A method for determining high performance non-preheating welding process for marine engineering steel

Abstract

The present invention belongs to the field of welding technology, and discloses a method for determining a high-performance non-preheating welding process for marine engineering steel, comprising: obtaining a first cold crack sensitivity index required for non-preheating welding at a specific temperature and a critical constraint distance and a critical constraint degree of a base material sample; obtaining a minimum diffusible hydrogen content of a welding material required for non-preheating welding, and selecting an actual welding material based on the content; optimizing the carbon equivalent of the base material sample using the cold crack sensitivity coefficient to obtain a new base material; obtaining a second cold crack sensitivity index that is less than the first cold crack sensitivity index, and using the new base material corresponding to the sensitivity index as the actual base material; obtaining the time for the actual welding material and the actual base material to cool to 100°C after the peak temperature of the welding is cooled to 100°C under different welding heat inputs. t 100 and critical cooling time of welded joints t cr ,by t 100 and t cr The welding heat input when the difference is the largest is the actual welding heat input. This application provides a quantitative analysis theory system to develop welding technology, avoiding orthogonal experiments and the method has strong universality.

Description

Technical Field

[0001] The present invention belongs to the field of welding technology, and more specifically, relates to a method for determining a high-performance non-preheating welding process for marine engineering steel. Background Art

[0002] When constructing marine engineering equipment in certain sea areas, the ambient temperature may reach minus 5 to 20°C. The problem of cold cracks in welding construction is very prominent, and the hysteresis of cold cracks makes it particularly harmful, which poses a huge hidden danger to the safety of marine engineering structures. Welding preheating provides temperature and time conditions for the diffusion and escape of hydrogen. At the same time, it can appropriately improve the organization, reduce the hardenability, and reduce residual stress to a certain extent. At present, for welding processes in low temperature environments, preheating treatment before welding is required to eliminate the influence of cold cracks. However, in complex structures of thick plates, it is difficult to preheat the entire structure together in actual production or the facilities at the construction site do not have the conditions for preheating before welding. In the existing non-preheating welding process, the main measure of designing low-matching welded joints is to reduce the tendency of cold cracks, but this will cause the problem of reduced bearing capacity of the joints.

[0003] Chinese patent CN117778898A discloses a high-performance marine engineering steel and its preparation method, which can realize non-preheating welding at room temperature, but it is necessary to prepare special welding wire and special steel for non-preheating welding, which has certain limitations in application and cannot be applied to various welding scenarios. Most non-preheating welding processes avoid the generation of cold cracks in welded joints by selecting low-strength matching welding materials for welding. Chinese patent CN117226213A discloses an arc welding process for marine corrosion-resistant steel with a yield strength of 420MPa. The patent obtains a process for non-preheating welding of steel at room temperature by continuously trying welding parameters through orthogonal experiments. The disadvantages are high cost, long test time and low efficiency. The existing methods for non-preheating welding have poor universality, and most of them develop welding processes through a limited number of repeated attempts, and do not have a complete quantitative analysis theoretical system. Therefore, in order to meet the efficient manufacturing needs of large offshore equipment such as deepwater jacket platforms in extreme environments and improve welding efficiency, there is an urgent need for a method to obtain a high-performance welding process for thick plate 420MPa grade offshore steel without preheating in a low temperature environment. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide a method for determining a high-performance non-preheating welding process for marine steel, aiming to solve the problems of low efficiency and poor universality of current methods for developing welding processes.

[0005] To achieve the above object, the present invention provides a method for determining a high-performance non-preheating welding process for marine engineering steel, which is characterized by comprising the following steps:

[0006] S1 obtains the first cold crack sensitivity index required for welding without preheating at a specific temperature;

[0007] S2 obtains the critical restraint distance L of the parent material sample at the specific temperature cr and the critical constraint R cr ; Based on the first cold crack sensitivity index, the minimum diffusible hydrogen content [H] of the welding material required for non-preheating welding is obtained cr , and based on [H] cr Select the actual welding material;

[0008] S3 uses the cold crack sensitivity coefficient of the parent material sample to optimize its carbon equivalent to obtain a new parent material;

