Longitudinal hot crack preparation method

Abstract

The invention discloses a longitudinal hot crack preparation method which comprises the following steps: providing a first test plate and a second test plate, and only forming a groove in a to-be-welded area on the first test plate; wherein the to-be-welded area on the first test plate is located on one side face of the first test plate; performing surfacing treatment on a to-be-welded area on the second test plate to obtain a surfacing layer; wherein the to-be-welded area on the second test plate is located on one side face of the second test plate; the to-be-welded area of the first test panel and the to-be-welded area of the second test panel are oppositely arranged, and a welding gap is formed between the groove of the first test panel and the surfacing layer of the second test panel; welding a welding gap between the first test plate and the second test plate by adopting a vertical position welding position; and after the welding flux is cooled to the room temperature, flaw detection is conducted on the welding flux, and the flaw detected through flaw detection is the longitudinal hot crack.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and in particular to a method for preparing longitudinal thermal cracks. Background Art

[0002] Ultra-high-strength steel plates, typically above 400 MPa, are extensively used in marine engineering structures. Longitudinal thermal cracking during welding is common in products. To analyze the origin and propagation of these cracks, actual crack samples are required. Longitudinal thermal cracks in conventional products can only be repaired, but the damage they cause makes them difficult to use as crack samples. Small test plate testing, however, has a lower probability of generating longitudinal thermal cracks. Therefore, it is currently difficult to produce longitudinal thermal crack samples that meet the requirements of vertical gas-electric welding testing.

[0003] Currently, the window-shaped restrained crack test is widely used to simulate thermal cracking. However, this method is primarily used to determine the sensitivity of transverse cracking in multi-layer welds and is not suitable for studying longitudinal cracking in vertical gas-electric welding of thick plates. Furthermore, simulating longitudinal cracking in vertical gas-electric welding is difficult using conventional materials and processes, and in most cases, the probability of cracking is low. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a longitudinal thermal crack preparation method, which can solve the problem of low incidence of longitudinal cracks in vertical gas-electric welding of ultra-high strength steel thick plates (steel plate grade is generally above 400Mpa).

[0005] To achieve the above objectives, this application adopts the following technical solutions: In one aspect, a longitudinal thermal crack preparation method is provided, comprising: Providing a first test plate and a second test plate, and forming a groove only in the area to be welded on the first test plate; wherein the area to be welded on the first test plate is located on one side of the first test plate; Performing a surfacing treatment on the area to be welded on the second test plate to obtain a surfacing layer; wherein the area to be welded on the second test plate is located on one side of the second test plate; Arranging the area to be welded of the first test plate and the area to be welded of the second test plate opposite to each other, and setting a welding gap between the groove of the first test plate and the weld overlay layer of the second test plate; Welding the welding gap between the first test plate and the second test plate in a vertical welding position; After the solder cools to room temperature, it is inspected and the defects detected are longitudinal thermal cracks.

[0006] Optionally, in the step of performing surfacing welding on the area to be welded on the second test plate to obtain a surfacing layer, two to three layers are surfacing welded on the area to be welded on the second test plate, and the total surfacing thickness is 4 to 6 mm.

[0007] Optionally, in the step of performing surfacing welding on the area to be welded on the second test plate to obtain a surfacing layer, the Ni element content in the surfacing welding rod is greater than or equal to 55.0%, the Cr element content in the surfacing welding rod is 12.0% to 17.0%, the Fe element content in the surfacing welding rod is less than or equal to 10.0%, the Mo element content in the surfacing welding rod is 5.0% to 9.0%, the Mn element content in the surfacing welding rod is 2.0% to 4.0%, the Si element content in the surfacing welding rod is less than or equal to 1.1%, the W element content in the surfacing welding rod is 1.0% to 2.0%, the Nb+Ta element content in the surfacing welding rod is 0.5% to 2.0%, the C element content in the surfacing welding rod is less than or equal to 0.1%, the Cu element content in the surfacing welding rod is less than or equal to 0.5%, the P element content in the surfacing welding rod is less than or equal to 0.03%, and the S element content in the surfacing welding rod is less than or equal to 0.02%.

[0008] Optionally, after performing surfacing welding on the area to be welded on the second test plate to obtain a surfacing layer, the step further includes: polishing the surfacing layer to make it smooth.

[0009] Optionally, the step arranges the area to be welded of the first test plate and the area to be welded of the second test plate relative to each other, and sets a welding gap between the groove of the first test plate and the weld overlay of the second test plate, wherein the welding gap is 4 to 6 mm.

