阅读说明：本技术 一种适用于低碳钢的水下埋弧焊接药芯焊丝及其制备方法与应用 (Underwater submerged arc welding flux-cored wire suitable for low-carbon steel and preparation method and application thereof ) 是由 贾传宝 张茂富 韩焱飞 董胜法 郑镇钢 贺晨 武传松 于 2021-09-03 设计创作，主要内容包括：本发明提供一种适用于低碳钢的水下埋弧焊接药芯焊丝及其制备方法与应用。本发明药芯焊丝包括外皮材料和药芯；所述外皮材料为低碳钢,含碳量为0.01-0.1wt％；所述药芯包括如下质量份数的原料组成：金红石30～50份,氧化铁15～22份,铝1～3份,硅铁1～4份,锰8～12份,镍1～3份,氟化锂1～4份,铁2～28份,纳米氧化铝颗粒0.5～15份。发明药芯焊丝中加入纳米氧化铝颗粒,可以细化晶粒,结合其它原料的协同作用提高了焊缝的力学性能。(The invention provides an underwater submerged arc welding flux-cored wire suitable for low-carbon steel, and a preparation method and application thereof. The flux-cored wire comprises a sheath material and a flux core; the sheath material is low-carbon steel, and the carbon content is 0.01-0.1 wt%; the medicine core comprises the following raw materials in parts by weight: 30-50 parts of rutile, 15-22 parts of ferric oxide, 1-3 parts of aluminum, 1-4 parts of ferrosilicon, 8-12 parts of manganese, 1-3 parts of nickel, 1-4 parts of lithium fluoride, 2-28 parts of iron and 0.5-15 parts of nano aluminum oxide particles. The nano alumina particles are added into the flux-cored wire, so that the grains can be refined, and the mechanical property of the welding line is improved by combining the synergistic effect of other raw materials.)

1. The flux-cored wire suitable for underwater submerged arc welding of low-carbon steel is characterized by comprising a sheath material and a flux core; the sheath material is low-carbon steel, and the carbon content is 0.01-0.1 wt%; the medicine core comprises the following raw materials in parts by weight: 30-50 parts of rutile, 15-22 parts of ferric oxide, 1-3 parts of aluminum, 1-4 parts of ferrosilicon, 8-12 parts of manganese, 1-3 parts of nickel, 1-4 parts of lithium fluoride, 2-28 parts of iron and 0.5-15 parts of nano aluminum oxide particles.

2. Submerged arc welding flux-cored wire suitable for mild steel according to claim 1, characterized in that the carbon content of the mild steel is 0.02-0.06 wt%, preferably 0.04 wt%.

3. The flux-cored welding wire suitable for underwater submerged arc welding of low carbon steel according to claim 1, wherein the flux core comprises the following raw materials in parts by mass: 35-45 parts of rutile, 18-20 parts of ferric oxide, 2-3 parts of aluminum, 2-3 parts of ferrosilicon, 9-10 parts of manganese, 2-3 parts of nickel, 3-4 parts of lithium fluoride, 14-20 parts of iron and 1-10 parts of nano aluminum oxide particles.

4. The submerged arc welding flux cored welding wire suitable for mild steel of claim 1, comprising one or more of the following conditions:

i. the particle size of the rutile is 80-100 meshes;

ii. The particle size of the iron oxide is 80-100 meshes;

iii, the particle size of the aluminum is 80-100 meshes;

iv, the particle size of the ferrosilicon is 80-100 meshes;

v, the particle size of the manganese particles is 80-100 meshes;

vi, the particle size of the nickel particles is 80-100 meshes;

vii, the particle size of the lithium fluoride is 80-100 meshes;

viii, the particle size of the iron powder is 80-100 meshes.

5. The flux-cored welding wire for submerged arc welding of low carbon steel as claimed in claim 1, wherein the nano alumina particles have a particle size of 20-80 nm.

6. The flux-cored wire suitable for underwater submerged arc welding of low carbon steel according to claim 1, wherein the flux-cored wire has a diameter of 1-2mm, preferably 1.6mm, and a filling rate of 30-32%.

