JP2011131224A - Method for evaluating hardness of build-up part and propriety determining method for reinforcing bead part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply evaluating hardness of a build-up part formed on a metal plate by a build-up welding in a non-destructive manner. <P>SOLUTION: The propriety determining method for a reinforcing bead part includes: a dimension obtaining step of obtaining dimensions of a plurality of reinforcing bead parts formed on a vehicle body constituting part of the metal plate as a component by the build-up welding; a numerical actual measuring step of evaluating the hardness of the plurality of the reinforcing bead parts by actual measurement; and a correlation obtaining step of obtaining correlation between the dimensions of the reinforcing bead parts obtained by the dimension obtaining step and the actual measured values of the hardness of the reinforcing bead parts obtained by the numerical actual measuring step. The hardness of the reinforcing bead parts is evaluated based on the correlation obtained by the correlation obtaining step. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for evaluating the hardness of a build-up portion formed on a metal plate by build-up welding, and the case where this build-up portion is provided as a reinforcing bead portion on a vehicle body structural component having a metal plate as a component. The present invention relates to a quality determination method for the reinforcing bead portion.

  In recent years, the application of high-strength steel sheets called high-tensile materials or ultra-high-tensile materials to car body structural parts has begun to be studied in order to improve the safety of automobiles and reduce the environmental burden by reducing weight. However, this type of steel sheet is generally expensive and has high workability due to its high rigidity. For this reason, the application of high-strength steel sheets is still limited.

  For this reason, for example, in the case of a vehicle body structural part made of a steel plate that constitutes a vehicle body frame, a method for processing the steel plate to increase the strength while reducing the weight has been studied and proposed. Here, for example, in Patent Document 1 below, build-up welding is performed on the inner surface or the outer surface of the frame as the vehicle body structural component along the load input direction of the frame, thereby reinforcing the bead portion for reinforcement at the reinforcing portion of the frame. A frame structure provided with a built-up portion and a method for manufacturing the frame structure are disclosed. According to this processing method, partial reinforcement is possible by setting a portion where the bead portion should be formed according to strength characteristics and the like required for the frame structure, and by selecting a suitable welding material, Necessary strength characteristics and the like can be imparted to the frame structure without significantly increasing the frame weight. Moreover, since it can be constructed by general welding equipment, it is highly versatile.

JP 2003-112260 A

  As described above, when overlay welding is performed on a vehicle body component having a metal plate as a component using a build-up material (welding material) according to the purpose, the above-described build-up welding is appropriately performed. It is necessary to determine whether or not. Specifically, a method of actually evaluating the strength and rigidity of the frame structure after build-up welding by a test is conceivable. Or the method of evaluating the degree of the reinforcement effect by actually measuring the hardness of the bead part for reinforcement formed in the metal plate by overlay welding is considered. However, when performing a strength test on a metal plate that has undergone build-up welding, it is necessary to perform a strength test on a metal plate that has not undergone build-up welding. Increase. In addition, when measuring the hardness (for example, Vickers hardness) of the reinforcing bead part, in principle, the reinforcing bead part must be cut and the hardness at the cut surface must be measured with an appropriate hardness tester. Therefore, it takes a lot of man-hours for the measurement work. In addition, by any method, a predetermined load is applied to the reinforcing bead portion for destruction, so that the evaluated part needs to be disposed of, which also increases waste.

  For example, in the case of the Shore hardness test, the testing machine is also relatively small, and it seems that measurement can be performed by simply pressing a diamond indenter on the surface without cutting the reinforcing bead portion. However, many of these types of components (vehicle body components) have a hollow frame structure in order to achieve both weight reduction and high strength, and the plate thickness is thinner than other structural plate materials. (Several mm or less). Therefore, when the hardness test is performed, the metal plate constituting the frame is deformed or vibrated and absorbs the pressing force from the diamond indenter, so that there is a problem that the hardness cannot be measured accurately.

  This kind of problem is not limited to the case where a reinforcing bead is provided, but other metal plates or general articles composed of metal plates are used for overlay welding to improve the specified physical properties. This also applies to the case where the build-up part is formed.

