CN110369838B

CN110369838B - Welding waveform control method for nickel-based alloy consumable electrode gas shielded welding

Info

Publication number: CN110369838B
Application number: CN201910655523.2A
Authority: CN
Inventors: 华学明; 刘轶玮; 李芳�; 张跃龙; 蔡艳; 沈忱
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2019-07-19
Filing date: 2019-07-19
Publication date: 2020-12-11
Anticipated expiration: 2039-07-19
Also published as: CN110369838A

Abstract

The invention discloses a welding waveform control method for nickel-based alloy consumable electrode gas shielded welding, which comprises a basic value stage: setting base voltage, base current, duration t₁(ii) a The pulse stage is as follows: setting a first voltage, a first current, and a duration t₂(ii) a And at the later stage of the pulse stage: setting a second voltage, a second current, and a duration t₃(ii) a And (5) ending the pulse phase: setting base voltage, base current, duration t₄(ii) a And a short-circuit current suppression stage: setting a third voltage, a third current, and a duration t₅(ii) a An arc striking stage: setting the arcing voltage, the arcing current and the duration t₆. The method provided by the invention can solve the problems of P-GMAW molten drop transition and difficult molten pool spreading, and can solve the defects of side wall incomplete fusion and root incomplete penetration. The invention is beneficial to realizing all-position welding, and simultaneously realizes automation and higher deposition efficiency.

Description

Welding waveform control method for nickel-based alloy consumable electrode gas shielded welding

Technical Field

The invention relates to the technical field of welding processes, in particular to a welding waveform control method for nickel-based alloy consumable electrode gas shielded welding.

Background

The nickel-based alloy has excellent high-temperature or low-temperature performance, better corrosion resistance and excellent wear resistance, and is widely applied to the fields of nuclear power, ocean, aerospace and the like. To ensure the performance of nickel-based alloys, tight control of the weld heat input is often required. Especially under the condition of non-flat welding, the welding current must be strictly controlled in order to prevent the flowing of the molten pool. The nickel-based alloy has large surface tension and high viscosity, deposited metal is difficult to spread during welding, the defects of side wall incomplete fusion, root incomplete penetration and the like are easily generated, and meanwhile, molten drops are difficult to transit.

At present, the commonly used welding methods of the Ni-based alloy mainly comprise shielded metal arc welding, submerged arc welding and tungsten inert gas shielded welding. Shielded metal arc welding can be used for all-position welding, but has low welding efficiency and is easy to generate defects. Submerged arc welding is efficient, but back chipping is complex and can only be used for thick plate flat welding. The tungsten inert gas shielded welding is suitable for welding at various positions, the appearance and the mechanical property of a welding line are easy to ensure, but the method has low efficiency and higher cost.

In addition to the above methods, some of the prior art uses gas shielded flux cored wire welding to improve the problems of molten drop transition and molten pool spreading during the welding of nickel-based alloys. The flux-cored wire contains the arc stabilizer, so that stable combustion of electric arc can be maintained, stable drop injection transition is formed, molten slag generated in the welding process can greatly reduce the surface tension of molten pool metal, the wettability of the molten pool metal to base metal is increased, the spreading of the molten pool is promoted, and high-quality welding seams can be obtained.

In other prior arts, a cold metal transfer welding technology CMT (cold metal transfer) is adopted to realize build-up welding of inconel625 cladding layer, intermittent wire feeding is performed through the CMT technology, the output current of a digital power supply is almost zero after a molten drop and a molten pool are controlled to form a short circuit, and meanwhile, the molten drop is promoted to fall off by drawing back a welding wire, so that stable molten drop transfer can be formed. This technique is only suitable for build-up welding and welding of thin plates.

In the better prior art, pulse gas metal arc welding (P-GMAW) is adopted to realize jet transition under smaller average current, so that the welding wire is very suitable for welding of nickel-based alloy, meanwhile, the solid welding wire is adopted, so that the welding wire has no chemical powder wetting and metallurgical reaction gas, no welding slag is generated to block gas from escaping, gas holes can be avoided, and the welding wire has the advantages of easiness in realizing automation, low cost, high deposition efficiency, strong adaptability and the like. But because the surface tension of the nickel-based alloy is large, molten drops are not easy to separate from the welding wire and difficult to neck, and can not separate from the end part of the welding wire after being elongated along the axial direction, a short circuit can be formed without obvious necking in the transition process, a short-circuit liquid phase bridge is thick, a large amount of splashing is generated after fracture, and more liquid metal is remained at the end part of the welding wire after transition.

