Longitudinal hot cracking preparation method

Abstract

The application discloses a longitudinal hot crack preparation method, comprising the following steps: providing a first test plate and a second test plate, and opening a groove only on a to-be-welded area of the first test plate; wherein the to-be-welded area on the first test plate is located on one side surface of the first test plate; carrying out surfacing treatment on a to-be-welded area of 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 surface of the second test plate; arranging the to-be-welded area of the first test plate and the to-be-welded area of the second test plate oppositely, and arranging a welding gap between the groove of the first test plate and the surfacing layer of the second test plate; adopting a vertical welding position to weld the welding gap between the first test plate and the second test plate; and after the welding material is cooled to room temperature, carrying out flaw detection on the welding material, and defects detected by the flaw detection are longitudinal hot cracks.

Description

Technical Field

[0001] This application relates to the field of welding technology, and in particular to a method for preparing longitudinal hot cracks. Background Technology

[0002] Ultra-high strength steel plates are widely used in marine engineering structures, with plate grades generally exceeding 400 MPa. Longitudinal hot cracks during welding are common in these products. To analyze the causes and propagation types of these cracks, actual crack samples are needed. Longitudinal hot cracks in general products can only be repaired, causing damage and making them unsuitable as crack samples. Furthermore, the probability of generating longitudinal hot cracks through small-scale plate testing is low. Therefore, it is currently difficult to manufacture longitudinal hot crack samples that meet the requirements of vertical gas-electric welding tests.

[0003] Currently, window-shaped restraint crack tests are frequently used to simulate hot cracks. However, this method is mainly used to determine the sensitivity of welds to transverse cracks during multi-layer welding and is not suitable for studying longitudinal cracks in thick plates during vertical gas welding. Furthermore, it is difficult to simulate longitudinal cracks in vertical gas welding using ordinary materials and processes; in most cases, the probability of crack occurrence is relatively low. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing longitudinal hot cracks, which can solve the problem of low incidence of longitudinal cracks in vertical gas welding of ultra-high strength steel thick plates (steel plate grades are generally above 400 MPa).

[0005] To achieve the above objectives, this application adopts the following technical solution: On the one hand, a method for preparing longitudinal hot cracks is provided, including: A first test plate and a second test plate are provided, and a bevel is made 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; A weld overlay layer is obtained by performing a weld overlay process on the area to be welded on the second test plate; wherein, the area to be welded on the second test plate is located on one side of the second test plate; The areas to be welded on the first test plate and the areas to be welded on the second test plate are arranged opposite to each other, and a welding gap is set between the bevel of the first test plate and the weld overlay of the second test plate. The welding gap between the first test plate and the second test plate is welded using a vertical welding position; After the solder cools to room temperature, it is inspected for defects. The defects detected by the inspection are longitudinal hot cracks.

[0006] Optionally, after performing a welding process on the area to be welded on the second test plate to obtain a weld overlay layer, two to three layers are welded on the area to be welded on the second test plate, with a total weld overlay thickness of 4 to 6 mm.

[0007] Optionally, after performing a welding process on the area to be welded on the second test plate, the welding electrode used for welding, by mass percentage, contains Ni content greater than or equal to 55.0%, Cr content 12.0%–17.0%, Fe content less than or equal to 10.0%, Mo content 5.0%–9.0%, Mn content 2.0%–4.0%, Si content less than or equal to 1.1%, W content 1.0%–2.0%, Nb+Ta content 0.5%–2.0%, C content less than or equal to 0.1%, Cu content less than or equal to 0.5%, P content less than or equal to 0.03%, and S content less than or equal to 0.02%.

[0008] Optionally, after performing welding on the area to be welded on the second test plate to obtain the weld overlay, the step further includes: grinding the weld overlay smooth.

[0009] Optionally, the step involves arranging the areas to be welded on the first test plate and the areas to be welded on the second test plate opposite to each other, and setting a welding gap of 4 to 6 mm between the bevel of the first test plate and the weld overlay of the second test plate.

[0010] Optionally, the step involves welding the gap between the first and second test plates in a vertical welding position, 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 a bevel is made only in the area to be welded on the first test plate. The material of both the first test plate and the second test plate is FH420 steel plate.

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

[0013] Optionally, after the solder cools to room temperature, the solder is subjected to flaw detection. The defect detected by the flaw detection is a longitudinal hot crack. Ultrasonic flaw detection is performed on the solder filling the welding gap from one side of the first side plate of the first test plate and the second test plate and one side of the second side plate of the first test plate and the second test plate, respectively. The first side plate of the first test plate and the second test plate are opposite to the second side plate of the first test plate and the second test plate.

