CN113695788B

CN113695788B - Amorphous state smelting flux and preparation method and application thereof

Info

Publication number: CN113695788B
Application number: CN202111251261.7A
Authority: CN
Inventors: 王聪; 张燕云; 王占军; 钟明; 袁晓波
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2021-10-27
Filing date: 2021-10-27
Publication date: 2022-02-22
Anticipated expiration: 2041-10-27
Also published as: CN113695788A

Abstract

The invention relates to the technical field of welding, in particular to an amorphous state melting welding flux and a preparation method and application thereof. The amorphous melting flux is prepared from the following components in percentage by mass: CaF₂ 20%~25%，CaO 30%~35%，SiO₂30-35% and TiO₂5% -15%. The amorphous smelting flux has the advantages of no moisture absorption, good slag detachability, capability of effectively reducing the content of harmful elements such as P, S in a welding line and the like by adopting specific components and the dosage thereof. Meanwhile, the welding flux is in an amorphous state, the components of a welding seam obtained after welding are uniform, the mechanical property of the welding seam is excellent, and particularly the low-temperature toughness of the welding seam is good.

Description

Amorphous state smelting flux and preparation method and application thereof

Technical Field

The invention relates to the technical field of welding, in particular to an amorphous state melting welding flux and a preparation method and application thereof, and more particularly relates to an amorphous state melting welding flux and a preparation method thereof, and a welding method of structural steel for ship and ocean engineering.

Background

With the development of resource exploitation from shallow sea to deep sea areas and extremely cold areas, the application environment of ocean engineering equipment is more complex, and thus the requirement on materials is higher and higher. The marine steel is welded by adopting large heat input in the using process, and the large heat input submerged arc welding technology can obviously improve the welding operation efficiency, so the large heat input submerged arc welding technology gradually becomes an important means for efficiently manufacturing the marine steel.

However, when marine steel is welded at a high heat input, particularly at a heat input of more than 50kJ/cm, the mechanical properties of the weld are severely reduced, even lower than those of the base steel sheet, and hydrogen embrittlement may occur. The above problems affect the safety use performance of the marine equipment, so that the marine equipment cannot meet the service requirements. In addition, with increasingly harsh service environments of marine equipment, higher requirements are correspondingly put forward on equipment manufacturing technology and process, and not only is equal strength matching between weld metal and base metal required, but also the requirement on low-temperature toughness is higher.

The welding flux is one of the most main consumable materials of submerged arc welding, and plays important roles of stabilizing electric arcs, mechanically protecting, controlling welding seam forming, alloy transition and the like in the welding process. The components of the flux determine the welding process performance and the chemical metallurgical performance, and further influence the structure and the mechanical property of a welding seam. S, P in the weld joint mainly comprises FeS, MnS and Fe₃P、Fe₂The P exists in a form, and the P is hard and brittle and is distributed in a grain boundary, so that the bonding force between grains is reduced, and the cold brittleness of a welding line is increased.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The first purpose of the invention is to provide the amorphous melting welding flux which has the advantages of no moisture absorption, good slag detachability, capability of effectively reducing the content of harmful elements such as P, S in a welding line and the like by adopting specific components and dosage thereof. Meanwhile, the welding flux is in an amorphous state, the components of a welding seam obtained after welding are uniform, the mechanical property of the welding seam is excellent, and particularly the low-temperature toughness of the welding seam is good.

The second purpose of the invention is to provide the preparation method of the amorphous melting welding flux, which is characterized in that the welding flux is in an amorphous state by water quenching the molten material; and the preparation method has the advantages of simple operation, suitability for mass production and the like.

A third object of the present invention is to provide a welding method of structural steel for ships and oceanographic engineering, which can further improve the uniformity and mechanical properties of a weld by welding a specific steel using a specific welding flux and a specific welding method.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

the invention provides an amorphous smelting flux prepared fromThe coating is prepared from the following components in percentage by mass: CaF ₂20%~25%，CaO 30%~35%，SiO₂30-35% and TiO ₂ 5%~15%。

The chemical composition and the dosage ratio of the flux are one of the important factors influencing the capability of the molten flux to change from a liquid phase to an amorphous state. Whether the flux solution is amorphous or not is related to chemical components of the flux solution, and the amorphous forming capability is different for different flux systems; in the same flux system, the amorphous phase is usually formed within a certain amount. The invention can lead the melting welding flux to be in an amorphous state by adopting the components with specific types and specific dosage.

