JP6140068B2 - Weld crack introduction test body and weld crack introduction method - Google Patents

Description

  The present invention relates to a weld crack introduction test body and a weld crack introduction method for verifying the detection performance of a nondestructive test for a welded portion of a steel material.

  Introduced various defects such as poor fusion, poor penetration, hot cracking, blowhole and slag entrainment as test specimens to verify the detection performance of nondestructive testing such as ultrasonic testing, magnetic particle testing, and penetration testing Is used. In particular, specimens with cracked defects are a major material for verifying the detection performance of nondestructive testing techniques, and there is a great need for them.

  Conventionally, as a crack introduction method for manufacturing such a test body, for example, as shown in FIG. 7A, by performing electric discharge machining on a weld metal 2 in which the base materials 3 are fillet welded to each other. In some cases, defects are introduced by forming cracks 1 or forming cracks 1 by subjecting the base material 3 to electric discharge machining as shown in FIG. 7B. Further, as shown in FIG. 8, for example, a V-shaped groove is formed on the base material 3, and a weld metal is formed on the groove under relatively high current and high-speed welding conditions by a consumable electrode arc welding method. There is one in which a so-called pear-shaped crack 1 is generated in the weld metal 2 by welding under the conditions of high current and high speed welding. In addition, there is a method in which solidification cracks are generated by adding a low melting point compound such as S, P and Bi to the welding material and generating a low melting point compound in the weld metal.

  In addition, as a technique for preventing weld cracking, there is a technique for examining the influence of boron dissolved in the weld metal. In Patent Document 1, in order to prevent weld cracking of stainless steel, the welding material is actively used. Boron is added to increase boron in the weld metal.

JP-A-7-268564

  However, the method of introducing a crack defect by electric discharge machining shown in FIG. 7 is that the introduced defect is an artificial defect to the last. The shape of the crack is flat and the gap between crack-like defects is as wide as 0.25 mm or more, which is different from natural weld defects, so the detection performance of nondestructive testing technology is verified. For this purpose, there is a problem that it cannot be said to be a preferable specimen.

  The pear-shaped crack-like defect generation method by consumable electrode arc welding shown in FIG. 8 has a crack height Hc of even when cracks do not occur or crack defects occur depending on the welding conditions. The crack does not occur in the entire penetration depth P of the weld metal 2 due to variations. Furthermore, since it is difficult to control in which range of the penetration depth P the crack 1 is generated, it is difficult to introduce a crack-like defect with excellent dimensional accuracy.

  As shown in FIG. 9, the method of adding an element that easily generates a low-melting-point compound such as S, P, Bi or the like to the welding material or welded portion to cause solidification cracking is as follows. Since a plurality of radial or mesh-like shapes are generated along the solidified structure, there is a problem that the direction, size, quantity, and generation position of the crack 1 can hardly be controlled.

  In this way, in the conventional method for introducing crack defects, the method of ensuring the dimensional accuracy of cracks is to verify detection performance in nondestructive testing because the cracks obtained are artificial defects and not natural weld defects. Is unsuitable. On the other hand, the method of introducing natural weld defects cannot control the size, shape, occurrence position, quantity, direction, etc. of cracked defects with high accuracy.

  The present invention has been made in view of such problems, and is capable of controlling the size, shape, occurrence position, quantity, direction, etc. of cracked defects with high accuracy and introducing natural welding defects. An object of the present invention is to provide a weld crack introduction test body and a weld crack introduction method capable of verifying the detection performance of a nondestructive test with high accuracy.

The weld crack introduction test body according to the present invention is:
By welding a steel material containing boron-containing powder, a weld metal part having a boron content of 0.03 to 2% by mass is obtained, and cracked defects are introduced into the weld metal part. To do.

  In this weld crack introduction test body, it is preferable that the average hardness of the weld metal part into which the crack-like defect is introduced is 400 to 700 Hv in terms of Vickers hardness.

Further, the method for introducing a weld crack according to the present invention is as follows.
Boron-containing powder is sprayed on the welding target portion of the steel material, and the region containing the boron-containing powder is welded by laser welding or electron beam welding, so that the boron content is 0.03 to 2% by mass. While obtaining a metal part, a crack-like defect is introduced into the weld metal part.