[0009] S4 is based on the minimum diffusible hydrogen content [H] cr , the critical constraint R cr and the cold crack sensitivity coefficient of the new base material, to obtain the second cold crack sensitivity index corresponding to the new base material;

[0010] S5 determines the actual parent material: when the second cold crack sensitivity index is less than the first cold crack sensitivity index, a new parent material corresponding to the second cold crack sensitivity index is used as the actual parent material; when the second cold crack sensitivity index is greater than or equal to the first cold crack sensitivity index, steps S3-S5 are repeated until the second cold crack sensitivity index is less than the first cold crack sensitivity index;

[0011] S6 obtains the time t when the peak temperature of the actual welding material and the actual base material after welding cools to 100° C. under different welding heat inputs 100 Based on t 100 Get the critical cooling time t of the welded joint cr , t 100 and t cr The welding heat input E corresponding to the maximum difference between them is taken as the actual welding heat input.

[0012] This application simultaneously considers the influence of the adjustment of the chemical composition of the base material, the diffusible hydrogen content of the welding material and the welding heat input on the cold cracks of the welded joint. Through a complete quantitative analysis theoretical system, it realizes the development of a non-preheating welding process for steels such as thick plate 420MPa grade marine steel under various low temperature environments. The development process is convenient and has stronger universality to the environment. It can obtain welding processes without preheating for various temperature environments; the welding joints obtained after actual welding using the obtained welding process have excellent performance.

[0013] Furthermore, in step S6, a double ellipsoid heat source model is selected, and the welding heat input is changed by changing the welding current. The double ellipsoid heat source model has the advantages of high simulation accuracy, high flexibility, high efficiency and wide application range, and can be applied to various welding process types.

[0014] Furthermore, the welding current gradually increases within the range of 140A to 190A, which can enhance the stability of the molten pool and reduce arc drift and instability caused by insufficient current. If the welding current is lower than 140A, the weld may not be fully penetrated, and if the welding current is higher than 190A, it may cause defects such as weld undercut and burn-through.

[0015] Furthermore, the welding current increases in sequence according to a gradient value of 5A.

[0016] Further, in step S2, the critical restraint distance L is obtained by a rigid restraint welding crack test. cr and the critical constraint R cr Before the test, the test equipment was pre-cooled to a specific temperature, and the ambient humidity was the same during each rigid restraint weld crack test.

[0017] Furthermore, in step S2, the welding end of the parent material sample is processed into an oblique Y-shaped groove, and the groove angle is not greater than 60°.

[0018] Furthermore, the root spacing of the welding ends of the parent material specimen is 1 mm to 2 mm.

[0019] Furthermore, in step S2, gas chromatography is used to obtain the minimum diffusible hydrogen content, and the inner diameter of the chromatographic column used is not less than 4 mm. The carrier gas when the gas chromatography obtains the minimum diffusible hydrogen content is argon with a concentration of not less than 99.9%; preferably, the carrier gas flow rate of the argon is 20 ml / min to 40 ml / min. Within this flow rate range, the separation efficiency and analysis speed of the welding sample in the chromatographic column are higher.

[0020] Furthermore, after step S6, an inclined Y-groove welding crack test is performed using the actual welding material, actual base material and actual welding heat input obtained in steps S1-S6, and double-sided welding is performed on the restrained weld during the inclined Y-groove welding crack test.

[0021] Furthermore, in the inclined Y-groove welding crack test, the angular deformation of the test plate was controlled within 5°.

[0022] In general, the above technical solution conceived by the present invention has the following beneficial effects compared with the prior art:

[0023] (1) Considering that most of the existing non-preheating welding processes are only applicable to room temperature environments, the present application proposes a method for developing a non-preheating welding process in a low-temperature environment. The method uses a complete quantitative analysis theoretical system to efficiently develop non-preheating high-performance welding processes for various types of marine engineering steels in various low-temperature environments; specifically, by obtaining the cold crack sensitivity index that can achieve non-preheating welding at a specific temperature, and then determining the critical constraint degree through a welding crack test with adjustable rigidity, the carbon equivalent of the parent material, the diffusible hydrogen content of the weld material and the actual constraint state of the weld joint are fully considered, and the welding cold crack sensitivity of the marine engineering steel is quantitatively evaluated, and then the diffusible hydrogen content of the weld material is limited to optimize the weld material, and the parent material is optimized according to the cold crack sensitivity coefficient related to the parent material composition, so that the chemical composition of the parent material, the diffusible hydrogen content of the weld material and the constraint degree of the weld joint meet the cold crack sensitivity index for achieving non-preheating welding; in addition, numerical simulation calculations are performed on butt welded joints under different welding heat inputs, and according to the critical cooling time t cr The criterion formula is used to select the optimal welding heat input.

