阅读说明：本技术 基于双丝埋弧焊的低碳微合金钢高热输入焊接性评估方法 (Low-carbon micro-alloy steel high-heat input weldability evaluation method based on twin-wire submerged arc welding ) 是由 刘硕 于 2020-05-27 设计创作，主要内容包括：本发明涉及一种基于双丝埋弧焊的低碳微合金钢高热输入焊接性评估方法,其步骤依次包括：选用试验板为低碳微合金钢板；低碳微合金埋弧焊丝和碱性烧结焊剂配合使用；所述一对试验板进行平焊位置对接焊,钢板厚度t＞35mm时其坡口形式为一侧直边的带钝边双V型坡口,钢板厚度t≤35mm时其坡口形式为一侧直边的带钝边V型坡口,坡口背面设置同质垫板；采用双丝自动埋弧焊接的方式对试验板进行焊接,双丝同时共熔池焊接,热输入为3.0～6.0kJ/mm；完成焊接后,观察和检测焊接接头裂纹倾向以评估材料的工艺焊接性,并通过焊接接头力学性能检测以评估材料的使用焊接性。本发明兼顾工艺焊接性和使用焊接性评估需求,对不同领域使用的低碳微合金钢焊接性评估具有普适性。(The invention relates to a low-carbon micro-alloy steel high-heat input weldability assessment method based on twin-wire submerged arc welding, which sequentially comprises the following steps: selecting a test plate as a low-carbon microalloy steel plate; the low-carbon microalloy submerged arc welding wire and the alkaline sintered flux are matched for use; the pair of test plates are subjected to butt welding at flat welding positions, the groove form is a blunt-edged double V-shaped groove with a straight edge at one side when the thickness t of the steel plate is larger than 35mm, the groove form is a blunt-edged V-shaped groove with a straight edge at one side when the thickness t of the steel plate is smaller than or equal to 35mm, and a homogeneous base plate is arranged on the back of the groove; welding the test plate by adopting a double-wire automatic submerged arc welding mode, simultaneously welding the double wires by using a molten pool, and controlling the heat input to be 3.0-6.0 kJ/mm; after welding is completed, the crack tendency of the welding joint is observed and detected to evaluate the process weldability of the material, and the service weldability of the material is evaluated through the mechanical property detection of the welding joint. The method gives consideration to both the requirements of process weldability and use weldability evaluation, and has universality for evaluation of the weldability of the low-carbon micro-alloy steel used in different fields.)

1. A low-carbon micro-alloy steel high-heat input weldability assessment method based on twin-wire submerged arc welding is characterized in that: the method comprises the following steps:

selecting a test plate as a low-carbon microalloy steel plate;

selecting a low-carbon micro-alloy submerged arc welding wire and an alkaline sintered flux, wherein the diameter of the welding wire is 2.5-5.0 mm;

step three, performing butt welding on the flat welding positions of the pair of test plates:

when the thickness t of the steel plate is more than 35mm, the groove is in the form of a double V-shaped groove with a truncated edge and a straight edge on one side, the truncated edge deflects outwards to form a lower V-shaped groove, the lower V-shaped groove deflects outwards to form an upper V-shaped groove, and an angle alpha is formed between the lower V-shaped groove and the central axis of the groove₁The upper V-shaped groove forms an angle beta with the central axis of the groove, and a homogeneous base plate is arranged on the back of the groove, wherein alpha is₁55-70 degrees, beta 20-40 degrees, and the height of the truncated edge a₁2-6 mm, the height b of the lower V-shaped groove is 4-12 mm, b is smaller than 1/3 of the thickness t of the steel plate, and the thickness c of the backing plate₁6-20 mm, the width d of the base plate covering the groove₁The thickness of the test plate is 50-300 mm, and the assembly gap of the test plate is 0-1 mm;

when the thickness t of the steel plate is less than or equal to 35mm, the groove is a V-shaped groove with a blunt edge and a straight edge on one side, and the bevel surface forms an angle alpha with the central axis of the groove₂And a homogeneous backing plate is arranged on the back of the groove, wherein alpha is₂35-60 degrees of blunt edge height a₂2-6 mm, thickness c of the backing plate₂6-20 mm, the width d of the base plate covering the groove₂The thickness of the test plate is 50-300 mm, and the assembly gap of the test plate is 0-1 mm;