Specifically, the invention is realized by adopting CaF with specific dosage₂、SiO₂CaO and TiO₂The oxygen content in the welding line can be adjusted, crystal grains are refined, the stability of the welding process is ensured, the slag is easy to remove, the components of the prepared welding line are uniform, and the mechanical property (especially the low-temperature impact toughness at minus 40 ℃) of the welding line is improved; moreover, the welding flux does not absorb moisture, and can effectively reduce the content of harmful elements such as P, S in the welding seam.

In particular, the invention is achieved by using higher SiO contents₂And TiO₂And the low-temperature toughness of the welding seam is improved. Because of the specific amount of SiO₂And TiO₂Composite inclusions containing Si and Ti are formed in the weld, and these composite inclusions can promote the formation of acicular ferrite, which can improve the strength and toughness of the weld metal.

It has been conventionally thought that acidic oxides significantly increase the oxygen content in the weld, and higher oxygen content results in the formation of large amounts of inclusions and a decrease in weld toughness. Thus, prior art flux designs have used as much basic oxide as possible to reduce the weld oxygen content and improve the toughness of the weld.

However, in the present invention, an appropriate amount of the acidic oxide SiO is used₂And TiO₂The O content of the welding line can be controlled to be 200-350 ppm, and the toughness of the welding line is not reduced but increased. The reason is mainly divided into two aspects: first, when transformation from austenite to ferrite occurs, inclusions containing Si and Ti promote intragranular transformationForming acicular ferrite; secondly, when the oxygen content is about 300ppm, about 1 μm tiny inclusions are remarkably increased, and tiny dispersed inclusions pin austenite grains are grown, so that the purpose of refining weld grains is achieved.

More specifically, in the amorphous melting flux composition of the present invention:

CaF₂can improve the air hole resistance of the welding line and reduce the oxygen content of the welding line metal. CaF₂The melting point is low, the content of welding seam O can be limited controlled, the high-temperature viscosity of the slag can be effectively reduced, the flow of the slag is increased, and the formability is improved. CaF₂Can form HF gas which is not dissolved in liquid metal with H in a welding area, and reduces the H content in a welding seam and the tendency of generating hydrogen holes, thereby improving the impact toughness of the welding seam metal. The CaF provided by the invention₂The amount of the catalyst is proper, because if the amount is too small, the alkalinity of the welding flux is small, the melting point of the welding flux is high, the H removing effect is poor, and the impact toughness of the welding seam is low; if the amount is too large, the high ionization element F will destroy the arc stability, making the AC welding process performance poor.

SiO₂The main functions of the method are slagging, increasing weld penetration and transition of Si element into the weld. SiO 2₂Is an acidic oxide with CaF₂The air hole resistance of the welding line can be improved by matching the use of the components. SiO 2₂The silicate melt structure is a network forming body, so that the high-temperature viscosity of the slag can be increased, the melting point and the surface tension of the welding flux can be adjusted, and the formability of the welding seam is influenced. The transitional Si is the main alloy component in the welding seam, and can improve the strength and the impact toughness of the welding seam. The SiO provided by the invention₂The dosage range of the welding flux is proper, because if the dosage is too small, the high-temperature viscosity of the welding flux is small, the weld penetration is shallow, and the Si content in the weld is low, so that the impact toughness of the weld is low; if the dosage is too large, the high-temperature viscosity of the welding flux is high, and gas generated by welding cannot escape, so that defects such as air holes and surface indentation are generated in a welding seam.

The main functions of CaO are slagging, increasing the alkalinity of molten slag, and adjusting the viscosity of a welding flux and the slagging temperature. In the high-temperature welding process, part of P and S in the welding flux can be transited into a welding seam, and the CaO can remove the P and S in the welding seam, so that the content of the P and S in welding seam metal is reduced, and the toughness of the welding seam is improved. In addition, the CaO has low ionization potential, and the addition of a proper amount of CaO can stabilize electric arcs. In the present invention, the amount of CaO is in a suitable range because if the amount is too low, the flux basicity is low and the impact toughness is poor; if the amount is used in a relatively high amount, weld formability is deteriorated, and the flux slagging temperature is high, so that craters are likely to be generated on the weld surface.