A schematic diagram of a conventional P-GMAW welding process is shown in fig. 1. FIG. 1-a shows the maintenance of the arc 3 burning at the base current, because the droplet 1 is not completely transferred under this welding method, the droplet at the end of the welding wire 2 is larger at the base phase; FIG. 1-b shows the welding entering the pulse phase, the current rising rapidly, the welding wire 2 melting, and the droplet 1 growing; fig. 1-c shows that under the electromagnetic pinch force and plasma jet force, the droplet 1 is elongated and approaches the molten pool on the workpiece 4, forming a droplet 5 with no significant necking. The surface tension of the nickel-based alloy molten drop is high, and the large-size molten drop is difficult to generate necking, so that the necking is not obvious; FIG. 1-d shows that the droplet 5, which is not significantly constricted, continues to move towards the bath and forms a short circuit in contact with the bath, but the short-circuit liquid phase bridge 6 is thicker because the constriction is not significant; FIG. 1-e shows that the high viscosity droplets are not easy to separate from the welding wire, and the liquid phase bridge 6 is exploded after a long time short circuit, so that a large amount of splashing particles 7 are generated; fig. 1-f shows a state that a large amount of liquid metal which does not enter a molten pool retracts under the action of surface tension after a liquid phase bridge is broken, the liquid metal is suspended at the end part of the welding wire 2, molten drops are not completely transited, and more liquid metal is remained at the tip of the welding wire 2. Therefore, under the conventional P-GMAW, the molten drop 1 is difficult to transit, a large amount of splashing particles 7 are formed, the molten drop is not completely transited, and the welding effect is poor.

In order to solve the problem of droplet transfer, in the prior art, the length of a welding arc can be increased, P-GMAW is carried out under a long arc, and sufficient transfer space is provided for a droplet to form pulse droplet ejection transfer. As shown in fig. 2. Wherein, in the base value stage, the base value current maintains the electric arc 3 to burn, and because the molten drop 1 under the long electric arc is basically completely transited, the molten drop 1 at the end part of the welding wire 2 is smaller (as shown in figure 2-a); then, a pulse stage is carried out, the current rises, the welding wire 2 is melted, and the molten drop 1 grows (as shown in figure 2-b); under the action of plasma flow force and electromagnetic contraction force, the molten drop 1 is elongated, and the arc 3 is longer, so that the molten drop 1 has sufficient spatial transition and forms a necked molten drop 5 after being elongated, and the necked molten drop 5 is not contacted with a molten pool (as shown in figure 2-c); then, under the action of electromagnetic contraction force, the molten drop 5 of the necking is broken at the necking position and is separated from the welding wire 2, and the residual liquid metal at the end part of the welding wire 2 is in a pencil point shape (as shown in a figure 2-d); the pencil point-shaped residual liquid metal drops further form fine molten drops 8 and are transited to a molten pool (as shown in figure 2-e); in this way the droplet is substantially completely in transition and little residual liquid metal is left at the end of the final wire (see fig. 2-f). Although the long arc P-GMAW can realize stable drop injection transition, the arc length is too long, the heat of the arc is dispersed, the heat transmitted to a molten pool and a base material is less, and the risk that the root is not welded through and the side wall is not fused is increased. Meanwhile, the arc is too long, and the arc force acting on the molten pool is small, so that the molten pool which is difficult to spread is stacked on the surface of the plate more easily and is difficult to spread. In addition, an excessively long arc may also lead to reduced arc stability, further inducing weld defects.

Accordingly, those skilled in the art have been devoted to developing a method for controlling a welding waveform of a gas metal arc welding of a nickel-based alloy, which utilizes the advantages of a short arc and simultaneously performs short circuit control, solves the problems of the conventional P-GMAW droplet transfer and the difficulty in spreading a molten pool, and simultaneously solves the defects of sidewall lack of fusion and root lack of penetration.

Disclosure of Invention

In view of the above defects of the prior art, the technical problems to be solved by the invention are that the conventional P-GMAW is difficult in droplet transfer, can form a large amount of spatters, is incomplete in droplet transfer and is poor in welding effect.

