re-tested, and the microstructure of each group of samples is observed and compared. Before furnace testing, the mechanical properties of product test plates with different welding heat inputs are basically consistent, while the metallographic structure varies slightly. After several cycles, only the X-groove product test plate with a moderate welding heat input shows obvious fine grain bands near the weld fusion line. According to the sampling and testing results from the scrapped reaction unit, the weld with the above-mentioned structure exhibits better high-temperature creep resistance and corrosion resistance. Therefore, the welding process parameters corresponding to this group are determined as the optimal welding process parameters.

[0010] Furthermore, in step three, the bevel deviation value is checked. If the bevel deviation value does not meet the process requirements, the bevel is reworked and adjusted until it meets the requirements, then proceeding to the next process. The dynamic monitoring and control system monitors the fluctuations of welding parameters in real time to see if they meet the process requirements. If the welding parameters exceed the requirements, the welding machine automatically locks and stops welding; if they meet the requirements, the product welding and manufacturing proceeds normally. After the manufacturing is completed and the entire machine passes inspection, the reaction device is completed.

[0011] Furthermore, in step four, tracking its periodic operation specifically includes: the reaction device first undergoes a pretreatment process stage, and then enters a periodic operation stage; if the weld condition is good, the periodic cycle continues; otherwise, the weld is repaired, and after the repair is completed, the device continues to operate in a cycle until the weld of the reaction device cannot be repaired and the reaction device is scrapped and eliminated.

[0012] Furthermore, in step two, the tensile strength of the samples taken before and after the furnace test is greater than 520 MPa and the elongation is greater than 25%.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention adjusts the chemical composition of welding materials for specific product usage environments, and, in conjunction with the target bevel and reasonable welding process, precisely controls the welding heat input within a suitable range. This solves the problem of easy cracking and difficult repair of key welds in sponge titanium reactors used for long cycles and high frequencies, and effectively increases the number of cycles of the reactor.

[0014] 2. This invention utilizes finite element numerical simulation technology, combined with material property analysis, to verify the theoretical value of the optimal bevel for the product. The calculation results match the actual requirements, reducing material costs in the early verification stage and further shortening the verification cycle.

[0015] 3. This invention controls the welding heat input of the longitudinal and circumferential welds of the reaction device by adjusting the welding process parameters, thereby obtaining a target microstructure suitable for service under high temperature conditions. After several cycles, obvious fine grains appear near the fusion line between the weld and the base material, which greatly improves the creep resistance of the weld under high temperature conditions and effectively improves the weld quality.

[0016] 4. This invention uses a welding machine dynamic monitoring system to monitor the welding machine's operating status in real time and accurately control the welding process parameters, ensuring that the welding heat input during product manufacturing meets the improved process requirements. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process development flow for the welding method of the present invention.

[0018] Figure 2 This is a schematic diagram of the finite element analysis process for the product bevel type in this invention.

[0019] Figure 3 This is a stress calculation contour map for the optimal bevel type in this invention.

[0020] Figure 4 This is a strain calculation contour map of the optimal bevel type in this invention.

[0021] Figure 5 This is a schematic diagram of the optimal welding process parameter output flow in this invention.

[0022] Figure 6 This is a schematic diagram of the optimal product microstructure (×50 magnification) in this invention.

[0023] Figure 7 This is a schematic diagram of the optimal product microstructure (×100 magnification) in this invention.

[0024] Figure 8 This is a schematic diagram of the product manufacturing and usage cycle verification process in this invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a welding method for a rotor-level sponge titanium circulating reactor. The method consists of four stages: welding material selection, welding procedure qualification, product manufacturing, and production cycle verification. For detailed procedures, please refer to the appendix. Figure 1 .

[0027] Example: Phase 1: Welding Material Selection Phase In this embodiment, the main body of the reaction device uses titanium-containing stainless steel medium-thick plate material. After the plates arrive at the factory, samples are taken for chemical composition retesting, according to the standard GB / T 713.7-2023 "Steel Plates and Strips for Pressure Equipment - Part 7: Stainless Steel and Heat-Resistant Steel". This standard clearly requires that its C content not exceed 0.08%, Si not exceed 0.75%, P content ≤ 0.035%, S content ≤ 0.015%, Cr content range 17.00%~19.00%, Ni content range 9.00%~12.00%, and Ti content ≥ 5C~0.70%. Based on the material characteristics, the matching welding materials are E347-15 welding rods and ER347 welding wires, both with a diameter of 3.2mm.

