Preparation method and application of thick plate high heat input welding CTOD sample

Abstract

The invention provides a preparation method and application of a thick plate high heat input welding CTOD sample. The preparation method comprises the following steps: 1) assembling plates to be butted; wherein one plate is provided with a K-shaped groove, the angle range of the groove is 17.5-35 degrees, and the two plates are assembled according to a gap of 0-1 mm; 2) welding the first surface of the to-be-butted plate by adopting vertical gas welding to obtain a welding seam 1; (3) groove root treatment is conducted on the second face of the plate to be in butt joint; (4) welding the second surfaces of the steel plates to be butted by adopting vertical gas welding to obtain a welding seam 2; (5) flaw detection is conducted on internal defects of the weld joint through an ultrasonic flaw detector; and 6) processing the CTOD test sample. According to the method, the K-shaped groove is adopted for welding of the prefabricated weld joint, and preparation of the CTOD sample needing high heat input welding of 200-350 KJ / cm can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of marine engineering, and particularly relates to a preparation method and application of a thick plate high-energy input welding CTOD sample. Background Art

[0002] CTOD (Crack Tip Opening Displacement) refers to the relative distance between the two surfaces after the crack tip is subjected to an opening load, which is often expressed as δ and the common unit is millimeter. For the crack tip opening displacement test sampling, according to the international general specification BS7448, the specimens can be made according to the actual thickness (i.e. full thickness specimens). Since the specification requires the CTOD test to test the fracture toughness of the heat-affected zone of the weld of metal materials, it is recommended to use the maximum thickness material when making the specimen, and the groove shape should be K-shaped, single-sided V-shaped or J-shaped. Thick plates with thicknesses of 40mm, 80mm, 120mm, etc. are widely used in marine engineering, and generally can only be welded by CO2 gas shielded welding or submerged arc welding.

[0003] However, the existing thick plate CTOD test specimens have a large amount of single-sided V-shaped or J-shaped groove welding, and are generally prepared with K-shaped grooves. The welding line energy can only reach about 100KJ / cm, which cannot meet the line energy requirement of 200-350KJ / cm, and cannot be prepared for specimens that require high line energy welding. In addition, the efficiency of welding thick plates with CO2 gas shielded welding or submerged arc welding is low, the welding time is long, and welding defects are prone to occur inside thick plates. Especially for CO2 gas shielded welding, since hundreds of welds need to be welded, welding defects such as slag inclusion and lack of fusion are very likely to occur inside the weld. Summary of the invention

[0004] The present invention provides a method for preparing a CTOD sample for high-input energy welding of thick plates and its application, which adopts a "K" type groove to weld a prefabricated weld to realize the preparation of a CTOD sample that requires high-input energy (200-350KJ / cm) welding. The CTOD sample preparation method is suitable for the preparation of samples for the crack tip opening displacement (CTOD) test of metal materials for high-input energy welding of thick plates in marine engineering.

[0005] In a first aspect, the present invention provides a method for preparing a thick plate high-input energy welding CTOD specimen, comprising the following steps:

[0006] 1) Assemble the plates to be butted;

[0007] 2) vertical gas-electric welding is used to weld the first side of the plates to be butted together to obtain a weld 1;

[0008] 3) Processing the root of the groove on the second side of the plate to be butted;

[0009] 4) vertical gas-electric welding is used to weld the second side of the steel plates to be butted to obtain weld 2;

[0010] 5) Use ultrasonic flaw detector to detect internal defects of welds;

[0011] 6) Processing of CTOD test specimens.

[0012] As an optional implementation manner, the thickness of the plates to be butted is ≥40 mm, and preferably, the thickness of the plates to be butted is 40 mm to 120 mm.

[0013] As an optional implementation, in step 1), two plates to be butt-jointed are obtained, one of which is symmetrically provided with double-sided grooves, i.e., K-shaped grooves, with a groove angle ranging from 17.5° to 35°, and the two plates are assembled with a gap of 0 to 1 mm.

[0014] As an optional implementation, in the step 1), according to the magnitude of the linear energy, the linear energy corresponding to the groove is 150KJ / cm to 350KJ / cm.

[0015] The invention adopts vertical gas-electric welding to weld the entire groove surface at one time, with large welding current and slow speed. The welding speed is 25-60cm / min, and the welding line energy can reach 150KJ / cm-350KJ / cm.

[0016] As an optional implementation, in step 2), during the first side welding, the welding gun angle is adjusted to be parallel to the groove surface.

