Welding material and welding method suitable for forward load transfer fillet weld of non-bearing accessory

Abstract

According to the welding material and the welding method suitable for the non-bearing accessory forward transfer load fillet weld, the components of the welding material are controlled, and on the basis that stable molten drop transition and molten pool reaction are controlled to be formed, the welding efficiency is greatly improved; control optimization for reducing bonding force between atoms, control optimization for reducing non-metallic inclusions, control optimization for forming low-melting-point eutectic substances and control optimization for forming low-melting-point compounds are formed, and optimization for liquidity of a liquid molten pool and wettability of a heterogeneous interface is formed according to control optimization of four dimensions; according to the welding method, on the basis that the welding materials are combined, the to-be-welded faces of the accessories and the to-be-welded faces of the base metal bottom plate are arranged to be in the space structure relation that gaps are formed between the accessories and the base metal bottom plate before welding; and a fatigue strength mechanism which is characterized by local microcell cyclic plastic strain accumulated damage controlled by the yield strength of the base metal is established under the condition that fatigue failure does not occur after early fatigue crack circulation for 1000-5000 times.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding, and particularly relates to a welding material and a welding method suitable for fillet welds of non-load-bearing accessories for forward load transfer. Background Art

[0002] For large thick-walled steel structural members in most important industrial fields, fatigue failure is the main failure mode. Due to the existence of three main factors at the welded joint part, namely, stress concentration at the weld toe, initial fatigue crack sources formed by geometric discontinuities caused by welding, and the superposition of welding residual tensile stress and external loads. Especially under the condition of bearing forward fatigue loads, compared with the base metal material, it often becomes the weak point of the structural member's fatigue service. Compared with the uniform base material, the fatigue grade will also be significantly reduced, and the reduction amplitude is related to the influence degree of the above three main influencing factors.

[0003] On large thick-walled steel structural members in dynamic load service, in addition to the butt joints or corner joints that bear forward loads, there are also accessories for pipeline or cable layout fixation, operation monitoring and maintenance, decoration, etc., which are generally fixed at the corresponding positions on the surface of the structural member in the form of single-sided non-penetrating fillet joints. Although the fillet welds of these accessories do not bear forward loads, they play a role in forward load transfer during the service of the structural member, and stress concentration is formed at the weld toe position on the base plate side of the structural member's base material. Coupled with the early fatigue crack sources formed by the inherent macroscopic and microscopic defects at the weld toe, the existence of the fillet welds of the accessories reduces the fatigue performance of the overall structure. In the early fatigue design standards for dynamic load structural members, it was considered that the fatigue strength level of steel material welded joints or structures was not related to the yield strength level of the material, but only related to joint form design, joint detail features, welding quality grade, and post-weld treatment status, etc. For example: in mainstream standards such as EN 1993 standard, IIW-2259-15 standard, DNV-RP-C203, etc., a set of S-N curves available for fatigue design were given according to different design forms and quality grades of steel materials, and the stress range values corresponding to the number of cycles of 2*10 6 were extracted from each S-N curve and defined as fatigue strength characteristic values, which were used as the basis for the fatigue design of dynamic load structural members. For example: in the EN 1993 standard, for the welded joint of double-sided welded full-penetration retained welds, the S-N curve corresponds to DC90, and the fatigue strength characteristic value is 90 MPa. Other standards have almost the same definition.

[0004] The invention application with the application number: CN201610764555.2 discloses "A construction method for single-sided penetration welding of the connecting corner seam between the closed longitudinal rib and the bridge deck", including the following construction steps: Assemble multiple closed longitudinal ribs and the bridge deck to form a bridge deck unit, and place it on the jig of the plate unit welding production line to make it in a horizontal state. Install welding pads at the two internal longitudinal corner seams; Rotate the jig to weld one side longitudinal corner seam located outside; Rotate the jig to weld the other side longitudinal corner seam located outside; Rotate the jig to make it in a horizontal state, and remove the completed welded bridge deck unit.

[0005] The invention application with the application number: CN201080042624.X discloses "A fillet weld arc welding for high-strength steel plates for use in, for example, vehicle frame structural components and a steel plate welded with a welding wire having a preset silicon content". When performing arc fillet welding of high-strength thin steel plates with a tensile strength of 700 MPa or more by gas shielded arc welding with a welding speed greater than 110 cm / minute and less than or equal to 150 cm / minute, the steel plate is a steel plate containing C = 0.02 - 0.15%, Si = 0.2 - 1.8%, Mn = 0.5 - 2.5%. When the Si content (mass%) of the steel plate is denoted as Si(steel plate) and the Si content (mass%) of the welding wire used for the arc fillet welding is denoted as Si(welding wire), they are combined in such a way that {Si(steel plate) + 0.1 × Si(welding wire)} ≥ 0.32.

[0006] The invention application with the application number: CN201110181450.1 discloses "A fillet weld of a steel plate having a welding metal with a martensite transformation start temperature set to satisfy a predetermined difference". It forms a weld seam using a flux cored wire containing 0.08 - 0.32 mass% of carbon (C), 0.40 - 3.00 mass% of silicon (Si), 1.00 - 5.00 mass% of manganese (Mn), 0.030 mass% or less of phosphorus (P), 0.030 mass% or less of sulfur (S), and a total oxide content of 1.0 mass% or less; The fillet weld has a welding metal with a martensite phase transformation start temperature set in the range of 400°C - 550°C, and the ratio of the toe radius of the weld toe to the plate thickness of the base material is set to 0.25 or more. The martensite phase transformation start temperature of the weld metal is set to be less than or equal to 320 - 375 times the ratio of the toe radius to the plate thickness.