welding the test board by adopting a double-wire automatic submerged arc welding mode, wherein the double wires comprise a front wire and a rear wire, and are simultaneously welded in a eutectic pool, and the method comprises the following steps of:

the welding process parameters used were: the welding heat input E is 3.0-6.0 kJ/mm; welding current I of front wire_{Front side}And the diameter R of the front filament_{Front side}Has a relationship of_{Front side}＝(150～250)R_{Front side}(ii) a Welding current I of rear wire_{Rear end}And rear filament diameter R_{Rear end}Has a relationship of_{Rear end}＝(120～200)R_{Rear end}(ii) a The welding voltage of each wire is respectively matched with the welding current and the dry elongation of the welding wire, and the combination of the welding current, the welding voltage and the welding traveling speed of each wire can be matched with the welding heat input value required by the test;

during welding, the forward inclination angle of the front wire welding gun along the welding direction is delta₁10-30 DEG, the backward inclination angle delta of the rear wire welding gun₂5-25 degrees; forming an included angle theta between the front wire welding gun and the straight side of the groove by 10-30 degrees along the width direction of the groove, and vertically arranging the rear wire welding gun; the distance L between each wire end and the straight side of the groove is equal to E/2+2.0, the unit of L is mm, and E is welding heat input;

and step five, obtaining a welding joint after welding, observing and detecting the crack tendency of the welding joint to evaluate the technological weldability of the material, and evaluating the service weldability of the material through the mechanical property detection of the welding joint.

2. The method for evaluating the high heat input weldability of low carbon micro alloy steel based on twin wire submerged arc welding according to claim 1, characterized in that: in the welding process parameters of the fourth step: the welding current of the front wire is 380-1200A, and the welding voltage is 28-38V; the welding current of the rear wire is 300-1000A, and the welding voltage is 31-40V; the welding walking speed of each welding wire is 400-1200 mm/min, and the distance between the welding wires is 15-35 mm.

3. The method for evaluating the high heat input weldability of low carbon micro alloy steel based on twin wire submerged arc welding according to claim 1, characterized in that: and in the fifth step, the mechanical property detection comprises low-temperature impact and fracture toughness of a coarse crystal area of a welding heat affected area adjacent to the single-side straight-edge fusion line.

Technical Field

The invention relates to a microalloy steel welding technology, in particular to a method for evaluating the high heat input weldability of low-carbon microalloy steel based on twin-wire submerged arc welding.

Background

For an important engineering structure using low-carbon microalloy steel, welding is a key process of field installation and construction, the welding quality and efficiency also determine the quality and efficiency of an engineering project, and the quality of the field weldability of the low-carbon microalloy steel material directly influences the quality and safety service of a welded joint. Generally, the weldability of a material includes process weldability, which mainly refers to the ability to avoid welding defect problems (including various types of welding crack sensitivity) and obtain a continuous and complete welding joint during welding, and use weldability, which mainly refers to the use properties (including mechanical properties such as strength, plasticity, toughness and the like) of the welding joint.

Recently, foreign high-grade pipeline pipe users put forward pipeline steel pipe field weldability evaluation requirements under certain welding heat input conditions, including process weldability and use weldability, particularly the welding heat affected zone coarse grain zone (CGHAZ) which is the weakest theoretically is required to be located at the test position of low-temperature impact and fracture toughness of a welded joint, and therefore embrittlement tendency of materials under certain welding heat input conditions is evaluated systematically. Here, for low-carbon microalloy pipeline steel with a certain specification, welding heat input has important influence on solid-state phase change and microstructure evolution of a welding joint, and further influences integral embrittlement and service safety of the joint. Therefore, low carbon microalloyed pipeline steel tends to exhibit different weldability under different welding heat input conditions. In addition, in other industrial fields where a large number of low-carbon micro-alloy steel thick plates are applied, such as ship manufacturing, ocean engineering structures, pressure vessels, high-grade building structures and the like, during manufacturing and construction, in order to improve welding efficiency, the heat input is generally higher than 3.0kJ/mm, and the high-heat-input welding material has high requirements on field weldability.