[0017] As an optional implementation, in step 2), during the first side welding, the welding gun is swung in the molten pool (for example, back and forth) so that the molten pool can fill the entire groove to form a weld.

[0018] As an optional implementation, in the step 2), during the first side welding, the welding gun swings by 10 to 20 mm.

[0019] As an optional implementation, in the step 2), during the first side welding, the welding current is 350A to 450A, and the welding voltage is 35V to 45V.

[0020] As an optional implementation, in the step 2), during the first side welding, the welding speed is 25 to 60 cm / min.

[0021] As an optional implementation, in step 3), the processing of the root of the groove of the second side of the plate to be joined includes the following steps: firstly, carbon planing is performed on the root of the groove of the second side of the plate to be joined, then grinding is performed, and then CO2 gas shielded welding is used for welding.

[0022] In the present invention, after the first side welding is completed, the second side welding of the plate to be butted is carried out; first, the root of the groove of the second side (i.e., the other side) of the plate to be butted is carbon planed to remove the surface welding slag and the unfused part of the root, and then it is polished to be smooth, and then CO2 gas shielded welding is used for welding to ensure good fusion of the root.

[0023] As an optional implementation, in step 4), the welding method used for welding the second surface of the steel plates to be butted to obtain the weld 2 by vertical gas-electric welding is the same as the method used in step 2).

[0024] That is, in step 4), as an optional implementation, during the second side welding process, the welding gun angle is adjusted to be parallel to the groove surface.

[0025] As an optional implementation, in step 4), during the second side welding, the welding gun is swung back and forth.

[0026] As an optional implementation, in step 4), during the second side welding, the welding gun swings by 10 to 20 mm.

[0027] As an optional implementation, in the step 4), during the second side welding, the welding current is 350A to 450A, and the welding voltage is 35V to 45V.

[0028] As an optional implementation, in the step 2), during the second side welding, the welding speed is 25 to 60 cm / min.

[0029] As an optional implementation manner, during the first-side welding or the second-side welding process, the welding line energy is 150KJ / cm to 350KJ / cm.

[0030] As an optional implementation, in step 5), an ultrasonic flaw detector is used to detect internal defects of the plate weld from both sides of the plate to ensure that there are no defects inside the weld.

[0031] As an optional implementation, in step 6), a sawing machine is used to process CTOD specimens on the welded steel plates with the weld as the center.

[0032] As an optional implementation, in step 6), the dimensions of the CTOD sample are: the height is the thickness of the plate, the width is twice the thickness of the plate, the length is ≥4.5 times the thickness of the plate, and a groove is opened in the center.

[0033] In the second aspect, the present invention provides an application of the above-mentioned thick plate high-input energy welding CTOD sample preparation method, which is suitable for the preparation of samples for CTOD (crack tip opening displacement) test of thick plate high-input energy welding metal materials in marine engineering. For example, it can be applied to the preparation of CTOD samples for steel plate performance testing of thick plate ships such as box ships and polar ships.

[0034] The invention is mainly used for preparing samples for crack tip opening displacement (CTOD) test of thick plate high energy input welding metal materials in marine engineering.

[0035] The invention solves the problem of making thick plate high-energy input CTOD specimens by adopting vertical gas-electric welding and CO2 welding of K-type grooves, and is successfully used for detecting the crack resistance of steel plates after high-energy input welding.

[0036] In the present invention, the above technical features can be freely combined to form a new technical solution without conflicting with each other.

[0037] The beneficial effects brought by the present invention are as follows:

[0038] (1) The present invention provides a method for preparing a thick plate high-energy-input welding CTOD specimen and its application, which adopts a "K" type groove to weld the butted plates at a groove angle range of 17.5° to 35° and a gap of 0 to 1 mm, and can realize the preparation of CTOD specimens that require high energy-input (200 to 350 KJ / cm) welding; and solves the problem that a high energy-input cannot be used when making CTOD specimens using a K type groove;

[0039] (2) The method for preparing CTOD specimens for thick plate high-energy input welding provided by the present invention solves the problem of slow welding efficiency when welding thick plates. High-energy input welding can weld more than 40 mm at a time, reducing the number of welds from hundreds to 4 to 5.