[0014] Optionally, the step involves welding the gap between the first test plate and the second test plate in a vertical welding position, with a first cooling pad provided on the first side plate surface of the first test plate and the second test plate, and a second cooling pad provided on the second side plate surface of the first test plate and the second test plate.

[0015] The beneficial effects of this application are as follows: This application employs a method combining surfacing welding with high heat input vertical gas electric welding to prepare longitudinal cracks in high heat input welding of ultra-high strength steel thick plates for marine engineering. This method can be mass-produced and used for research and application on the welding mechanism of high heat input vertical gas electric welding of ultra-high strength steel thick plates for marine engineering. Attached Figure Description

[0016] The present application will now be described in further detail with reference to the accompanying drawings and embodiments.

[0017] Figure 1 A flowchart of the longitudinal hot crack preparation method provided in this application is shown; Figure 2 A schematic diagram of the structure of the first and second test plates after processing in step S100 is shown. Figure 3 A schematic diagram of the structure of the second test plate after processing in step S200 is shown; Figure 4 The diagram shows the structure of the first and second test plates arranged in step S300; Figure 5 The diagram shows a top view of the first and second test plates in step S400. Figure 6 A schematic diagram of the longitudinal crack structure obtained in step S500 is shown.

[0018] In the picture: 100. First test plate; 101. Bevel; 200. Second test plate; 201. Weld overlay; 300. First cooling pad; 400. Second cooling pad; 500. Longitudinal hot crack; t, thickness; α, bevel angle; d, welding gap; S100~S500, steps. Detailed Implementation

[0019] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of this application are further described in detail below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0022] One embodiment of this application provides a method for preparing longitudinal hot cracks, comprising: providing a first test plate and a second test plate, and opening a bevel 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 weld overlay treatment on the area to be welded on the second test plate to obtain a weld overlay layer; wherein the area to be welded on the second test plate is located on one side of the second test plate; arranging the areas to be welded on the first test plate and the areas to be welded on the second test plate opposite to each other, and setting a welding gap between the bevel 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 using a vertical welding position; and after the solder cools to room temperature, performing flaw detection on the solder, wherein the defect detected by the flaw detection is the longitudinal hot crack.

[0023] This application employs a method combining surfacing welding with high heat input vertical gas electric welding to prepare longitudinal cracks in high heat input welding of ultra-high strength steel thick plates for marine engineering. This method can be mass-produced and used for research and application on the welding mechanism of high heat input vertical gas electric welding of ultra-high strength steel thick plates for marine engineering.

[0024] Figure 1 A flowchart of the longitudinal hot crack preparation method provided in this application is shown, as follows: Figure 1 As shown, one embodiment of this application provides a method for preparing a longitudinal hot crack, comprising: Step S100: Provide a first test plate 100 and a second test plate 200, and open a bevel 101 only on the welding area on the first test plate 100; wherein the welding area on the first test plate 100 is located on one side of the first test plate 100. Step S200: After performing a welding process on the area to be welded on the second test plate 200, a weld overlay layer 201 is obtained; 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: Arrange 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 set a welding gap d between the bevel 101 of the first test plate 100 and the weld overlay 201 of the second test plate 200. Step S400: Using a vertical welding position, weld the welding gap between the first test plate 100 and the second test plate 200; In step S500, after the solder cools to room temperature, the solder is inspected for defects. The defects detected by the inspection are longitudinal hot cracks 500.

[0025] Figure 2 The diagram shows the structure of the first and second test plates after processing in step S100, as follows. Figure 2 As shown, in step S100, a bevel 101 is made only in the area to be welded on the first test plate 100, and no bevel is made 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 are not differentiated. The welding areas of both the first test plate 100 and the second test plate 200 are located on the side of the plate surface. The welding areas of the first test plate 100 and the second test plate 200 are the same size. This setting is more conducive to fully simulating the application scenario of vertical gas 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, good 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 maintain high toughness and impact resistance, making them suitable for the construction of polar vessels and marine engineering facilities. However, due to their high strength and toughness, the welding process for FH420 steel plates is more demanding.

[0028] The first test plate 100 and the second test plate 200 are both made of FH420 steel plate, which can better simulate the scenario of generating longitudinal hot cracks in welding, so as to produce longitudinal hot crack samples that meet the requirements of vertical gas electric welding test.