[0024] (2) This application simultaneously considers the influence of the chemical composition of the base material, the diffusible hydrogen content of the welding material and the welding heat input on the cold cracks of the welded joint. Through the above-mentioned complete quantitative analysis theoretical system, the development of a non-preheating welding process for thick plates of 420MPa grade marine steel and other steels under various low temperature environments is realized. The welding process development process is relatively convenient and does not require orthogonal experiments. The acquisition method is more universal for various welding environments. In actual welding, equal strength matching welding materials can be used for welding, and the comprehensive performance of the welded joint will be better.

[0025] (3) This application uses different welding heat input simulations to set the current gradient to increase to change the welding heat input, and the welding current gradually increases in the range of 140A to 190A, which can enhance the stability of the molten pool and reduce arc drift and instability caused by insufficient current. If the welding current is lower than 140A, the weld will not be fully melted through. If the welding current is higher than 190A, it may cause defects such as weld undercut and burn-through.

[0026] (4) The argon gas used in the gas chromatography method of the present application has a large relative molecular weight and a small thermal conductivity coefficient, which can ensure the purity of the sample during the analysis and the accuracy of the analysis results, while also ensuring the stability of the baseline and the sensitivity of the measuring instrument. Within the preset flow rate range, the separation efficiency and analysis speed of the welding sample in a chromatographic column larger than 4 mm are higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a method for determining a high-performance non-preheating welding process for marine engineering steel provided in Example 1;

[0028] Figure 2Schematic diagram of the welding specimen structure in the rigid restrained welding crack test selected in Example 2;

[0029] Figure 3 It is a schematic diagram of the welding sample structure after the rigid restraint welding crack test of Example 2.

[0030] In all the drawings, the same reference numerals are used to denote the same elements or structures, where: 1 - movable end, 2 - test weld, 3 - fixed end. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0033] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0034] In the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0035] In the description of the embodiments of the present invention, unless otherwise specified, “multiple” means two or more than two. For example, multiple processing units means two or more processing units, etc.; multiple elements means two or more elements, etc.

[0036] Example 1

[0037] This embodiment provides a method for determining a high-performance non-preheating welding process for marine engineering steel. Figure 1 As shown, the specific steps include:

[0038] S1 obtains the first cold crack sensitivity index required for welding without preheating at a specific temperature;

[0039] Specifically, based on the ambient temperature T0, the cold crack sensitivity index P that can be achieved without preheating welding in a low temperature environment is obtained according to the following preheating temperature determination formula: w ;

[0040] T0(℃)=1440P w -392 (1)

[0041] Where T0 is the preheating temperature, i.e. the ambient temperature, P w is the cold crack sensitivity index.

[0042] S2 obtains the critical restraint distance L of the parent material sample at a specific temperature cr and the critical constraint R cr ; Obtain the minimum diffusible hydrogen content of welding materials required for welding without preheating based on the first cold crack sensitivity index [H] cr , and based on [H] cr Select the actual welding material.

[0043] Specifically, a special inclined Y-groove specimen is designed and processed, and a rigid restraint welding crack test is carried out at a predetermined ambient temperature to obtain the critical restraint distance L for the specimen to crack or not crack. cr and the critical constraint R cr .

[0044] In the rigid restrained welding crack test, the type of welding method selected is consistent with the welding process to be developed. This embodiment can develop a variety of welding processes such as arc welding, flux-cored gas shielded welding, and metal arc welding. In addition, the type of welding materials is consistent with the welding method, such as the welding rod, flux-cored wire, solid wire, etc. corresponding to each welding method; the type of shielding gas can be determined based on the obtained welding materials; the size of the test weld and the groove form adopt an inclined Y-shaped groove; before the test, the test equipment needs to be pre-cooled to a specific temperature to ensure the accuracy of the results.

