JP4842665B2 - Two-electrode arc welding method for high alloy steel - Google Patents

Description

  The present invention relates to a two-electrode arc welding method for high alloy steel for improving arc welding performance for high alloy steel.

In MIG welding of high alloy steel such as stainless steel, it is common to use argon gas in which about 2% by volume of oxygen is added to the shielding gas. This is because the formation of the cathode cathode spot is stabilized by the oxygen in the shielding gas, and the arc generation state is stabilized. High safety and reliability are required in the welding of high alloy steel used for pressure vessels, nuclear power plant structures, and the like. However, when argon gas to which oxygen is added is used in high quality high alloy steel welding, oxygen is dissolved in the weld metal and the quality of the welded portion is lowered. Therefore, when high quality steel is welded with high quality, the shielding gas is 100% by volume of inert gas such as pure argon gas.
The shielding gas is used.

  However, when MIG welding is performed in a pure argon gas atmosphere, arc wandering and droplet rotation transfer occur, so that the arc becomes unstable and stable welding cannot be performed. Wandering is a phenomenon in which the arc fluctuates and occurs when the cathode spot formation position of the arc constantly moves because oxygen is not contained in the shield gas. Rotation shift is a phenomenon in which the arc is not stable because the tip of the welding wire rotates at a high speed in a high current region. This phenomenon occurs when a strong magnetic field and electric field are formed by a high current passing through the welding wire, and a rotational force is generated at the tip of the welding wire. Therefore, TIG welding is generally used because MIG welding cannot be used for high-quality welding of high alloy steel. However, TIG welding has problems that production efficiency is lower than MIG welding and automation is difficult. For this reason, recently, a conventional technique for improving the arc instability of MIG welding described above has been proposed. Hereinafter, these conventional techniques will be described.

  FIG. 6 is a cross-sectional view of a welding wire having a special two-layer structure that can suppress instability of high alloy steel MIG welding in a pure argon gas atmosphere. This welding wire has a coaxial two-layer structure, and uses, for example, Inconel having a low melting point as a core material, and uses, for example, stainless steel having a high melting point as a clothing material. The reverse structure may be used. If this welding wire is used, it is possible to perform MIG welding that does not cause arc instability due to wandering and rotation. However, this welding wire is difficult to produce and very expensive due to its special structure. For this reason, it is hardly popular in practical use.

  FIG. 7 is a configuration diagram of a two-electrode arc welding apparatus. Two welding wires 1a and 1b are fed through the nozzle 5 attached to the tip of one welding torch, and two arcs 3a and 3b are generated between the base metal 2 and the welding wire 1a and 1b. The first welding power source PS1 supplies power to the first welding wire 1a via the first power feed tip 4a and outputs a first feed control signal Fc1 for controlling the first feed motor M1. The second welding power source PS2 supplies power to the second welding wire 1b via the second power feed tip 4b and outputs a second feed control signal Fc2 for controlling the second feed motor M2. The first welding wire 1a and the second welding wire 1b are electrically insulated from each other.

  When high alloy steel MIG welding is performed in a pure argon gas atmosphere by the two-electrode arc welding method using the above-described apparatus, arc instability due to wandering and rotation transfer described above is suppressed. The reason why wandering is suppressed is that the energizing directions of the welding power sources for energizing the two welding wires 1a and 1b are the same, so that the two arcs 3a and 3b are attracted to each other and the arc is prevented from fluctuating. is there. The reason why the rotation shift does not occur is that a high current can be energized separately for the two welding wires 1a and 1b, so that the current value for energizing one welding wire becomes small and no rotational force is generated ( (See Patent Documents 1 and 2).

JP 2001-205444 A JP 2002-35936 A

  As described above, when high alloy steel is welded in a pure argon gas atmosphere, welding can be performed without arc instability if a two-electrode arc welding method is used. However, high alloy steel welding has another major problem that cracks are likely to occur in the weld. Hereinafter, this cracking problem will be described by taking an example of build-up welding using a high alloy steel welding wire.

