JP4887276B2 - Solid wire for electroslag welding - Google Patents

Description

  The present invention relates to a solid wire for electroslag welding that can obtain a welded portion having excellent toughness with high heat input.

  In general, electroslag welding can be performed with high efficiency in one pass. However, if the welding is stopped for some reason, the plate thickness is large and the groove is closed. Productivity is significantly reduced.

  In addition, if the welding stops halfway, the performance of the joint will be adversely affected. For example, when the welding is stopped halfway and it takes time to return the welding, the base material is cooled, so that deep penetration cannot be obtained as compared with the case where the welding is not stopped. Further, when returning from the stop, the slag on the bead cannot be completely removed, and there is an adverse effect that the slag is caught in the weld metal.

  On the other hand, copper plating is given to the surface of the conventional electroslag welding wire. The expected effect of copper plating is an improvement in electrical conductivity between the wire and the contact chip. However, if the copper plating is uniform, the effect of improving the electrical conductivity can be obtained, but in electroslag welding, the wire length required for one pass is enormous compared to other welding methods, and such a uniform copper plating layer It is very difficult to secure the wire over the entire length of the wire.

  In practice, if the plating thickness is uneven, the copper plating is locally oxidized, or there are non-conductive impurities between the steel wire and the copper plating, the electrical conductivity between the wire and the contact tip Deteriorates, the welding current is disturbed, and the heat input varies. In the worst case, the welding power source cannot follow the change in current, and the welding is stopped.

  On the other hand, Patent Document 1 attempts to solve this problem by improving the wire feedability by using a wire obtained by applying a lubricating mixture to a copper-plated wire. Even taking the proper measures is still inadequate for preventing welding outages. The inventors of the present application have found that, as the cause, problems such as welding stoppage are largely caused by the properties of copper plating rather than wire feedability.

  In addition, non-uniform copper plating not only stops welding, but also greatly affects the mechanical properties of the weld. This is because the electric current and voltage during welding, that is, the heat input fluctuates due to changes in the conductivity of the wire and the contact chip over time due to variations in plating. As a result, when the weld is viewed microscopically, the heat input varies depending on the location, so that the mechanical properties also vary.

  Recently, in the construction field, from the viewpoint of improving production efficiency, the demand for higher heat input of welding has increased, and the demand for improved earthquake resistance of structures has also increased. Is required. Also in electroslag welding, a wire whose toughness is improved by high heat input welding as in Patent Document 2 is proposed, but this is achieved only when welding is performed soundly, and there is a large variation in heat input. If the welding is stopped, it can be easily imagined that the desired performance cannot be obtained for the above-mentioned reason.

Japanese Patent No. 3707554 JP 2005-349466 A

  As described above, with the increasing demand for large heat input of welding, there has been a demand for the development of a technique capable of stably obtaining a high toughness weld metal when increasing the heat input in electroslag welding. However, no solid wire for electroslag welding that can realize this has been obtained.

  This invention is made | formed in view of this problem, Comprising: It aims at providing the solid wire for electroslag welding which can obtain a high-toughness weld part stably also with large heat input.

The solid wire for electroslag welding according to the present invention is a solid wire without plating. And the wire body
C: 0.02 to 0.12% by mass
Si: 0.1 to 0.8% by mass
Mn: 0.5 to 2.0% by mass
P: 0.025 mass% or less S: 0.025 mass% or less Cu: 0.8 mass% or less Mo: 0.10 to 1.50 mass%
N: 0.010% by mass or less, with the balance being composed of Fe and inevitable impurities.

  Further, one or more kinds of mineral oil and vegetable oil of 0.3 to 1.20 g per 10 kg of the wire main body adhere to the surface of the wire main body.

  Further, the arithmetic average roughness Ra in the longitudinal direction of the wire body is 0.1 to 0.5 μm.

  In this solid wire for electroslag welding, Ni: 1.40% by mass or less, Ti: 0.10 to 0.25% by mass, B: 0.0010 to 0.0200% by mass, Al: 0.015 to It is preferable to contain at least one selected from the group consisting of 0.050% by mass.