At present, many methods for evaluating weldability, i.e. weld crack sensitivity, of a steel material process are available, such as: the ISO17642-2 standard provides a TEKKEN test for evaluating the cold crack sensitivity of a plate, which is similar to the oblique Y-shaped groove welding crack test method described in GB 4675.1, welding of a small-scale test welding seam is carried out under a high constraint condition, so that the cold crack sensitivity of a material under a certain welding condition is evaluated, however, the constraint condition of the test method is too harsh, and the test welding seam is a single welding seam with an irregular shape, so that high welding residual stress exists, and cold cracks are more favorably induced. GB/T13817 provides a rigidity restraint welding crack test method, which completely fixes a test steel plate on a bottom plate with a very large thickness, residual stress cannot be released in the welding process, cold cracks are easily induced in a joint area, the method is also conservative, and the welding joint form is greatly different from the common joint form of a low-carbon microalloy steel structure, and has no direct field construction welding guidance function. An improved oblique Y-shaped groove welding crack sensitivity test specimen disclosed in Chinese patent 201611208203.5 and a manufacturing method thereof, and a constrained weld manufacturing method for an oblique Y-shaped groove welding crack test disclosed in Chinese patent 201510012348.7 can only solve the problem of indirect evaluation of weldability under certain conditions. The patent and non-patent documents disclosed above are both focused on indirect evaluation of process weldability, have certain referential significance for on-site welding construction of low-carbon microalloy steel structures, but have no direct guidance, mainly cannot consider use weldability, have larger difference with high-heat input welding conditions, and have larger difference with implementation details of welding process methods and construction welding conditions of mainstream low-carbon microalloy steel structures.

Chinese patent 201410516996.1 discloses a steel plate welding method for an ocean platform, and Chinese patent 201110181417.9 discloses a submerged arc welding process for a T-shaped joint of an extra-thick steel plate, both of which adopt a general K-shaped groove form, if the implementation process of the welding process is properly controlled, a fusion line with certain straightness on one side can be obtained after welding, and the requirements of CGHAZ position impact and fracture toughness sampling are met, but the welding process is a specific extra-thick plate (for example, 50-150 mm) product structure and has no universality in various industrial fields. Meanwhile, the method does not have a guarantee measure related to the straightness of the fusion line with the straight edge on the single side, the straightness of the fusion line after welding is easily guaranteed when the steel plate is thick, and the straightness of the fusion line is easily damaged by a welding pool when the steel plate is thin. Chinese patent 201510385434.2 discloses a CTOD test method for a large thick plate welding repair joint, and chinese patent 201510605044.1 discloses a welding repair CTOD test method, both of which have certain characteristics of a single-side straight-edge weld line even when the plate thickness is thick, but both of which belong to repair processing measures after defects are found in a finished product welded part, and cannot meet the requirements of low-carbon microalloyed steel with universality in a certain welding heat input range for simultaneously evaluating technological weldability and using weldability. In addition, in the field of double-wire or multi-wire automatic submerged arc welding, chinese patent 201710439703.8 discloses a double-wire submerged arc welding method for high-strength extra-thick steel plates for high heat input welding, and chinese patent 201410009083.0 discloses a preparation method for high weather-resistant multi-wire submerged arc welded steel pipes for marine environments, both of which are specific industrial fields and materials, adopt asymmetric X-shaped grooves, and provide a solution for manufacturing specific products by using technical advantages of double-wire or multi-wire submerged arc welding, and also can not meet the requirements of low-carbon microalloyed steel with universality for simultaneously evaluating technological weldability and using weldability within a certain welding heat input range.

In view of this, a safe, reliable and complete weldability evaluation method close to the field construction conditions is needed for low-carbon microalloyed steel.

Disclosure of Invention

The invention aims to provide a low-carbon microalloy steel high-heat input weldability assessment method based on twin-wire submerged arc welding.