  On the other hand, whether or not the reinforcing bead portion is good when the built-up portion is provided as the reinforcing bead portion depends not only on the hardness of the bead portion but also on the size and the degree of penetration into the base material (metal plate). Can also be judged. However, the conventional evaluation methods, except for the evaluation of hardness, simply visually recognize the bead part after build-up welding, and the bead part is formed without interruption or there is no part with a narrow width. However, there is no method for quantitatively evaluating and judging whether or not this type of bead portion is properly formed.

  In view of the above circumstances, the present specification provides a first method that should be solved to provide a method capable of easily and non-destructively evaluating the hardness of a built-up portion formed on a metal plate by build-up welding. Technical issue.

  Further, in view of the above circumstances, the present specification provides a method capable of quantitatively and simply determining the quality of a reinforcing bead portion formed by build-up welding on a vehicle body component having a metal plate as a component. This is the second technical problem to be solved.

  The present invention has been made to solve the first technical problem. That is, the method for evaluating the hardness of the built-up portion according to the first aspect of the present invention includes a dimension obtaining step for obtaining the dimensions of a plurality of built-up portions formed on a metal plate by build-up welding, and a plurality of built-up portions. Hardness measurement step for actually measuring the hardness of the workpiece, and a correlation acquisition step for acquiring a correlation between the dimension of the build-up portion obtained in the dimension acquisition step and the measured value of the hardness of the build-up portion obtained in the hardness measurement step And based on the correlation obtained in the correlation acquisition step, the hardness of the built-up portion is evaluated.

  The build-up material (welding material) used for this type of build-up welding is usually made of a material different from the base material because it is used for the purpose of improving predetermined physical properties with respect to the metal plate as the base material. . Therefore, when the build-up material includes, for example, a predetermined alloy component, a phenomenon in which the alloy component in the welded portion is diluted by the base material, so-called dilution, occurs as the penetration into the metal plate proceeds. Although it is known that there is a correlation between the degree of dilution (dilution rate) and hardness, the amount of penetration needs to know the size of the part that has melted into the metal plate as well as the build-up part. Therefore, there was a problem that had to rely on destructive inspection. Here, the hardness is generally determined by the structure of the material (if it is a metal, its crystal structure). As a result of intensive studies, the present inventors have grasped the quantitative size from the outside. Focusing on the dimensions of the built-up portion that is easy to do, a predetermined correlation was found between the dimensions and the hardness from the dimension measurement result of the build-up portion described later and the hardness measurement result.

  The hardness evaluation method according to the present invention was created based on the above knowledge, and the dimensions and hardness of the built-up portion formed when a predetermined metal plate and a built-up material are used in advance are obtained by actual measurement. And a step of acquiring these correlations. As a result, the hardness of the build-up part can be managed as long as the dimensions of the build-up part formed of the same or the same type of metal plate and build-up material as the build-up part used for obtaining the correlation are obtained by measurement or the like. (Control). Therefore, the quality control of the built-up portion can be easily performed without performing the hardness test and measuring the hardness as in the conventional case.

  Here, with respect to the correlation between the dimension of the build-up portion and the actually measured hardness value, as a result of further intensive studies by the inventors, as shown in FIG. Then, the dimension of the direction perpendicular to the welding progress direction of the build-up portion is pointed out) and the hardness measurement value is found to have a high correlation. Therefore, if the width dimension of the build-up part is acquired in the dimension acquisition process and the correlation between the acquired width dimension and the measured value of hardness is obtained, then the width dimension of the same type of build-up part formed thereafter is acquired. It is possible to evaluate the hardness nondestructively and with high accuracy simply by doing. Specifically, the height of the built-up portion (in this specification, from the surface on the built-up portion side of the metal plate when it is assumed that no built-up portion is provided, the line and the built-up portion intersecting the surface perpendicularly. A certain correlation was also found between the hardness and the hardness of the outer surface of the surface.) However, the narrow range and slight measurement error are the major differences. It is easy to appear. On the other hand, the width dimension shows high correlation over a relatively wide range, and the measurement scale is relatively large, so that the measurement error is small. Therefore, it is possible to accurately evaluate the hardness of the built-up portion.