TiO₂The main functions of the method are to adjust the alkalinity of the slag, form slag, improve the high-temperature fluidity of the flux and transition Ti element into the welding seam. Due to TiO₂Relative to SiO₂O is not easy to decompose, so that the content of O in the welding seam due to the transition of the welding flux is reduced, and the low-temperature impact toughness of the welding seam is increased. The transitional alloy component Ti can improve the mechanical property of the welding seam in three modes of solid solution strengthening, precipitation strengthening and grain refining. In addition, the Ti-containing inclusion can effectively promote the acicular ferrite nucleation and increase the volume fraction of the acicular ferrite in the weld joint, so that the impact toughness of the weld joint is enhanced. In the present invention, TiO is used₂The dosage range of the welding seam is proper, because if the dosage is too small, the content of Ti in the welding seam is low, and the strengthening effect is not obvious; if the amount is too large, the flux is less likely to be amorphous and a large amount of CaTiO is likely to be produced₃This results in poor slag detachability of the weld.

Furthermore, in the prior art, the composition of the fluxing agent is complex and typically comprises five or more components. However, the complex components easily generate a high-melting-point phase which is not easy to remove in the smelting process, and the amorphous forming capability is poor, so that the problems of uneven weld components, relative difficulty in slag removal, large mechanical property fluctuation and the like are caused. The amorphous melting welding flux provided by the invention has the advantages of simple components, no high-melting-point phase, low slagging temperature, uniform welding line components and stable welding line mechanical property.

In conclusion, the amorphous smelting flux provided by the invention is amorphous, and has the advantages of no moisture absorption, good slag detachability, capability of effectively reducing the content of harmful elements such as P, S in a welding line and the like; and the welding seam obtained by the welding flux after welding has uniform components, excellent mechanical property of the welding seam and good low-temperature impact toughness at minus 40 ℃.

Preferably, the slag forming temperature of the amorphous melting flux is 1250-1350 ℃, including but not limited to any one of 1260 ℃, 1270 ℃, 1280 ℃, 1290 ℃, 1300 ℃, 1310 ℃, 1320 ℃, 1330 ℃ and 1340 ℃ or a range value between any two.

The slagging temperature refers to the temperature at which the amorphous melting flux starts to change from a solid state to a liquid state, i.e. the temperature at which the flux starts to melt.

In the prior art, the smelting temperature for preparing the smelting flux is generally higher, while the smelting temperature of the amorphous smelting flux provided by the invention is lower, so that the electricity and energy are saved, and the cost is reduced.

Preferably, the viscosity of the amorphous melting flux at 1400 ℃ is 0.15-0.25 pas, including but not limited to any one of 0.16 pas, 0.17 pas, 0.18 pas, 0.19 pas, 0.20 pas, 0.21 pas, 0.22 pas, 0.23 pas, 0.24 pas or a range therebetween.

The amorphous melting welding flux provided by the invention has proper viscosity after melting, and the melting welding flux can uniformly cover a welding line, so that the welding line obtained after welding by adopting the amorphous melting welding flux has good formability, and is not easy to generate defects such as air holes, slag inclusion and the like.

The invention also provides a preparation method of the amorphous smelting flux, which comprises the following steps:

smelting the uniformly mixed raw materials to obtain a molten material; and sequentially carrying out water quenching, solid-liquid separation and crushing on the molten material to obtain the amorphous melting flux.

The ability of a liquid flux to change to an amorphous state depends not only on the flux composition, but also on the cooling rate. The invention uses water quenching technology to quench the components with specific types and specific dosage, so that the prepared smelting flux is amorphous.

Meanwhile, the preparation method has the advantages of simple operation, suitability for mass production and the like.

Preferably, the pressure of the water quenching is 150-200 MPa, and 160MPa, 170MPa, 180MPa or 190MPa can be selected;

more preferably, in the water quenching process, the mass ratio of the molten material to water used for water quenching is 1: 12-1: 15.

Preferably, the mixing time is 10-30 min, and can be 15min, 20min or 25 min.

Preferably, the solid-liquid separation may be carried out by any conventional method, such as decantation, filtration, centrifugation, and gravity settling. In some specific embodiments of the invention, the solid-liquid separation is performed by a filtration method, specifically, a water filter bucket is used for filtering for 8-12 hours, and may be selected from 9 hours, 10 hours or 11 hours.