  According to the present invention, since crack-like defects are introduced by welding such as laser welding or electron beam welding, natural welding defects can be introduced. Further, according to the present invention, the size, shape, occurrence position, quantity, direction, etc. of the cracked defect can be controlled with high accuracy.

It is front sectional drawing which shows the test body of embodiment of this invention. It is a perspective view which similarly shows the implementation method of the embodiment. It is front sectional drawing which shows the raw material of the test body of other embodiment of this invention. It is front sectional drawing which similarly shows the implementation method. It is front sectional drawing which similarly shows the test body. It is a figure explaining the effect of this invention, (a) is front sectional drawing of a weld metal part, (b) is a top view, (c) is a longitudinal cross-sectional view along the joint welding direction of (b), (d) Is a front sectional view. It is a figure which shows the conventional crack introduction method, (a) is based on fillet welding, (b) is based on electric discharge machining. It is a figure which shows the conventional method which introduce | transduces a crack into a V-shaped groove | channel by consumable electrode type arc welding. It is a figure which shows the method of generating the conventional solidification crack.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a specimen according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a method for introducing the cracked defect. As shown in FIG. 2, boron-containing powder 4 is sprayed on the base material 3, and a laser beam 6 is irradiated from thereover to perform laser welding. Alternatively, electron beam welding is performed using an electron beam. At the time of this welding, the laser beam 6 is moved in the direction 7 to form the weld bead 5. FIG. 1 is a cross section orthogonal to the longitudinal direction of the weld bead 5. In the weld metal 2 constituting the weld bead 5, a crack 1 having a length corresponding to the penetration depth P of the weld metal 2 occurs.

  The inventors of the present application cracked the weld metal 2 by defining the amount of boron-containing powder to be dispersed so that the boron content in the weld metal 2 is 0.03 to 2% by mass. 1 and the crack 1 can be formed to extend in the depth direction of the weld metal 2, and the length of the crack 1 corresponds to the penetration depth P of the weld metal 2 (almost coincident). Found that it can be. The present invention has been completed based on such knowledge.

  When the boron-containing powder 4 is dispersed on the base material 3 and the boron-containing powder together with the steel material of the base material 3 is melted by laser welding, the boron melts into the molten metal and the molten metal solidifies. The effect of boron in the inside suppresses the ferrite transformation and upper bainite transformation of the weld metal, promotes martensitic transformation at a low temperature, and can produce a weld metal having poor ductility. Thereby, the vertical crack 1 can be generated over the entire penetration depth of the welded portion (welded metal 2). Therefore, by adjusting the welding conditions and adjusting the penetration depth P of the welded portion (welded metal 2), as a result, the length of the vertical crack 1 is adjusted to the desired one (penetration depth P). be able to.

  6A is a longitudinal sectional view of the front of the weld metal part, FIG. 6B is a plan view, and FIG. 6C is a longitudinal sectional view in a direction perpendicular to FIG. 6A. As shown in FIG. 6A, when the laser beam is moved in the arrow direction (welding direction) and welding is performed in the presence of boron powder 4, the length corresponding to the penetration depth P of the weld metal 2 as described above. Crack 1 occurs. A large number of cracks 1 are formed in a straight line in the moving direction (welding direction) of the laser beam. The generation position of the crack 1 is the center of the weld metal cross section, and the crack 1 occurs over the entire cross section. As shown in FIGS. 1 and 2, the weld crack introduction test body is mainly cracked in the weld line direction, but as shown in FIG. 6 (b), the weld formed as shown in FIG. 6 (a). By moving the wire in the joint welding direction, the crack 1 can be formed in a two-dimensional region in a direction perpendicular to the welding line. Thus, according to the present embodiment, the length, occurrence position, quantity, direction, and the like of the crack 1 can be arbitrarily adjusted.

  In the case of laser welding, the penetration depth P can be controlled by selecting the welding conditions based on the laser output and the welding speed. In the case of electron beam welding, the penetration voltage, beam current, and welding speed are controlled. It can be controlled by selecting.

  Moreover, it is preferable that the weld metal 2 which introduce | transduced this crack-like defect has the average hardness of 400 to 700 Hv in Vickers hardness. This is because when the hardness of the weld metal 2 is as high as 400 Hv or more in terms of Vickers hardness, the vertical crack 1 is likely to be generated in the weld metal 2.