[0045] Furthermore, the ambient humidity was the same during each rigid restrained weld crack test.

[0046] The welding parameters of the rigid restraint welding crack test in this embodiment are designed as follows:

[0047] 1. For arc welding, select 4.0mm electrode, welding current 170A, welding speed 150mm / min;

[0048] 2. For MIG / MAG welding, select 1.2mm welding wire. If CO2 shielding gas is selected, the welding current is 200A and the welding speed is 190mm / min. If 80% Ar and 20% CO2 shielding gas are mixed, the welding current is 270A and the welding speed is 400mm / min.

[0049] 3. Flux-cored gas shielded welding, welding current is 280A, welding speed is 350mm / min.

[0050] The selected restraint distance starts from 1.60mm. If cracks appear on the surface or cross-section of the test weld in the rigid restraint welding crack test, the restraint distance is increased; if no cracks appear on the surface and cross-section, the restraint distance is reduced. The critical restraint distance finally measured in this embodiment is accurate to 50mm.

[0051] Then, according to the following high-strength steel welding cold crack sensitivity index formula, the method for determining diffusible hydrogen in the deposited metal in the "Determination Method for Diffusible Hydrogen in Deposited Metal (GB / T 3965-2012)" is used to obtain the minimum diffusible hydrogen content [H] in the deposited metal that can achieve non-preheating welding. cr ;

[0052]

[0053] Where P w is the cold crack sensitivity index, P cm is the cold crack sensitivity coefficient, [H] is the diffusible hydrogen content in the deposited metal (mL / 100g), R cr is the critical restraint (MPa); and based on the above obtained [H] cr Select the actual welding material.

[0054] In this embodiment, gas chromatography is used to obtain the minimum diffusible hydrogen content. The inner diameter of the chromatographic column used is not less than 4 mm, such as 4 mm, 4.6 mm, 5 mm, etc. If it is less than 4 mm, it is difficult to achieve the best separation efficiency.

[0055] In this embodiment, the carrier gas used to obtain the minimum diffusible hydrogen content by gas chromatography is argon gas with a concentration of not less than 99.9%, and the carrier gas flow rate of the argon gas is 20 ml / min.

[0056] In this embodiment, based on the actual welding material obtained above, the actual parent material after optimization, and the optimal welding heat input E obtained in S5, an inclined Y-groove welding crack test is carried out at low temperature to verify whether the preferred welding material, the optimized parent material, and the selected welding heat input can achieve welding without preheating and whether cold cracks can be generated in the welded joint.

[0057] In other preferred embodiments, the carrier gas flow rate of argon is 20 ml / min to 40 ml / min, such as 20 ml / min, 25 ml / min, 30 ml / min, 35 ml / min, 40 ml / min, or any flow rate value between any two of the above values.

[0058] S3 uses the cold crack sensitivity coefficient of the parent material sample to optimize its carbon equivalent multiple times to obtain a variety of new parent materials with different compositions;

[0059] The parent material sample used in this embodiment is EH420 marine engineering steel, and its chemical composition is shown in Table 1. The cold crack sensitivity coefficient P of the steel is cm It is 0.159.

[0060] Table 1 Composition of EH420 marine engineering steel (wt%)

[0061]

[0062] When adjusting the chemical composition of the parent material sample, first consider reducing the content of Mn and Si elements, with the Mn element adjusted by 0.01% each time and the Si element content adjusted by 0.005% each time; if necessary, reduce the content of C, Cu, and Cr elements in turn, with a gradient of 0.001% each time. When adjusting the chemical composition of the steel, it is necessary to consider the mechanical properties, grain size, and ferrite, pearlite, and bainite content of the steel, and select the chemical composition of the steel with the best mechanical properties and the best performance. Ultimately, the optimized parent material composition satisfies the predetermined cold crack sensitivity index that can be achieved without preheating in a low temperature environment. The specific optimization method belongs to the prior art and will not be repeated here.