[0040] (3) The method for preparing CTOD specimens for thick plate high-energy line welding provided by the present invention solves the problem that defects are easily generated inside thick plates during welding. Since conventional welding methods have more welds and defects are easily generated, the method of the present invention has fewer welds and reduces the probability of defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram showing the assembly structure of steel plates to be butted together according to Embodiment 1 of the present invention;

[0042] Figure 2 A schematic diagram showing vertical gas-electric welding of steel plates to be butted together during welding according to Example 1 of the present invention;

[0043] Figure 3 A schematic diagram showing the angle and swing direction of the welding gun during welding in Embodiment 1 of the present invention;

[0044] Figure 4 A schematic diagram showing the carbon planing of the groove root of the second surface of the steel plates to be butted in Example 1 of the present invention;

[0045] Figure 5 A schematic diagram showing CO2 gas shielded welding of the groove root of the second surface of the steel plates to be butted in Example 1 of the present invention;

[0046] Figure 6 A schematic diagram showing the structure after the welding of the steel plates to be butted is completed in Example 1 of the present invention;

[0047] Figure 7 A schematic diagram showing ultrasonic flaw detection after the welding of the steel plates to be butted is completed in Example 1 of the present invention;

[0048] Figure 8 A schematic diagram showing the processing structure of the CTOD sample in Example 1 of the present invention;

[0049] Fig. 9 A schematic diagram of CO2 gas shielded welding in Comparative Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Some embodiments of the present invention provide a method for preparing a thick plate high-input energy welding CTOD specimen, comprising the following steps:

[0052] S1: Assemble the plates to be butted; wherein, a steel plate is symmetrically provided with double-sided grooves, i.e., K-shaped grooves, and the groove angle is designed to be 17.5° to 35° (for example, 18°, 20°, 25°, 30° or 32°), and the two plates are assembled with a gap of 0 to 1 mm (for example, 0.2 mm, 0.5 mm or 0.8 mm);

[0053] S2: vertical gas-electric welding is used to weld the first side of the plates to be butted to obtain a weld 1;

[0054] S3: Processing the root of the groove of the second side of the plate to be butted;

[0055] S4: welding the second side of the steel plate to be butted by vertical gas-electric welding to obtain a weld 2; specifically, after the root treatment in step S3 is completed, the second side of the steel plate to be butted is welded by the same welding method as in step S2 to complete the welding of the entire test plate;

[0056] S5: Use ultrasonic flaw detector to detect internal defects of welds;

[0057] S6: Processing of CTOD test specimens.

[0058] In some embodiments of the present invention, the thickness of the plates to be butted is ≥40 mm, preferably 40 mm to 120 mm (for example, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, or 110 mm).

[0059] In some embodiments of the present invention, in step S1, according to the magnitude of the linear energy, the linear energy corresponding to the groove is 150KJ / cm to 350KJ / cm (for example, 200KJ / cm, 250KJ / cm, 300KJ / cm or 320KJ / cm).

[0060] In some embodiments of the present invention, in step S2, during the welding of the first surface, the welding gun angle is adjusted to be parallel to the groove surface, and the welding gun swings back and forth to ensure that the molten pool is fused to the root and the surface; during the welding process, the welding current is 350A-450A (for example, 380A, 400A or 420A), the welding voltage is 35V-45V (for example, 38V, 40V or 42V), the welding gun swing amplitude is 10-20mm (for example, 12mm, 15mm or 18mm), the welding speed is 25-60cm / min (for example, 30cm / min, 40cm / min, 50cm / min or 55cm / min), and the welding line energy is 150KJ / cm-350KJ / cm (for example, 200KJ / cm, 250KJ / cm, 300KJ / cm or 320KJ / cm).

[0061] In some embodiments of the present invention, in step S3, the processing of the root of the groove of the second surface of the plate to be joined includes the following steps: first, carbon planing is performed on the root of the groove of the second surface of the plate to be joined, then grinding is performed, and then CO2 gas shielded welding is used for welding.

[0062] In some embodiments of the present invention, in step S4, during the welding of the second surface, the welding gun angle is adjusted to be parallel to the groove surface, and the welding gun swings back and forth to ensure that the molten pool is fused to the root and the surface; during the welding process, the welding current is 350A~450A (for example, 380A, 400A or 420A), the welding voltage is 35V~45V (for example, 38V, 40V or 42V), the welding gun swing amplitude is 10~20mm (for example, 12mm, 15mm or 18mm), the welding speed is 25~60cm / min, and the welding line energy is 150KJ / cm~350KJ / cm.

[0063] Example 1

[0064] A method for preparing a thick plate high-energy input welding CTOD sample, which adopts a K-type groove to perform high-energy input welding to prepare the CTOD sample, comprises the following steps.