[0010] Optionally, the step adopts a vertical welding position to weld the welding gap between the first test plate and the second test plate, with a welding current of 400A to 460A, a welding voltage of 40V to 46V, a welding speed of 20mm / min to 50mm / min, a welding heat input of 200KJ / cm to 350KJ / cm, and a welding gas flow rate of 20L / min to 30L / min.

[0011] Optionally, the step provides a first test plate and a second test plate, and opens a groove only in the area to be welded on the first test plate, and the materials of the first test plate and the second test plate are both FH420 steel plates.

[0012] Optionally, the step provides a first test plate and a second test plate, and opens a groove only in the area to be welded on the first test plate, the thickness of the first test plate and the second test plate are both 12mm to 40mm, and the groove angle is 30° to 35°.

[0013] Optionally, in the step of performing flaw detection on the solder after the solder has cooled to room temperature, the defect detected by the flaw detection being a longitudinal thermal crack, and performing ultrasonic flaw detection on the solder filled in the welding gap from one side of the first side panel surface of the first test plate and the second test plate and from one side of the second side panel surface of the first test plate and the second test plate; wherein the first side panel surface of the first test plate and the second test plate are opposite to the second side panel surface of the first test plate and the second test plate.

[0014] Optionally, the step adopts a vertical welding position, and when welding the welding gap between the first test plate and the second test plate, a first cooling pad is set on the first side plate surface of the first test plate and the second test plate; and a second cooling pad is set on the second side plate surface of the first test plate and the second test plate.

[0015] The beneficial effects of this application are: This application adopts the method of surfacing welding combined with high-line energy vertical gas-electric welding to realize the preparation of longitudinal cracks in high-line energy welding of ultra-high-strength steel thick plates for marine engineering. It can be mass-produced and used for research and application of the welding mechanism of high-line energy vertical gas-electric welding of ultra-high-strength steel thick plates for marine engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present application is further described in detail below with reference to the accompanying drawings and examples.

[0017] Figure 1 A flowchart of the longitudinal thermal crack preparation method provided by the present application is shown; Figure 2 It shows a schematic structural diagram of the first test plate and the second test plate after being processed in step S100; Figure 3 shows a schematic structural diagram of the second test plate after processing in step S200; Figure 4 It shows a schematic structural diagram of the first test plate and the second test plate arranged in step S300; Figure 5 A schematic diagram showing the structure of the first test plate and the second test plate viewed from above in step S400 is shown; Figure 6 FIG. 4 shows a schematic diagram of the longitudinal crack structure obtained in step S500 .

[0018] In the picture: 100, first test plate; 101, groove; 200, second test plate; 201, surfacing layer; 300, first cooling pad; 400, second cooling pad; 500, longitudinal thermal crack; t, thickness; α, groove angle; d, welding gap; S100~S500, steps. DETAILED DESCRIPTION

[0019] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved more clearly, the technical solutions of the embodiments of this application are further described in detail below. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of this application.

[0020] In the description of this application, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0021] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0022] In one embodiment of the present application, a method for preparing a longitudinal thermal crack is provided, comprising: providing a first test plate and a second test plate, and opening a groove only in the area to be welded on the first test plate; wherein the area to be welded on the first test plate is located on one side of the first test plate; performing a surfacing treatment on the area to be welded on the second test plate to obtain a surfacing layer; wherein the area to be welded on the second test plate is located on one side of the second test plate; arranging the area to be welded of the first test plate and the area to be welded of the second test plate relative to each other, and setting a welding gap between the groove of the first test plate and the surfacing layer of the second test plate; welding the welding gap between the first test plate and the second test plate in a vertical welding position; after the solder is cooled to room temperature, performing a nondestructive testing on the solder, and the defect detected by the nondestructive testing is a longitudinal thermal crack.

[0023] This application adopts the method of surfacing welding combined with high-line energy vertical gas-electric welding to realize the preparation of longitudinal cracks in high-line energy welding of ultra-high-strength steel thick plates for marine engineering. It can be mass-produced and used for research and application of the welding mechanism of high-line energy vertical gas-electric welding of ultra-high-strength steel thick plates for marine engineering.