[0063] S4 based on minimum diffusible hydrogen content [H] cr , the critical constraint R cr and the cold crack sensitivity coefficient of the new base material, to obtain the second cold crack sensitivity index corresponding to the new base material;

[0064] S5: determining the actual parent material: when the second cold crack sensitivity index is less than the first cold crack sensitivity index, taking the new parent material corresponding to the second cold crack sensitivity index as the actual parent material; when the second cold crack sensitivity index is greater than or equal to the first cold crack sensitivity index, repeating steps S3-S5 until the second cold crack sensitivity index is less than the first cold crack sensitivity index;

[0065] S6 obtains the time t of the actual welding material and the actual base material cooling to 100°C after the peak temperature of the welding material under different welding heat inputs 100 Based on t 100 Get the critical cooling time t of the welded joint cr , t 100 and t cr The welding heat input E corresponding to the maximum difference between the two values ​​is taken as the actual welding heat input;

[0066] Specifically, numerical simulation calculations are performed on butt welded joints under different welding heat inputs E. During numerical simulation, the welding heat source selects a double ellipsoid heat source model, and the welding heat input is changed by changing the size of the welding current. Specifically, the current of the arc welding starts from 140A and increases by 5A each time until it reaches 190A, so that there are a total of 10 groups of welding heat inputs. In other preferred embodiments, the gradient increase can also be made smaller to obtain more groups of welding heat inputs, such as selecting gradient values ​​of 2A, 4A, etc.

[0067] Under each set of different welding heat inputs, the weld center of the weld joint in the middle stage of stable welding condition is selected as the test node for temperature measurement. The node temperature is defined as a time variable, the simulated thermal cycle curve of the node is extracted, and the time t for cooling from the peak temperature to 100°C is calculated. 100 Then analyze the time t from the peak temperature after welding to 100℃ 100 , the welding heat input E, the actual base material P after optimizing the composition cm , the diffusible hydrogen content [H] of the deposited metal of the actual selected welding material and the critical restraint R cr Substitute the critical cooling time t of low alloy high strength steel into cr The criterion formula and select t 100 -t cr The corresponding welding heat input E at the maximum is taken as the actual welding heat input;

[0068] t cr =370.84P cm +73.22lg([H]+1)+1.46E+0.012(R+ΔR)-43.59 (3)

[0069] In the above formula, t cr is the critical cooling time, P cm is the cold crack sensitivity coefficient, [H] is the diffusible hydrogen content of the deposited metal of the selected welding material, E is the selected welding heat input, R cr is the critical constraint, ΔR is the additional constraint of local preheating, and the non-preheating welding process is adopted here, so ΔR=0.

[0070] In other preferred embodiments, the Y-groove angle of the parent material sample is not greater than 60°, and the root spacing of the welding ends of the parent material sample is 1 mm to 2 mm to ensure the quality of the weld after welding.

[0071] In this embodiment, the special specimen for the rigid restraint welding crack test, the oblique Y-groove welding crack test specimen and the welding materials all need to be processed before welding, such as grinding the groove with a grinder or a wire brush to remove rust and burrs, and removing oil stains on the surface of the sample groove with alcohol or acetone; the welding materials are dried at the specified temperature according to the instructions for use, and kept warm for use.

[0072] Example 2

[0073] The method steps for obtaining the welding process in this embodiment are the same as steps S1-S5 in the embodiment, including:

[0074] S1 obtains the first cold crack sensitivity index required for welding without preheating at a specific temperature;

[0075] S2 obtains the critical restraint distance L of the parent material sample at a specific temperature cr and the critical constraint R cr ; Obtain the minimum diffusible hydrogen content of welding materials required for welding without preheating based on the first cold crack sensitivity index [H] cr , and based on [H] cr Select the actual welding material;

[0076] S3 uses the cold crack sensitivity coefficient of the parent material sample to optimize its carbon equivalent to obtain a new parent material with a changed composition;

[0077] S4 based on minimum diffusible hydrogen content [H] cr , critical constraint R cr and the cold crack sensitivity coefficient of the new base material, to obtain the second cold crack sensitivity index corresponding to the new base material;