  The present invention has been made in order to solve the second technical problem. That is, the quality determination method of the reinforcing bead part according to the second aspect of the present invention is a dimension for acquiring the dimensions of a plurality of reinforcing bead parts formed by overlay welding on a vehicle body component having a metal plate as a constituent element. The acquisition process, the numerical measurement process that evaluates numerical values related to the mechanical characteristics of multiple reinforcing bead parts by actual measurement, the dimensions of the reinforcing bead part obtained in the dimension acquisition process, and the reinforcement obtained in the numerical measurement process A correlation acquisition process that acquires correlations with actual measurement results related to the mechanical properties of the bead part, and features that the mechanical characteristics of the reinforcing bead part are evaluated based on the correlation obtained in the correlation acquisition process Attached.

  In conventional overlay welding, except for the case of Patent Document 1, for example, for the purpose of improving wear resistance and corrosion resistance, the surface of the target base material is covered with a buildup part (welded part). Since it was usual to form in such a manner, the three-dimensional shape was not considered. On the other hand, when considering using the build-up part by build-up welding as a bead part for reinforcement of a metal plate, the shape and size are important. The present invention has been made paying attention to this point, and utilizes the newly found correlation between the dimensions of the reinforcing bead portion and the numerical values related to the mechanical characteristics as described above. This is a non-destructive method for evaluating the mechanical properties of the reinforcing bead portion. Therefore, it is possible to quantitatively evaluate the mechanical characteristics of the reinforcing bead part simply by measuring the dimensions of the reinforcing bead part, for example, the height dimension and the width dimension thereof, thereby making it easy to determine whether the reinforcing bead part is good or bad. It can be determined with high accuracy.

  Here, examples of mechanical properties that can be quantitatively evaluated include strength and rigidity, and the numerical values related to these properties include the hardness of the reinforcing bead portion. In addition, since vehicle body components provided with these reinforcing bead parts are required to have resistance to bending (bending strength and bending rigidity), numerical values related to these bending strengths and bending rigidity can be used as reinforcing bead parts for metal plates. The section modulus or the moment of inertia of the section of the portion provided with s. The section modulus and the section moment of inertia can be obtained from the section shape and the section area of the portion where the reinforcing bead portion is provided.

  Here, for example, when trying to measure and evaluate the section modulus or the second moment of section of the reinforcing bead portion, it is necessary to cut the reinforcing bead portion, which causes the same problem as described above. In this respect, for example, if a certain correlation can be found between the predetermined dimension of the reinforcing bead part and the cross-sectional shape or cross-sectional area of the penetration part of the reinforcing bead part or the metal plate, for example, the bead part By measuring only the height dimension and the width dimension, it is possible to evaluate the section modulus and the section moment of inertia of the portion where the reinforcing bead portion is provided. Thus, for example, it is possible to accurately evaluate the bending strength and bending rigidity of the vehicle body component provided with the reinforcing bead portion from the tensile strength and Young's modulus obtained from the above-described hardness.

  Further, if the correlation between the height dimension and the width dimension and the penetration depth (for example, the dimension indicated by reference sign d in FIG. 1 described later) in the welded portion is known, it must be cut like a cross-sectional hat-shaped member. Even if a vehicle body component has a shape that cannot be determined whether it has burned out or not, it is easy to obtain the protrusion height (melting point) from the lower surface of the metal plate simply by obtaining the width and height of the reinforcing bead, for example. The value obtained by subtracting the thickness dimension of the metal plate from the depth of penetration) can be evaluated, whereby the presence or absence of burnout can be easily determined.

  Further, in order to evaluate the strength and rigidity of the reinforcing bead part, when evaluating the hardness of the bead part as a numerical value related to the strength and rigidity, for example, in the numerical measurement process, the hardness of the reinforcing bead part is determined. The thickness may be measured as a numerical value related to the mechanical characteristics, and the correlation between the dimension of the reinforcing bead portion and the measured value of the hardness may be acquired in the correlation acquisition step.

  In this way, by utilizing a part of the hardness evaluation method described above, even the hardness of the reinforcing bead portion can be evaluated non-destructively and easily with high accuracy. Also in this case, by utilizing the fact that a high correlation is observed between the width dimension and the hardness of the reinforcing bead part, it is possible to obtain the width dimension of the reinforcing bead part by measurement or the like and to obtain non-destructiveness. The hardness of the reinforcing bead portion can be evaluated easily and with high accuracy.