[0007] The invention application with the application number: CN202210410818.5 discloses "a Fe-Cr-Mn welding wire and its preparation method and welding process". The welding wire includes a welding skin and a powder wrapped in the welding skin. The powder includes components by mass percentage: 45.0 - 48.0% of Cr powder, 12.0 - 14.0% of Ni powder, 25.0 - 28.0% of Mn powder, 1.4 - 1.8% of Ti powder, 0.6 - 1.0% of Al powder, 4.0 - 5.0% of V powder, 0.3 - 0.6% of graphene, and the rest is Fe powder; among them, the sum of the mass percentages of the above components is 100%. In the powder composition of the Fe-Cr-Mn welding wire, both Mn and Ni have the function of stabilizing the austenite phase region, and the price of Mn is cheaper than that of Ni. Mn not only has the ability to inhibit the cracking of austenitic welds, but also helps with the deoxidation of the clad metal during welding, thereby reducing the generation of porosity defects. By reducing the Ni content and increasing the Cr and Mn contents, the production cost of the welding wire is effectively reduced on the premise of ensuring the service performance of the welding wire. Summary of the Invention

[0008] The purpose of this technical solution is to break the above common understanding and establish a fatigue strength mechanism of a welded structure characterized by local microzone cyclic plastic strain accumulation controlled by the yield strength of the base material.

[0009] To achieve the above technical purposes, the present invention provides a welding material and a welding method suitable for fillet welds of non-load-bearing accessories for forward transmission of loads. The technical solution is as follows:

[0010] A welding material suitable for fillet welds of non-load-bearing accessories for forward transmission of loads,

[0011] By controlling the components of the welding material, on the basis of controlling the formation of stable droplet transfer and molten pool reaction,

[0012] Control optimizations for reducing the atomic binding force, control optimizations for reducing non-metallic inclusions, control for forming low-melting eutectics, and control for forming low-melting compounds are formed. Based on these four-dimensional control optimizations, optimizations of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface are formed.

[0013] Further,

[0014] The control optimization for reducing the atomic binding force is completed by controlling the Te content;

[0015] The control optimization for reducing non-metallic inclusions is completed by controlling the Si content;

[0016] The control for forming low-melting eutectics is completed by controlling the P and S contents;

[0017] The control for forming low-melting compounds is completed by controlling the Ti and Mg contents;

[0018] The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is achieved by controlling the above component contents and also by controlling the contents of Mn and Al.

[0019] Furthermore,

[0020] The control of the Te content is specifically as follows: controlling the mass percentage of Te to be 0.008 - 0.025%.

[0021] The control of the Si content is specifically as follows: controlling the mass percentage of Si to be 0.9 - 1.8%.

[0022] The control of the P content is specifically as follows: controlling the mass percentage of P to be 0.015 - 0.030%.

[0023] The control of the S content is specifically as follows: controlling the mass percentage of S to be 0.012 - 0.025%.

[0024] The control of the Ti content is specifically as follows: controlling the mass percentage of Ti to be 0.12 - 0.36%.

[0025] The control of the Mg content is specifically as follows: controlling the mass percentage of Mg to be 0.012 - 0.035%.

[0026] The control of the Mn content is specifically as follows: controlling the mass percentage of Mn to be 0.4 - 1.1%.

[0027] The control of the Al content is specifically as follows: controlling the mass percentage of Al to be less than 0.06%.

[0028] Furthermore,

[0029] The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is achieved by establishing a comprehensive regulation of the contents of Te, Si, P, S, Ti, Mg, Mn, and Al through the set wettability index of the heterogeneous interface of the liquid metal in the molten pool, and controlling the wettability index of the heterogeneous interface of the liquid metal in the molten pool within the range of the closed interval [3.0, 7.0], specifically as follows:

[0030]

[0031] In the above formula,

[0032] M: The wettability index of the heterogeneous interface of the liquid metal in the molten pool, M ∈ [3.0, 7.0].

[0033] Furthermore,

[0034] The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is also achieved by establishing control over the contents of C, O, and N;

[0035] Specifically:

[0036] Control the mass percentage of C to be 0.12 - 0.23%;

[0037] Control the mass percentage of O to be less than 0.0045%;

[0038] Control the mass percentage of N to be less than 0.006%.

[0039] A welding method suitable for fillet welds of non - load - bearing accessories for forward load transfer,

[0040] First, by establishing control over the components of the welding material, on the basis of forming stable droplet transfer and molten pool reactions, control optimizations for reducing the inter - atomic binding force, reducing non - metallic inclusions, controlling the formation of low - melting - point eutectics, and controlling the formation of low - melting - point compounds are formed. Based on these four - dimensional control optimizations, the optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is formed;

[0041] Secondly, the surfaces to be welded of the accessory and the base - metal floor are set to have a spatial structural relationship with a gap formed between them before welding;

[0042] Based on the completed welding structure, a fatigue strength mechanism characterized by the cumulative damage of local micro - zone cyclic plastic strain controlled by the yield strength of the base metal can be established under the condition that no fatigue failure occurs during 1000 - 5000 cycles of early fatigue cracks. Then, the base - metal floor is made of high - strength steel, thereby achieving an improvement in the fatigue strength of the non - load - bearing accessory.