[0078] S5: determining the actual parent material: when the second cold crack sensitivity index is less than the first cold crack sensitivity index, taking the new parent material corresponding to the second cold crack sensitivity index as the actual parent material; when the second cold crack sensitivity index is greater than or equal to the first cold crack sensitivity index, repeating steps S3-S5 until the second cold crack sensitivity index is less than the first cold crack sensitivity index;

[0079] S6 obtains the time t of the actual welding material and the actual base material cooling to 100°C after the peak temperature of the welding material under different welding heat inputs 100 Based on t 100 Get the critical cooling time t of the welded joint cr , t 100 and t cr The welding heat input E corresponding to the maximum difference between them is taken as the actual welding heat input.

[0080] In this embodiment, the specific ambient temperature is set to -10°C. When obtaining the welding process, Figure 2 As shown in the figure, the welded specimen in the rigid restraint weld crack test is EH420 marine engineering steel, and the thickness t is the typical specification of marine engineering steel 40mm thickness (structure as shown in Figure 2As shown), an oblique Y-shaped groove is opened on its welding end, the groove angle is 60°, and the root gap during welding is 1mm to 2mm, such as 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, or any gap value between the above two gap values, which is determined to be 1.5mm in this embodiment. After obtaining the welding process, the sample for the oblique Y-shaped groove welding crack test is selected as EH420 marine steel with a thickness of 40mm. The size and groove form are processed according to the sample size described in the national standard CB / T 4364 (oblique Y-shaped groove welding crack test method).

[0081] Without preheating before welding, according to formula (1) in Example 1, the minimum welding cold crack sensitivity coefficient that does not generate welding cold cracks is 0.2653.

[0082] The welding machine, auxiliary equipment and test plate used in the rigid restraint welding crack test and the inclined Y-groove welding crack test were placed in a low temperature environment of -10℃ 4 hours before the start of the test. At the same time, special equipment (such as humidification device) was used to ensure that the humidity of each welding test environment was consistent.

[0083] In step S2, a rigid restraint welding crack test is performed using an existing rigid adjustable restraint welding joint crack test device, and a special specimen for the inclined Y-shaped groove is installed on the rigid adjustable restraint welding joint crack test device, such as Figure 3 As shown, adjusting the movable end 1 can change the adjustable restraint distance W between the movable end 1 and the fixed end 3. During welding, the selected restraint distance is strictly guaranteed to remain unchanged, and the restraint load is applied to the sample, and the restraint stress is kept at the load for 48 hours. Then, the Figure 3 The adjustable restraint distance W (i.e., restraint degree) of the sample in the above test is repeated for at least 3 groups to obtain the critical restraint stress of cracking / non-cracking of the test weld 2. According to formula (4) and formula (5), the critical restraint stress σ cr Converted to critical restraint R cr (This method is also used in Example 1 to obtain the critical constraint degree).

[0084]

[0085] Where m is the constraint stress conversion coefficient, a is the linear expansion coefficient, and h is w is the weld height, η is the welding thermal efficiency, E is the welding heat input, C v is the volume specific heat, l w is the average width of the weld.

[0086] In this embodiment, the diffusible hydrogen content of the deposited metal of different welding materials is measured by gas chromatography, and each group of tests needs to be measured multiple times. In order to reduce the test error, the final result takes the average value of multiple measurement values ​​while ensuring that the test data is correct. In addition, the determination of the diffusible hydrogen content in the deposited metal by gas chromatography is a prior art, and no further elaboration is made here.

[0087] In this embodiment, the numerical simulation calculation in step S5 needs to simulate the actual welding process according to the actual welding process of 40 mm thick plate butt joint at an ambient temperature of -10°C, calculate the temperature field after welding, and analyze the time t when the peak temperature after welding cools to 100°C for different welding heat inputs E. 100 .

[0088] In addition, the critical cooling time t in step S5 cr The meaning of the judgment formula is: the time from the peak temperature to 100°C after welding under actual welding conditions is t 100 , if t 100 >t cr , then cold cracks in welded joints can be avoided.

[0089] More specifically, the optimal welding parameters of the final arc welding in this embodiment are determined as follows: welding current 130±10A, arc voltage 24±1V, welding speed 15±1cm / min, and welding heat input 10.4-15kJ / cm.