The invention is realized by the following steps:

a low-carbon micro-alloy steel high-heat input weldability evaluation method based on twin-wire submerged arc welding comprises the following steps:

selecting a test plate as a low-carbon microalloy steel plate;

selecting a low-carbon micro-alloy submerged arc welding wire and an alkaline sintered flux, wherein the diameter of the welding wire is 2.5-5.0 mm;

step three, performing butt welding on the flat welding positions of the pair of test plates:

when the steel plate is usedWhen the thickness t is more than 35mm, the groove form is a double V-shaped groove with a truncated edge and a straight edge at one side, the truncated edge deflects outwards to form a lower V-shaped groove, the lower V-shaped groove deflects outwards to form an upper V-shaped groove, and an angle alpha is formed between the lower V-shaped groove and the central axis of the groove₁The upper V-shaped groove forms an angle beta with the central axis of the groove, and a homogeneous base plate is arranged on the back of the groove, wherein alpha is₁55-70 degrees, beta 20-40 degrees, and the height of the truncated edge a₁2-6 mm, the height b of the lower V-shaped groove is 4-12 mm, b is smaller than 1/3 of the thickness t of the steel plate, and the thickness c of the backing plate₁6-20 mm, the width d of the base plate covering the groove₁The thickness of the test plate is 50-300 mm, and the assembly gap of the test plate is 0-1 mm;

when the thickness t of the steel plate is less than or equal to 35mm, the groove is a V-shaped groove with a blunt edge and a straight edge on one side, and the bevel surface forms an angle alpha with the central axis of the groove₂And a homogeneous backing plate is arranged on the back of the groove, wherein alpha is₂35-60 degrees of blunt edge height a₂2-6 mm, thickness c of the backing plate₂6-20 mm, the width d of the base plate covering the groove₂The thickness of the test plate is 50-300 mm, and the assembly gap of the test plate is 0-1 mm;

welding the test board by adopting a double-wire automatic submerged arc welding mode, wherein the double wires comprise a front wire and a rear wire, and are simultaneously welded in a eutectic pool, and the method comprises the following steps of:

the welding process parameters used were: the welding heat input E is 3.0-6.0 kJ/mm; welding current I of front wire_{Front side}And the diameter R of the front filament_{Front side}Has a relationship of_{Front side}＝(150～250)R_{Front side}(ii) a Welding current I of rear wire_{Rear end}And rear filament diameter R_{Rear end}Has a relationship of_{Rear end}＝(120～200)R_{Rear end}(ii) a The welding voltage of each wire is respectively matched with the welding current and the dry elongation of the welding wire, and the combination of the welding current, the welding voltage and the welding traveling speed of each wire can be matched with the welding heat input value required by the test;

during welding, the forward inclination angle of the front wire welding gun along the welding direction is delta₁10-30 DEG, the backward inclination angle delta of the rear wire welding gun₂5-25 degrees; along the width direction of the groove, an included angle is formed between the front wire welding gun and the straight side of the grooveTheta is 10-30 degrees, and the rear wire welding gun is vertically arranged; the distance L between each wire end and the straight side of the groove is equal to E/2+2.0, the unit of L is mm, and E is welding heat input;

and step five, obtaining a welding joint after welding, observing and detecting the crack tendency of the welding joint to evaluate the technological weldability of the material, and evaluating the service weldability of the material through the mechanical property detection of the welding joint.

In the welding process parameters of the fourth step: the welding current of the front wire is 380-1200A, and the welding voltage is 28-38V; the welding current of the rear wire is 300-1000A, and the welding voltage is 31-40V; the welding walking speed of each welding wire is 400-1200 mm/min, and the distance between the welding wires is 15-35 mm.

And in the fifth step, the mechanical property detection comprises low-temperature impact and fracture toughness of a coarse crystal area of a welding heat affected area adjacent to the single-side straight-edge fusion line.

