CN108296584A - A kind of titanium-double heat source low_input_power method for welding of steel board docking - Google Patents

Abstract

The invention belongs to materials processing engineering fields, and in particular to a kind of double heat source low_input_power method for welding of titanium steel plank docking.The soldering connection for realizing titanium steel is welded using double heat source low_input_powers, the different heat expansion coefficient of titanium and steel can be directed to, by controlling two heat-source energy parameter of positive and negative, location parameter, improve the distribution of two intermetallic heat of welding process, reduces the thermal mismatching between titanium and steel metal, not only effectively inhibit the generation of Ti Fe frangible compounds, connector residual stress is effectively reduced simultaneously, realizes the high efficient and reliable connection of connector.In addition, the reverse side heat source butt joint back side directly heat and gas shielded, promote filling metal the connector back side wetting with sprawl, significantly improve appearance of weld.The present invention in the welding process, can be by changing along welding direction, and the relative position of positive plane heat source and reverse side heat source provides and is equivalent to the techniques such as weld preheating or post weld heat treatment.The method of the present invention operation is easy, and is applicable to be brazed, the welding forms such as fusion welding and molten soldering.

Description

A kind of brazing method of titanium-steel plate butt joint with dual heat sources and low heat input

technical field

The invention relates to the field of material processing engineering, in particular to a brazing method for butt jointing of titanium-steel plates with dual heat sources and low heat input.

Background technique

Titanium and titanium alloys have good low-temperature toughness and high-temperature strength, especially high specific strength, and are widely used in the manufacture of structures in the aerospace field. However, the high cost of titanium limits its popularization and application in the engineering field. As a widely used engineering material, stainless steel is cheap and has good thermal conductivity and mechanical properties. The welding of titanium and steel can not only make full use of the advantages and characteristics of their respective materials, but also reduce costs and improve economic benefits, and has broad application prospects.

Although the connection of titanium-steel dissimilar metals has the dual advantages of performance and economy, the welding of titanium-steel has always been a difficult problem in the field of dissimilar metal connection. The reason is that during the welding process of titanium and steel, Ti-Fe intermetallic compounds will be generated. Compared with the Ti-Al and Fe-Al intermetallic compounds formed during the welding of titanium-aluminum and steel-aluminum dissimilar metals, Ti- Fe compounds are extremely brittle, and once they are continuously generated, they will directly lead to joint cracking. More seriously, the thermal expansion coefficient difference between titanium alloy and stainless steel is large, and the thermal stress mismatch between the two materials worsens the cracking tendency of the joint during the welding cooling process. Because of this, there is still no effective method to solve the efficient and reliable connection of titanium-steel.

In order to ensure the welding of titanium-steel, a third metal must be used as a filler material to suppress the formation of Ti-Fe intermetallic compounds. Because of its good chemical compatibility with titanium and steel and its excellent mechanical properties, copper has become the most commonly used filler metal in the current research on titanium-steel connections. More importantly, the melting point of copper is about 1080°C, which is lower than that of titanium (1680°C) and steel (1530°C). Solid titanium and steel can be wetted by melting copper metal to achieve pure brazing of titanium-steel connection to inhibit the formation of brittle intermetallic compounds. However, the traditional furnace brazing method needs to heat the workpiece as a whole. The size of the furnace chamber limits the size and structure of the workpiece. At the same time, the welding efficiency is low, and it is difficult to apply to the engineering connection of titanium-steel plates. The use of fusion welding to realize titanium-steel brazing connection can not only inhibit the formation of Ti-Fe brittle compounds in the joint, but also improve the quality of the joint. Compared with the traditional brazing method, the welding efficiency is significantly improved. However, at present there is no document disclosing the use of a fusion welding method for brazed titanium-steel connections. The main reason is that the current fusion welding is mainly based on single heat source heating, the heat source heats the joint locally, the heat distribution of the joint is extremely uneven, and a large temperature gradient will be formed in the thickness direction of the plate—the side close to the heat source has a higher temperature, and the farther away from the heat source is especially It is the lower heat on the back of the connector. In order to ensure that the back of the joint is formed, the welding heat input must be increased, often resulting in overheating of the heating area of the heat source. Once the base metal melts, the base metal copper and steel rapidly melt and rapidly diffuse and react in the liquid filling metal copper to form Ti-Fe intermetallic compounds. At the same time, the uneven heating of the joint further deteriorates the distribution of residual stress in the joint and deteriorates the performance of the joint. Yan Jiuchun from Harbin Institute of Technology used the TIG welding method to weld titanium alloy-stainless steel with Cu as the filler material. The results showed that it was difficult to effectively suppress the formation of Ti-Fe brittle compounds by using the TIG welding method, and it was difficult to obtain a titanium-steel joint with reliable performance . Once the base metal of the joint is melted, the interface is connected by a liquid/liquid interface, and the atomic diffusion speed is fast, so it is difficult to suppress the formation of Ti-Fe intermetallic compounds, and the performance of the joint is difficult to meet the requirements.