Preferably, before the crushing, a drying step is further included; the drying temperature is 250-300 ℃, including but not limited to the point value of any one of 255 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃ and 295 ℃ or the range value between any two; the drying time is 1.5-2 h.

The drying can remove the moisture in the materials, thereby improving the welding performance.

Preferably, during the drying process, the laying thickness of the flux material is 40-50 mm, and also can be 42mm, 44mm, 46mm, 48mm or 49 mm.

The laying thickness is favorable for quickly removing moisture, and the aim of quickly drying is fulfilled.

Preferably, in the mixing process, the granularity of each raw material is 80-120 meshes; 100 mesh can also be selected.

In some embodiments of the present invention, the raw materials may be crushed into powder with a particle size of 80-120 mesh, or may be purchased directly to obtain raw materials with a particle size of 80-120 mesh.

And/or the grain size of the amorphous smelting flux is 8-30 meshes, and can also be selected from 10 meshes, 12 meshes, 14 meshes, 16 meshes, 18 meshes, 20 meshes or 25 meshes.

The grain size of the amorphous melting flux is limited to a specific range in order to adjust the bulk density during welding. When the marine steel is welded by large heat input, the thickness of the welding flux layer is higher; if the granularity of the welding flux is small, the gaps are few, the welding flux has poor ventilation, the air pressure of an arc cavity is increased, the length of an arc is reduced, and bulges and pressing pits can be formed in a welding seam; if the granularity of the welding flux is larger, air in the clearance of the welding flux is more, the welding seam is not well protected, and welding defects are easy to occur.

Therefore, in the invention, by controlling the granularity of the welding flux to be 8-30 meshes, the components of the welding seam are more uniform, the mechanical property is more excellent, and the generation of defects is reduced.

Preferably, in the smelting process, the smelting temperature is 1450-1500 ℃, including but not limited to the point value of any one of 1455 ℃, 1460 ℃, 1465 ℃, 1470 ℃, 1475 ℃, 1480 ℃, 1490 ℃ and 1490 ℃ or the range value between any two; in the smelting process, the heat preservation time is 15-20 min, including but not limited to the point value of any one of 16min, 17min, 18min and 19min or the range value between any two.

The amorphous melting welding flux provided by the invention has low melting temperature and short melting time, thereby being more beneficial to energy conservation and cost reduction.

In some embodiments of the invention, the mixing is performed in a blender or mixer.

In some specific embodiments of the invention, the smelting is carried out in an electric furnace.

In some specific embodiments of the invention, the drying is performed in a forced air drying oven.

The invention also provides a welding method of the structural steel for the ship and the ocean engineering, which is used for welding the structural steel for the ship and the ocean engineering by using the amorphous smelting flux or the amorphous smelting flux prepared by the preparation method;

wherein the welding method comprises double-wire submerged arc welding;

and/or the structural steel for ships and ocean engineering comprises high-strength structural steel for ships and ocean engineering.

Among them, the twin-wire submerged arc welding is an arc welding method having two welding wires, and has a high deposition rate and a high welding speed.

In some embodiments of the invention, the twin wire submerged arc welding is a twin wire dual power welding process.

Preferably, the high-strength structural steel for ships and oceanographic engineering includes at least one of AH32, DH32, EH32, FH32, AH36, DH36, EH36, FH36, AH40, DH40, EH40, and FH 40.

In some embodiments of the present invention, the welding method of structural steel for ships and ocean engineering can be used for welding ships, ocean platforms and oil and gas storage containers.

The welding seam prepared by welding the structural steel for ships and ocean engineering by adopting the amorphous state melting welding flux and the welding method provided by the invention has excellent performance, and can meet the service environment of a thick marine steel plate.

The invention can further improve the uniformity and mechanical property of the welding seam by adopting the specific welding flux and the specific welding method to weld the specific type of steel.

Preferably, in the welding process, the stacking height of the welding flux is 35-40 mm; including but not limited to a point value of any one of 36mm, 37mm, 38mm, 39mm or a range of values between any two.

And/or the welding speed is 23-30 cm/min; including but not limited to, a point value of any one of 24cm/min, 26cm/min, 27cm/min, 28cm/min, 29cm/min, or a range value between any two.