In order to achieve the aim, the invention provides a welding waveform control method for nickel-based alloy consumable electrode gas shielded welding, which specifically comprises the following steps:

step 1, a basic value stage: setting welding voltage as basic value voltage, welding current as basic value current, and lasting for t₁Maintaining stable combustion of the electric arc;

step 2, pulse stage early stage: setting welding voltage to first voltage, welding current setIs set to a first current for a time period t₂So that the welding wire is melted rapidly and the molten drop grows rapidly;

step 3, pulse stage later stage: setting the welding voltage to a second voltage, the welding current to a second current, and the duration t₃Causing the droplet to elongate and produce a constriction;

and 4, finishing the pulse stage: setting a welding voltage to the base voltage, a welding current to the base current, and a duration t₄So that the molten drop contacts the molten pool to generate a short circuit phenomenon;

step 5, short circuit current suppression stage: after the short circuit phenomenon is detected, the welding voltage is set as a third voltage, the welding current is set as a third current, and the duration time t is₅The molten drop is transited by means of surface tension between the molten drop and a molten pool, and splashing is avoided;

step 6, an arc striking stage: after the short circuit phenomenon stops, the welding voltage is set as the arc starting voltage, the welding current is set as the arc starting current, and the duration time t₆Carrying out arc striking;

and 7, repeating the steps 1 to 6 until the welding is finished.

Further, the welding process adopts short arc welding, and short circuit is generated and the short circuit current is restrained in the welding process.

Further, the first voltage is higher than the base voltage; the first current is higher than the background current.

Further, the second voltage is higher than the first voltage; the second current is higher than the first current.

Further, the third voltage is lower than the base voltage; the third current is less than the background current.

Further, the arcing voltage is higher than the base voltage; the arcing current is equal to the base current.

Further, the base voltage is 19-21V; the base value current is 25-45A; said t is₁Is 7.5 to 8.5 ms.

Further, the first voltage is41-43V; the first current is 460-480A; said t is₂Is 0.9 to 1.1 ms.

Further, the second voltage is 44-46V; the second current is 520-540A; said t is₃Is 1.2 to 1.4 ms.

Further, the base voltage is 19-21V; the base value current is 25-45A; said t is₄Is 0.2 to 0.5 ms.

Further, the third voltage is 0V; the third current is 0A; said t is₅Is 0.1 to 0.4 ms.

Further, the third voltage is 2-3V; the third current is 15-25A; said t is₅Is 0.1 to 0.4 ms.

Further, the arcing voltage is 28-30V; the arcing current is 25-45A; said t is₆Is 1.6 to 2.0 ms.

Compared with the prior art, the invention at least has the following beneficial effects:

1. compared with flux-cored wire gas shielded welding, the solid welding wire is more beneficial to eliminating air holes, has lower cost and is beneficial to reducing the production cost;

2. compared with the flux-cored wire and submerged arc welding, the method avoids the trouble of removing the slag layer on the surface of the welding seam after welding, and is beneficial to improving the production efficiency;

3. compared with the cold metal transition technology CMT, the welding of the medium plate can be realized;

4. the invention is beneficial to realizing all-position welding, and meanwhile, the automation is realized, and the deposition efficiency is higher;

5. the method utilizes the advantages of short arc and simultaneously performs short circuit control, solves the problems of P-GMAW molten drop transition and difficult molten pool spreading, and can solve the defects of side wall incomplete fusion and root incomplete penetration. The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a schematic diagram of a conventional P-GMAW welding process;

FIG. 2 is a schematic view of a long arc P-GMAW welding process;

FIG. 3 is a schematic diagram of a short arc P-GMAW welding process;

FIG. 4 is a schematic diagram of a voltage and current control curve corresponding to a welding process in accordance with an embodiment of the present invention;

fig. 5 is a schematic diagram of a voltage and current control curve corresponding to a welding process according to another embodiment of the present invention.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

FIG. 1 is a schematic view of a conventional P-GMAW welding process, and FIG. 2 is a schematic view of a welding process for performing P-GMAW under a long arc. Wherein, 1-molten drop; 2-welding wires; 3-electric arc; 4-a workpiece; 5-necking down the molten drop; 6-short circuit liquid phase bridge; 7-splash particles; 8-fine molten drop. Specific welding procedures have been set forth in the background. This will not be repeated here.

FIG. 3 is a schematic view of the welding process of the present invention for short arc pulse gas metal arc welding (S-P-GMAW) with the further improvement of the present invention based on P-GMAW to shorten the welding arc length. Short arc welding is adopted, so that on one hand, the heat of the electric arc 3 is concentrated, the energy loss is small, the heat input of the molten drop 1 is increased, the temperature of the molten drop 1 is increased, the surface tension is reduced, and the transition of the molten drop 1 is facilitated; on the other hand, the arc length is reduced, the characteristics of the electric arc 3 are changed, the electric arc wraps the whole molten drop in the transition process of the molten drop 1, so that the promotion effect of electromagnetic shrinkage force on molten drop transition is enhanced, the necking molten drop 5 is favorably formed, and the molten drop transition can be improved. Further, when the arc 3 is shortened, the arc force acting on the molten pool increases, which contributes to the promotion of the molten pool spreading. Welding under a short arc, while having the advantages described above, a short arc length of the weld produces a short circuit. In order to avoid the spatter generated by the short circuit, it is necessary to perform electric signal control to suppress the welding current under the short circuit, thereby suppressing the spatter.