Contents of the invention

In order to realize the pure brazing connection of titanium-steel and suppress the generation of Ti-Fe brittle compounds, the present invention provides a low heat input brazing method for titanium-steel plates butt joint with dual heat sources. When the method is welding titanium-steel plates, The dual heat sources heat the front and back of the joint at the same time, using the synergistic effect of the dual heat sources on the same molten pool to reduce the welding heat input, and by controlling the energy parameters and position parameters of the two heat sources, the energy distribution of the joint is improved, and the pure titanium-steel is realized. Brazing joints can suppress the generation of Ti-Fe brittle compounds and reduce the residual stress of joints, and obtain high-quality titanium-steel joints.

Further, the dual heat sources are MIG shielded welding heat source (front heat source) and tungsten inert gas shielded welding heat source (reverse heat source); wherein, the front heat source is responsible for heating the workpiece, filling wire and providing gas shielding , The power supply adopts DC reverse connection; the reverse heat source is responsible for heating and gas protection on the back of the workpiece, and the power supply adopts DC reverse connection or AC.

Further, the two heat sources on the front and back sides are protected by argon (Ar), and the gas flow rate is 15-30 L/min.

Further, the energy parameters of the two heat sources on the front and back mainly include the welding voltage and welding current of the front heat source; the welding voltage and welding current of the back heat source; the welding speed; the position parameters of the two heat sources include along the welding direction (the front heat source is + , the rear is -), the distance from the front heat source to the back heat source; perpendicular to the welding direction (close to the titanium side is +, close to the steel side is -), the distance from the front heat source to the center of the weld, and the distance from the back heat source to the center of the weld.

Further, in the dual heat source low heat input brazing method, the position parameters of the front and back heat sources are controlled to shift to the steel side, so as to reduce the energy at the base material on the titanium side and suppress the melting of the low thermal conductivity metal titanium base material.

Further, the material of the welding wire used for the front heat source is copper or copper alloy welding wire, the diameter of the welding wire is 0.8-1.6 mm, and the dry elongation of the welding wire is 15 mm.

Further, the method includes the following steps:

Step 1: Place the titanium-steel plate to be welded on the workbench in a parallel manner along the direction of the surface to be welded, reserve a weld gap of 0-1mm, and clamp it with tooling;

Step 2: Place the welding heat source of MIG arc welding vertically above the front of the weldment, and the welding heat source of tungsten inert gas arc welding vertically below the back of the weldment, and the tip of the welding torch points to the welding workpiece;

Step 3: Set the relative position of the welding torch: along the welding direction (the front heat source is +, and the rear is -), the front heat source is -2—+2mm away from the back heat source; perpendicular to the welding direction (close to the titanium side is +, close to the steel The side is -), the front heat source is -0.4-0mm from the center of the weld, and the back heat source is -2-0mm from the center of the weld, and the two heat sources are fixed with a clamp;

Step 4: Set welding energy parameters: front heat source welding voltage 13-25V, welding current 2-150A, reverse heat source welding voltage 8-15V, welding current 20-150A, welding speed 3-30mm/s, during welding, two heat sources welding parameters fixed;

Step 5: Turn on the two heat sources, and turn on the welding tool at the same time, so that the tool moves at a constant speed along the welding direction to complete the welding process.

The beneficial effects of the present invention include the following points:

1. Use dual heat sources to heat the front and back of the joint at the same time, improve the heat distribution of the joint, reduce the peak welding temperature, and use the synergy of the dual heat sources to act on the same molten pool to reduce the heat input required for welding, and control the energy parameters of the two heat sources , position parameters, improve joint energy distribution, and realize pure brazing connection of titanium-steel.

2. The brazing connection of titanium-steel is realized by welding with dual heat sources and low heat input, which not only effectively inhibits the formation of Ti-Fe brittle compounds, but also effectively reduces the residual stress of the joints and realizes efficient and reliable joints.

3. The reverse heat source directly heats the back of the joint to provide the required welding heat for the back of the joint, and at the same time provides gas protection to ensure the joint is formed under low heat input welding conditions.