7. The method for preparing the flux-cored wire for submerged arc welding underwater suitable for mild steel as claimed in any one of claims 1 to 6, comprising the steps of:

fully mixing rutile, ferric oxide, aluminum, ferrosilicon, manganese, nickel, lithium fluoride, iron and nano aluminum oxide particles to obtain a medicine core; and coating the flux core with a low-carbon steel strip, and then drawing to obtain the flux-cored wire.

8. The method for preparing the flux-cored wire for underwater submerged arc welding of low carbon steel according to claim 7, wherein the width of the low carbon steel strip is 7 to 9mm and the thickness is 0.2 to 0.4 mm.

9. The use of the flux cored welding wire for submerged arc welding of low carbon steel according to any one of claims 1 to 6 for submerged arc welding of low carbon steel.

Technical Field

The invention relates to an underwater submerged arc welding flux-cored wire suitable for low-carbon steel, and a preparation method and application thereof, and belongs to the field of welding materials.

Background

Underwater welding is classified into a dry method, a partial dry method and a wet method. The underwater wet method has the advantages of simple operation, strong accessibility, wide adaptability, economy and practicality, is most widely applied in the three methods, and is more deeply researched.

The underwater wet welding can be classified into shielded metal arc welding and flux-cored arc welding according to the difference of welding materials. The great britain company named Hydroweld has developed a welding rod with excellent performance suitable for low-carbon steel as early as the 20 th century after the research and application of shielded metal arc welding and underwater welding rods, the tensile strength of the welding rod can reach 520Mpa, and the welding rod completely meets the requirements of the American underwater welding standard AWSD 3.6. However, in the welding process of the electrode arc welding, the electrode needs to be replaced frequently, and automation is difficult to realize, so that a welder needs to submerge to operate; this requires that the welder has the ability of a diver at the same time, and bubbles and smoke can interfere with the sight during underwater welding, which further increases the welding difficulty, so that it is difficult to cultivate a professional underwater welder. Moreover, the welding operation under the condition of water depth exceeding 50 meters can not be realized at present. Flux-cored arc welding has the advantages of no need of frequent replacement of welding wires, high welding efficiency and easy realization of automation, and has gained more and more attention and is developed rapidly in recent years. Especially, an unmanned automatic solution is provided for the welding under the deep water condition, and a foundation is provided for the development of deep water exploration.

In the underwater wet welding process, water can bring many negative effects to the welding process. In underwater wet welding, the arc burning causes the water to become a bubble which maintains the arc burning. However, the bubbles do not exist stably, and periodically grow, and are broken or floated, so that the arc stability is deteriorated. And the specific heat capacity of water is much greater than that of air, which causes the molten pool to cool rapidly, resulting in a reduction in weld ductility. The decomposition of a large amount of water also causes hydrogen elements to enter the weld joint, increases the content of diffused hydrogen and increases the possibility of hydrogen-induced cracking. Chinese patent document CN104057214A discloses a self-protecting flux-cored wire for underwater wet welding, which uses N6 nickel strip as the metal sheath of the wire, and uses alkaline calcium fluoride-alumina type slag system as the flux-cored basic slag system, the inner flux core is composed of calcium fluoride, aluminum powder, iron powder, magnesium oxide, silicon iron, lithium fluoride, manganese powder and metal chromium, and the weight percentages of the components are: 40-55% of calcium fluoride, 8-13% of aluminum powder, 5-9% of iron powder, 0.5-5% of magnesium oxide, 3-7% of ferrosilicon, 3-9% of lithium fluoride, 6-11% of manganese powder and 4-10% of metal chromium. When the flux-cored wire is used for underwater wet welding, the flux-cored wire is easy to start arc, the arc combustion is stable, the re-striking performance is good, the welding seam formability is good, the tensile strength of deposited metal after welding is not lower than 460MPa, and the low-carbon steel and low-alloy high-strength steel knot with common strength requirements can be met; however, the welding process is still exposed in a water environment, so that the welding process is unstable, the cooling speed of the welding line is high, and the mechanical property of the welding line is poor.