[0065] Step S1: Assembling the plates to be butted;

[0066] Specifically, Figure 1 As shown, two steel plates cut into 1000mm*200mm*80mm are prepared, one of which is symmetrically provided with double-sided grooves, i.e., K-type grooves. According to the amount of linear energy, the groove angle is designed to be 17.5°~35°, corresponding to a linear energy amount of 150KJ / cm~350KJ / cm, and the two plates are assembled with a gap of 0~1mm.

[0067] Step S2: welding the first side of the steel plates to be butted by vertical gas-electric welding;

[0068] Specifically, after the steel plates are assembled in step S1, the first side of the steel plates to be butted is first welded at the bottom of the groove using vertical gas-electric welding, and then welded from bottom to top. Figure 2 As shown in the figure; due to the K-type groove, the welding gun angle is adjusted to be parallel to the groove surface. During the welding process, the welding gun swings back and forth in the molten pool so that the molten pool can fill the entire groove, ensuring that the molten pool is fused to the root and the surface to form a weld, as shown in the figure. Figure 3 and Figure 4 As shown; then the welding of the first side is completed; during the welding process, the welding current is 350A~450A, the welding voltage is 35V~45V, and the swing amplitude of the welding gun is 10~20mm.

[0069] Step S3: using CO2 gas shielded welding to perform root treatment on the second surface of the steel plate to be butted;

[0070] Specifically, after the first side welding is completed, the root of the groove on the other side of the butted steel plate is carbon planed (i.e., the root of the carbon planed). Figure 4As shown in the figure, the carbon planer removes the surface welding slag and the unfused part of the root, then grinds it smooth, and then uses CO2 gas shielded welding for welding. Figure 5 As shown, the root fusion is ensured to be good. Among them, the welding current is 160-180A, the welding voltage is 23-26V, and the welding speed is 15-25cm / min.

[0071] Step S4: welding the second side of the steel plates to be butted by vertical gas-electric welding;

[0072] Specifically, after the root treatment in step S3 is completed, the second side of the butted steel plate is welded using the same welding method as in step S21 to complete the welding of the entire test plate. Figure 6 shown.

[0073] Step S5: After welding is completed, an ultrasonic flaw detector is used to detect internal defects of the steel plate weld from both sides of the steel plate to ensure that there are no defects inside the weld, such as Figure 7 shown.

[0074] Step 6: After the flaw detection is qualified, the welded steel plate is processed by a sawing machine with the weld as the center, such as Figure 8 As shown, the specimen dimensions are: height is the thickness of the steel plate, width is 2 times the thickness of the plate, length is ≥ 4.5 times the thickness of the plate, and a groove is opened in the center.

[0075] Example 2

[0076] The difference between this embodiment and embodiment 1 is that the steel plate grade used is EH420. In step S2, the process parameters during welding are as follows:

[0077] The welding current is 440A, the welding voltage is 45V, the welding gun swing amplitude is 10-20mm, the welding speed is 38cm / min, and the welding line energy is 312kJ / cm.

[0078] The V-type impact performance test of the welded joint of this embodiment was carried out using the China Classification Society Material and Welding Specifications, and the results are shown in Table 1. The specification of the sample is 10mm*10mm*55mm, the temperature of the test sample (or sample) is -40°C, 3 samples are selected at different positions for testing, and then the average value is obtained.

[0079] Table 1:

[0080]

[0081] In addition, the thick plate after welding in this embodiment was tested, and the yield strength of the steel plate was 534N / mm 2 , tensile strength 628N / mm 2 , the tensile strength of the welded joint after welding is 541N / mm2 , meet the requirements of classification society materials and welding specifications (i.e., the yield strength of the steel plate is greater than 420N / mm 2 , tensile strength is 520~680N / mm 2 ).

[0082] Comparative Example 1

[0083] A method for preparing a thick plate CTOD specimen comprises the following steps.

[0084] Step S1: Assembling the plates to be butted;

[0085] Specifically, Figure 1 As shown, two steel plates cut into 1000mm*200mm*80mm are prepared, and one of the steel plates is symmetrically opened with double-sided grooves, i.e., K-type grooves, with a depth of 2 / 3 of the plate thickness on one side and a depth of 1 / 3 of the plate thickness on the other side; according to the amount of linear energy, the groove angle is designed to be 17.5°~35°, corresponding to a linear energy of 15~40KJ / cm, and the two plates are assembled with a gap of 0~3mm.