  For the purpose of rust prevention, build-up welding is performed using a stainless steel high alloy steel welding wire on a mild steel material. In this case, cracks are likely to occur in the weld. As shown in FIG. 8, the cross section of the weld bead is formed from the surplus portion Sb and the penetration portion Sa. The surplus portion Sb and the penetration portion Sa have a metal structure in which the high alloy steel component of the welding wire and the mild steel component of the base material are melted together. When this metal structure becomes a complete austenite structure, hot cracking occurs. Moreover, when martensite precipitates in the metal structure, it hardens and cracks occur.

In order to prevent cracking, the metal structure of the welded portion is estimated using the well-known Schaeffler structure diagram shown in FIG. 9, and this metal structure falls within the safety region (A) + (F) shown in FIG. It is important to set the welding materials to enter. The safety region (A) + (F) is a region of a metal structure in which a small amount of a ferrite structure (F) is mixed with an austenite structure (A). As one guideline for preventing cracking, it is important that the metal structure of the welded portion is within the safety region (A) + (F). The range of the safety area (A) + (F) is not absolute, and may vary depending on books, materials for welding materials, and the like. In the figure, the horizontal axis represents the chromium equivalent of the metal structure, and the vertical axis represents the nickel equivalent of the metal structure. Both equivalents are defined by the following formula.
Chromium equivalent =% Cr +% Mo + 1.5 x% Si + 0.5 x% Nb
Nickel equivalent =% Ni + 30 x% C + 0.5 x% Mn
Here,% is mass%. When the intersection of the chromium equivalent and the nickel equivalent of the weld indicates the state of the metal structure, cracks do not occur when the intersection is within the safety region (A) + (F).

  FIG. 10 is a diagram for explaining a method for estimating the metal structure of the weld using the Schaeffler structure chart described above from the composition components of the base material and the welding wire. In FIG. 9, for the sake of easy understanding, the horizontal axis and the vertical axis in FIG. 9 are the same, and only the safety area (A) + (F) is displayed. Mild steel SS400 (JIS standard) is used for the base metal, and stainless steel high-alloy steel wire Y309 (JIS standard) is used for both welding wires. The case where it went is assumed. Hereinafter, a description will be given with reference to FIG.

  As shown in the figure, the plot position of the base material SS400 is P1 from the chromium equivalent and nickel equivalent of SS400. Similarly, the plot position of the welding wire Y309 is point P2. Therefore, the state of the metal structure of the welded portion is located on the line segment P1-P2. This is because the base metal component and the welding wire component are melted together in the metal structure of the welded portion, and on the line segment P1-P2 depending on the volume ratio of the penetration portion Sa and the surplus portion Sb described above with reference to FIG. To move. That is, when the position of the metal structure of the welded portion is at the point Q11 on the line segment P1-P2, (the length of the line segment P1-Q11) :( the length of the line segment Q11-P2) = Sb: Sa become. Here, if the penetration rate is defined as (Sa / (Sa + Sb)), the penetration rate at the Q11 point = (length of the line segment Q11-P2) / (length of the line segment P1-P2).

  Here, in order to prevent cracking of the welded portion, the state position of the metal structure of the welded portion must be within the safety region (A) + (F) shown in FIG. Therefore, when the intersection of the safety region (A) + (F) and the line segment P1-P2 is Q10 and Q11, the state position of the metal structure of the welded portion is on the line segment Q10-Q11 in order to prevent cracking. There must be. These two points Q10 and Q11 correspond to a penetration rate of 20% and 8% as described above. Therefore, in order to prevent cracking, the welding speed and the total welding current must be set so that the penetration rate falls within the range of 8 to 20%. This total welding current is a total value of welding currents for energizing two welding wires.