[0090] In this embodiment, after step S6, the aforementioned selected EH420 marine engineering steel is used to carry out an inclined Y-type specimen groove welding crack test, and the restrained weld is double-sided welded to strictly ensure the quality of the assembly gap and the restrained welds on both sides, and the angular deformation of the test plate is controlled within 5° to ensure that the restrained weld is crack-free; specifically, the inclined Y-type groove welding crack test requires three groups of parallel tests, and the final result is the average value of the three groups of test results; more specifically, the inclined Y-type groove welding crack test is carried out according to the method described in the aforementioned CB / T4364 to measure the surface crack rate, cross-sectional crack rate, and root crack rate of the weld joint.

[0091] It should be understood that the various numerical numbers involved in the embodiments of the present invention are only used for the convenience of description and are not used to limit the scope of the embodiments of the present invention.

[0092] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining a high-performance non-preheating welding process for marine engineering steel, characterized in that: The following steps are involved: S1 obtains the first cold crack sensitivity index required for welding without preheating at a specific temperature; S2 obtains the critical restraint distance of the parent material sample at the specific temperature L cr and critical constraint R cr ; Based on the first cold crack sensitivity index, the minimum diffusible hydrogen content of the welding material required for non-preheating welding is obtained [H] cr , and based on [H] cr Select the actual welding material; S3 uses the cold crack sensitivity coefficient of the parent material sample to optimize its carbon equivalent to obtain a new parent material; S4 is based on the minimum diffusible hydrogen content [H] cr , the critical degree of restraint R cr and the cold crack sensitivity coefficient of the new base material, to obtain the second cold crack sensitivity index corresponding to the new base material; S5 determining the actual parent material: when the second cold crack sensitivity index is less than the first cold crack sensitivity index, taking a new parent material corresponding to the second cold crack sensitivity index as the actual parent material; When the second cold crack sensitivity index is greater than or equal to the first cold crack sensitivity index, repeating steps S3-S5 until the second cold crack sensitivity index is less than the first cold crack sensitivity index; S6 obtains the time for the actual welding material and the actual base material to cool to 100° C. after the peak temperature of the welding material is cooled to 100° C. under different welding heat inputs t 100 ;based on t 100 Obtaining the critical cooling time of welded joints t cr ,Will t 100 and t cr The welding heat input corresponding to the maximum difference between E As the actual welding heat input.

2. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 1, characterized in that: In step S6, a double ellipsoid heat source model is selected, and the welding heat input is changed by changing the welding current.

3. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 2, characterized in that: The welding current gradually increases within the range of 140A to 190A.

4. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in any one of claims 2 to 3, characterized in that: The welding current increases in sequence according to a gradient value of 5A.

5. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 1, characterized in that: In step S2, the critical restraint distance is obtained by a rigid restraint welding crack test. L cr and the critical degree of restraint R cr , and before the test, the test equipment is pre-cooled to a specific temperature; and the ambient humidity is the same during each rigid restraint weld crack test.

6. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 5, characterized in that: In step S2, the welding end of the base material sample is processed into an oblique Y-shaped groove, and the groove angle is not greater than 60°.

7. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in any one of claims 5 to 6, characterized in that: The root spacing of the welding end of the parent material specimen is 1mm~2mm.

8. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 1, characterized in that: In step S2, the minimum diffusible hydrogen content is obtained by gas chromatography, the inner diameter of the chromatographic column used is not less than 4 mm, and the carrier gas when the minimum diffusible hydrogen content is obtained by gas chromatography is argon with a concentration of not less than 99.9%; the carrier gas flow rate of the argon is 20 ml / min~40 ml / min.

9. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 1, characterized in that: After step S6, the actual welding material, actual base material and actual welding heat input obtained in steps S1-S5 are used to perform an inclined Y-groove welding crack test. Double-sided welding is used for the restrained weld during the inclined Y-groove welding crack test.

10. A method for determining a high performance non-preheating welding process for marine engineering steel as claimed in claim 9, characterized in that: In the inclined Y-groove welding crack test, the angular deformation of the test plate was controlled within 5°.

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