  As described above, according to the method for evaluating the hardness of the built-up portion according to the present invention, the hardness of the built-up portion formed on the metal plate by build-up welding can be easily and non-destructively evaluated.

  In addition, according to the method for determining the quality of the reinforcing bead portion according to the present invention, quantitative and simple determination of the quality of the reinforcing bead portion formed by overlay welding on a vehicle body component having a metal plate as a constituent element can be performed. Can do.

It is sectional drawing of the build-up part which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the width dimension of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 1, and the electric current value at the time of welding. It is a graph which shows the relationship between the width dimension of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 2, and the electric current value at the time of welding. It is a graph which shows the relationship between the height dimension of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 1, and the electric current value at the time of welding. It is a graph which shows the relationship between the height dimension of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 2, and the electric current value at the time of welding. It is a graph which shows the cross-sectional area of the build-up part obtained when the build-up welding was performed using the welding material which concerns on Example 1, and having different electric current values, and the cross-sectional area of a penetration part, respectively. It is a graph which shows the cross-sectional area of the build-up part and the cross-sectional area of a penetration part which were obtained when the build-up welding was performed by using the welding material which concerns on Example 2, and varying current value. It is a graph which shows the relationship between the dilution rate and the Vickers hardness of the build-up part obtained when the build-up welding was performed by using the welding material which concerns on Example 1, and varying current value. It is a graph which shows the relationship between the dilution rate and the Vickers hardness of the build-up part obtained when the build-up welding was performed using the welding material which concerns on Example 2, and varying an electric current value. It is a graph which shows the relationship between the Vickers hardness of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 1, and the electric current value at the time of welding. It is a graph which shows the relationship between the Vickers hardness of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 2, and the electric current value at the time of welding. Using the welding material according to Example 1, the relationship between the Vickers hardness of the build-up portion obtained when build-up welding was performed on a steel sheet having a plate thickness of 1.0 mm, and the width dimension of the build-up portion, and It is a graph which shows the relationship with a height dimension. Using the welding material according to Example 1, the relationship between the Vickers hardness of the build-up portion obtained when overlay welding was performed on a steel sheet having a plate thickness of 1.2 mm, and the width dimension of the build-up portion, and It is a graph which shows the relationship with a height dimension. Using the welding material according to Example 1, the relationship between the Vickers hardness of the build-up portion obtained when build-up welding was performed on a steel plate having a plate thickness of 1.4 mm, and the width dimension of the build-up portion, and It is a graph which shows the relationship with a height dimension.

  Hereinafter, an embodiment of a hardness evaluation method for a built-up portion and a quality determination method for a reinforcing bead portion according to the present invention will be described. In this embodiment, the hardness of the reinforcing bead portion is evaluated when the reinforcing bead portion is formed by build-up welding on a vehicle body component having a metal plate as a constituent element, thereby determining the quality of the bead portion. A case where this is performed will be described as an example. That is, an example of the quality determination method for the reinforcing bead portion using the method for evaluating the hardness of the built-up portion according to the present invention will be described below.

  The reinforcing bead part quality determination method according to this embodiment includes a dimension acquisition step (P1) for acquiring dimensions of a plurality of reinforcing bead parts formed by overlay welding on a vehicle body component having a metal plate as a constituent element. The numerical measurement step (P2) for evaluating numerical values related to the mechanical characteristics of the plurality of reinforcing bead portions by actual measurement, the dimensions of the reinforcing bead portion obtained in the dimension acquisition step (P1), and the numerical measurement step (P2) The correlation acquisition step (P3) for acquiring the correlation with the actual measurement result of the numerical value related to the mechanical characteristics of the reinforcement bead portion obtained in (1), and the reinforcement bead portion based on the correlation obtained in the correlation acquisition step (P3) And a mechanical property evaluation step (P4) for evaluating the mechanical properties. Here, in the numerical measurement step (P2), the hardness of the reinforcing bead portion is actually measured as a numerical value related to mechanical characteristics, and in the correlation acquisition step (P3), the dimensions and hardness of the reinforcing bead portion are actually measured. The correlation with the value is acquired. Hereinafter, each process is explained in full detail.