  According to the solid wire for electroslag welding of the present invention, even when electroslag welding is performed under welding conditions of high heat input, the temporal variation of welding heat input determined by the welding current and welding voltage is extremely reduced, and heat input is performed. The toughness can be stably obtained without stopping the welding, and the joint performance can be improved.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. The inventors examined the influence of Cu added to the weld metal from Cu plating on the wire surface and components in the wire when performing electroslag welding. As a result, Cu plating is not provided, the composition of the wire body is properly defined, a predetermined oil content is provided on the surface of the wire body, and the arithmetic average roughness of the surface of the wire body is defined within a predetermined range. As a result, it has been found that the temporal variation of the welding current and the welding voltage, that is, the temporal variation of the welding heat input can be extremely stabilized. In this way, by stabilizing the time-dependent fluctuation of the welding heat input with a large heat input, it is possible to stably form a weld metal with higher toughness than before over the entire length of the weld without stopping the welding. This can improve joint performance.

  Industrially, making copper plating completely uniform is extremely difficult and requires high cost and low productivity. Therefore, the inventors of the present application considered that it is advantageous in terms of current-carrying stability in electroslag welding that the conventional idea is changed, rather than performing copper plating. Furthermore, in gas shielded arc welding, if there is no copper plating, the wear of the tip becomes significant due to the influence of arc heat. Does not occur. Therefore, in the present invention, copper plating is not performed.

  Next, the composition of the wire body will be described.

“C: 0.02 to 0.12 mass%”
C is an element necessary for improving the strength of the weld metal, but if added more than necessary, the toughness is lowered. In order to improve the strength, it is necessary to add 0.02% by mass or more, and if it exceeds 0.12% by mass, the toughness decreases. For this reason, C is 0.02 to 0.12 mass%.

“Si: 0.1 to 0.8 mass%”
Si acts as a deoxidizer in the molten metal and has the effect of stabilizing the hot water flow. For this reason, if Si is less than 0.1 mass%, the hot water flow becomes unstable, the toughness varies, and stable joint performance cannot be obtained. On the other hand, since Si is also an element that improves the hardenability of the weld metal, when Si is added excessively, the weld metal becomes hard and toughness decreases. For this reason, 0.1 to 0.8 mass% of Si is added.

“Mn: 0.5 to 2.0 mass%”
Mn improves hardenability and acts as a deoxidizer. However, when Mn is less than 0.5% by mass, deoxidation is insufficient, and the tensile strength and toughness of the welded portion become unstable. On the other hand, when Mn is added excessively, the toughness of the weld metal decreases due to excessive quenching. Therefore, 0.5 to 2.0% by mass of Mn is added.

“P: 0.025 mass% or less”
“S: 0.025 mass% or less”
P and S are components that are inevitably included as wire components, although they do not significantly affect welding stability even if they are positively added. If these components are excessively contained in the wire, hot cracking and toughness deterioration of the weld metal are caused, so the upper limit value of these components is 0.025% by mass.

“Cu: 0.8% by mass or less”
Cu has the effect of improving the strength of the weld metal, but if Cu is added excessively, cracks are likely to occur in the weld metal. For this reason, the upper limit of Cu is set to 0.8 mass%.

“Mo: 0.10 to 1.50 mass%”
Mo has an effect of preventing the formation of grain boundary ferrite, and therefore is an essential additive element for securing the tensile strength and toughness by suppressing the formation of grain boundary ferrite in high heat input electroslag welding. If Mo is less than 0.10% by mass, the effect of addition cannot be obtained. Conversely, if Mo is added in excess of 1.50% by mass, the weld metal becomes hard and high toughness is obtained. Disappear. For this reason, content of Mo shall be 0.10 to 1.50 mass%.

“N: 0.010 mass% or less”
N is an element inevitably contained in the wire body. However, as the N content increases, N in the weld metal also increases and causes a decrease in toughness. For this reason, content of N shall be 0.010 mass% or less.

"Ni: 1.40 mass% or less"
Ni has an effect of improving toughness, but when Ni is added, the weld metal becomes hard. Therefore, when Ni is selectively added, the Ni content needs to be suppressed to 1.40% by mass or less.

“Ti: 0.10 to 0.25 mass%”
Ti is an element that improves the strength and toughness by forming an oxide in the weld metal. However, if Ti is less than 0.10% by mass, the effect of improving toughness cannot be obtained. Moreover, when Ti enters excessively in a weld metal, excess Ti will become inclusions and reduce the toughness of the weld metal. For this reason, Ti is selectively added, but the addition amount is 0.10 to 0.25% by mass.