The welding method of the short arc pulse gas metal arc welding (S-P-GMAW) comprises the following specific processes:

under the welding method of S-P-GMAW, the molten drop 1 is basically completely transited, and the molten drop 1 at the end part of the welding wire 2 is less in the base value stage (as shown in figure 3-a); after the pulse stage, the current rises, the welding wire 2 is melted, and the molten drop 1 grows up (as shown in figure 3-b); then under the action of the electromagnetic shrinkage force and the plasma current force, the molten drop is elongated, and meanwhile, the electromagnetic shrinkage force promotes the generation of the molten drop 5 with the necking (as shown in figure 3-c); then the necking molten drop 5 continuously approaches to the molten pool, and a short circuit is formed after the necking molten drop and the molten pool are contacted, wherein a short-circuit liquid phase bridge 6 at the necking position is fine (figure 3-d); the current is restrained in the short-circuit stage, the short-circuit liquid phase bridge 6 at the necking part is broken under the action of the surface tension between the molten pool and the molten drop, and no splash is generated at the broken part 9 (as shown in figure 3-e); the method has the advantages that the molten drop transition is basically complete, and the residual liquid metal at the end of the welding wire is less (as shown in figure 3-f). Therefore, the invention can solve the problems of the nickel-based alloy molten drop transition and the difficult spreading of a molten pool, and realize the stable welding.

Example 1

In the welding method of S-P-GMAW, welding current control is a core technique of suppressing spatter. As shown in FIG. 4, the present invention provides a preferred embodiment of a welding waveform control method for gas metal arc welding of nickel-based alloy. The specific control period corresponds to the welding process.

Stage A in FIG. 4 is the base value stage (corresponding to FIG. 3-a): setting the welding voltage to 20V, the welding current to 35A, and the duration t₁Setting the time to 8ms, and maintaining the stable combustion of the electric arc 3;

in FIG. 4, stage B is the early stage of the pulse phase (corresponding to FIG. 3-B): the welding voltage was set to 43V, the welding current was set to 480A, and the duration t₂The setting is 0.9ms, so that the welding wire 2 is rapidly melted, and the molten drop 1 is rapidly grown;

stage C in FIG. 4 is the later pulse stage (corresponding to FIG. 3-C): welding voltage was set to 44V, welding current was set to 520A, duration t₃Set to 1.4ms, so that the droplet is elongated and creates a constriction;

stage D in FIG. 4 is the end of the pulse stage (corresponding to FIG. 3-D): setting welding voltage to 20V, weldingCurrent is set to 35A for a time period t₄Set to 0.5ms so that the droplet contacts the molten pool to cause a short-circuit phenomenon and a short-circuited liquid-phase bridge 6 is generated.

Stage E in fig. 4 is the short circuit current suppression stage (corresponding to fig. 3-E): after the short circuit phenomenon is detected, the welding voltage is set to be 0, the welding current is set to be 0, and the duration time t is₅The time is set to 0.4ms, so that the molten drop is transited by virtue of the surface tension between the molten drop and a molten pool, and the generation of splashing is avoided;

in fig. 4, the F stage is an arc striking stage: when the short circuit phenomenon stops, the welding voltage is set to be 28V, the welding current is set to be 35A, and the duration time t₆Set to 1.7ms, arc starting is performed.

The G phase in fig. 4 is the base value phase of the next droplet transfer cycle, and each droplet is completed by the same welding process until the whole welding work is completed.

Example 2

As shown in FIG. 5, another preferred embodiment of the welding waveform control method for gas metal arc welding of nickel-based alloy is provided by the present invention. The specific control period corresponds to the welding process.