[0028] To address the extreme high temperature, high pressure, and chloride ion-rich environment of the reactor, the key components of the welding consumable, carbon (C) and ferrite (FN), were adjusted. The goal was to better meet the high-temperature operating requirements for a lower C content while maintaining the material's mechanical properties, ensuring the FN content remained within a reasonable range. After adjustment, welding tests were conducted to verify whether the FN and C contents in the deposited metal met the target requirements, ultimately outputting the target welding consumable chemical composition.

[0029] Phase Two: Welding Procedure Qualification Phase This stage is divided into two parts: finite element analysis of the product bevel and confirmation of the optimal welding process parameters.

[0030] Part 1: Establishing a 3D geometric model of the product based on bevel type, specifically creating V-shaped and X-shaped bevel models. The chemical composition of the weld metal and base material is set, the mesh type and size are defined and generated, then boundary conditions are set and various loads are applied. The model is solved, and the numerical stress-strain calculation results are output. The optimal numerical simulation solution is output for each of the two bevel types, and the best bevel type is determined by comparing the two. See Appendix for the workflow. Figure 2 .

[0031] Numerical simulation results show that the optimal solution for the V-groove forming weld is subjected to the tensile stress F. max =2.0598MPa, the tensile stress F of the optimal solution for the X-groove forming weld is... max =1.3364 MPa. The stress of the V-groove weld is 1.54 times that of the X-groove weld, which is greater. Therefore, the X-groove is the optimal groove type for the product. The stress calculation cloud diagram is attached. Figure 3 The strain calculation cloud diagram is attached. Figure 4 .

[0032] Part 2: Product beveling based on the optimal bevel type (X-shaped bevel). Welding process parameters are set according to the welding heat input, with three sets of parameters set for low, moderate, and high welding heat input. Detailed welding parameters are shown in Table 1. The welding heat input for parameters 1 and 2 does not exceed 25 kJ / cm, while the welding heat input for parameter 3 ranges from 25 to 32 kJ / cm.

[0033] Three X-shaped bevel test plates were welded as the test group. Additionally, three V-shaped bevel test plates were welded as the control group, keeping the welding process parameters unchanged. After welding, mechanical property and metallographic samples were taken from each test plate and sent for testing. The remaining material was furnace-fired along with the raw material for in-furnace testing. After several cycles, the mechanical properties and metallographic structure of each sample were retested, and the microstructure of each group of samples was observed and compared. In the mechanical property test results before and after the in-furnace test, the tensile strength was >520 MPa and the elongation was >25%. A simplified procedure is attached. Figure 5 .

[0034] Before furnace loading, the mechanical properties of the test plates with different welding heat inputs were basically consistent, with slight differences in metallographic structure. After several cycles, only the X-groove test plates (parameter group 2) with moderate welding heat input showed obvious fine grain bands near the weld fusion line. According to the sampling and testing results of the scrapped reactor, the welds with the above-mentioned structure exhibited better high-temperature creep resistance and corrosion resistance. Under the same operating conditions, the number of cycles during the first maintenance was about 5-8 times higher than that of the reactor without the above-mentioned metallographic structure, and the overall number of cycles increased by 6-10 times. The target microstructure is shown in the appendix. Figure 6 (×50x) and attached Figure 7 (×100 times). Therefore, based on comprehensive comparison, parameter group 2 (moderate welding heat input) is the optimal welding process parameter, as shown in Table 1.

[0035] Table 1 Welding process parameters

[0036] Phase Three: Product Manufacturing Phase Phase 1 involves preparing customized welding materials and product materials. For the longitudinal and circumferential welds of the reaction unit, the target type of bevel (X-shaped bevel) is created, and the bevel deviation value is checked to ensure it meets the process requirements. If not, the bevel is reworked and adjusted; once the requirements are met, the process proceeds to the next step. The optimal welding parameters determined in Phase 2 are input into the dynamic monitoring and control system. This system monitors the fluctuations of welding parameters in real time to ensure they meet the process requirements. If the welding parameters exceed the requirements, the welding machine automatically locks and stops welding; if they meet the requirements, product welding and manufacturing proceed normally. After manufacturing is completed, the reaction unit is completed after passing the overall inspection. The suggested process is attached. Figure 8 upper part.

[0037] Phase Four: Product Usage Cycle Validation The product is put into production. It first undergoes a pretreatment stage, then enters a cyclical operation phase. If the weld condition is good, the cyclical operation continues; otherwise, weld repair is performed. After repair, production resumes cyclical operation until the reactor welds cannot be repaired, at which point the reactor is scrapped and phased out. A simplified process is attached. Figure 8 lower part.

[0038] In summary, this invention, through a systematic four-stage approach—from optimizing welding materials at the source, simulating bevel design, precisely controlling process parameters, to actual production and cyclic verification—forms a complete and effective welding method for rotor-level sponge titanium circulating reactors, significantly improving the quality and service life of critical welds in the reactor.