“B: 0.0010 to 0.0200 mass%”
B segregates at grain boundaries and has the effect of suppressing grain boundary ferrite to improve toughness, but is also an element that easily causes hot cracking. For this reason, in order to obtain this effect of improving toughness, B is selectively added. In this case, it is necessary to add 0.010% by mass or more of B to the wire. On the other hand, when adding B, in order to avoid a hot crack, it is necessary to suppress the content to 0.0200 mass% or less.

“Al: 0.015 to 0.050 mass%”
Al has a high deoxidation effect, and when added in a small amount, Al has an effect of reducing the oxygen in the weld metal and improving the toughness of the weld metal. However, if Al is added excessively, the cracking sensitivity of the weld metal increases. For this reason, when adding Al, it is 0.015 thru | or 0.050 mass%.

"Cu plating: No Cu plating"
When Cu plating is applied to the surface of the wire body, it is welded due to current instability due to fluctuations in the plating layer oxidation, peeling, impurities contained in the plating layer, which are industrially inevitable phenomena. A stop occurs and the welding heat input becomes unstable. This causes toughness variations in the weld metal.

“Amount of oil: 0.3 to 1.20 g of one or more of mineral oil and vegetable oil per 10 kg of wire body on the wire surface”
When the amount of oil is less than 0.3 g per 10 kg of wire, the lubricity of the wire is lowered, the feeding load is increased, and welding is stopped. On the other hand, if the amount of oil exceeds 1.20 g per 10 kg of wire, oily solids accumulate near the joint between the tip and the water-cooled nozzle. become.

“Arithmetic mean roughness: Arithmetic mean roughness Ra in the longitudinal direction of the wire is 0.1 to 0.5 μm”
By providing unevenness on the surface of the wire, even if the appropriate amount of oil is distributed inside the concave shape and the feeding cable is long, stable feeding can be ensured by the oil, and a multi-point energization point is secured between the chip and the wire. Can be energized and stabilized. Note that the adjustment of the arithmetic average roughness Ra in the longitudinal direction of the wire is preferably carried out not by a die drawing method but by a wire drawing method by roller rolling extrusion.

  In this roller rolling extrusion drawing, a pair of rotating rollers provided with semicircular grooves in the circumferential direction are arranged with the rotation axis in parallel, and the wire rod is rolled at the groove portion, whereby the wire rod has a small diameter. It is a wire drawing means. The average roughness Ra of the wire can be adjusted by using the rolling roller whose surface roughness is adjusted and transferring the irregularities on the roller surface to the wire surface.

  Arithmetic average roughness Ra can measure the arithmetic average group of a wire longitudinal direction according to JISB0601. And in this invention, this arithmetic mean roughness Ra shall be 0.1 micrometer or more. When Ra is less than 0.1 μm, when the feed cable is long, oil is carried away on the inner wall of the conduit liner, and the feed resistance between the wire and the chip increases. In addition, the energization point between the wire and the tip becomes a single point, the wire is easily fused to the tip, and welding becomes unstable. On the other hand, if Ra exceeds 0.5 μm, the power supply between the tip and the wire becomes unstable due to excessive unevenness, and the heat input greatly varies, so that welding may be stopped. For this reason, the arithmetic average roughness Ra in the longitudinal direction of the wire is set to 0.1 to 0.5 μm.

  Hereinafter, the results of tests conducted to verify the effects of the present invention will be described. Table 1 below shows the composition of the base material (steel plate). Moreover, FIG. 1 shows the cross section of the test material assembled in the welding test, and the following Table 2 shows the dimension of each member. The skin plate 1 and the diaphragm 2 shown in FIG. 1 are steel plates having the compositions shown in Table 1, and the metal 3 is installed with a gap of 25 mm with respect to the skin plate 1.

  The following Table 3-1, Table 3-2, Table 3-3, and Table 3-4 show the compositions of the solid wires of Examples and Comparative Examples of the present invention. In the wire compositions described in these tables, the balance is Fe and inevitable impurities. All the solid wires had a diameter of 1.6 mm. As the flux, a JIS Z3353 FS-FG3 compatible product was used.

  The welding conditions were such that the wire feed speed was fixed at 7.8 m / min, the wire diameter was 1.6 mm, the welding voltage was 52 V, and the welding speed was 1.45 cm / min. In order to make the feeding resistance relatively strict, the conduit liner was 6 m, and a radius of 30 cm was made halfway along the way to give a relatively large feeding resistance.

  The obtained test results are shown in Tables 4-1 and 4-2 below.