[0043] Furthermore,

[0044] The control optimization for reducing the inter - atomic binding force is achieved by controlling the content of Te;

[0045] The control optimization for reducing non - metallic inclusions is achieved by controlling the content of Si;

[0046] The control of the formation of low - melting - point eutectics is achieved by controlling the contents of P and S;

[0047] The control of the formation of low - melting - point compounds is achieved by controlling the contents of Ti and Mg;

[0048] The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface, on the basis of establishing control over the above - mentioned component contents, is also achieved by establishing control over the contents of Mn and Al.

[0049] Furthermore,

[0050] The control of the Te content specifically means: controlling the mass percentage of Te to be 0.008 - 0.025%;

[0051] The control of the Si content specifically means: controlling the mass percentage of Si to be 0.9 - 1.8%;

[0052] The control of the P content specifically means: controlling the mass percentage of P to be 0.015 - 0.030%;

[0053] The control of the S content specifically means: controlling the mass percentage of S to be 0.012 - 0.025%;

[0054] The control of the Ti content specifically means: controlling the mass percentage of Ti to be 0.12 - 0.36%;

[0055] The control of the Mg content specifically means: controlling the mass percentage of Mg to be 0.012 - 0.035%;

[0056] The control of the Mn content specifically means: controlling the mass percentage of Mn to be 0.4 - 1.1%;

[0057] The control of the Al content specifically means: controlling the mass percentage of Al to be less than 0.06%.

[0058] Furthermore,

[0059] The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is achieved by establishing a comprehensive regulation of the contents of Te, Si, P, S, Ti, Mg, Mn, and Al through the set wettability index of the heterogeneous interface of the liquid metal in the molten pool, and the wettability index of the heterogeneous interface of the liquid metal in the molten pool is controlled within the range of the closed interval [3.0, 7.0], specifically as follows:

[0060]

[0061] In the above formula,

[0062] M: The wettability index of the heterogeneous interface of the liquid metal in the molten pool, M ∈ [3.0, 7.0].

[0063] Furthermore,

[0064] The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is also achieved by establishing the control of the contents of C, O, and N;

[0065] Specifically:

[0066] Controlling the mass percentage of C to be 0.12 - 0.23%;

[0067] Controlling the mass percentage of O to be less than 0.0045%;

[0068] The mass percentage of N is less than 0.006%.

[0069] Furthermore,

[0070] The gap between the respective welding surfaces of the accessory and the base metal bottom plate is controlled to be 0.5 - 2.2 mm.

[0071] Furthermore,

[0072] The welding is carried out by a direct drawing method,

[0073] The welding wire is controlled to be a solid wire with a diameter of 1.2 mm,

[0074] The welding current is controlled to be 140 - 190 A;

[0075] The welding voltage is controlled to be 16 - 21 V;

[0076] The welding speed is controlled to be 210 - 280 mm / min.

[0077] Furthermore,

[0078] By arranging a circulating water cooling device on the back of the base metal bottom plate, a contact conduction heat exchange with the circulating water temperature less than 45°C during the welding process is provided, and accordingly, a control of less than 5° for the angular deformation of the welded structure is established.

[0079] A welding material and a welding method for the fillet weld of a non - load - bearing accessory for forward - transferring loads according to the present invention, through first establishing control optimizations in four dimensions of reducing the inter - atomic binding force, reducing non - metallic inclusions, controlling the formation of eutectics with low melting points, and controlling the formation of low - melting - point compounds for the welding material components, form optimizations for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface, so that the welding material has the characteristics of smooth weld toe transition, uniform spreading, strong gap - filling ability and edge - bridging ability; then combined with setting the respective welding surfaces of the accessory and the base metal bottom plate as a spatial structure relationship with a gap formed between them before welding and an appropriate range of welding process parameters, reducing or even eliminating the sharp transitions, undercutting and local discontinuities at the macroscopic and microscopic scales of the weld toes on the base metal bottom plate side of the accessory structure, thereby reducing or eliminating early fatigue crack sources during the overall fatigue service process of the structure and reducing the stress concentration effect; that is, the welded structure formed after welding can be controlled to have a fatigue strength mechanism characterized by the cumulative damage of local micro - area cyclic plastic strain controlled by the yield strength of the base metal under the condition that no fatigue failure occurs after 1000 - 5000 cycles of early fatigue cracks, and then by setting the base metal bottom plate as high - strength steel, the fatigue strength of the non - load - bearing accessory is improved. A welding material and a welding method for the fillet weld of a non - load - bearing accessory for forward - transferring loads according to the present invention also disclose a welding material that can achieve the above corresponding functions. Brief Description of the Drawings

[0080] Figure 1 It is a schematic diagram of the spatial structure relationship between the accessory and the base material bottom plate in the present invention;

[0081] Figure 2 is Figure 1 top view of;

[0082] Figure 3 It is a schematic diagram of the spatial structure relationship and set dimensions between the accessory and the base material bottom plate in the embodiment of the present invention;

[0083] Figure 4 is Figure 3 top view of.

[0084] In the figure,

[0085] 1 - Base material bottom plate;

[0086] 2 - Accessory;

[0087] 3 - Longitudinal fillet weld of the accessory. Detailed Implementation Manner

[0088] Next, according to the drawings in the specification and the detailed implementation manner, a welding material and a welding method for a fillet weld suitable for non - load - bearing accessories to transfer load forward in the present invention will be further specifically described.

[0089] To fully understand this technical solution, the following will specifically introduce this technical solution in two parts. The first part points to the overview of this technical solution, and the second part points to the specific process and principle explanation based on the overview.