  In general, an appropriate value for the penetration of the base material workpiece is determined by the required mechanical characteristics of the welded part. Therefore, once the base material workpiece is determined, an appropriate penetration rate is determined. However, as described above, in order to prevent cracking, the allowable penetration rate range is limited. Therefore, there is no problem when the penetration rate to be set is within the allowable penetration rate range that does not break. However, otherwise, the penetration rate cannot be set to a desired value. In the above example, when the desired penetration rate is 7%, it is outside the allowable crack range of 8 to 20%, so it cannot be set to the desired value. Therefore, the case where the desired penetration rate was ensured and the crack of a welding part was not able to be generated had occurred.

  Therefore, the present invention provides a high alloy steel two-electrode arc welding capable of shifting the allowable penetration rate range in which cracks do not occur in a weld zone to a desired range in high alloy steel welding in an inert gas 100% atmosphere. Provide a method.

In order to solve the above-described problems, the first invention feeds a first welding wire and a second welding wire that are insulated from each other and have different compositions of chromium equivalent and nickel equivalent in an atmosphere of 100% inert gas. In a two-electrode arc welding method for high alloy steel in which two adjacent arcs are generated to weld a base material of high alloy steel,
Set the chromium equivalent and nickel equivalent of the weld to form a structure consisting of an austenite structure and a small amount of ferrite structure in the weld,
Feeding each of the first welding wire and the second welding wire by using as input the chromium equivalent and nickel equivalent of the base metal, the first welding wire and the second welding wire, and the set values of the chromium equivalent and nickel equivalent of the weld. A feeding speed calculating step for calculating the speed;
The feeding speed calculation step is such that the plot position of the chromium equivalent and nickel equivalent of the base metal in the graph in which the x axis is chromium equivalent and the y axis is nickel equivalent is P1, and the chromium equivalent and nickel equivalent of the first welding wire are The plot position is set as P2, the plot position of chromium equivalent and nickel equivalent of the second welding wire is set as P3 point, and the plot position of the set value of chromium equivalent and nickel equivalent of the weld is input as R1 point, The step of calculating the intersection R2 of the straight line passing through the points P1 and R1 and the straight line passing through the points P2 and P3 and the ratio of the lengths of the line segments P1-R2 and the line segments R1-R2 A step of calculating a penetration rate, and a step of calculating a combined feed rate of the first welding wire and the second welding wire according to a predetermined relationship from the penetration rate. And calculating the respective feeding speeds of the first welding wire and the second welding wire by distributing the total feeding speed by the ratio of the lengths of the line segment P2-R2 and the line segment R2-P3; Consist of
This is a two-electrode arc welding method for high alloy steel.

According to the first invention, arc instability due to wandering and rotation transfer is suppressed by using a two-electrode arc welding method in arc welding of high alloy steel in an inert gas 100% atmosphere. And stable welding can be performed. Furthermore, two welding wires having different chromium equivalents and nickel equivalents are used, and the combined feeding speed of the two welding wires is set to an appropriate value at which a desired penetration is formed. By setting the feeding speeds of the two welding wires so as to form a structure composed of a ferrite structure, it is possible to prevent cracking of the welded portion while ensuring a desired penetration. Moreover, the allowable penetration rate range in which cracks do not occur can be shifted to a desired range. Furthermore, according to 1st invention, the feeding speed of the 1st and 2nd welding wire for forming the metal structure which has a desired chromium equivalent and nickel equivalent in a welding part can be calculated automatically. For this reason, the metal structure which does not generate | occur | produce a crack in a welding part can be formed by simple operation.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a schematic diagram of a metal structure based on a Schaeffler structure diagram for explaining a two-electrode arc welding method for high alloy steel according to Embodiment 1 of the present invention. This figure corresponds to FIG. 10 described above, and shows only the safety region (A) + (F) where no cracks are generated based on the Schaeffler organization chart. The two-electrode arc welding apparatus is the same as that shown in FIG. That is, the first welding wire 1a and the second welding wire 1b are fed in a pure argon gas atmosphere to generate two arcs 3a and 3b, thereby performing high alloy steel welding. Hereinafter, a description will be given with reference to FIG.