[0029] It should be noted that the bevel angle is mainly related to the material and plate thickness. In this embodiment, the first test plate 100 is made of FH420 steel plate, so the thickness t of the first test plate 100 can be set to 12mm–40mm, and the bevel angle α can be set to 30°–35°.

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

[0031] Figure 3 This shows a schematic diagram of the structure of the second test plate after processing in step S200, for reference. Figure 3 As shown, in step S200, two to three layers can generally be deposited on the area to be welded on the second test plate 200, with a total deposit thickness of 4 to 6 mm.

[0032] The chemical composition of the welding electrode used in step S200 is described below. In the welding electrode used for surfacing, by mass percentage, the Ni content is greater than or equal to 55.0%, the Cr content is 12.0%–17.0%, the Fe content is less than or equal to 10.0%, the Mo content is 5.0%–9.0%, the Mn content is 2.0%–4.0%, the Si content is less than or equal to 1.1%, the W content is 1.0%–2.0%, the Nb+Ta content is 0.5%–2.0%, the C content is less than or equal to 0.1%, the Cu content is less than or equal to 0.5%, the P content is less than or equal to 0.03%, and the S content is less than or equal to 0.02%.

[0033] However, it should be noted that if the chemical composition of the welding electrode used is different from that of the welding electrode mentioned above, but the welding layer obtained in step S200 can still be obtained, it can also be used. The chemical composition of the welding electrode mentioned above is not a limitation.

[0034] The process after step S200 further includes: grinding the weld overlay 201 flat. Grinding the weld overlay 201 flat before combining it with the first test plate 100 helps to ensure the effect of solder filling in step S400, thereby preparing the desired longitudinal hot crack 500.

[0035] Figure 4 The diagram shows the structure of the first and second test plates arranged in step S300. (Refer to...) Figure 4 As shown, in step S300, the first test plate 100, with its pre-cut bevel, and the second test plate, with its weld overlay layer already formed, are assembled in preparation for subsequent welding steps. First, both the first test plate 100 and the second test plate 200 are placed vertically on a flat surface, with the planes of the first and second test plates perpendicular to the placement plane. Then, one side of the first test plate 100, serving as the area to be welded, is positioned opposite to one side of the second test plate 200, also serving as the area to be welded (i.e., the bevel on the first test plate 100 is opposite to the weld overlay layer on the second test plate 200), and a welding gap is established between the bevel on the first test plate 100 and the weld overlay layer 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 is difficult to control, the electrode is prone to short circuit with the workpiece, the stability of the electroslag process is poor, and defects are easily generated.

[0037] In step S400, it is important to understand that the vertical welding position can 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 welding from bottom to top in a vertical welding position. The welding torch initiates the arc at the bottom of the welding gap, and the wire feeding mechanism feeds the wire at a constant speed. The arc burns within the welding gap, melting the welding wire and base metal to form a molten pool, which becomes part of the weld metal. The welding wire is fed into the molten pool through the contact tip. The contact tip and welding torch move vertically upwards along the welding gap. Generally, the moving speed needs to match the solidification speed of the molten pool to ensure good weld formation. When the welding torch moves to the top of the welding gap, the welding current and wire feeding speed are gradually reduced. After filling the crater, the arc is extinguished to avoid cracks or shrinkage cavities.

[0039] Figure 5 This shows a top view of the first and second test plates in step S400, for reference. Figure 5 As shown, in step S400, a first cooling pad 300 is provided on the first side surface of the first test plate 100 and the second test plate 200 to cool the molten pool metal during welding; a second cooling pad 400 is provided on the second side surface of the first test plate 100 and the second test plate 200 to cool the molten pool metal during welding. Here, the first cooling pad 300 and the second cooling pad 400 are set 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 constraint 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 installed on one side of the first test plate 100 and the second test plate 200, and the second cooling pad 400 is slidably installed 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 in 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 weld filling the welding gap from one side of the first test plate 100 and the first side plate of the first test plate 100, and from one side of the second side plate of the first test plate 100 and the second test plate 200, respectively; wherein the first side plate of the first test plate 100 and the second test plate 200 are opposite to the second side plate of the first test plate 100 and the second test plate 200. That is, after welding is completed and cooled to room temperature, ultrasonic testing is used to inspect the interior of the weld between the first test plate 100 and the second test plate 200 from both side plates of the first test plate 100 and the second test plate 200. Figure 6 A schematic diagram of the longitudinal crack structure obtained in step S500 is shown, with reference to... Figure 6 As shown, flaw detection revealed a defect in the center of the entire weld. The weld was then processed and cut for metallographic testing. The metallographic test revealed a longitudinal hot crack at the center of the weld.