  In this embodiment, the penetration depth P of the weld metal to be formed is controlled to a desired value by appropriately selecting welding conditions such as laser welding or electron beam welding. At this time, the weld metal 2 obtained by adjusting the amount of the boron-containing powder sprayed on the base material (steel material) so that the boron content in the weld metal is 0.03 to 2% by mass. Becomes inferior in ductility, and can generate longitudinal cracks 1 in the entire depth direction of weld metal 2, that is, in the entire penetration depth P of weld metal 2. Thereby, the length of the crack 1 can be controlled to a predetermined value, and the natural weld crack whose length is controlled to the predetermined value can be introduced into the steel material.

  When the boron content of the weld metal is less than 0.03% by mass, the microstructure of the weld metal is not completely martensite, the hardness is insufficient, and cracks are not induced. On the other hand, when the boron content exceeds 2% by mass, the ductility of the weld metal is extremely lowered and becomes a so-called glass shape, so that cracks are randomly generated in the vertical and horizontal directions. Therefore, the boron content of the weld metal is 0.03 to 2% by mass. Furthermore, as described above, the vertical crack 1 is easily formed in the weld metal 2 by setting the average hardness of the weld metal 2 to 400 to 700 Hv in terms of Vickers hardness. Although it is related to the boron content, when the Vickers hardness is less than 400 Hv, it does not become complete martensite, the hardness is insufficient, and cracks are not induced. Moreover, when Vickers hardness exceeds 700 Hv, the ductility of a weld metal will fall extremely and a crack will generate | occur | produce vertically and horizontally. Therefore, the average hardness of the weld metal 2 is preferably 400 to 700 Hv.

  Next, another embodiment of the present invention will be described. In this embodiment, a crack is formed inside a steel material (base material), and a test body in which the crack is enclosed is obtained. 3 to 5 are diagrams showing a process for manufacturing a test body in which cracks are enclosed in the steel material. For example, a steel material having a steel type of JIS SM490 is used. From this steel material, for example, a test piece having a thickness of 32 mm, a width of 200 mm, and a length of 300 mm is cut out as the base material 3. Then, as shown in FIG. 3, a V-shaped groove 8 is formed on the surface of the base material 3. The groove angle of the groove 8 is, for example, 60 °, the root interval (groove gap) x is 6 mm, and the groove depth y is 12 mm. Moreover, the thickness t of this test body is 32 mm, for example.

  Thus, after forming the above-mentioned groove on one side of the base material 3, as shown in FIG. 4, the boron-containing powder 4 is sprayed on the groove route, for example, the welding speed is 1 m / min, laser Under the condition that the output is 8 kW, the laser beam 6 is irradiated to perform laser welding, and the vertical crack 1 is generated.

  Thereafter, as shown in FIG. 5, the remainder of the groove 8 is filled with molten metal (weld bead 5) by arc welding, and the crack 1 is enclosed in the groove. In this way, the crack 1 can be enclosed in the base material 3. Moreover, the crack 1 has a length corresponding to the penetration depth of the weld metal, and therefore the length of the crack 1 can be controlled to a desired length.

  Next, the effect of the embodiment of the present invention will be described in comparison with a comparative example that is out of the scope of the present invention. First, the result of the laser welding test by spraying boron-containing powder will be described. As a base material, a steel material of JIS SM490 was used and adjusted to a test piece having a thickness of 25 mm, a width of 150 mm, and a length of 300 mm. The test piece was subjected to bead-on-plate welding by laser welding, and the presence or absence and crack height of the weld metal part were investigated. During welding, welding was performed on Example 1 in which boron-containing powder was sprayed on a site to be welded to a height of about 1 mm and a comparative example in which boron-containing powder was not sprayed. The welding test method is shown in FIG. The composition of the boron-containing powder is Fe-20 mass% B-balance impurities ferroboron. The particle size of the boron-containing powder is 50 to 150 μm.

  Table 1 below shows the laser welding conditions, the measurement results of the penetration depth by the cross-sectional macro test, the presence or absence of cracks, and the length of the cracks. In the cross section macro test, a cross section of the welded portion in a direction perpendicular to the weld line was cut, and a sample for the macro test was taken. This sample was wet-polished with about # 1200 abrasive paper, then buffed, and then etched with a 5% nitric acid-alcohol solution. And the presence or absence of the crack was observed with the digital projector, and also the length of the crack was observed.