And/or the weld line energy is 50-70 kJ/cm, including but not limited to a point value of any one of 52kJ/cm, 55kJ/cm, 57kJ/cm, 58kJ/cm, 59kJ/cm, 60kJ/cm, 61kJ/cm, 62kJ/cm, 63kJ/cm, 64kJ/cm, 67kJ/cm, or a range value between any two.

Preferably, in the welding process, a front wire and a rear wire with the distance of 20-25 mm are adopted; 21mm, 22mm, 23mm or 24mm may also be selected.

The front wire adopts direct current, and the welding current of the direct current is 450-500A, including but not limited to the point value of any one of 460A, 470A, 480A and 490A or the range value between any two; the welding voltage of the direct current is 25-30V, including but not limited to the point value of any one of 26V, 27V, 28V and 29V or the range value between any two.

And/or the rear wire adopts an alternating current, and the welding current of the alternating current is 350-400A, including but not limited to the point value of any one of 360A, 370A, 380A and 390A or the range value between any two; the welding voltage of the alternating current is 30-35V, including but not limited to the point value of any one of 31V, 32V, 33V and 34V or the range value between any two.

By adopting the welding parameters, the mechanical properties such as slag removal property, uniformity and toughness of the welding seam and the like can be further improved, and the contents of P element and S element in the welding seam can be further reduced.

In some embodiments of the invention, the amorphous melting flux may be used with low carbon high manganese welding wires, including H10Mn2 type wires and/or H08Mn2SiA type wires.

Compared with the prior art, the invention has the beneficial effects that:

(1) the welding flux prepared by adopting the components with specific types and specific dosage is in an amorphous state, the amorphous state smelting welding flux can adjust the oxygen content in the welding seam, refine crystal grains, ensure the stability of the welding process, facilitate slag removal, and ensure the uniformity of the components of the prepared welding seam, thereby improving the mechanical property of the welding seam, in particular improving the low-temperature impact toughness of the welding seam; the welding flux also has the advantages of no moisture absorption and capability of effectively reducing the content of harmful elements such as P, S in the welding seam.

(2) The amorphous melting welding flux provided by the invention has low slagging temperature and low melting temperature, is beneficial to saving electricity and energy and reduces the cost.

(3) The amorphous melting welding flux provided by the invention has proper viscosity after melting, so that the obtained welding line has good forming performance and can reduce the generation of defects.

(4) The special welding flux and the special welding method are adopted to weld the special steel, so that the slag removal property, the uniformity of the welding seam and the toughness of the welding seam are further improved, and the content of P, S element in the welding seam can be further reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is an X-ray diffraction pattern of the amorphous melting flux of examples 1 to 3 provided in the experimental examples of the present invention;

FIG. 2 is an X-ray diffraction pattern of the fluxes of comparative example 2 and comparative example 4 provided in the experimental example of the present invention;

FIG. 3 is a macro-topography of a weld of examples 1-3 provided in the experimental examples of the present invention;

FIG. 4 is a macro-topography of a weld of comparative example 5 provided in an experimental example of the present invention;

FIG. 5 is a scanning electron microscope image of a weld joint provided in an experimental example of the present invention;

FIG. 6 is a scanning electron microscope image of another weld joint provided in the experimental example of the present invention;

FIG. 7 is a scanning electron microscope image of another weld joint provided in the experimental example of the present invention.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

The amorphous melting flux provided by the embodiment is prepared from the following components in percentage by mass: CaF₂25%，CaO 35%，SiO₂35% and TiO ₂ 5%。

The preparation method of the amorphous melting flux provided by this embodiment includes the following steps:

(1) crushing the raw materials until the granularity is 80 meshes, weighing according to the mass percentage, then pouring the weighed raw materials into a stirrer, mixing and stirring for 30min, uniformly stirring, putting the raw materials into an electric furnace for smelting at 1450 ℃, and preserving heat for 20min to obtain a molten material;

(2) carrying out water quenching granulation on the molten material obtained in the step (1) to obtain a semi-finished product of gray-black amorphous welding flux particles; the mass ratio of the molten material to water used for water quenching is 1: 12;

(3) placing the semi-finished product of the amorphous welding flux particles obtained in the step (2) in a water filtering bucket for filtering for 8 hours, then placing the semi-finished product in a forced air drying oven at 250 ℃ for drying for 1.5 hours to remove moisture, wherein the thickness of the welding flux during drying is 40 mm; and then crushing the powder to the granularity of 8-30 meshes to obtain the amorphous melting flux.