The invention relates to a low-carbon microalloy steel high heat input weldability assessment method based on twin-wire submerged arc welding, which is realized by firstly according to the forming characteristics of a welding pool and a welding seam under the condition that the high heat input is 3.0-6.0 kJ/mm and combining the technical characteristics of best applicability and quality stability of twin-wire submerged arc welding in the heat input range, and the twin-wire submerged arc welding can fully ensure the welding quality and success rate of a welding assessment test, and is particularly beneficial to solving the problem of fusion quality on the straight side. Secondly, by designing a special welding joint groove form with a single-side straight edge, constructing and optimizing scientific and reasonable welding process parameter combinations (including welding current, welding voltage, welding walking speed and welding wire spacing) and welding gun position setting, and controlling the quality of a welding process, particularly a weld line straightness control technology, the welding joint with the single-side weld line with good straightness can be obtained. By observing and detecting the crack tendency of the welded joint, the process weldability of the material can be evaluated. Through the mechanical property detection of a welding joint, particularly the low-temperature impact and fracture toughness detection of a coarse grain zone (CGHAZ) of a welding heat affected zone adjacent to a single-side straight-edge fusion line, and the straightness of the single-side straight-edge fusion line can ensure that 80% of impact toughness sampling notch grooves are positioned in the CGHAZ, the use weldability of the material under the condition of high heat input can be evaluated. The method simultaneously considers the evaluation requirements of process weldability and use weldability, considers the requirements of high-efficiency welding in the production of low-carbon microalloy steel structures in various industrial fields and the adaptability of twin-wire submerged arc welding to the heat input range, and has universality for evaluation of the weldability of the low-carbon microalloy steel used in different industries and fields in a given higher welding heat input range. Meanwhile, the characteristic of the single-side straight-edge fusion line ensures that the tested position is accurately positioned at the theoretically weakest CGHAZ of the welding joint in the sampling process of impact toughness and fracture toughness.

Compared with the prior art, the invention has the following beneficial effects: the method has universal applicability, can simultaneously meet the evaluation requirements of process weldability and use weldability under the condition of high heat input, and has the advantages of convenient implementation, flexible operation, low requirement on hardware equipment, low implementation cost and good reproducibility.

Drawings

FIG. 1 is a schematic structural diagram of a welding joint groove form with a steel plate thickness exceeding 35mm according to the low-carbon micro-alloy steel high-heat input weldability evaluation method based on twin-wire submerged arc welding of the invention;

FIG. 2 is a schematic structural view of the present invention in the form of a weld joint groove having a steel plate thickness of not more than 35 mm;

FIG. 3 is a schematic view of the inclination angles of the front and rear wire torches of the present invention in the welding direction;

FIG. 4 is a schematic diagram of the angle of inclination of the lead wire torch of the present invention in the direction along the width of the bevel;

FIG. 5 is a schematic diagram of the angle of inclination of the rear wire torch of the present invention in the direction along the width of the bevel;

FIG. 6 is a schematic diagram of a specific weld joint groove form employed by an embodiment of the present invention.

In the figure, 1 test plate, 2 backing plate, 3 front wire welding gun, 4 rear wire welding gun.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

Referring to fig. 1 to 5, a low-carbon micro-alloy steel high heat input weldability evaluation method based on twin-wire submerged arc welding mainly aims at the occasions with a high welding heat input range of 3.0-6.0 kJ/mm related to the manufacturing process of products and structures in various industrial fields, low-carbon micro-alloy steel submerged arc welding wires with the diameter of 2.5-5.0 mm and common sintered flux are applied, the characteristics of a welding arc and a molten pool under the condition of high heat input are combined, a welding process parameter combination, welding gun position setting and welding process quality control, particularly a weld line straightness control technology and the like are constructed and optimized through a groove form of a single-side straight-edge welding joint which is specially designed and adapts to the welding condition, and a welding joint with good quality and no defect is obtained, and the method comprises the following steps:

step one, selecting a test plate 1 as a low-carbon microalloy steel plate.

And step two, selecting a low-carbon micro-alloy submerged arc welding wire and a common alkaline sintered flux for matching use, wherein the diameter of the welding wire is 2.5-5.0 mm.