[0043] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used merely for descriptive distinction and have no special meaning.

[0044] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0045] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0046] The technical principles of this application have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this application without inventive effort, and these embodiments will all fall within the scope of protection of this application.

Claims

1. A method for preparing longitudinal hot cracks, characterized in that, include: A first test plate (100) and a second test plate (200) are provided, and a bevel (101) is made only on the welding area of ​​the first test plate (100); wherein the welding area on the first test plate (100) is located on one side of the first test plate (100); a weld overlay layer (201) is obtained after welding treatment on the welding area of ​​the second test plate (200); wherein the welding area on the second test plate (200) is located on one side of the second test plate (200); the welding area of ​​the first test plate (100) and the welding area of ​​the second test plate (200) are arranged opposite to each other, and a welding gap is set between the bevel (101) of the first test plate (100) and the weld overlay layer (201) of the second test plate (200); using a vertical welding position, the welding gap between the first test plate (100) and the second test plate (200) is... Welding is performed during the welding gap; after the solder cools to room temperature, the solder is inspected for defects, and the defects detected by the inspection are longitudinal hot cracks (500); two to three layers are deposited on the area to be welded on the second test plate (200), with a total deposit thickness of 4 to 6 mm; the welding rods used for the deposited welding contain, by mass percentage, Ni content greater than or equal to 55.0%, Cr content 12.0% to 17.0%, Fe content less than or equal to 10.0%, Mo content 5.0% to 9.0%, Mn content 2.0% to 4.0%, Si content less than or equal to 1.1%, W content 1.0% to 2.0%, Nb+Ta content 0.5% to 2.0%, C content less than or equal to 0.1%, Cu content less than or equal to 0.5%, P content less than or equal to 0.03%, and S content less than or equal to 0.02%.

2. The method for preparing longitudinal hot cracks according to claim 1, characterized in that, After performing welding on the area to be welded on the second test plate (200) to obtain the weld overlay layer (201), the process further includes: grinding the weld overlay layer (201) flat.

3. The method for preparing longitudinal hot cracks according to claim 1, characterized in that, The welding area of ​​the first test plate (100) is arranged opposite to the welding area of ​​the second test plate (200), and a welding gap of 4 to 6 mm is set between the bevel (101) of the first test plate (100) and the weld overlay (201) of the second test plate (200).

4. The method for preparing longitudinal hot cracks according to claim 1, characterized in that, The welding gap between the first test plate (100) and the second test plate (200) is welded using a vertical welding position. The welding current is 400A to 460A, the welding voltage is 40V to 46V, the welding speed is 20mm / min to 50mm / min, the welding heat input is 200KJ / cm to 350KJ / cm, and the welding gas flow rate is 20L / min to 30L / min.

5. The method for preparing longitudinal hot cracks according to claim 1, characterized in that, A first test plate (100) and a second test plate (200) are provided, and a bevel (101) is made only in the area to be welded on the first test plate (100). The materials of the first test plate (100) and the second test plate (200) are both FH420 steel plates.

6. The method for preparing longitudinal hot cracks according to claim 1, characterized in that, A first test plate (100) and a second test plate (200) are provided, and a bevel (101) is made only in the area to be welded on the first test plate (100). The thickness of the first test plate (100) and the second test plate (200) is 12mm to 40mm, and the bevel angle is 30° to 35°.

7. The method for preparing longitudinal hot cracks according to any one of claims 1 to 6, characterized in that, After the solder cools to room temperature, the solder is subjected to flaw detection. The defect detected by the flaw detection is the longitudinal hot crack (500). Ultrasonic flaw detection is performed on the solder filling the welding gap from one side of the first side plate of the first test plate (100) and the second test plate (200) and one side of the second side plate of the first test plate (100) and the second test plate (200); wherein the first side plate of the first test plate (100) and the second test plate (200) are opposite to the second side plate of the first test plate (100) and the second test plate (200).

8. The method for preparing longitudinal hot cracks according to claim 7, characterized in that, During the welding of the gap between the first test plate (100) and the second test plate (200) in a vertical welding position, 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); 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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