[0090] Technical Overview:

[0091] Through research by the applicant's research team, it is found that: by establishing control and optimization of the welding stress concentration effect, establishing control and optimization of the initial fatigue crack source, and establishing control and optimization of the welding residual tensile stress, a comprehensive control and optimization effect can be found, enabling the fatigue performance of the welded structure to be converted to the fatigue strength mechanism characterized by the cumulative damage of local micro - area cyclic plastic strain controlled by the yield strength of the base material. Then, based on the positive correlation between the fatigue strength and static load strength of the metal, the material to be welded is set as high - strength steel, thereby improving the fatigue performance of the welded structure.

[0092] This technical solution is a solution that realizes the above technical purpose by optimizing the combination of the components of the welding material and setting the spatial structure relationship between the areas to be welded before welding, and then combining the corresponding welding process. The optimization of the components of the welding material aims to control and reduce or eliminate the sharp transitions, undercuts, and local discontinuities at the macroscopic and microscopic scales of the weld toes on the base metal bottom plate side, so as to reduce or eliminate early fatigue crack sources and reduce the stress concentration effect during the overall fatigue service of the structure. This is achieved by establishing the control and optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface. The control and optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface are achieved by establishing the control of the components of the welding material. On the basis of forming stable droplet transfer and molten pool reactions, four-dimensional control optimizations are formed, namely, the control optimization of reducing the atomic bonding force, the control optimization of reducing non-metallic inclusions, the control of forming low-melting eutectics, and the control of forming low-melting compounds, combined with the establishment of the control of the Mn and Al contents. The control optimization of reducing the atomic bonding force is completed by controlling the Te content; the control optimization of reducing non-metallic inclusions is completed by controlling the Si content; the control of forming low-melting eutectics is completed by controlling the P and S contents; the control of forming low-melting compounds is completed by controlling the Ti and Mg contents. The regulation of the Te, Si, P, S, Ti, Mg, Mn, and Al contents is achieved through the comprehensive regulation formed by setting the wettability index of the heterogeneous interface of the liquid metal in the molten pool, and the wettability index of the heterogeneous interface of the liquid metal in the molten pool is controlled within the closed interval [3.0, 7.0]. At the same time, in order to better serve this purpose, the C content, O content, and N content are separately regulated. The specific control process and principle are as follows:

[0093] A welding material and welding method for fillet welds of non-load-bearing accessories suitable for forward transfer of loads according to the present invention provides a flux-cored arc welding solid wire with uniform spreading ability and a supporting welding method. It is used for the fillet weld welding of non-load-bearing accessories that only transfer loads on dynamic load structural members. By designing the correlation between the surface activity of the welding molten pool and the wettability of the interface chemical elements, by providing a flux-cored arc welding solid wire with smooth weld toe transition, uniform spreading, strong gap filling ability and edge bridging ability, and matching the corresponding welding process method, it is possible to obtain fillet welds of accessories with good overall quality of the weld toes on the base metal bottom plate side, reduce or even eliminate the sharp transitions, undercuts, and local discontinuities at the macroscopic and microscopic scales of the weld toes on the base metal bottom plate side, so as to reduce or eliminate early fatigue crack sources during the overall fatigue service of the structure, reduce the stress concentration effect, and thus ensure the fatigue performance of the overall structure. The specific steps are as follows:

[0094] Step 1: Design of a flux-cored arc welding solid wire with uniform spreading ability for non-penetrating fillet welding of accessory structures

[0095] In view of the service characteristics of non-penetration fillet welds of non-load-bearing accessory structures that only transfer loads in the positive direction, the sharp transition, undercut and local discontinuity at the macro and micro scales between the fillet weld and the base plate side of the parent material become the source of early fatigue cracks during the fatigue service of the structure, and the stress concentration effect caused by the sudden change of the weld toe geometry will lead to a decrease in the fatigue performance of the overall structure. Therefore, the design principle of the solid consumable gas shielded welding wire with uniform spreading ability for non-penetration fillet welding of accessory structures is to ensure smooth transition and uniform spreading at the fillet weld toe, and have good gap filling ability and edge bridging ability, while reducing or avoiding the macro or micro defects and stress concentration effect of the fillet weld toe on the base plate side of the parent material, and essentially improving the fatigue performance of the overall structure.

[0096] Accordingly, the present invention adopts a combination of multiple chemical elements that can improve the surface activity and interface wettability of the welding pool. While ensuring the transition of the welding droplet and the stability of the molten pool reaction, the viscosity of the molten pool metal is appropriately reduced, and the fluidity of the liquid molten pool is improved, thereby improving the uniform spreading ability of the fillet weld and ensuring the uniform and smooth transition of the weld toe on the base plate side of the parent material. At the same time, controlling the viscosity of the liquid molten pool within a certain range and appropriately increasing the content of low-melting-point eutectics and complex intermetallic compounds in the molten pool will help improve the wettability of the heterogeneous interface during the molten pool spreading process, thereby ensuring the gap filling ability and the ability to bridge the local space at the edge, which is very beneficial to eliminating potential fatigue crack sources such as undercut and local discontinuity at the edge of the weld toe.