  In the present embodiment, a first welding wire 1a and a second welding wire 1b having different compositions of chromium equivalent and nickel equivalent are used. Similarly to FIG. 10, when SS400 is used for the base material, the plot position is P1 point, and when Y309 is used for the first welding wire 1a, the plot position is P2 point. Here, when Y410 (JIS standard) having a chromium equivalent and a nickel equivalent different from those of the first welding wire 1a is used for the second welding wire 1b, the plot position becomes the point P3.

  When the base material workpiece and the required quality are determined, the penetration rate is determined accordingly. The total welding current value and the welding speed are set so as to achieve this desired penetration rate. Since the total welding current value is a total value of welding currents passing through both welding wires 1a and 1b, the total welding current value is set by setting a total value of feeding speeds. That is, the total feeding speed is set to an appropriate value so as to obtain a desired penetration rate.

  The feeding speed of the first welding wire 1a and the feeding speed of the second welding wire 1b are distributed at 3: 1 while the total feeding speed is fixed at the appropriate value. As a result, a virtual welding wire in which the components of both welding wires 1a and 1b are mixed is created, and the plot position of this welding wire is Q2 point obtained by internally dividing the line segment P2-P3 by 3: 1. Accordingly, as described above, the state position of the metal structure of the welded portion is on the line segment P1-Q2. Assuming that the intersection of this line segment P1-Q2 and the safety area (A) + (F) is Q3, (length of line segment Q3-Q2) / (length of line segment P1-Q2) = 0.17 Become. As described above, since this line segment ratio becomes the penetration rate, the penetration rate is 17% or less in order to put the state of the metal structure of the welded portion in the safety region (A) + (F). I just need it. For this reason, even if the penetration rate is set to 8% or less, which is not possible with the prior art, it is possible to prevent cracking.

  As shown in the figure, when the distribution ratio of the feeding speeds of the first welding wire 1a and the second welding wire 1b is changed while the total feeding speed is fixed, the point Q2 moves on the line segment P2-P3. Moving. As a result, the allowable penetration rate range in which cracks do not occur can be shifted to a desired range. In the prior art, when the base material composition and the welding wire composition are determined, the allowable penetration rate range is uniquely determined. On the other hand, in this Embodiment, since an allowable penetration rate range can be adjusted by using two types of welding wires having different compositions, the condition tolerance is expanded.

  FIG. 2 is a view when the composition of the first welding wire 1a is changed in FIG. 1 described above. As shown in the figure, the first welding wire 1a has the same Y309, but the plot position has moved to point P21. This is because even Y309 of the same standard has a slightly different composition depending on the brand. Therefore, the plot position changes from the point P2 in FIG. 1 to the point P21 in FIG. 1 depending on the brand. At this time, if the distribution ratio of the first welding wire 1a and the second welding wire 1b is changed to 4: 1 while the total feeding speed is fixed, the plot position of the virtual welding wire in which the components are mixed is Q4 points. become. The intersection of the line segment P1-Q4 and the safety area (A) + (F) is Q5. Since (length of line segment Q5-Q4) / (length of line segment P1-Q4) = 0.19, the penetration rate at point Q5 is 19%. For this reason, even if the components of the welding wire change, the allowable penetration rate range in which cracks do not occur can be maintained in the substantially same range as FIG. 1 by changing the distribution ratio of the combined feeding speed.