Submerged arc welding can completely isolate the influence of water. Submerged arc welding is similar to land submerged arc welding in that solder is placed in the area to be welded, but is different in that the solder is formed by mixing land submerged arc welding flux and epoxy resin according to a certain proportion. And the epoxy resin is insoluble in water, so that a welding line in the underwater submerged arc welding process can not be contacted with water. Meanwhile, the cavity generated by arc combustion can stably exist in the solder, so that the stability of the welding process is greatly improved. Therefore, the mechanical property of the welding seam of the underwater submerged arc welding is greatly improved. However, the burning of the epoxy brings more heat, which causes the heat input to be larger, promotes the growth of weld grains and hinders the further improvement of the weld performance.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an underwater submerged arc welding flux-cored wire suitable for low-carbon steel, and a preparation method and application thereof. The nano alumina particles are added into the flux-cored wire, so that the grains can be refined, and the mechanical property of the welding line is improved by combining the synergistic effect of other raw materials.

The technical scheme of the invention is as follows:

an underwater submerged arc welding flux-cored wire suitable for low-carbon steel comprises a sheath material and a flux core; the sheath material is low-carbon steel, and the carbon content is 0.01-0.1 wt%; the medicine core comprises the following raw materials in parts by weight: 30-50 parts of rutile, 15-22 parts of ferric oxide, 1-3 parts of aluminum, 1-4 parts of ferrosilicon, 8-12 parts of manganese, 1-3 parts of nickel, 1-4 parts of lithium fluoride, 2-28 parts of iron and 0.5-15 parts of nano aluminum oxide particles.

Preferably, according to the invention, the low-carbon steel has a carbon content of 0.02 to 0.06 wt.%, preferably 0.04 wt.%.

According to the invention, the medicine core preferably comprises the following raw materials in parts by mass: 35-45 parts of rutile, 18-20 parts of ferric oxide, 2-3 parts of aluminum, 2-3 parts of ferrosilicon, 9-10 parts of manganese, 2-3 parts of nickel, 3-4 parts of lithium fluoride, 14-20 parts of iron and 1-10 parts of nano aluminum oxide particles.

According to the invention, the rutile has TiO as the main component₂The content can reach more than 95 wt%. The slag forming agent is a main slag forming component in the welding wire, and can promote slag to uniformly cover a welding seam and improve the slag removing performance in the welding process. It is also a main arc stabilizer, and can improve the arcing performance and the stability of electric arc combustion. The particle size of the rutile is 80-100 meshes.

According to the invention, iron oxide mainly acts like rutile and is a common slagging component in welding materials. The particle size of the iron oxide is 80-100 meshes.

According to the invention, aluminum is a common arc stabilizer and deoxidizer in welding materials, and particularly for underwater welding, the stable combustion of electric arcs is maintained, and the reduction of the oxygen content of welding seams is very important. The particle size of the aluminum particles is 80-100 meshes.

According to the invention, the ferrosilicon has a deoxidizing and alloying effect. Silicon has a higher affinity for oxygen than iron and readily forms SiO₂Can prevent the oxidation of iron element and reduce FeO, which plays the role of deoxidation. Silicon is an important alloy, and a small amount of silicon can improve the lightness and the hardness of a welding joint. The grain diameter of the ferrosilicon is 80-100To achieve the purpose.

According to the invention, the manganese element mainly plays roles of deoxidation, desulfurization and solid solution strengthening in underwater welding, and has a certain effect on the improvement of the microstructure of a welding seam. The deoxidizing capacity of the manganese element is slightly poorer than that of the silicon element, and the purpose of using the manganese element is to adopt silicon-manganese combined deoxidizing. Deoxidation with silicon or manganese alone produces SiO₂Or MnO, easily forms slag inclusion defects in the molten bath. The combined deoxidation of silicomanganese can form MnO. SiO₂(silicate) which is easily floated in the molten bath. Manganese can react with sulfur to form MnS, thereby removing the sulfur in the weld and reducing the hot cracking tendency. The manganese element is also an important alloy element, and the proper amount of the manganese element can improve the toughness of the welding seam. The particle size of the manganese particles is 80-100 meshes.

According to the invention, nickel is an important alloy element in the welding material, and the addition of a certain amount of nickel has obvious effects on improving the weld joint structure and improving the joint strength. The particle size of the nickel is 80-100 meshes.

According to the invention, because the hydrogen content of the welding seam welded underwater is high, lithium fluoride is often added into the welding material as a main dehydrogenating agent so as to achieve the purpose of reducing the hydrogen content of the welding seam. The particle size of the lithium fluoride is 80-100 meshes.