(P1) Dimension Acquisition Step First, the parts supplied to this step will be described in detail. As shown in FIG. 1, the part to be subjected to build-up welding may be a part made of a steel plate 1 (metal plate), for example, a cross-sectional hat such as a center pillar, a front pillar, or a front side member. Various vehicle body components made of a steel plate 1 including a member can be welded. Also, the welding site is not particularly limited, and the surface of the wall portion made of steel plate 1 or the surface of the corner portion (outside or inside) connecting the two wall portions is omitted although not shown. Can be a site. Moreover, various welding materials can be applied to the welding material (building material) used for the purpose of improving the characteristics of the base material (steel plate 1), including welding wire materials usually used for building welding. is there. In the present embodiment, a welding material having a hardness higher than that of the base material (steel plate 1) can be used. For example, a stainless steel welding wire material or a so-called high carbon steel wire material having a larger carbon content can be used. is there. Among them, high carbon steel wire material has a very high carbon compounding ratio (0.4% C to 0.7% C) compared to normal steel wire material, so that the base material and welding material are fused by welding. Part 2 is baked. Or the steel plate 1 is alloyed because the carbon in a wire material melt | dissolves in a base material (steel plate 1) as an alloy component. By these actions, the hardness of the melting portion 2 (the portion raised from the steel plate 1 becomes the reinforcing bead portion 3 and the portion melted inward from the surface of the steel plate 1 becomes the penetration portion 4 of the melting portion 2). Can be increased. Here, various kinds of arc welding such as covering arc welding, MIG welding, MAG welding, TIG welding, submerged arc welding, and plasma arc welding can be used for the above-described overlay welding. In the above description, the steel plate 1 is exemplified as the base material, but, of course, a metal plate other than the steel plate 1, such as a metal plate made of aluminum or aluminum alloy, can be used as the base material. Moreover, when using an aluminum-type metal plate for a base material, a composite wire material of aluminum and copper can be mentioned as a suitable example as a wire material.

  As described above, the dimensions of the reinforcing bead portion 3 as the build-up portion obtained by performing build-up welding on the steel plate 1 are acquired. Here, the acquired part has a good dimension related to the external shape of the reinforcing bead part 3, and can be exemplified by, for example, the width dimension W and the height dimension h of the reinforcing bead part 3 (both refer to FIG. 1). ). The method for obtaining the above dimensions is arbitrary. For example, the dimensions of the reinforcing bead part 3 may be directly measured using a caliper or a shape limit gauge, and non-contact measurement such as a position sensor or a displacement sensor. The above dimensions may be measured using means. Alternatively, the dimensions may be acquired by imaging the reinforcing bead portion 3 and performing appropriate image processing on the appearance image of the obtained reinforcing bead portion 3.

(P2) Numerical measurement process Next, the hardness of the plurality of reinforcing bead portions 3 whose dimensions have been acquired, here, the Vickers hardness is evaluated by actual measurement. Specifically, the reinforcing bead portion 3 is cut in a direction perpendicular to the longitudinal direction so that the cross section shown in FIG. 1 is exposed, and the cut portion that appears is a portion that penetrates into the reinforcing bead portion 3 or the steel plate 1. The Vickers hardness at 4 is measured with a predetermined hardness tester. Thereby, the same number of hardness values as the acquired dimensions are acquired. The hardness to be acquired is not particularly limited as long as it is generally used as an evaluation index of hardness with respect to a metal material in addition to Vickers hardness.

(P3) Correlation acquisition step As described above, the dimension of the reinforcement bead portion 3 is acquired in the dimension acquisition step (P1), and the measured value of the hardness of the reinforcement bead portion 3 is acquired in the numerical measurement step (P2). After that, the correlation between these actually measured values is acquired. Here, for example, when the width dimension W of the reinforcing bead portion 3 is measured, by taking the Vickers hardness [Hv] on the horizontal axis and the width dimension W [mm] on the vertical axis as shown in FIG. There is a high correlation between the two. Therefore, by obtaining an appropriate approximate straight line from this correlation diagram, the correlation can be easily used for the characteristic evaluation step (P4) as the next step.