[0024] Figure 1 The flowchart of the longitudinal thermal crack preparation method provided by the present application is shown in FIG. Figure 1 As shown, a longitudinal thermal crack preparation method provided in one embodiment of the present application includes: Step S100: providing a first test plate 100 and a second test plate 200, and forming a groove 101 only in the area to be welded on the first test plate 100; wherein the area to be welded on the first test plate 100 is located on one side of the first test plate 100; Step S200, performing a surfacing process on the area to be welded on the second test plate 200 to obtain a surfacing layer 201; wherein the area to be welded on the second test plate 200 is located on one side of the second test plate 200; Step S300, arranging the area to be welded of the first test plate 100 and the area to be welded of the second test plate 200 opposite to each other, and setting a welding gap d between the groove 101 of the first test plate 100 and the weld overlay 201 of the second test plate 200; Step S400: Welding the welding gap between the first test plate 100 and the second test plate 200 in a vertical welding position; In step S500 , after the solder is cooled to room temperature, the solder is inspected. The defect detected by the inspection is the longitudinal thermal crack 500 .

[0025] Figure 2 FIG. 1 shows a schematic structural diagram of the first test plate and the second test plate after processing in step S100. Figure 2 As shown, in step S100 , a groove 101 is only formed in the area to be welded on the first test plate 100 , and no groove is processed on the second test plate 200 .

[0026] It should be noted that the dimensions of the first test plate 100 and the second test plate 200 are generally the same, and no distinction is made. The welding areas of the first test plate 100 and the second test plate 200 are both located on the side surfaces of the plate, and the welding areas of the first test plate 100 and the second test plate 200 are of the same size. This configuration is more conducive to fully simulating the application scenario of vertical gas-electric welding.

[0027] In step S100, both the first test plate 100 and the second test plate 200 are FH420 steel plates. A brief introduction to FH420 steel plates is provided here. Due to its high strength, high toughness, excellent weldability, and corrosion resistance, FH420 steel plates have a tensile strength exceeding 420 MPa and a yield strength exceeding 300 MPa. Even in low-temperature environments, FH420 steel plates can maintain high toughness and impact resistance, making them suitable for polar navigation vessels and the construction of marine engineering facilities. However, due to their high strength and toughness, FH420 steel plates also place more stringent requirements on welding processes.

[0028] Here, the first test plate 100 and the second test plate 200 are both made of FH420 steel plates to better simulate the scene of generating longitudinal thermal cracks in welding, so as to produce longitudinal thermal crack samples that meet the requirements of vertical gas-electric welding test.

[0029] Regarding the groove angle, it should be noted that it is mainly related to the material and plate thickness. Based on the FH420 steel plate used for the first test plate 100 in this embodiment, the thickness t of the first test plate 100 can be set to 12mm-40mm, and the groove angle α can be set to 30°-35°.

[0030] In a specific embodiment, the first test plate 100 and the second test plate 200 are both made of FH420 steel plates, and the dimensions of the first test plate and the second test plate are both set to 1000mm*200mm*40mm. In this case, the angle α of the groove 101 processed on the first test plate can be 35°.

[0031] Figure 3 The schematic diagram of the structure of the second test plate after step S200 is shown. Figure 3 As shown, in step S200, generally two to three layers of surfacing welding can be performed on the area to be welded on the second test plate 200, and the total surfacing thickness is 4 to 6 mm.

[0032] Here, the chemical composition of the surfacing welding rod used in step S200 is introduced as follows: the Ni content in the surfacing welding rod is greater than or equal to 55.0%, the Cr content in the surfacing welding rod is 12.0%-17.0%, the Fe content in the surfacing welding rod is less than or equal to 10.0%, the Mo content in the surfacing welding rod is 5.0%-9.0%, the Mn content in the surfacing welding rod is 2.0%-4.0%, the Si content in the surfacing welding rod is less than or equal to 1.1%, the W content in the surfacing welding rod is 1.0%-2.0%, the Nb+Ta content in the surfacing welding rod is 0.5%-2.0%, the C content in the surfacing welding rod is less than or equal to 0.1%, the Cu content in the surfacing welding rod is less than or equal to 0.5%, the P content in the surfacing welding rod is less than or equal to 0.03%, and the S content in the surfacing welding rod is less than or equal to 0.02%.

[0033] However, it should be noted that if the chemical composition of the surfacing welding rod used is different from the chemical composition of the above-mentioned surfacing welding rod, but the surfacing layer obtained by surfacing in step S200 can also be obtained, it can also be selected. The chemical composition of the above-mentioned surfacing welding rod is not used as a limitation here.

[0034] After step S200, the method further includes: grinding the surfacing layer 201 to be smooth. The polished surfacing layer 201 is then combined with the first test plate 100 to ensure the solder filling effect in step S400, thereby preparing the longitudinal thermal cracks 500 that meet the requirements.