According to the invention, the iron powder can improve the deposition rate in the welding process and improve the welding efficiency. The particle size of the iron powder is 80-100 meshes.

According to the invention, the nano alumina particles can be used as nucleation particles at the solidification stage of a molten pool, so that the further refinement of weld grains is realized, and the effect of improving the mechanical property of a welding joint is achieved. Meanwhile, the thermal conductivity of the fluid can be increased by adding nano alumina particles. During the welding process, the welding wire is melted by the concurrent heating of the arc and the liquid droplet. Since the thermal conductivity of the liquid droplet is increased after the nanoparticles are added, the liquid droplet can conduct more heat to the unmelted welding wire, causing it to melt. The welding power source thus only needs to provide a small current to melt the wire. The particle size of the nano alumina particles is 10-80 nanometers.

According to the invention, the diameter of the flux-cored wire is preferably 1-2mm, preferably 1.6mm, and the filling rate is 30-32%.

The preparation method of the underwater submerged arc welding flux-cored wire suitable for the low-carbon steel comprises the following steps:

fully mixing rutile, ferric oxide, aluminum, ferrosilicon, manganese, nickel, lithium fluoride, iron and nano aluminum oxide particles to obtain a medicine core; and coating the flux core with a low-carbon steel strip, and then drawing to obtain the flux-cored wire.

Preferably, according to the invention, the low-carbon steel strip has a width of 7-9mm and a thickness of 0.2-0.4 mm.

According to the invention, the conditions in the preparation process of the flux-cored wire are as the prior art.

The flux-cored wire suitable for underwater submerged arc welding of low-carbon steel is applied to underwater submerged arc welding of low-carbon steel.

The invention has the following beneficial effects:

the nano alumina particles with specific dosage and specific particle size are added into the flux-cored wire, so that the nano alumina particles can serve as nucleation particles at the solidification stage of a molten pool, further refinement of weld grains is realized, and the effect of improving the mechanical property of a welding joint is achieved; meanwhile, the heat conductivity of the fluid can be improved, the current value in the welding process can be reduced under the condition of constant pressure, the energy consumption is reduced, and the heat input is reduced. The nano aluminum oxide particles with specific dosage and granularity combine with other raw materials with specific dosage to play a synergistic effect, thereby realizing the improvement of the mechanical properties of the weld joint, such as tensile strength, plastic toughness and the like.

Detailed Description

The present invention is further illustrated by the following specific embodiments.

Meanwhile, the raw materials used in the following examples are all commercially available unless otherwise specified; the methods and equipment used, unless otherwise specified, are conventional.

Examples 1 to 3

An underwater submerged arc welding flux-cored wire suitable for low-carbon steel comprises a sheath material and a flux core; the sheath material is low-carbon steel, and the carbon content is 0.04 wt%; the medicine core comprises the following raw materials in parts by weight: rutile (particle size of 80-100 meshes), ferric oxide (particle size of 80-100 meshes), aluminum (particle size of 80-100 meshes), ferrosilicon (particle size of 80-100 meshes), manganese (particle size of 80-100 meshes), nickel (particle size of 80-100 meshes), lithium fluoride (particle size of 80-100 meshes), iron (particle size of 80-100 meshes) and nano-alumina (particle size of 15-25 nanometers). The raw material formulation is shown in table 1.

The preparation method of the underwater submerged arc welding flux-cored wire suitable for the low-carbon steel comprises the following steps:

rutile, iron oxide, aluminum, ferrosilicon, manganese, nickel, lithium fluoride, iron and nano-alumina particles are put into a powder mixer for 5 hours, and are mixed sufficiently and uniformly. Rolling low carbon steel strip (8 mm in width and 0.3mm in thickness) into U shape, and filling the flux core. And changing the U-shaped low-carbon steel strip into an O shape through a wire drawing die. And the diameter of the welding wire is gradually thinned to 1.6 mm. The filling rate of the flux-cored wire is 30-32%.

TABLE 1 core composition

Comparative example 1

A flux cored welding wire, as in example 1, except that: no nano alumina particles are added; the other raw material compositions and preparation methods were identical to example 1. The specific raw material composition is shown in table 1.