[Embodiment 2]
FIG. 3 is a schematic diagram of a metal structure based on Schaeffler's structure seat for explaining the two-electrode arc welding method for high alloy steel according to the second embodiment of the present invention. This figure is the same as FIG. 1 described above. That is, the plot position of the chromium equivalent and nickel equivalent of the base material is P1, the plot position of chromium equivalent and nickel equivalent of the first welding wire is P2, and the plot of chromium equivalent and nickel equivalent of the second welding wire The position is point P3. The region of chromium equivalent and nickel equivalent of the welded portion for preventing cracks in the welded portion is the safety region (A) + (F). Here, let the chromium equivalent and nickel equivalent of a target weld part be R1 points. In the present embodiment, when the R1 point is set, the feeding speed calculation for calculating the feeding speeds Fr1 and Fr2 of the first and second welding wires at which the chromium equivalent and nickel equivalent of the welded part become the R1 point. Provided is a method for two-electrode arc welding of high alloy steel comprising a process.

  FIG. 4 is a configuration diagram of the two-electrode arc welding apparatus according to the second embodiment. In the figure, the same components as those in FIG. 7 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, the structure shown with the dotted line different from FIG. 7 is demonstrated.

  The chromium equivalent and nickel equivalent input circuit SR sets the chromium equivalent and nickel equivalents P1, P2, P3, and R1 of the base material, the first welding wire, the second welding wire, and the welded portion, as described above with reference to FIG. A chromium equivalent and nickel equivalent signal Sr is output. The feed speed calculation circuit FR receives the chromium equivalent and nickel equivalent signal Sr as input, calculates the feed speed of each welding wire by the process described later in FIG. 5, and supplies the first feed speed setting signal Fr1 and the second feed speed setting signal Fr1. The feed speed setting signal Fr2 is output. The first welding power source PS1 feeds the first welding wire 1a at the feeding speed of the first feeding speed setting signal Fr1, and the second welding power source PS2 feeds the second feeding speed setting signal Fr2. The second welding wire 1b is fed at a speed to perform welding.

  FIG. 5 is a flowchart showing the processing of the feeding speed calculation circuit FR described above. The description of the figure will be made with reference to FIG. 3 described above.

  In step ST1, chromium equivalent and nickel equivalent signals Sr are input, and chromium equivalents and nickel equivalents P1, P2, P3, and R1 of the base material, the first welding wire, the second welding wire, and the welded portion are input.

In step ST2, the following processing is performed.
(1) An equation of a straight line P1-R1 passing through the points P1 and R1 is calculated from the coordinate values of the points P1 and R1.
(2) An equation of a straight line P2-P3 passing through the points P2 and P3 is calculated from the coordinate values of the points P2 and P3.
(3) The coordinate value of the intersection R2 is calculated from the equation of the straight line P1-R1 and the straight line P2-P3.

In step ST3, the following processing is performed.
(1) The length of the line segment P1-R2 is calculated.
(2) The length of the line segment R1-R2 is calculated.
(3) Penetration rate = (Line segment R1-R2) / (Line segment P1-R2) is calculated.

  In step ST4, the total feeding speed of the first welding wire and the second welding wire is calculated from the above penetration rate according to a relationship determined in advance by experiments or the like. As described above, when the material, shape, welding speed, etc. of the base material workpiece are determined, the penetration rate described above with reference to FIG. 8 can be set by the total welding current value, and the total welding current value is added up. It can be set according to the feeding speed. Therefore, the penetration rate can be set by the total feeding speed.

In step ST5, the following processing is performed.
(1) The lengths of the line segment P2-R2 and the line segment R2-P3 are calculated from the coordinate values of P2, R2, and P3.
(2) First feed speed setting signal Fr1 = (total feed speed) · (line segment R2-P3) / (line segment P2-R2 + line segment R2-P3) is calculated.
(3) Second feed speed setting signal Fr2 = (total feed speed) · (line segment P2-R2) / (line segment P2-R2 + line segment R2-P3) is calculated.
(4) The first feed speed setting signal Fr1 and the second feed speed setting signal Fr2 are output.