[0097] The chemical composition types and ranges of the solid gas shielded welding wire with uniform spreading ability for non-penetration fillet welding of non-load-bearing accessory structures are designed as follows:

[0098] C: 0.12~0.23%;

[0099] Si: 0.9-1.8%;

[0100] Mn: 0.4-1.1%;

[0101] P: 0.015~0.030%;

[0102] S: 0.012~0.025%;

[0103] Ti: 0.12~0.36%;

[0104] Mg: 0.012~0.035%;

[0105] Te: 0.008~0.025%;

[0106] Al: <0.06%;

[0107] O: <0.0045%;

[0108] N: <0.0060%

[0109] The chemical composition design of the flux-cored wire with uniform spreading ability for non-penetrating fillet welding of non-load-bearing accessory structures is mainly to ensure the wettability of the heterogeneous interface of the molten metal in the molten pool in addition to meeting the most basic strength index for accessory connection. Define the wettability index M of the heterogeneous interface of the molten metal in the molten pool as follows:

[0110]

[0111] Among them, M represents the wettability index of the heterogeneous interface of the molten metal in the molten pool, [Te] represents the tellurium content (%), [P] represents the phosphorus content (%), [S] represents the sulfur content (%), [Si] represents the silicon content (%), [Ti] represents the titanium content (%), [Mg] represents the magnesium content (%), [Mn] represents the manganese content (%), and [Al] represents the aluminum content (%). Different chemical elements have different degrees of correlation with the fluidity of the molten pool and the wettability of the heterogeneous interface during the spreading and solidification stages of the liquid welding molten pool. This difference is reflected in the contribution coefficient to the wettability index M of the heterogeneous interface. The relevant chemical elements do not act alone but have clear quantitative relationships and correlations. At the same time, the effects of the chemical elements strongly related to the interface wettability index M are also closely related to the oxygen and nitrogen contents in the liquid molten pool and act synergistically. However, most of the chemical elements that can significantly improve the fluidity of the liquid molten pool and the wettability of the heterogeneous interface are non-metallic elements, which are highly sensitive to cold cracks and hot cracks. If the content is too high, it is easy to cause weld cracking. The limited range of the optimal heterogeneous interface wettability index M is 3.0 - 7.0.

[0112] The main functions of the chemical elements of the flux-cored wire with uniform spreading ability for non-penetrating fillet welding of non-load-bearing accessory structures are as follows:

[0113] Carbon is the most basic non-metallic element inherent in steel materials and is an important guarantee for the strength of the wire. At the same time, with the increase of the carbon content, the fluidity of the liquid molten pool can be significantly improved, the viscosity can be reduced, and the wettability at the heterogeneous interface can be enhanced, which is significant for ensuring the uniform spreading effect of the molten pool. However, when the carbon content is too high, the crack resistance and toughness indexes of the weld metal decrease significantly. Therefore, the control range of the carbon element is 0.12 - 0.23%.

[0114] Silicon is an important deoxidizer during the welding process, which is beneficial to ensuring the purity of the weld metal. At the same time, it can significantly reduce the surface tension and viscosity of the molten pool, improve the fluidity of the weld metal, and is beneficial to the uniform spreading of the weld metal. At the same time, the thermal expansion coefficient difference between the oxide of silicon and the weld metal is very large, and the slag is easy to be removed after welding and will not have an adverse impact on the welding quality. The control range of the silicon element is 0.9 - 1.8%.

[0115] Manganese is an important solid solution strengthening element in low alloy steel welds, and its contribution to weld strength is second only to carbon. However, manganese significantly reduces the fluidity of the molten pool and the wettability of the interface, which is very unfavorable for the uniform and smooth transition of the weld toe and the control of welding discontinuity defects. Especially when the sulfur content is high, its desulfurization product MnS also significantly increases the viscosity of the molten pool, which is unfavorable for spreadability. Therefore, in the case of accessory structures where the strength of the weld itself is not high, the control range of manganese is 0.4-1.1%.

[0116] Phosphorus is strictly restricted as a harmful element in general low-alloy steel welding wires. However, a certain phosphorus content in the weld metal can promote the formation of low-melting eutectic in a lower temperature range, prolong the local molten pool solidification time, help the remaining molten iron flow in the formed solid phase gap, and improve the liquid metal gap filling ability and edge bridging ability. However, phosphorus can form brittle compounds with iron and cause severe segregation, making the weld metal significantly embrittled. Therefore, the control range of phosphorus is 0.015-0.030%.

[0117] The effect of sulfur is similar to that of phosphorus. Too high a content can lead to welding hot crack defects and embrittlement of weld metal. However, sulfur is a surface active element and can also form a low melting point eutectic with iron at a lower temperature, which can significantly improve the surface tension of the liquid molten pool, increase the fluidity of the molten pool and the wettability of the edge of the heterogeneous interface, thereby reducing the occurrence of weld toe undercut and edge unfusion defects. If the sulfur content is too low, this effect of improving the wettability of the interface is not significant, and even reduces the fluidity after forming a compound with manganese. The control range of sulfur element is 0.012~0.025%.

[0118] Titanium is an element with low ionization potential, which plays a role in stabilizing the arc during welding. Titanium has high activity and plays a role in deoxidation, carbon fixation and nitrogen fixation in the molten pool reaction, improving the purity of the weld metal and ensuring the comprehensive performance of the joint after welding. At the same time, titanium can form complex low-melting-point complexes with oxygen, sulfur, iron, etc. during the molten pool reaction stage, which is beneficial to improve the fluidity of the molten pool and the wettability of the interface. The role of titanium is closely related to the oxygen and nitrogen content in the molten pool. If the oxygen and nitrogen content is too high, it will preferentially form high-melting-point nitrogen oxides with titanium, which is not conducive to the improvement of the gap filling ability and edge bridging ability of the liquid molten pool. The control range of titanium element is 0.12~0.36%.