(P4) Characteristic Evaluation Step When the correlation between the size and hardness of the reinforcing bead portion 3 is obtained through the steps (P1) to (P3), the size of the reinforcing bead portion 3 to be actually evaluated. To get. Here, the reinforcing bead portion 3 to be evaluated was formed by the same type of welding method using the same or the same type of steel plate 1 and welding material used in the previous steps (P1) to (P3). And Also, the dimensions to be acquired in this step are the same as the dimensions acquired in the dimension acquisition step (P1). The dimension acquisition method is not necessarily the same as in the previous step (P1). And if the dimension (for example, width dimension W) of the said bead part 3 for a reinforcement is acquired, the dimension acquired by this process will be added to the correlation acquired by the correlation acquisition process (P3), specifically the expression of an approximate linear straight line. By applying, the hardness corresponding to the dimension (here, Vickers hardness) is calculated. Accordingly, the steel plate 1 provided with the reinforcing bead portion 3 by using a conversion table from hardness (Vickers hardness) to strength (for example, tensile strength), for example, which has been publicly known, or this steel plate. It is possible to evaluate the strength and rigidity of a vehicle body component having 1 as a component. Further, by comparing the mechanical characteristic value evaluated in this way with a threshold value of each mechanical characteristic (such as tensile strength and Young's modulus) determined for each vehicle body component, the reinforcing bead 3 It is also possible to determine whether the product is good or bad.

  As mentioned above, although one Embodiment of the quality determination method of the reinforcement bead part which concerns on this invention was described, this evaluation method takes arbitrary forms within the scope of the present invention, without being limited to the form of the said illustration. Of course you get.

  Since the reinforcing bead part 3 to be evaluated may be subjected to evaluation of mechanical characteristics that affect the cross-sectional shape and cross-sectional area such as bending strength depending on the reinforcing part, for example, a hardness measurement step ( During the numerical measurement process (P2)), the section modulus or section moment is calculated from the sectional shape and sectional area of the melted part 2 (or the steel plate 1 including the melted part 2), and the section modulus or section is calculated. A correlation between the secondary moment and a predetermined dimension of the reinforcing bead portion 3 may be obtained. If the correlation between the section modulus and the like and the predetermined dimension of the reinforcing bead portion 3 is obtained in this way, the bending strength of the portion where the reinforcing bead portion 3 of the steel plate 1 is provided from, for example, the hardness evaluation result described above. It is also possible to evaluate bending rigidity. Further, if the mechanical properties of the reinforcing bead part 3 can be evaluated with an evaluation value other than the hardness as described above, it is not always necessary to actually measure or evaluate the hardness of the reinforcing bead part 3.

  Moreover, in the said embodiment, these correlations were acquired by actually creating the build-up part (reinforcement bead part 3) and actually measuring the width dimension and hardness of the created build-up part by cutting. However, it is not always necessary to actually measure the hardness or the like. If there is a database regarding the dimensions and hardness of the built-up portion using the same or the same type of steel plate 1 (metal plate) and welding material, the correlation may be obtained using the database.

  Of course, other specific forms can be adopted for matters other than the above as long as the technical significance of the present invention is not lost.

  In order to confirm the effect of the present invention, the following tests and examinations were conducted. Specifically, the width and height dimensions of the build-up part obtained when the build-up amount was changed by changing the current value during welding were measured, and the hardness of the build-up part was measured. The existence of these correlations was examined.

First, test conditions will be described. Three types of steel plates (SPC590) having different plate thicknesses were used as test pieces. The plate thicknesses are 1.0 mm, 1.2 mm, and 1.4 mm, respectively. Overlay welding was performed at the center of the steel plate so that the longitudinal dimension was 60 mm, and a predetermined overlaid portion was formed on the surface of the steel plate. As the welding material, a stainless steel welding wire material and a high carbon steel welding wire material were used. Hereinafter, Example 1 is used for build-up welding using the former (stainless steel welding wire material), and Example 2 is used for build-up welding using the latter (high carbon steel welding wire material). . The welding method used was short arc welding (short circuit arc welding). Further, the build-up welding was performed until the melt-off occurred while gradually increasing the current value in increments of 15 A from 60 A, 60 A, 75 A, 90 A. The voltage at this time was (adopted current value) × 0.02 + 14 [V]. The following are the fixed conditions.
Wire protrusion: 15mm
Aiming angle: Straight welding speed: 60cm / min
Advance angle: 0 °
Shield gas: MAG (Ar 80% + CO ₂ 20%)

  The built-up portion formed as described above is cut so that, for example, the cross section shown in FIG. 1 appears, and the width dimension, the height dimension, the cross-sectional area, and the penetration portion into the steel plate at each cut surface The cross-sectional area of was measured. Moreover, the Vickers hardness of the fusion | melting part in each cut surface was measured over several places, and the average value was calculated | required as Vickers hardness of the built-up part in each cut surface. The number of cut surfaces was 2 (corresponding to N1 and N2 in FIGS. 8 and 9 described later).