4. According to the different thermal expansion coefficients of titanium and steel, by controlling the energy parameters and position parameters of the two heat sources on the front and back sides, the heat distribution between the two metals during the welding process can be improved, the thermal mismatch between titanium and steel can be reduced, and the welding residual stress can be relieved.

5. The method of the present invention is easy to operate, and can be applied to welding forms such as brazing, fusion welding and fusion brazing;

6. In the welding process of the welding method of the present invention, by changing the relative position of the front heat source and the back heat source along the welding direction, processes such as pre-weld preheating or post-weld heat treatment can be provided; when the front heat source is placed in the welding position of the back heat source In front, during the welding process, the heat source on the opposite side is in front, which is equivalent to providing pre-welding preheating for the welding process of the front heat source, which is beneficial to the forming of the joint; during the welding process, the heat source on the back side is behind, which is equivalent to welding melting The pool has undergone post-weld heat treatment, and slows down the cooling rate of the weld seam, which is beneficial to reduce the welding residual stress;

7. The present invention adopts the welding heat source of molten inert gas shielded welding as the wire filling heat source. During the welding process, different welding wires can be selected according to the welding requirements, and the operation is simple and convenient.

Description of drawings

Fig. 1 is the schematic diagram of the low heat input brazing method of titanium-steel dissimilar metals of the present invention with dual heat sources;

Among them, workbench 1, MIG welding heat source (front heat source) 2, front heat source shielding gas 201, filler wire 202, tungsten inert gas shielded welding (back heat source) 3, back heat source shielding gas 301, back heat source Tungsten electrode 302, fixture 4, titanium plate 5, steel plate 6;

Figure 2 is the cross-sectional appearance of the brazing joint with dual heat sources and low heat input brazing of 2mm titanium-steel plate with silicon bronze welding wire;

Fig. 3 is the cross-sectional morphology of the brazing joint with dual heat sources and low heat input brazed on a 3mm titanium-steel plate with copper-nickel welding wire.

Detailed ways:

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. On the contrary, the invention covers any alternatives, modifications, equivalent methods and schemes within the spirit and scope of the invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, in the following detailed description of the present invention, some specific details are described in detail, and those skilled in the art can fully understand the present invention without the description of these details.

In this embodiment, the welding heat source of MIG shielded welding adopts the Invision 352MPa welding machine produced by Miller Company, and the size of the welding current can be adjusted according to the thickness of the plate during welding. The welding heat source of tungsten inert gas shielded welding adopts the Syncrowave 250LX welding machine produced by Miller Company. During welding, the relative positions of the front and back welding torches are kept unchanged at all times, so that the plate and the two welding torches move relative to each other along the welding direction, and the front heat source and the back heat source are simultaneously heated on both sides of the workpiece to complete the welding.

Specific embodiment 1

As shown in Figure 1, in this example, dual heat sources are used to heat the front and back of the joint at the same time, and the synergistic effect of the dual heat sources acting on the same molten pool is used to reduce the welding heat input, and by controlling the energy parameters and position parameters of the two heat sources, improve The energy distribution of the joint realizes the pure brazing connection of titanium-steel. The selected welding base materials are commercial TC4 (Ti6Al4V) plate and 304ss (1Cr18Ni9Ti) plate, both of thickness are 2mm, and the dual heat sources are melting inert gas shielded welding heat source (front heat source) and tungsten inert gas shielded welding Welding heat source (reverse heat source); the front heat source is responsible for heating the workpiece, filling wire and providing gas protection, and the power supply adopts DC reverse connection; the reverse heat source is responsible for heating and gas protection on the back of the workpiece, and the power supply adopts DC reverse connection or AC. The energy parameters of the front and back heat sources mainly include the welding voltage and welding current of the front heat source; the welding voltage and welding current of the back heat source; ), the distance from the front heat source to the back heat source; perpendicular to the welding direction (+ near the titanium side, - near the steel side) the distance from the front heat source to the center of the weld, and the distance from the back heat source to the center of the weld. During the welding process, the position parameters of the front and back heat sources are controlled to shift to the steel side, so as to reduce the energy at the base metal on the titanium side and suppress the melting of the low thermal conductivity metal titanium base metal; at the same time, the two heat sources on the front and back are protected by argon (Ar), The gas flow rate is 15-30L/min; the material of the welding wire used by the front heat source is silicon bronze welding wire (Si _wt% =3.5), the welding wire diameter is 1.0mm, and the welding wire dry elongation is 15mm;

Specifically follow the steps below to implement welding:

Step 1: Place the titanium-steel plate to be welded on the workbench parallel to the direction of the surface to be welded, reserve a weld gap of 0.3mm, and clamp it with tooling;