[0119] Magnesium is a more active element. Its low ionization potential makes it have a high electron emission ability in the welding arc area, which can significantly improve the welding arc combustion and droplet transfer stability. At the same time, magnesium can generate low-melting-point composite oxides or sulfides with aluminum in the molten pool reaction stage, reducing the adverse effects of aluminum and its oxides brought into the smelting process on reducing the fluidity of the molten pool and the wettability of the interface. The control range of magnesium is 0.012-0.035%.

[0120] Tellurium is an important active transition element, with chemical properties similar to those of oxygen and sulfur, and at the same time having certain metallic properties, that is: while fully improving the activity of the liquid molten pool, reducing viscosity and increasing fluidity and interfacial wettability, it will not cause obvious embrittlement like oxygen and sulfur. The presence of an appropriate amount of tellurium is very effective in enhancing the local edge bridging ability of the liquid molten pool, helping to form a uniform and smooth transition at the weld toe edge and maximizing the avoidance of undercut defects. The control range of tellurium element is 0.008 - 0.025%.

[0121] Aluminum is a residual element introduced during the smelting of welding wire steel due to deoxidation requirements. Excessive aluminum content not only causes embrittlement of the weld metal, but also can form high-melting-point aluminum oxide during the molten pool stage, thereby reducing the fluidity of the liquid metal and local interfacial wettability, which is not conducive to the smooth transition and uniform spreading of the weld toe. The aluminum element is controlled within 0.06%.

[0122] Although oxygen element also has high activity and can significantly enhance the fluidity of the liquid molten pool, however, if the oxygen content is too high, it will affect the stability of the welding process and generate a large amount of spatter. At the same time, it causes the burning loss of a large number of beneficial alloy elements, limiting the beneficial effects of specifically added alloy elements. The oxygen element is controlled within 0.0045%.

[0123] Nitrogen element is an impurity element mixed in from the air. Excessive content will form aggregates of high-melting-point nitrides with relevant alloy elements, reducing the fluidity of the molten pool and the filling ability of the weld toe edge, and at the same time, it can also cause local embrittlement. The nitrogen element is controlled within 0.0060%.

[0124] Based on the above design principle of the correlation between the surface activity of the molten pool and the chemical element combination of interfacial wettability, comprehensively considering the influence of various chemical elements on the gap filling ability and the weld toe edge bridging ability, within the design range of the wettability index M of the heterogeneous interface of the liquid metal in the molten pool, the chemical composition of the flux-cored wire for gas shielded solid wire of the fillet weld of the accessory is designed, and vacuum electric furnace smelting, casting, bar hot rolling, annealing, wire drawing, copper plating, winding and packaging are carried out to form the finished wire.

[0125] The solid wire described in the present invention is applicable to the welding of fillet welds for non-load-bearing accessories with positive load transfer, and can also be used in other welding manufacturing occasions with high requirements for edge gap filling ability and weld toe edge bridging ability and no special requirements for the mechanical properties of the weld. Under certain welding process conditions, a weld with uniform spreading and smooth transition can be obtained, which is beneficial to ensuring the dynamic load fatigue performance of relevant structural parts.

[0126] Step Two: Welding Process Method for Non-Penetrating Fillet Weld of Non-Load-Bearing Accessory Structure

[0127] For the rectangular plate-shaped accessories commonly used on large thick-walled steel structures under dynamic load service scenarios, a structural form is designed where the bottom of the accessory is suspended and a gap is reserved between the accessory and the base metal of the bottom plate, such as Figure 1 , 2 shown. In the figure, 1 is the base metal bottom plate; 2 is the accessory; 3 is the longitudinal fillet weld of the accessory. Adopting this structural form is beneficial to giving full play to the advantages of the gas shielded solid wire with smooth transition, uniform spreading, strong gap filling ability and edge bridging ability in freely spreading on the surface of the base metal bottom plate, ensuring the consistency of the molten pool spreading on both the inner and outer sides, and helping to achieve smooth transition and uniform spreading at the weld toe position. The control range of the reserved gap g between the accessory and the base metal bottom plate is 0.5 - 2.2 mm. If the gap is too small, it is not easy to achieve uniform spreading on both sides of the fillet weld, and the unidirectional asymmetric spreading of the molten pool outside the weld toe will impact the formation of the weld toe and affect the forming quality. If the reserved gap is too large, not only the wire material is wasted, but also the weld thickness between the accessory and the base metal bottom plate is increased, which will instead cause additional stress concentration during the transmission of the load and is not conducive to ensuring the fatigue performance of the overall structure.

[0128] The solid wire with strong gap filling ability and weld toe edge bridging ability of the present invention is used for the gas metal arc fillet welding of the accessory structure. Before welding, the welding area is cleaned to remove pollutants such as moisture, oil stain, rust, etc. that may cause welding defects. At the same time, avoid starting and stopping arcs at the transverse fillet weld with the function of transmitting load, and the starting and stopping arc positions should be located at the longitudinal fillet weld of the accessory. In order to reduce the influence of the welding heat input on the deformation of the overall structure, a circulating water cooling device is set on the back of the base metal bottom plate, and the overall structure angular deformation α < 5° is controlled through forced cooling during the welding process of the accessory structure.