Example 2

The amorphous melting flux provided by the embodiment is prepared from the following components in percentage by mass: CaF₂23%，CaO 33%，SiO₂33% and TiO₂ 11%。

(1) crushing the raw materials until the granularity is 120 meshes, weighing according to the mass percentage, then pouring the weighed raw materials into a stirrer, mixing and stirring for 20min, putting the raw materials into an electric furnace after stirring uniformly, smelting at the smelting temperature of 1480 ℃, and preserving heat for 20min to obtain a molten material;

(2) carrying out water quenching granulation on the molten material obtained in the step (1) to obtain a semi-finished product of gray-black amorphous welding flux particles; the mass ratio of the molten material to water used for water quenching is 1: 15;

(3) placing the semi-finished product of the amorphous welding flux particles obtained in the step (2) in a water filtering bucket for filtering for 8 hours, then placing the semi-finished product in a forced air drying oven at 300 ℃ for drying for 1.5 hours to remove moisture, wherein the thickness of the welding flux during drying is 50 mm; and then crushing the powder to the granularity of 8-30 meshes to obtain the amorphous melting flux.

Example 3

The amorphous melting flux provided by the embodiment is prepared from the following components in percentage by mass: CaF ₂20%，CaO 32.5%，SiO₂32.5% and TiO₂ 15%。

(1) crushing the raw materials until the granularity is 100 meshes, weighing according to the mass percentage, then pouring the weighed raw materials into a stirrer, mixing and stirring for 25min, putting the raw materials into an electric furnace for smelting after stirring uniformly, wherein the smelting temperature is 1500 ℃, and preserving heat for 15min to obtain a molten material;

(2) carrying out water quenching granulation on the molten material obtained in the step (1) to obtain a semi-finished product of gray-black amorphous welding flux particles; the mass ratio of the molten material to water used for water quenching is 1: 14;

(3) placing the semi-finished product of the amorphous welding flux particles obtained in the step (2) in a water filtering bucket for filtering for 10 hours, then placing the semi-finished product in a 280 ℃ blast drying oven for drying for 2 hours to remove moisture, wherein the laying thickness of the welding flux is 45mm during drying; and then crushing the powder to the granularity of 8-30 meshes to obtain the amorphous melting flux.

Example 4

The amorphous melting flux prepared in examples 1 to 3 was mixed with a CHW-S3 welding wire (H10 Mn2 type, atlantic welding materials ltd, sichuan) and welded to EH36 steel by a two-wire submerged arc welding method. The welding parameters of each group are the same, and are as follows: the stacking height of the welding flux is 40mm, the front wire adopts 500A/30V direct current, the rear wire adopts 400A/33V alternating current, the distance between the front wire and the rear wire is 25mm, the welding speed is 28cm/min, and the energy of the welding line is 60 kJ/cm.

Example 5

The amorphous melting flux prepared in example 3 was mixed with a CHW-S3 welding wire (H10 Mn2 type, Atlantic welding materials, Sichuan Co., Ltd.) and welded to EH36 steel by a twin wire submerged arc welding method. Wherein the stacking height of the welding flux is 35mm, the front wire adopts 450A/25V direct current, the rear wire adopts 350A/30V alternating current, the distance between the front wire and the rear wire is 20mm, the welding speed is 23.5cm/min, and the energy of a welding line is 55 kJ/cm.

Comparative example 1

The amorphous melting flux provided by the comparative example is prepared from the following components in percentage by mass: CaF₂30% of CaO, 35% of CaO and SiO₂35 percent. The preparation method of the amorphous melting flux provided by the comparative example is completely the same as that of the example 3.

Comparative example 2

The amorphous melting flux provided by the comparative example is prepared from the following components in percentage by mass: CaF₂35% of CaO, 40% of CaO and TiO₂25 percent. The preparation method of the amorphous melting flux provided by the comparative example is completely the same as that of the example 3.

Comparative example 3

The amorphous melting flux provided by the comparative example is prepared from the following components in percentage by mass: CaF₂35%，SiO ₂40% and TiO₂25 percent. The preparation method of the amorphous melting flux provided by the comparative example is completely the same as that of the example 3.