Step 2: Place the welding heat source of MIG arc welding vertically above the front of the weldment, and the welding heat source of tungsten inert gas arc welding vertically below the back of the weldment, and the tip of the welding torch points to the welding workpiece;

Step 3: Set the relative position of the welding torch: along the welding direction (the front heat source is +, the rear is -), the front heat source is 0mm away from the back heat source; perpendicular to the welding direction (close to the titanium side is +, close to the steel side is -) , the front heat source is 0mm from the center of the weld, and the back heat source is -2mm from the center of the weld, and the two heat sources are fixed with a clamp;

Step 4: Set the welding energy parameters: the welding voltage of the front heat source is 15V, the welding current is 65A, the welding voltage of the back heat source is 14V, the welding current is 70A, and the welding speed is 11mm/s. During the welding process, the welding parameters of the two heat sources are fixed;

Step 5: Turn on the two heat sources, and turn on the welding tool at the same time, so that the tool moves at a uniform speed along the welding direction to complete the welding process

Acute observation of the appearance of the front and back of the joint shows that the front and back of the joint are well spread, the spread width is uniform, and there is basically no deformation of the weldment after welding. Figure 3 shows the cross-sectional appearance of the welded joint. No cracks were found. The pure brazing connection of titanium-steel was realized by the dual heat source low heat input welding method, and no Ti-Fe compound was formed in the weld composition detection. The tensile strength of the welded joint can reach up to 350MPa. Compared with the existing arc welding, the welding heat input is significantly reduced, the formation of Ti-Fe brittle compounds in the joint is suppressed, and the joint strength is significantly higher than that of the titanium-steel joint welded by traditional arc welding. The front side adopts MIG shielded welding, and the welding wire bridging ability improves the tolerance of the base metal assembly, increases the flexibility of operation, and improves the welding efficiency.

Specific embodiment two:

As shown in Figure 1, in this example, dual heat sources are used to heat the front and back of the joint at the same time, and the synergistic effect of the dual heat sources acting on the same molten pool is used to reduce the welding heat input, and by controlling the energy parameters and position parameters of the two heat sources, improve Joint energy distribution to achieve titanium-steel brazing connection. The selected welding base metals are commercial TC4 (Ti6Al4V) plate and 304ss (1Cr18Ni9Ti) plate, both of thickness are 3mm, and the dual heat sources are melting inert gas shielded welding heat source (front heat source) and tungsten inert gas shielded welding Welding heat source (reverse heat source); the front heat source is responsible for heating the workpiece, filling wire and providing gas protection, and the power supply adopts DC reverse connection; the reverse heat source is responsible for heating and gas protection on the back of the workpiece, and the power supply adopts DC reverse connection or AC. The energy parameters of the front and back heat sources mainly include the welding voltage and welding current of the front heat source; the welding voltage and welding current of the back heat source; the welding speed; the position parameters of the two heat sources include along the welding direction (the front heat source is +, and the rear is -) , the distance from the front heat source to the back heat source; perpendicular to the welding direction (+ near the titanium side, - near the steel side), the distance from the front heat source to the center of the weld, and the distance from the back heat source to the center of the weld. During the welding process, the position parameters of the front and back heat sources are controlled to shift to the steel side, so as to reduce the energy at the base metal on the titanium side and suppress the melting of the low thermal conductivity metal titanium base material. At the same time, the two heat sources on the front and back are protected by argon (Ar), and the gas flow rate is 15-30L/min; the welding wire material used by the front heat source is commercial copper-nickel welding wire (ErCuNi-30), the diameter of the welding wire is 1.2mm, and the dry elongation of the welding wire is 15mm;

Specifically follow the steps below to implement welding:

Step 1: Place the titanium-steel plate to be welded on the workbench parallel to the direction of the surface to be welded, reserve a weld gap of 0.3mm, and clamp it with tooling;

Step 2: Place the welding heat source of MIG arc welding vertically above the front of the weldment, and the welding heat source of tungsten inert gas arc welding vertically below the back of the weldment, and the tip of the welding torch points to the welding workpiece;

Step 3: Set the relative position of the welding torch: along the welding direction (the front heat source is +, the rear is -), the front heat source is 0mm away from the back heat source; perpendicular to the welding direction (close to the titanium side is +, close to the steel side is -) , the front heat source is 0mm from the center of the weld, and the back heat source is -1.5mm from the center of the weld, and the two heat sources are fixed with a clamp;

Step 4: Set the welding energy parameters: the welding voltage of the front heat source is 16V, the welding current is 70A, the welding voltage of the back heat source is 12V, the welding current is 40A, and the welding speed is 18mm/s. During the welding process, the welding parameters of the two heat sources are fixed;