Comparative example 2

A flux cored welding wire, as in example 2, except that: adding non-nano alumina particles, namely, the particle diameter of the alumina particles is 80-100 meshes; the other raw material compositions and preparation methods were identical to example 1. The specific raw material composition is shown in table 1.

Comparative example 3

A flux cored welding wire, as in example 1, except that: the addition amount of the nano alumina particles is larger and is 20 parts; the other raw material compositions and preparation methods were identical to example 1. The specific raw material composition is shown in table 1.

Comparative example 4

A flux cored welding wire, as in example 1, except that: nickel is not added; the other raw material compositions and preparation methods were identical to example 1. The specific raw material composition is shown in table 1.

Test examples

And (3) welding test:

and placing a workpiece, wherein the selected base material is low-alloy high-strength steel Q345B, the thickness is 14mm, and a trapezoidal groove is formed. Placing a mixture, wherein the mixture consists of submerged arc welding agent HJ431 and epoxy resin in a mass ratio of 5: 4. And adjusting the position of a welding gun to enable the dry length of the welding wire to be 15mm, and extending the welding wire out of the contact tube. Setting welding parameters, setting a constant voltage mode, setting the voltage to be 30V, adaptively adjusting the welding current, and starting welding. The welding speed is 120mm/min, and the wire feeding speed is 5 m/min. And in the welding process, an electric signal acquisition device is used for acquiring an electric signal in the welding process. And finally, analyzing and testing the electric signal in the welding process and the welding seam obtained by welding. The test results are shown in table 2.

TABLE 2 welding current and weld mechanical properties of the examples and comparative examples of flux-cored wire

Serial number	Welding current	Tensile strength	Elongation percentage	Positive curve	Back bend	Impact toughness of 20 DEG C	Impact toughness 0 DEG C
								Example 1	215.3	560.3	10.5	122.5	115.5	68.5	62.3
Example 2	216.5	561.3	12.3	180.0	180.0	70.5	63.5
								Example 3	223.5	561.5	11.8	180.0	150.5	75.6	63.8
Comparative example 1	250.2	563.1	10.4	55.6	80.6	67.5	61.4
								Comparative example 2	251.3	553.2	10.2	60.5	70.3	65.5	60.3
Comparative example 3	220.6	545.5	9.8	72.5	61.5	60.5	55.6
								Comparative example 4	215.9	560.5	10.3	121.2	110.8	43.2	31.6

The experimental results show that the current is reduced to a different extent and the energy consumption is reduced in the three groups of examples compared with the comparative example 1. Tensile test results show that the tensile strength is high, the elongation is improved in different degrees, wherein the elongation of the welding sample in the embodiment 2 is the highest and reaches 12.47%, and compared with the elongation of the welding sample in the comparative example 1, the elongation is improved by 20.13%. In a bending test, two samples are respectively taken for back bending and front bending; the sample of example 2 exhibited the best shaping, all 4 samples reached a 180 ° bend angle; and the shaping of example 1 is also much better than the comparative example. The present invention exhibits more excellent effects than the comparative examples in terms of impact toughness at different temperatures. The butt joint is completed by multilayer welding, and the grain sizes of the fine grain regions of the three groups of embodiments are smaller than the comparison ratio; the average sizes of the crystal grains of examples 1, 2 and 3 were 5.45 μm, 4.34 μm and 4.08 μm, respectively; the average sizes of the crystal grains of comparative example 1 were 6.24 μm, respectively.

Compared with the comparative example 2, the three groups of examples have the advantages that the welding current is reduced, the heat input is reduced, and the comprehensive mechanical property of the welding seam is improved. The fine grain size of the fine grain region of the three examples is smaller than that of the comparative example 2, and the fine grain size of the fine grain region of the comparative example 2 is 6.32 μm.

Compared with the comparative example 3, the welding current of the three groups of examples has no obvious change, and the comprehensive mechanical property of the welding seam is improved. The grain sizes of the fine crystalline regions of the three examples are smaller than those of the comparative example 3, and the grain size of the fine crystalline region of the comparative example 3 is 6.15 μm.

Compared with the comparative example 4, the three groups of the implementation have the advantages that the welding current is not obviously changed, and the mechanical property and the impact toughness value are greatly improved. The fine grain size of the three examples was similar to the comparative example, and the fine grain size of comparative example 4 was 5.43 μm.