  As shown in Table 1 above, when boron-containing powder is dispersed to a height of about 1 mm and the boron content of the weld metal part is 0.03 to 2% by mass, cracking occurs, The length was almost the same as the penetration depth. Since the penetration depth can be controlled by welding conditions such as laser output, the results in Table 1 show that the crack length can be controlled as a result.

  As a result of the penetration inspection test on the surface of the weld bead, in each weld bead in which cracks occurred, one vertical crack occurred over the entire length of the weld metal part.

  Table 2 below shows the measurement results of the micro Vickers hardness test of the above Examples (No. 1 to 11) and Comparative Examples (No. 12 to 14). This test has a test load of 0.5 kg and an average value of three points.

  As shown in Table 2, Examples (Nos. 1 to 11) in which cracks were generated by spraying boron-containing powder showed a high value of micro Vickers hardness of 420 to 635 Hv. The comparative example (No. 12-14) which is not spread | dispersed has shown the micro Vickers hardness as low as 280-305Hv. In other words, as shown in Table 1, cracks with a length corresponding to the penetration depth of the weld metal part occur in the weld metal in which the weld metal part has a Vickers hardness of 400 to 700 Hv. I understand that.

  Next, the results of testing the relationship between the boron content of weld metal and the occurrence of cracks will be described. Using a base material of the same steel type as in Example 1, the amount of boron-containing powder sprayed and the laser welding conditions were changed, a bead-on-plate welding test was conducted, the presence or absence of cracks was examined, and boron contained in the weld metal The amount was analyzed. Table 3 below shows the analysis results of the presence or absence of cracking and the boron content of the weld metal.

  As shown in Table 3, when the boron content of the weld metal falls within the range of 0.03 to 2% by mass, the vertical crack 1 as shown in FIG. 1 occurs in the weld metal 2 and the weld metal is melted. A crack 1 with a length corresponding to the depth was obtained. However, when the boron content of the weld metal is less than the above range, cracks do not occur (Comparative Example (No. 19)), and when the boron content is greater than the above range, transverse cracks frequently occur in addition to vertical cracks. However, the desired form of crack was not obtained, and therefore the length of the crack could not be adjusted (Comparative Example No. 27, 28).

  Next, the result of the crack formation test by electron beam welding will be described. Using a base material of the same steel type as in Example 1, a bead-on-plate welding test by electron beam welding was performed, and the presence or absence of cracks in the weld metal part and the crack height were investigated. When welding, prepare a boron-containing powder with a height of about 1 mm and a non-sprayed one at the site to be welded, and provide a protective cover to prevent the powder from scattering during the deaeration process prior to welding. It was.

  And it welded on the electron beam welding conditions shown in following Table 4, and measured the penetration depth by the cross-sectional macro test, the presence or absence of a crack, and the crack height. The results are also shown in Table 4.

  As shown in Table 4, also in electron beam welding, by including a boron-containing powder and including a predetermined amount of boron in the weld metal, the penetration depth and the crack height almost coincide. Cracks could be formed in the weld metal.

  According to the present invention, natural cracks caused by welding can be introduced into the base material (steel material), and at this time, by adjusting the penetration depth of the weld metal that can be controlled by welding conditions, Since the direction and length of the crack can be controlled, a weld crack introduction test body having a crack of a desired size and shape with high accuracy can be obtained. For this reason, the present invention can easily provide a high-precision test body for verifying the detection performance of equipment in various nondestructive tests such as an ultrasonic flaw detection test, a magnetic particle flaw detection test, and a penetrant flaw detection test. it can.

1: Crack 2: Weld metal 3: Base material 4: Boron powder 5: Weld bead 6: Laser beam 7: Direction

Claims (3)

By welding a steel material containing boron-containing powder, a weld metal part having a boron content of 0.03 to 2% by mass is obtained, and cracked defects are introduced into the weld metal part. Weld crack introduction test body. The weld crack introduction test body according to claim 1, wherein an average hardness of the weld metal part into which the crack-like defect is introduced is 400 to 700 Hv in terms of Vickers hardness. Boron-containing powder is sprayed on the welding target portion of the steel material, and the region containing the boron-containing powder is welded by laser welding or electron beam welding, so that the boron content is 0.03 to 2% by mass. A weld crack introduction method characterized by obtaining a metal part and introducing a crack-like defect into the weld metal part.

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