[0035] Figure 4 The schematic diagram of the structure of the first test plate and the second test plate arranged in step S300 is shown. Figure 4 As shown, in step S300, the first test plate 100, which has been sloped, and the second test plate, which has been welded to form a weld overlay, are assembled in preparation for the subsequent welding steps. First, the first test plate 100 and the second test plate 200 are both placed upright on a plane, i.e., the plane where the surfaces of the first test plate 100 and the second test plate 200 lie is perpendicular to the placement plane. Then, a side surface of the first test plate 100, which is the area to be welded, is arranged opposite to a side surface of the second test plate 200, which is the area to be welded (i.e., the groove on the first test plate 100 and the weld overlay on the second test plate 200 are arranged opposite each other), and a welding gap is set between the groove on the first test plate 100 and the weld overlay on the second test plate 200.

[0036] Here, the welding gap d can be set to 4-6 mm. However, it should be noted that the welding gap should not be too small, because if the gap is too small, the slag pool will be difficult to control, the electrode will easily short-circuit with the workpiece, the electroslag process will be unstable, and defects will be easily generated.

[0037] In step S400, it should be understood that the vertical welding position may refer to welding from top to bottom along the welding gap or welding from bottom to top along the welding gap.

[0038] This example uses vertical gas-electric welding performed from bottom to top in a vertical position. The welding torch strikes the arc at the bottom of the weld gap, and the wire feed mechanism feeds the wire at a constant speed. The arc burns within the weld gap, melting the wire and base metal to form a molten pool, which becomes part of the weld metal. The wire is fed into the molten pool through a contact tip. The contact tip and welding torch move vertically upward along the weld gap. Generally, the movement speed must match the solidification rate of the molten pool to ensure a well-formed weld. When the welding torch reaches the top of the weld gap, the welding current and wire feed speed are gradually reduced. The arc is extinguished after the arc crater is filled to avoid cracks or shrinkage cavities.

[0039] Figure 5 The schematic diagram of the structure of the first test plate and the second test plate in step S400 is shown. Figure 5 As shown, in step S400, a first cooling pad 300 is installed on the first side surface of the first test plate 100 and the second test plate 200 to cool the molten pool metal during the welding process; and a second cooling pad 400 is installed on the second side surface of the first test plate 100 and the second test plate 200 to cool the molten pool metal during the welding process. Here, the first cooling pad 300 and the second cooling pad 400 are installed in close contact with the side surfaces of the first test plate 100 and the second test plate 200 and the welding gap, forcing the molten pool metal to solidify under the constraints of the first cooling pad 300 and the second cooling pad 400, thereby forming a weld.

[0040] Optionally, the first cooling pad 300 is fixedly mounted on one side of the first test plate 100 and the second test plate 200 , and the second cooling pad 400 is slidably mounted on the other side of the first test plate 100 and the second test plate 200 .

[0041] Here, the welding parameters involved in the welding process of step S400 are introduced as follows: the welding current can be set to 400A~460A, the welding voltage can be set to 40V~46V, the welding speed can be set to 20mm / min~50mm / min, the welding heat input can be set to 200KJ / cm~350KJ / cm, and the welding gas flow rate can be set to 20L / min~30L / min.

[0042] In step S500, after welding is completed and cooled to room temperature, ultrasonic testing is performed on the solder filling the welding gap from one side of the first side surface of the first test plate 100 and the first test plate 100, and from one side of the second side surface of the first test plate 100 and the second test plate 200; wherein the first side surface of the first test plate 100 and the second test plate 200 is opposite to the second side surface of the first test plate 100 and the second test plate 200. In other words, after welding is completed and cooled to room temperature, ultrasonic testing is used to perform flaw detection on the interior of the weld between the first test plate 100 and the second test plate 200 from both sides of the test plate. Figure 6 The longitudinal crack structure obtained in step S500 is shown in FIG. Figure 6 As shown in the figure, the flaw detection shows that there is a defect in the center of the entire weld. The weld was then processed and cut for metallographic testing. The metallographic test showed that there was a longitudinal thermal crack in the center of the weld.

[0043] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other positions or relationships are used solely for ease of description and simplified operation, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0044] In this specification, reference to terms such as "one embodiment" or "example" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0045] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0046] The technical principles of the present application have been described above in conjunction with specific embodiments. These descriptions are intended solely to explain the principles of the present application and are not to be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, those skilled in the art will be able to devise other specific implementations of the present application without inventive effort, and such implementations will fall within the scope of protection of the present application.