First, the results of overlay welding are shown in Table 1 below. In the same table, “○” indicates that the build-up portion is well formed as a result of visual observation of the appearance and cross section of the build-up portion, and “×” indicates that the build-up portion has melted down. “−” Means that no overlay welding is performed. Although not shown in Table 1, when the current value at the time of welding is 45 A, the build-up portion could not be stably formed on the steel plate, so 50 A is set as the current lower limit. As can be seen from Table 1, regardless of the plate thickness, the current value at which the burn-out occurred was almost the same regardless of which welding wire material was used.

  FIG. 2 shows the relationship between the width dimension of the build-up portion obtained when build-up welding is performed using the welding material according to Example 1, and the current value during welding. Moreover, FIG. 3 has shown the relationship between the width dimension of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 2, and the electric current value at the time of welding. As can be seen from these figures, the width dimension of the build-up portion increases as the current value during welding increases. Moreover, since the width dimension of the build-up part does not change so much in Examples 1 and 2, if a welding material for at least the reinforcing bead part is used, the difference in the welding material is that of the build-up part. It can be seen that the width dimension is not significantly affected. Further, when the influence due to the difference in the plate thickness is seen, it can be seen that the molten metal (welding material) does not leak and spread as the plate thickness increases, and the width dimension is smaller than that of the small plate thickness. This is thought to be because the heat capacity increases as the plate thickness increases.

  FIG. 4 shows the relationship between the height dimension of the build-up portion obtained when build-up welding is performed using the welding material according to Example 1, and the current value during welding. FIG. 5 shows the relationship between the height of the built-up portion obtained when overlay welding is performed using the welding material according to Example 2, and the current value during welding. As can be seen from these figures, the height of the built-up portion often increases as the current value during welding increases up to a predetermined current value, and then tends to decrease. I understood. Here, although illustration is omitted, when a cross-sectional photograph of the build-up portion and the penetration portion at each current value is seen, the current value at the time when the height dimension starts to decrease from the increase is the bottom portion of the steel plate ( It almost coincides with the point when it begins to protrude further downward than the end face on the opposite side of the build-up part. 4 and 5, it can be seen that, in principle, as the plate thickness increases, the current value when the height dimension changes from increasing to decreasing increases. From these facts, it is considered that when the melted portion starts to sag below the lower surface of the steel plate due to gravity, the height of the portion that becomes the build-up portion is reduced accordingly. In addition, although illustration is abbreviate | omitted, the tendency for the depth (penetration amount) of a penetration part to reduce as the plate | board thickness increased was seen.

  FIG. 6 shows the cross-sectional area of the build-up portion and the cross-sectional area of the penetration portion obtained when the welding material according to Example 1 is used and build-up welding is performed with different current values. . Moreover, FIG. 7 shows the cross-sectional area of the build-up part and the cross-sectional area of the penetration part obtained when using the welding material according to Example 2 and performing build-up welding with different current values. ing. The “cross-sectional area of the build-up part” and “cross-sectional area of the penetration part” here are respectively the area of the hatched part indicated by reference numeral 3 in FIG. 1 and the area of the hatched part indicated by reference numeral 4 in FIG. Equivalent to. The value obtained by dividing the “cross-sectional area of the build-up portion” by the “cross-sectional area of the penetration portion” corresponds to the above-described dilution rate. 6 and 7 are compared, when the welding material according to Example 2 (high carbon steel welding wire material) is used, compared with the case where the welding material according to Example 1 (stainless steel) is used. As a result, the dilution rate tended to increase at relatively low currents. This is considered to be due to the fact that the high carbon steel welding wire material has a larger initial penetration amount into the steel plate. Moreover, when the cross-sectional photograph which is not shown in figure and the result of FIG. 4, FIG. 5 are seen collectively, when a penetration part begins to protrude below the lower surface of a steel plate, a dilution rate will change about 50%, and the dilution rate by a welding material It can be seen that there is almost no difference.