  In Tables 4-1 and 4-2, the overall evaluation is as follows: (1) standard deviation of heat input is 100 kJ / cm or less, (2) welding does not stop, (3) tensile strength is 490 MPa or more, (4) All conditions were satisfied that no cracks occurred in the UT inspection, and (5) the three measured values of the impact value were 50 J or more, and the average value of the impact value was 70 J or more. In this case, a circle is marked. Furthermore, when all of (1) to (4) were satisfied, the three measured values of the impact value were 70 J or more, and the average value of the impact value was 100 J or more, ◎ was given. On the other hand, when even one of the above conditions (1) to (5) was not satisfied, x was given.

  The standard deviation of heat input was evaluated by measuring the current and voltage at a sampling rate of 50 / sec from the start to the end of welding, and calculating the standard deviation from the calculated heat input taking the welding speed into account. Note that the welding speed was calculated at a constant 1.45 cm / min since the wire feed speed was constant. Moreover, when welding stopped, the electric current and voltage until it stopped were evaluated.

  Thus, the reason for evaluating the heat input with the standard deviation is that the current and voltage during welding fluctuate when the feed system is strict and the plating is uneven as shown in FIG. This is because the heat also fluctuated, and as a result, it was found that the fluctuation of the heat input affects the variation of the impact value.

  On the other hand, as shown in FIG. 3, the non-plated wire does not vary the current voltage during welding, and thus stable toughness can be obtained.

  2 and 3 both show the welding position on the horizontal axis and the welding current, welding voltage, and average heat input on the vertical axis, and show changes in welding current, welding voltage, and average heat input at each welding position. FIG. FIG. 2 is a comparative example, and FIG. 3 is an example. The measurement sampling frequency of current and voltage was 50 / second. And the average heat input per 10 mm of weld length was computed.

  As can be seen from the comparison between FIGS. 2 and 3, the solid wire without plating (FIG. 3) has a smaller variation in welding speed and welding current than the solid wire with plating. Small fluctuations in heat.

  For the impact values in Tables 4-1 and 4-2, JIS Z2202 No. 4 test piece was used, and as shown in FIG. 4, the test piece 3 with the notch tip positioned at the center of the weld metal 5 was welded. Three pieces of metal 5 were collected. The impact test method was carried out based on JIS Z2242. The notch was 2 mmV and the test temperature was 0 ° C.

  As shown in FIG. 5, the tensile test was performed by taking a test piece 7 having a parallel portion diameter of 12.5 mm from the center of the weld metal 5 and performing a tensile test based on JIS Z3111.

  As a result, as shown in Tables 4-1 and 4-2, in the case of the examples of the present invention, both the impact value and the tensile strength were high. Further, in the case of the example of the present invention, the welding was not stopped, and no welding defect was observed even in the ultrasonic inspection (indicated by ◯). On the other hand, in the case of the comparative example, the welding stop occurred, the impact value was low, or the tensile strength was low.

It is sectional drawing which shows the assembly state of a weld test board. It is a wave form diagram which shows the change of the welding current of a comparative example, welding voltage, and average heat input. It is a wave form diagram which shows the change of the welding current of an Example, a welding voltage, and an average heat input. It is sectional drawing which shows the collection position of an impact test piece. It is sectional drawing which shows the collection position of a tensile test piece.

Explanation of symbols

1: Skin plate 2: Diaphragm 3: Gold 5: Weld metal 7: Test piece

Claims (2)

Solid wire without plating,
The wire body
C: 0.02 to 0.12% by mass
Si: 0.1 to 0.8% by mass
Mn: 0.5 to 2.0% by mass
P: 0.025 mass% or less S: 0.025 mass% or less Cu: 0.8 mass% or less Mo: 0.10 to 1.50 mass%
N: 0.010% by mass or less, with the balance being composed of Fe and inevitable impurities,
On the surface of the wire body, one or more of 0.3 to 1.20 g of mineral oil and vegetable oil are attached per 10 kg of the wire body,
A solid wire for electroslag welding, wherein an arithmetic average roughness Ra in a longitudinal direction of the wire body is 0.1 to 0.5 μm. Further, Ni: 1.40% by mass or less, Ti: 0.10 to 0.25% by mass, B: 0.0010 to 0.0200% by mass, Al: 0.015 to 0.050% by mass The solid wire for electroslag welding according to claim 1, comprising at least one selected type.

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