Claims

1. A method for preparing longitudinal thermal cracks, characterized in that: include: A first test plate (100) and a second test plate (200) are provided, and a groove (101) is provided only in the area to be welded on the first test plate (100); wherein the area to be welded on the first test plate (100) is located on one side of the first test plate (100); A surfacing layer (201) is obtained after surfacing treatment is performed on the area to be welded on the second test plate (200); wherein the area to be welded on the second test plate (200) is located on one side of the second test plate (200); Arranging the area to be welded of the first test plate (100) and the area to be welded of the second test plate (200) relative to each other, and setting a welding gap between the groove (101) of the first test plate (100) and the weld overlay (201) of the second test plate (200); Welding the welding gap between the first test plate (100) and the second test plate (200) in a vertical welding position; After the solder is cooled to room temperature, the solder is inspected, and the defect detected by the inspection is a longitudinal thermal crack (500).

2. The longitudinal thermal crack preparation method according to claim 1, characterized in that: In the step, after performing a surfacing treatment on the area to be welded on the second test plate (200), a surfacing layer (201) is obtained, wherein two to three layers are surfacing on the area to be welded on the second test plate (200), and the total surfacing thickness is 4 to 6 mm.

3. The longitudinal thermal crack preparation method according to claim 1, characterized in that: In the step, after performing a surfacing welding treatment on the area to be welded on the second test plate (200), a surfacing layer (201) is obtained, wherein the Ni content in the surfacing welding rod is greater than or equal to 55.0%, the Cr content in the surfacing welding rod is 12.0% to 17.0%, the Fe content in the surfacing welding rod is less than or equal to 10.0%, the Mo content in the surfacing welding rod is 5.0% to 9.0%, the Mn content in the surfacing welding rod is 2.0% to 4.0%, the Si content in the surfacing welding rod is less than or equal to 1.1%, the W content in the surfacing welding rod is 1.0% to 2.0%, the Nb+Ta content in the surfacing welding rod is 0.5% to 2.0%, the C content in the surfacing welding rod is less than or equal to 0.1%, the Cu content in the surfacing welding rod is less than or equal to 0.5%, the P content in the surfacing welding rod is less than or equal to 0.03%, and the S content in the surfacing welding rod is less than or equal to 0.02%.

4. The longitudinal thermal crack preparation method according to claim 1, characterized in that: After the surfacing treatment is performed on the area to be welded on the second test plate (200) to obtain the surfacing layer (201), the step further comprises: polishing the surfacing layer (201) to make it smooth.

5. The longitudinal thermal crack preparation method according to claim 1, characterized in that: The step arranges the area to be welded of the first test plate (100) and the area to be welded of the second test plate (200) relative to each other, and sets a welding gap between the groove (101) of the first test plate (100) and the surfacing layer (201) of the second test plate (200), wherein the welding gap is 4 to 6 mm.

6. The longitudinal thermal crack preparation method according to claim 1, characterized in that: The step adopts a vertical welding position to weld the welding gap between the first test plate (100) and the second test plate (200), with a welding current of 400A to 460A, a welding voltage of 40V to 46V, a welding speed of 20mm / min to 50mm / min, a welding heat input of 200KJ / cm to 350KJ / cm, and a welding gas flow rate of 20L / min to 30L / min.

7. The longitudinal thermal crack preparation method according to claim 1, characterized in that: The step provides a first test plate (100) and a second test plate (200), and opens a groove (101) only in the area to be welded on the first test plate (100), wherein the materials of the first test plate (100) and the second test plate (200) are both FH420 steel plates.

8. The longitudinal thermal crack preparation method according to claim 1, characterized in that: The step provides a first test plate (100) and a second test plate (200), and opens a groove (101) only in the area to be welded on the first test plate (100), wherein the thickness of the first test plate (100) and the second test plate (200) are both 12 mm to 40 mm, and the groove angle is 30° to 35°.

9. The longitudinal hot crack preparation method according to any one of claims 1 to 8, characterized in that: In the step, after the solder is cooled to room temperature, the solder is subjected to flaw detection, and the defect detected by the flaw detection is a longitudinal thermal crack (500), and ultrasonic flaw detection is performed on the solder filled in the welding gap from one side of the first side plate surface of the first test plate (100) and the second test plate (200) and one side of the second side plate surface of the first test plate (100) and the second test plate (200); wherein the first side plate surface of the first test plate (100) and the second test plate (200) are opposite to the second side plate surface of the first test plate (100) and the second test plate (200).

10. The longitudinal thermal crack preparation method according to claim 9, characterized in that: The step adopts a vertical welding position to weld the welding gap between the first test plate (100) and the second test plate (200), and a first cooling pad (300) is provided on the first side plate surface of the first test plate (100) and the second test plate (200); and a second cooling pad (400) is provided on the second side plate surface of the first test plate (100) and the second test plate (200).

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