[0129] For the solid wire of the present invention with a diameter of 1.2 mm, the optimized welding process parameters are as follows:

[0130] Welding current I = 140 - 190 A, welding voltage U = 16 - 21 V, welding speed v = 210 - 280 mm / min, and the welding shielding gas is an argon-rich mixed gas of 80% Ar + 20% CO 2 , and the gas flow rate f = 14 - 23 L / min. In view of the good fluidity of the molten pool metal and the wettability of the weld toe edge of the solid wire of the present invention, the straight-pull welding method is adopted without the need for the welding torch to swing.

[0131] Example

[0132] The welding material and welding method suitable for the positive load transmission fillet weld of the non-load-bearing accessory of the present invention are implemented to verify the feasibility of the technical solution.

[0133] Table 1 shows the chemical composition design of the solid wire for three embodiments. Based on this, the wire steel is smelted in a vacuum electric furnace, cast, hot-rolled into wire rods, annealed, drawn into wires, copper-plated, wound and packaged, and finally the finished wire is formed with a wire diameter of 1.2 mm. The solid wires of the three embodiments are applied, and an optimized welding process method is used to weld the non-load-bearing rectangular plate-shaped accessories, and the base plate material of the base metal is Q500M high-strength steel. Table 2 shows the welding process specifications for the accessories in the embodiments. In order to ensure the smooth progress of the subsequent fatigue test evaluation of the welded structures of the accessories for different embodiments, the welding structure form and dimensions of the accessories with the bottom suspended and a gap reserved between the base metal of the base plate as shown in Figure 3 , 4 are adopted. In the figure, 1 is the base plate of the base metal; 2 is the accessory; 3 is the longitudinal fillet weld of the accessory. Finally, a fillet weld of the accessory with a smooth weld toe transition and uniform spreading is obtained, the gap filling and edge bridging states are good, and there are no sharp transitions and undercut defects.

[0134] Table 1 Chemical composition design of the solid wire for three embodiments

[0135]

[0136] Table 2 Welding process specifications for the accessories in the embodiments

[0137]

[0138]

[0139] For the welded structures of the 1-3 rectangular plate-shaped accessories in the embodiments, a pull-pull dynamic fatigue performance comparison test is carried out under the conditions of stress ratio R = 0.5 and fatigue stress range Δσ = 80 MPa. The test stop condition is that the test frequency drops significantly due to the generation of fatigue cracks in the specimen or the number of cycles reaches 1×10 7 times. By comparing and contrasting the test results under this fatigue test condition with the current mainstream standard design values, the optimization effect of the method described in the present invention on the fatigue performance of the welded structure of the accessories is comprehensively evaluated.

[0140] Table 3 shows the fatigue life of the welded structure of the rectangular plate-shaped accessory when the stress ratio R = 0.5 obtained in the embodiment. It can be seen that for the welded structure of the accessory in the embodiment under the condition of the design stress range Δσ = 80 MPa commonly used in the current mainstream standard, the number of cycles obtained in the test is much higher than the corresponding number of cycles in the design standard. By implementing the welding material and welding method described in the present invention for the positive transfer of load fillet welds of non-load-bearing accessories, and comparing and contrasting the fatigue performance data under its specific conditions with the current mainstream standard design values, it is confirmed that the method of the present invention for improving the weld toe forming quality of the fillet weld and enhancing the fatigue performance of the overall structure has a significant effect.

[0141] Table 3 Fatigue life of welded structure of rectangular plate-shaped appendages when the stress ratio R = 0.5 obtained in the examples

[0142]

[0143] Note: The corresponding number of cycles of the design standard is the number of cycles corresponding to the fatigue stress range Δσ = 80 MPa on the typical rectangular appendage fatigue S-N curve specified in the EN 1993 standard. This stress range value is also commonly used in the fatigue design of structural members.

Claims

1. A welding material suitable for fillet welds of non-load-bearing accessories for positive load transfer, Characterized in that: By controlling the components of the welding material, on the basis of controlling the formation of stable droplet transfer and molten pool reaction, Control optimizations for reducing the interatomic binding force, control optimizations for reducing non-metallic inclusions, control for forming low-melting eutectics, and control for forming low-melting compounds are formed. Based on the control optimizations in these four dimensions, optimizations for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface are formed.

2. A welding material suitable for fillet welds of non-load-bearing accessories for positive load transfer according to claim 1, Characterized in that: The control optimization for reducing the interatomic binding force is achieved by controlling the Te content; The control optimization for reducing non-metallic inclusions is achieved by controlling the Si content; The control for forming low-melting eutectics is achieved by controlling the P and S contents; The control for forming low-melting compounds is achieved by controlling the Ti and Mg contents; The formation of the optimization for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface, on the basis of establishing the control of the above component contents, is also achieved by establishing the control of the Mn and Al contents.

3. A welding material suitable for fillet welds of non-load-bearing accessories for positive load transfer according to claim 2, Characterized in that: The control of the Te content is specifically: controlling the mass percentage of Te to be 0.008 - 0.025%; The control of the Si content is specifically: controlling the mass percentage of Si to be 0.9 - 1.8%; The control of the P content is specifically: controlling the mass percentage of P to be 0.015 - 0.030%; The control of the S content is specifically: controlling the mass percentage of S to be 0.012 - 0.025%; The control of the Ti content is specifically: controlling the mass percentage of Ti to be 0.12 - 0.36%; The control of the Mg content is specifically: controlling the mass percentage of Mg to be 0.012 - 0.035%; The control of the Mn content is specifically: controlling the mass percentage of Mn to be 0.4 - 1.1%; The control of the Al content is specifically: controlling the mass percentage of Al to be less than 0.06%.