  FIG. 8 shows the relationship between the dilution ratio of the build-up portion and Vickers hardness obtained when build-up welding was performed using the welding material according to Example 1 and different current values. FIG. 9 shows the relationship between the dilution ratio of the build-up part and the Vickers hardness obtained when the welding material according to Example 2 is used and build-up welding is performed with different current values. First, as shown in FIG. 8, when a stainless steel welding wire material is used (in the case of Example 1), it can be seen that variation in hardness is relatively small and stable hardness is obtained. On the other hand, until the dilution rate reaches 40%, a certain negative correlation is observed between the dilution rate and the hardness. However, when the dilution rate exceeds 40%, the hardness rapidly decreases. A trend can be seen. Next, when FIG. 9 is seen, when a high carbon steel welding wire material is used (in the case of Example 2), compared with Example 1, it has shown that hardness is a very high value at the time of low electric current. I understand. However, since the hardness varies depending on the cut surface, it is considered that the quench hardening effect by high carbon does not occur uniformly depending on the current value (especially when the current value is small). However, as a whole, it can be seen that the hardness does not drop sharply in the middle as in the case of stainless steel welding wire material, and a constant negative correlation is maintained until it melts.

  FIG. 10 shows the relationship between the Vickers hardness of the build-up portion obtained when build-up welding is performed using the welding material according to Example 1, and the current value during welding. Moreover, FIG. 11 has shown the relationship between the Vickers hardness of the build-up part obtained when build-up welding was performed using the welding material which concerns on Example 2, and the electric current value at the time of welding. Thus, when the relationship between hardness and an electric current value was seen, even when any welding material was used, the very high negative correlation was seen. It was also found that even if the plate thickness was different, the hardness would be close if the current value was the same.

  FIGS. 12 to 14 show the Vickers hardness of the build-up portion obtained when build-up welding was performed on steel plates having different plate thicknesses using the welding material according to Example 1, and the build-up portion of FIG. The relationship with the width dimension and the relationship with the height dimension are shown. These are the results of FIGS. 2, 4, and 10, that is, a very high positive correlation (proportional relationship) is observed between each dimension of the built-up portion and the current value, and Vickers hardness and current It was created in view of the fact that a very high negative correlation (inverse proportional relationship) was found between the values, the dimensions that can be obtained (measured) from the outside of the overlay, and the Vickers of the overlay It can be seen that there is a correlation with hardness. In particular, it can be seen that there is a high negative correlation between the width dimension of the built-up portion and the Vickers hardness. This tendency (correlation) can be seen regardless of the thickness t as far as FIGS.

1 Steel plate 2 Melting part 3 Reinforcing bead part (overlaying part)
4 penetration part width dimension (bead part for reinforcement)
h Height (reinforcing bead)
t Plate thickness (steel plate)

Claims (3)

A dimension acquisition step for acquiring the dimensions of a plurality of overlays formed on the metal plate by overlay welding;
A hardness measurement step of measuring the hardness of the plurality of build-up portions;
A correlation acquisition step of acquiring a correlation between the dimension of the build-up portion obtained in the dimension acquisition step and the measured value of the hardness of the build-up portion obtained in the hardness measurement step;
A method for evaluating the hardness of the built-up portion, wherein the hardness of the built-up portion is evaluated based on the correlation obtained in the correlation obtaining step.   The method for evaluating the hardness of the built-up portion according to claim 1, wherein the width of the built-up portion is acquired in the dimension acquiring step. A dimension acquisition step of acquiring dimensions of a plurality of reinforcing bead portions formed by overlay welding on a vehicle body component having a metal plate as a component;
A numerical measurement process for evaluating numerical values related to mechanical properties of the plurality of reinforcing bead portions by actual measurement;
A correlation acquisition step of acquiring a correlation between the dimension of the reinforcing bead portion obtained in the dimension acquisition step and a numerical measurement result related to mechanical characteristics of the reinforcing bead portion obtained in the numerical measurement step; Prepared,
A quality determination method for a reinforcing bead part, wherein mechanical characteristics of the reinforcing bead part are evaluated based on the correlation obtained in the correlation obtaining step.

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