[0039] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A welding method for a rotor-stage sponge titanium circulating reactor, characterized in that: Includes the following steps: Step 1, Welding Material Selection Stage: The chemical composition of the titanium-containing stainless steel medium-thick plate base material used for the main body of the reaction device is retested, and the welding material model is matched according to the characteristics of the base material; In view of the high temperature, high pressure and chloride ion-containing service conditions of the reaction device, the chemical composition of the matched welding material is adjusted so that the adjusted welding material meets the chemical composition requirements of the target deposited metal. Step 2, Welding Procedure Qualification Stage: Based on different groove types, establish finite element analysis models of the reaction device structure, simulate the stress on the weld during use, and determine the target groove type by comparison; Based on the determined target bevel type, product test plates are made, and welding process parameters with at least two different welding heat inputs are set for welding as test groups. Mechanical properties and metallographic structure are tested on the welded test plates, and the remaining material is put into the furnace along with the materials in the reaction device for furnace test. After several process cycles, the test plates are taken out and the mechanical properties and metallographic structure are retested. By comprehensively comparing the changes in mechanical properties and metallographic structure, the optimal welding process parameters were determined. Step 3, Product Manufacturing Stage: Based on the chemical composition of the welding materials determined in Step 1, customize the welding materials; based on the target groove type determined in Step 2, cut grooves for the longitudinal and circumferential welds of the reaction device, and inspect the groove deviation value; input the optimal welding process parameters determined in Step 2 into the dynamic monitoring and control system of the welding equipment, weld the longitudinal and circumferential welds, and complete the manufacturing of the reaction device. Step 4, Product Use Cycle Verification Phase: Put the manufactured reaction device into production and use, track its periodic operation, until the reaction device is scrapped and eliminated.

2. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 1, characterized in that: In step one, the base material is a medium-thick plate of titanium-containing stainless steel, and its chemical composition is retested according to GB / T 713.7-2023; the matching welding materials are E347-15 welding rods and ER347 welding wires, both with a diameter of 3.2mm; the adjustment of the chemical composition of the welding materials includes the adjustment of carbon element C and ferrite content FN, and the chemical composition of the deposited metal is verified by the overlay welding test after adjustment.

3. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 1, characterized in that: In step two, the establishment of finite element analysis models based on different bevel types specifically includes: establishing three-dimensional geometric models of V-shaped and X-shaped bevels, setting the chemical composition of the weld metal and the base material, dividing the mesh, setting boundary conditions and applying various loads, solving the model and outputting the numerical calculation results of stress and strain; by comparing the tensile stress of the optimal solution of the weld formed by V-shaped and X-shaped bevels, the X-shaped bevel is determined as the target bevel type for the product.

4. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 3, characterized in that: In step two, setting at least two sets of welding process parameters with different welding heat inputs specifically involves setting three sets of welding process parameters: small, moderate, and large welding heat inputs. The heat input parameters for small and moderate welding heat inputs have a heat input line energy of no more than 25 kJ / cm, while the heat input parameter for large welding heat inputs has a heat input line energy range of 25~32 kJ / cm. The X-shaped bevel product test plate is used as the test group, and the V-shaped bevel product test plate is used as the control group. Welding is performed under the same welding process parameters.

5. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 4, characterized in that: In step two, the determination of the optimal welding process parameters by comprehensively comparing the changes in mechanical properties and metallographic structure includes: comparing the mechanical properties and metallographic structure of each group of test plates before and after the furnace test. Among them, after the furnace test, fine grains were observed only near the weld fusion line of the X-shaped groove product test plate with appropriate welding heat input. The welding process parameters corresponding to this group were determined as the optimal welding process parameters.

6. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 1, characterized in that: In step three, the bevel deviation value is checked. If the bevel deviation value does not meet the process requirements, the bevel is reworked and adjusted.

7. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 1, characterized in that: In step three, the dynamic monitoring and control system monitors the fluctuations of welding parameters in real time. When the welding parameters exceed the process requirements, the welding machine automatically locks and stops welding.

8. The welding method for the rotor-stage sponge titanium circulating reactor according to claim 1, characterized in that: In step four, tracking its periodic operation specifically includes: the reaction device first undergoes a pretreatment process stage, and then enters a periodic operation stage; if the weld condition is good, the cycle continues; if the weld is abnormal, it is repaired, and after repair, the cycle continues until the reaction device is scrapped.

9. The welding method for the rotor-stage sponge titanium circulating reactor according to any one of claims 1-8, characterized in that: In step two, the mechanical property test results of the samples taken before and after the furnace test showed that the tensile strength was >520MPa and the elongation was >25%.

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