4. A welding material suitable for fillet welds of non-load-bearing accessories for positive load transfer according to claim 3, Characterized in that: The formation of the optimization for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is achieved by establishing a comprehensive regulation of the contents of Te, Si, P, S, Ti, Mg, Mn, and Al through the set wettability index of the heterogeneous interface of the liquid metal in the molten pool, and by controlling the wettability index of the heterogeneous interface of the liquid metal in the molten pool within the range of the closed interval [3.0, 7.0], specifically as follows: In the above formula, M: The wettability index of the heterogeneous interface of the liquid metal in the molten pool, M ∈ [3.0, 7.0].

5. A welding material suitable for fillet welds of non-load-bearing accessories for positive load transfer according to claim 2, Characterized in that: The formation of the optimization for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is also achieved by establishing the control of the C, O, and N contents; Specifically: Controlling the mass percentage of C to be 0.12 - 0.23%; The mass percentage of O is controlled to be less than 0.0045%; The mass percentage of N is controlled to be less than 0.006%.

6. A welding method suitable for fillet welds for non-load-bearing accessories to transmit loads in the forward direction, characterized in that: First, by establishing control over the components of the welding material, on the basis of forming stable droplet transfer and molten pool reactions, control optimizations for reducing the atomic bonding force, reducing non-metallic inclusions, controlling the formation of low-melting eutectics, and controlling the formation of low-melting compounds are formed. Based on these four-dimensional control optimizations, optimizations for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface are formed; Second, the respective weldable surfaces of the accessory and the base metal bottom plate are set to a spatial structural relationship with a gap formed between them before welding; According to the completed welded structure, a fatigue strength mechanism characterized by the cumulative damage of local microzone cyclic plastic strain controlled by the yield strength of the base metal can be established under the condition that no fatigue failure occurs during 1000 - 5000 cycles of early fatigue cracks. Then, the base metal bottom plate is made of high-strength steel, thereby achieving an improvement in the fatigue strength of the non-load-bearing accessory.

7. A welding method suitable for fillet welds for non-load-bearing accessories to transmit loads in the forward direction according to claim 6, characterized in that: The control optimization for reducing the atomic bonding force is achieved by controlling the Te content; The control optimization for reducing non-metallic inclusions is achieved by controlling the Si content; The control of the formation of low-melting eutectics is achieved by controlling the P and S contents; The control of the formation of low-melting compounds is achieved by controlling the Ti and Mg contents; The formation of the optimization for the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is achieved by combining the establishment of control over the contents of Mn and Al on the basis of establishing control over the above component contents.

8. A welding method suitable for fillet welds for non-load-bearing accessories to transmit loads in the forward direction according to claim 7, characterized in that: The control of the Te content is specifically: controlling the mass percentage of Te to be 0.008 - 0.025%; The control of the Si content is specifically: controlling the mass percentage of Si to be 0.9 - 1.8%; The control of the P content is specifically: controlling the mass percentage of P to be 0.015 - 0.030%; The control of the S content is specifically: controlling the mass percentage of S to be 0.012 - 0.025%; The control of the Ti content is specifically: controlling the mass percentage of Ti to be 0.12 - 0.36%; The control of the Mg content is specifically: controlling the mass percentage of Mg to be 0.012 - 0.035%; The control of the Mn content is specifically: controlling the mass percentage of Mn to be 0.4 - 1.1%; The control of the Al content is specifically: controlling the mass percentage of Al to be less than 0.06%.

9. A welding method suitable for fillet welds for non-load-bearing accessories to transmit loads in the forward direction according to claim 8, characterized in that: The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is achieved by establishing a comprehensive control of the contents of Te, Si, P, S, Ti, Mg, Mn, and Al through the set wettability index of the heterogeneous interface of the liquid metal in the molten pool, and by controlling the wettability index of the heterogeneous interface of the liquid metal in the molten pool within the range of the closed interval [3.0, 7.0], specifically as follows: In the above formula, M: The wettability index of the heterogeneous interface of the liquid metal in the molten pool, M ∈ [3.0, 7.0].

10. A welding method for a fillet weld suitable for non-load-bearing accessories to transmit load in the forward direction according to claim 6, characterized in that: The optimization of the fluidity of the liquid molten pool and the wettability of the heterogeneous interface is also achieved by establishing control over the contents of C, O, and N; specifically: Controlling the mass percentage of C to be 0.12 - 0.23%; Controlling the mass percentage of O to be less than 0.0045%; Controlling the mass percentage of N to be less than 0.006%.

11. A welding method for a fillet weld suitable for non-load-bearing accessories to transmit load in the forward direction according to claim 6, characterized in that: Controlling the gap between the respective weldable surfaces of the accessory and the base metal bottom plate to be 0.5 - 2.2 mm.

12. A welding method for a fillet weld suitable for non-load-bearing accessories to transmit load in the forward direction according to claim 6, characterized in that: The welding uses a direct-pull welding method, Controlling the welding wire to be a solid wire with a diameter of 1.2 mm, Controlling the welding current to be 140 - 190 A; Controlling the welding voltage to be 16 - 21 V; Controlling the welding speed to be 210 - 280 mm / min.

13. A welding method for a fillet weld suitable for non-load-bearing accessories to transmit load in the forward direction according to claim 6, characterized in that: By providing a circulating water cooling device on the back of the base metal bottom plate to provide contact conduction heat exchange with the circulating water temperature during welding less than 45°C, thereby establishing control over the angular deformation of the welded structure to be less than 5°.

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