Step 5: Turn on the two heat sources, and turn on the welding tool at the same time, so that the tool moves at a uniform speed along the welding direction to complete the welding process

Through the observation of the front and back of the joint, it is found that the front and back of the joint are well formed, and the width of the weld spread is uniform. Figure 3 shows the cross-sectional morphology of the welded joint, and there is no crack in the joint. The pure brazing connection of titanium-steel was realized by using the brazing method of dual heat sources and low heat input. The inspection of the weld composition found that the formation of brittle compounds in the joint was effectively suppressed, and the plates were evenly heated during the welding process without obvious deformation. The average tensile strength of welded joints reaches 312MPa. An efficient and reliable connection of titanium-steel dissimilar metals is obtained by a dual-heat-source low-heat-input welding method.

Claims (7)

1. A titanium-steel plate butt joint dual heat source low heat input brazing method is characterized in that: when welding titanium-steel plates, dual heat sources are used to heat the front and back sides of the joint simultaneously, and the synergistic effect of the dual heat sources acting on the same molten pool is utilized , reduce the welding heat input, and improve the energy distribution of the joint by controlling the energy parameters and position parameters of the two heat sources, realize the pure brazing connection of titanium-steel, suppress the formation of Ti-Fe brittle compounds and reduce the residual stress of the joint, and obtain high quality titanium-steel joints. 2. a kind of titanium-steel plate according to claim 1 butt double heat source low-heat input brazing method, it is characterized in that described double heat source is front heat source and reverse heat source, is respectively MIG welding heat source and tungsten Extremely inert gas shielded welding welding heat source; among them, the front heat source is responsible for heating the workpiece, filling wire and providing gas protection, and the power supply adopts DC reverse connection; the reverse heat source is responsible for heating and gas protection on the back of the workpiece, and the power supply adopts DC reverse connection or AC. 3. A low heat input brazing method for titanium-steel plate butt joint with dual heat sources according to claim 2, characterized in that the two heat sources on the front and back sides are protected by argon gas, and the gas flow rate is 15-30 L/min. 4. A kind of titanium-steel plate butt joint double heat source low heat input brazing method according to claim 2 is characterized in that the energy parameters of the two heat sources on the front and back sides mainly include the welding voltage and welding current of the front heat source; the welding of the back heat source Voltage, welding current; welding speed; the position parameters of the two heat sources include along the welding direction (the front heat source is +, the rear is -), the distance between the front heat source and the reverse heat source; perpendicular to the welding direction (close to the titanium side is +, close to The steel side is -), the distance from the heat source on the front side to the center of the weld, and the distance from the heat source on the back side to the center of the weld. 5. A kind of titanium-steel plate butt joint dual heat source low heat input brazing method according to claim 4, it is characterized in that in the dual heat source low heat input brazing method, the position parameters of the front and back heat sources are controlled to shift to the steel side, so as to Reduce the energy at the base material on the titanium side and suppress the melting of the titanium base material with low thermal conductivity. 6. A kind of titanium-steel plate butt joint dual heat source low heat input brazing method according to claim 2, characterized in that the material of the welding wire used by the front heat source is copper or copper alloy welding wire, the diameter of the welding wire is 0.8-1.6mm, and the welding wire is dry. The elongation is 15mm. 7. A kind of titanium-steel plate butt joint double heat source low heat input brazing method according to claim 1, is characterized in that the brazing step is as follows: Step 1: Place the titanium-steel plate to be welded on the workbench in a parallel manner along the direction of the surface to be welded, reserve a weld gap of 0-1mm, and clamp it with tooling; Step 2: Place the welding heat source of MIG arc welding vertically above the front of the weldment, and the welding heat source of tungsten inert gas arc welding vertically below the back of the weldment, and the tip of the welding torch points to the welding workpiece; Step 3: Set the relative position of the welding torch: along the welding direction (the front heat source is +, and the rear is -), the front heat source is -2—+2mm away from the back heat source; perpendicular to the welding direction (close to the titanium side is +, close to the steel The side is -), the front heat source is -0.4-0mm from the center of the weld, and the back heat source is -2-0mm from the center of the weld, and the two heat sources are fixed with a clamp; Step 4: Set welding energy parameters: front heat source welding voltage 13-25V, welding current 2-150A, reverse heat source welding voltage 8-15V, welding current 20-150A, welding speed 3-30mm/s, during welding, two heat sources Welding parameters are fixed; Step 5: Turn on the two heat sources, and turn on the welding tool at the same time, so that the tool moves at a constant speed along the welding direction to complete the welding process.