Stage A in FIG. 5 is the base value stage (corresponding to FIG. 3-a): setting the welding voltage to 21V, the welding current to 40A, and the duration t₁Setting the time to 7.5ms, and maintaining the stable combustion of the electric arc 3;

stage B in FIG. 5 is the early stage of the pulse phase (corresponding to FIG. 3-B): setting the welding voltage to 41V, the welding current to 460A, and the duration t₂The setting is 1.0ms, so that the welding wire 2 is rapidly melted, and the molten drop 1 is rapidly grown;

stage C in FIG. 5 is the later pulse stage (corresponding to FIG. 3-C): set welding voltage to 46V, welding current to 540A, duration t₃Set to 1.3ms, so that the droplet is elongated and creates a constriction;

stage D in FIG. 5 is the end of the pulse stage (corresponding to FIG. 3-D): setting the welding voltage to 21V, the welding current to 40A, and the duration t₄Set to 0.3ms so that the droplet contacts the molten pool to cause a short-circuit phenomenon and a short-circuited liquid-phase bridge 6 is generated.

Stage E in fig. 5 is the short circuit current suppression stage (corresponding to fig. 3-E): after the short circuit phenomenon is detected, the welding voltage is set to be 3V, the welding current is set to be 25A, and the duration time t is₅The time is set to 0.2ms, so that the molten drop is transited by virtue of surface tension and electromagnetic contraction force between the molten drop and a molten pool, and splashing is avoided;

stage F in fig. 5 is the arcing stage: when the short circuit phenomenon stops, the welding voltage is set to be 30V, the welding current is set to be 40A, and the duration time t₆Set to 2ms, arc starting is performed.

The G phase in fig. 5 is the base value phase of the next droplet transfer cycle, and each droplet is completed in the same welding process until the whole welding work is completed.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A welding waveform control method for nickel-based alloy consumable electrode gas shielded welding specifically comprises the following steps:

step 1, a basic value stage: setting the welding voltage as a basic value voltage, setting the welding current as a basic value current, and maintaining stable combustion of the electric arc for a time t 1;

step 2, pulse stage early stage: setting the welding voltage as a first voltage and the welding current as a first current for a time t2, so that the welding wire is rapidly melted and the molten drop grows rapidly;

step 3, pulse stage later stage: setting the welding voltage to a second voltage and the welding current to a second current for a time period t3 such that the droplet is elongated and a constriction is created;

and 4, finishing the pulse stage: setting the welding voltage as the basic value voltage and the welding current as the basic value current for a time t4, so that the molten drop contacts the molten pool to generate a short circuit phenomenon;

step 5, short circuit current suppression stage: after the short circuit phenomenon is detected, setting the welding voltage as a third voltage and the welding current as a third current, and lasting for t5, so that the molten drop is transited by means of surface tension between molten pools, and splashing is avoided; the third voltage is lower than the base voltage and the third current is lower than the base current;

step 6, an arc striking stage: after the short circuit phenomenon stops, setting the welding voltage as an arc starting voltage, setting the welding current as an arc starting current, and carrying out arc starting for a duration t 6;

and 7, repeating the steps 1 to 6 until the welding is finished.

2. The method according to claim 1, wherein the welding process is short arc welding, and wherein short circuit is generated and short circuit current is suppressed during the welding process.

3. The nickel-base alloy gas metal arc welding waveform control method of claim 1, wherein the first voltage is higher than the background voltage and the first current is higher than the background current; the second voltage is higher than the first voltage, and the second current is higher than the first current.

4. The nickel-base alloy gas metal arc welding waveform control method of claim 1, wherein the arc starting voltage is higher than the base voltage; the arcing current is equal to the base current.

5. The method for controlling the welding waveform of the nickel-based alloy consumable electrode gas shielded welding according to claim 4, wherein the base voltage is 19 to 21V; the base value current is 25-45A; the t1 is 7.5-8.5 ms.

6. The method according to claim 3, wherein the first voltage is 41 to 43V, the first current is 460 to 480A, and the t2 is 0.9 to 1.1 ms; the second voltage is 44-46V, the second current is 520-540A, and t3 is 1.2-1.4 ms.

7. The method for controlling the welding waveform of the nickel-based alloy consumable electrode gas shielded welding according to claim 4, wherein the base voltage is 19 to 21V; the base value current is 25-45A; the t4 is 0.2-0.5 ms.

8. The nickel-base alloy gas metal arc welding waveform control method of claim 3, wherein the third voltage is 0V; the third current is 0A; the t5 is 0.1-0.4 ms.

9. The method according to claim 3, wherein the third voltage is 2 to 3V; the third current is 15-25A; the t5 is 0.1-0.4 ms.

10. The method for controlling the welding waveform of the nickel-based alloy consumable electrode gas shielded welding according to claim 4, wherein the arc starting voltage is 28-30V; the arcing current is 25-45A; the t6 is 1.6-2.0 ms.