[0086] Step S2: Use conventional CO2 gas shielded welding to weld the first side of the steel plates to be butted. Fig. 9 As shown, the process parameters adopt the same CO2 gas shielded welding process parameters as in Example 1; wherein, the welding current is 160-180A, the welding voltage is 23-26V, and the welding speed is 15-25cm / min.

[0087] Step S3: Use conventional CO2 gas shielded welding to weld the second side of the steel plates to be butted. Fig. 9 As shown, the process parameters adopt the same CO2 gas shielded welding process parameters as in Example 1. Among them, the welding current is 160-180A, the welding voltage is 23-26V, and the welding speed is 15-25cm / min.

[0088] Step S5: After welding is completed, an ultrasonic flaw detector is used to detect internal defects of the steel plate weld from both sides of the steel plate to ensure that there are no defects inside the weld.

[0089] Step 6: After the flaw detection is qualified, the welded steel plate is processed by a sawing machine with the weld as the center, such as Figure 8 As shown, the specimen dimensions are: height is the thickness of the steel plate, width is 2 times the thickness of the plate, length is ≥ 4.5 times the thickness of the plate, and a groove is opened in the center.

[0090] In this comparative example, conventional CO2 gas shielded welding is used, and about 43 welds are welded on an 80 mm thick plate. Each weld has a thickness of 3 to 4 mm and a width of 10 to 15 mm. Many welds are required to weld a complete weld.

[0091] Using the preparation method of thick plate high-energy line welding CTOD specimens in Example 1, the entire steel plate only needs to weld welds 1 and 2, as well as weld 2 and the CO2 gas shielded weld between weld 2, and the total number of welds is 4 to 5.

[0092] Therefore, compared with the numerous welds required for the conventional CO2 gas shielded welding method for preparing thick plate CTOD specimens, such as Figure 8 As shown, the method for preparing CTOD specimens for thick plate high-energy line welding provided by the present invention solves the problem of slow welding efficiency during thick plate welding. High-energy line welding can weld more than 40 mm at a time, and the weld is significantly reduced.

[0093] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a thick plate high-heat input welding CTOD specimen, characterized in that: The following steps are involved: 1) Assemble the plates to be joined; one of the plates is symmetrically provided with double-sided grooves, i.e., K-shaped grooves, with a groove angle ranging from 17.5° to 35°, and the two plates are assembled with a gap of 0 to 1 mm; 2) vertical gas-electric welding is used to weld the first side of the plates to be butted together to obtain a weld 1; 3) Processing the root of the groove on the second side of the plate to be butted; 4) vertical gas-electric welding is used to weld the second side of the steel plates to be butted to obtain weld 2; 5) Use ultrasonic flaw detector to detect internal defects of welds; 6) Processing of CTOD test specimens.

2. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 1, characterized in that: The thickness of the plates to be butted is 40 mm to 120 mm.

3. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 2, characterized in that: In the step 1), according to the magnitude of the linear energy, the linear energy corresponding to the groove is 150KJ / cm to 350KJ / cm.

4. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 2, characterized in that: In the step 2), during the welding of the first surface, the welding gun angle is adjusted to be parallel to the groove surface.

5. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 4, characterized in that: In the step 2), during the welding of the first surface, the welding gun is swung in the molten pool so that the molten pool can fill the entire groove to form a weld.

6. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 5, characterized in that: In the step 2), during the welding of the first surface, the swing amplitude of the welding gun is 10 to 20 mm.

7. The method for preparing a thick plate high input energy welding CTOD specimen according to any one of claims 1 to 6, characterized in that: In step 3), the processing of the groove root of the second surface of the plate to be butted comprises the following steps: First, the root of the groove on the second side of the plate to be butted is carbon planed, then polished, and then welded using CO2 gas shielded welding.

8. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 7, characterized in that: In the step 4), the welding method used for welding the second side of the steel plates to be butted to obtain the weld 2 by using vertical gas-electric welding is the same as the method used for welding the first side of the plates to be butted by using vertical gas-electric welding in the step 2).

9. The method for preparing a thick plate high input heat welding CTOD specimen according to claim 7, characterized in that: In the step 2), during the welding of the first surface or the second surface, the welding current is 350A to 450A, the welding voltage is 35V to 45V, the welding speed is 25 to 60cm / min, and the line energy is 150KJ / cm to 350KJ / cm.

10. An application of the method for preparing a thick plate high-heat input welding CTOD specimen according to any one of claims 1 to 9, characterized in that: The CTOD sample preparation method is suitable for sample preparation for CTOD test of thick plate high-energy input welding metal materials in marine engineering.

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