Step three, performing butt welding on the flat welding positions of the pair of test plates 1:

referring to fig. 1, when the thickness t of the steel plate is more than 35mm, the groove is a double-V groove with a truncated edge and a straight edge on one side, the truncated edge deflects outwards to form a lower V-shaped groove, the lower V-shaped groove deflects outwards to form an upper V-shaped groove, and an angle alpha is formed between the lower V-shaped groove and the central axis of the groove₁The upper V-shaped groove forms an angle beta with the central axis of the groove, and a homogeneous base plate 2 is arranged on the back of the groove, wherein alpha is₁55-70 degrees, beta 20-40 degrees, and the height of the truncated edge a₁2-6 mm, the height b of the lower V-shaped groove is 4-12 mm, b is smaller than 1/3 of the thickness t of the steel plate, and the thickness c of the backing plate 2₁6-20 mm, the width d of the base plate 2 covering the groove₁Is 50-300 mm, and the assembly gap of the test plate 1 is 0-1 mm.

Referring to fig. 2, when the thickness t of the steel plate is less than or equal to 35mm, the groove is a V-shaped groove with a blunt edge and a straight edge on one side, and an angle alpha is formed between the groove surface and the central axis of the groove₂And a homogeneous backing plate 2 is arranged on the back of the groove, wherein alpha is₂35-60 degrees of blunt edge height a₂2-6 mm, a backing plate2 thickness c₂6-20 mm, the width d of the base plate 2 covering the groove₂Is 50-300 mm, and the assembly gap of the test plate 1 is 0-1 mm.

By adopting the welding joint groove form with the optimized design, the design requirement of a straight edge on a single side is ensured, and meanwhile, the auxiliary forming root welding method of adding the homogeneous base plate 2 on the back surface of the groove is adopted, so that the requirement on the size and the thickness of the base plate 2 is moderate, the root welding is ensured not to burn through, and the operation difficulty cannot be increased due to the over-thickness of the base plate 2. The truncated edge has larger size, and can fully utilize the advantage of strong penetration capability of the twin-wire submerged arc welding. The opening width of the groove can meet the setting requirement of a welding gun optimized according to the requirement, so that the straight edge of one side is fully melted through, and meanwhile, the opening width of the groove is not too wide, so that the welding efficiency is reduced.

And step four, welding the test plate 1 by adopting a double-wire automatic submerged arc welding mode, wherein the double wires comprise a front wire and a rear wire, and are simultaneously welded in a eutectic pool.

According to the requirements of double-wire submerged arc welding within a welding heat input range of 3.0-6.0 kJ/mm, and the characteristics of large penetration depth and strong fusion capability of the edge of a groove of the double-wire submerged arc welding, used welding process parameters are constructed and optimized, and the parameters comprise:

when the welding heat input E is 3.0-6.0 kJ/mm, the welding current I of the front wire_{Front side}And the diameter R of the front filament_{Front side}Has a relationship of_{Front side}＝(150～250)R_{Front side}(ii) a Welding current I of rear wire_{Rear end}And rear filament diameter R_{Rear end}Has a relationship of_{Rear end}＝(120～200)R_{Rear end}(ii) a The welding voltage of each wire is respectively matched with the welding current and the dry elongation of the welding wire, and the combination of the welding current, the welding voltage and the welding traveling speed of each wire can be matched with the welding heat input value required by the test.

According to the above relation, the current filament diameter R_{Front side}And rear filament diameter R_{Rear end}When the thickness is 2.5-5.0 mm, the welding current of the front wire is 380-1200A, and the welding voltage is 28-38V; the welding current of the rear wire is 300-1000A, and the welding voltage is 31-40V; the welding walking speed of each wire is 400-1200 mm/min, the distance between the front wire and the rear wire is 15-35 mm, and a double-wire common molten pool is ensured. In the welding process, according to actual needs, the front wire and the rear wire can be selected to have the same diameter, and welding wires with different diameters can also be combined.