  According to the second embodiment described above, it is possible to automatically calculate the feeding speeds of the first and second welding wires for forming a metal structure having desired chromium equivalent and nickel equivalent in the weld. For this reason, the metal structure which does not generate | occur | produce a crack in a welding part can be formed by simple operation.

It is a metal structure schematic diagram based on the structure chart of Schaeffler for demonstrating the 2 electrode arc welding method of the high alloy steel which concerns on Embodiment 1 of this invention. It is a metal structure schematic diagram when the composition of a welding wire changes in FIG. It is a metal structure schematic diagram based on the structure chart of Schaeffler for demonstrating the 2 electrode arc welding method of the high alloy steel which concerns on Embodiment 2 of this invention. 3 is a configuration diagram of a two-electrode arc welding apparatus according to Embodiment 2. FIG. It is a flowchart which shows the process of the feeding speed calculation circuit FR of FIG. It is sectional drawing of the welding wire of the 2 layer structure in a prior art. It is a block diagram of the 2 electrode arc welding apparatus of a prior art. It is sectional drawing which shows the penetration part Sa and the surplus part Sb of a welding part. It is the organization chart of Schaeffler which shows the metal structure of the welding part of high alloy steel welding. It is a metal structure schematic diagram based on the structure chart of Schaeffler for demonstrating the two-electrode arc welding method of the high alloy steel in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a 1st welding wire 1b 2nd welding wire 2 Base material 3a, 3b Arc 4a 1st electric power feeding tip 4b 2nd electric power feeding tip 5 Nozzle Fc1 1st feed control signal Fc2 2nd feed control signal FR Feed speed calculation circuit Fr1 1st feed speed setting signal Fr2 2nd feed speed setting signal M1 1st feed motor M2 2nd feed motor P1 Chrome equivalent and nickel equivalent P2 of base material, P21 Chrome equivalent and nickel equivalent P3 of first welding wire Chrome equivalent and nickel equivalent PS1 of the second welding wire PS1 first welding power source PS2 Second welding power source R1 Chromium equivalent and nickel equivalent of target weld Sa Sa penetration portion Sb Extra portion SR Chrome equivalent and nickel equivalent input circuit Sr Chromium Equivalent and nickel equivalent signals

Claims (1)

In an atmosphere of 100% inert gas, a first welding wire and a second welding wire which are insulated from each other and have different compositions of chromium equivalent and nickel equivalent are fed, and two adjacent arcs are generated to generate high alloy steel. In the two-electrode arc welding method of high alloy steel that welds the base material ,
Set the chromium equivalent and nickel equivalent of the weld to form a structure consisting of an austenite structure and a small amount of ferrite structure in the weld,
Feeding each of the first welding wire and the second welding wire by using as input the chromium equivalent and nickel equivalent of the base metal, the first welding wire and the second welding wire, and the set values of the chromium equivalent and nickel equivalent of the weld. A feeding speed calculating step for calculating the speed;
The feeding speed calculation step is such that the plot position of the chromium equivalent and nickel equivalent of the base metal in the graph in which the x axis is chromium equivalent and the y axis is nickel equivalent is P1, and the chromium equivalent and nickel equivalent of the first welding wire are The plot position is set as P2, the plot position of chromium equivalent and nickel equivalent of the second welding wire is set as P3 point, and the plot position of the set value of chromium equivalent and nickel equivalent of the weld is input as R1 point, The step of calculating the intersection R2 of the straight line passing through the points P1 and R1 and the straight line passing through the points P2 and P3 and the ratio of the lengths of the line segments P1-R2 and the line segments R1-R2 A step of calculating a penetration rate, and a step of calculating a combined feed rate of the first welding wire and the second welding wire according to a predetermined relationship from the penetration rate. And calculating the respective feeding speeds of the first welding wire and the second welding wire by distributing the total feeding speed by the ratio of the lengths of the line segment P2-R2 and the line segment R2-P3; Consist of
A two-electrode arc welding method for high alloy steel characterized by the above.

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