Referring to fig. 3, in the twin-wire submerged arc welding process, since the front wire mainly contributes to the penetration depth, in order to ensure sufficient penetration of the large-sized truncated edge, the front wire bonding gun 3 is set to be inclined forward in the welding direction by an angle δ₁10 ~ 30, because the back silk mainly plays the effect of filling the groove, back wire welding gun 4 sets up to angle of inclination delta backward along the welding direction₂＝5～25°。

Referring to fig. 4 and 5, in view of the sensitivity of the non-fusion defect of the straight side in the form of the single-side straight-side groove, the front wire welding gun 3 forms an included angle θ of 10 to 30 ° with the straight side of the groove along the width direction of the groove, and under the condition that the welding heat input E is 3.0 to 6.0kJ/mm, the size of the double-wire submerged arc welding molten pool is large, the fusion capability to the edge of the groove is strong, the included angle between the front wire welding gun 3 and the straight side of the groove is not too large, otherwise, the straightness of the welded fusion line is damaged, and in addition, the welding process is a double-wire co-molten pool, so that the rear wire welding gun 4 does not need to be inclined, i.e., is vertically arranged, and the fusion on the straight side is not affected.

In addition, considering the change of the size of a molten pool and the influence of the change on the fusion behavior of the edge of the groove when different welding heat inputs are input, when the welding heat input E is changed within the range of 3.0-6.0 kJ/mm, the distance L between the end of each wire and the straight side of the groove meets the relation: l ═ E/2+2.0, in mm, L and kJ/mm, E. Within a certain welding heat input range, when the distance between the end of the welding wire and the straight side of the groove is proper, the fusion of the straight side is good, the straightness of a fusion line on the straight side after welding cannot be damaged, a welding joint with good quality and no defect can be obtained, and the straightness of the fusion line on the straight side of the single side can ensure that 80 percent of the welding wire is positioned in the CGHAZ when impact toughness sampling grooving is carried out.

And fifthly, obtaining a welding joint after welding, observing and detecting the crack tendency of the welding joint to evaluate the technological weldability of the material, and evaluating the use weldability of the material by detecting the mechanical properties of the welding joint, particularly detecting the low-temperature impact and the fracture toughness of a coarse crystal area of a welding heat affected area adjacent to a single-side straight-edge fusion line.

Examples

Referring to fig. 6, a typical EH36 ship-building steel with a thickness t of 40mm is selected as a test plate 1, a homogeneous backing plate 2 is added on the back of a groove to assist a forming root welding method, and a weldability evaluation test is performed based on a twin-wire submerged arc welding with a welding heat input in a range of 3.0-6.0 kJ/mm, wherein a specific welding joint is a blunt-edged double-V-shaped groove with a straight edge at one side, and the specific welding joint is as follows: alpha is alpha₁＝60°，β＝30°，a₁＝2～6mm，b＝10mm，c₁＝10mm，d₁100 mm. The wire used was AWS F9a4-EG flux matched, and the wire diameter was 4.0 mm.

Table 1 lists specific welding process parameter combinations for examples 1-6, as follows:

table 2 lists the specific weld gun position settings, the distance L between each wire end and the straight edge side of the groove, the corresponding heat input values, and the obtained weld quality evaluation results of examples 1-6, as follows:

as can be seen from tables 1 and 2, all the examples have stable welding process and good welding quality, and can be used for the weldability evaluation of typical low-carbon micro-alloy steel thick plates with the characteristic of single-side straight-edge weld lines, wherein the welding heat input range of the typical low-carbon micro-alloy steel thick plates is 3.0-6.0 kJ/mm. The welding quality mainly comprises the appearance forming quality and the interior forming quality of a welding seam, and the judgment standard is as follows, ANSI/AWS D1.1: and (5) welding specification of a steel structure.

The low-carbon micro-alloy steel high-heat-input weldability evaluation method based on the twin-wire submerged arc welding considers the process weldability of materials in the welding process and the use weldability after welding, has universality and universality for evaluation of the weldability of low-carbon micro-alloy steel thick plates used in different industries and fields in a given higher welding heat input range, can be widely applied to related industrial fields, and has direct guiding significance and important practical value for rapid and accurate evaluation of the weldability with high safety requirements in the industrial application of low-carbon micro-alloy steel.

The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.