Comparative example 4

The amorphous melting flux provided by the comparative example is prepared from the following components in percentage by mass: CaO 39%, SiO₂38% and TiO₂23 percent. The preparation method of the amorphous melting flux provided by the comparative example is completely the same as that of the example 3.

Comparative example 5

The amorphous melting flux provided by the comparative example is prepared from the following components in percentage by mass: CaF₂35%，CaO 20%，SiO ₂20% and TiO₂25 percent. The preparation method of the amorphous melting flux provided by the comparative example is completely the same as that of the example 3.

Comparative example 6

The amorphous melting flux provided by the comparative example is prepared from the following components in percentage by mass: CaF₂19%，CaO 30%，SiO₂ 30%，TiO ₂ 5%，Al₂O₃8% and MnO 8%. The preparation method of the amorphous melting flux provided by the comparative example is completely the same as that of the example 3.

Experimental example 1

The solder compositions prepared in the examples and comparative examples were subjected to moisture absorption test, viscosity test (1400 ℃ C.) and slag formation temperature test, and the results are shown in Table 1.

The moisture absorption test method of each group of welding flux is as follows: 100g of each group of welding agent is taken and placed in a constant temperature box with the temperature of 25 ℃ and the relative humidity of 80 percent, a sample is taken and weighed immediately after 24 hours of moisture absorption, and the moisture absorption rate is calculated. Wherein, moisture absorption = mass increase of flux after 24 h/mass of flux before experiment (i.e. 100 g) × 100%.

The viscosity of each set of fluxes was measured using a rotary viscometer (Brookfield DV2T, boorley flyer, usa) as follows: 150g of each group of welding flux is placed in a molybdenum crucible (phi 80 x 100 mm), then the molybdenum crucible is placed in a constant temperature area of a heating furnace and heated to 1400 ℃ and is kept warm for 30min, then a measuring head with rotary viscosity is inserted into the melt and rotates at the speed of 100 revolutions per minute, the viscosity value is recorded by a viscometer every time the viscosity measuring head rotates, and the viscosity value is the average value of the test values within 3 min.

The slagging temperature of each group of welding flux is tested by a hemisphere method, and the specific method is as follows: taking a little of the welding flux in each group, respectively preparing cylindrical samples with phi 3 x 3mm, placing the samples in a melting point melting speed instrument (LZ-III, northeast university), and heating to a corresponding temperature when the height of the sample is 50% of the height of the original sample, namely the slagging temperature of the welding flux; each group was measured 3 times by repeating the above method and then averaged.

TABLE 1 test results of slagging temperature, viscosity and moisture absorption rate of each group

Group of	Slagging temperature (. degree. C.)	Viscosity at 1400 ℃ (Pa.s)	Moisture absorption (%)
				Example 1	1280	0.21	0
Example 2	1296	0.19	0
				Example 3	1310	0.20	0
Comparative example 1	1344	1.06	0
				Comparative example 2	1603	0.81	0.05
Comparative example 3	1329	2.14	0
				Comparative example 4	1407	3.61	0.03
Comparative example 5	1362	0.39	0
				Comparative example 6	1271	1.14	0

As can be seen from table 1, the slag forming temperature and viscosity of the fluxes obtained in examples 1 to 3 were about 1300 ℃ and about 0.2 Pa · s, respectively, and the fluxes obtained in examples 1 to 3 did not absorb moisture; compared with the comparative examples 2 and 4, the slagging temperature is high, the slag is easy to solidify the welding seam first, a pit is easy to form on the surface of the solidified welding seam, and certain moisture absorption is realized; the viscosity of comparative examples 1, 3, 4 and 6 at 1400 ℃ is more than 0.7 pas, the flux alloy transition ability is deteriorated, the weld formability is deteriorated, and defects such as slag inclusion and blowholes are easily generated.

Meanwhile, the respective groups of the solders prepared in the above examples and comparative examples were subjected to an X-ray diffraction (XRD) test, and the results are shown in fig. 1 and 2. Wherein, FIG. 1 is the XRD pattern of the welding flux of the examples 1-3, and FIG. 2 is the XRD pattern of the welding flux of the comparative example 2 and the comparative example 4.

As can be seen from fig. 1, the X-ray diffraction patterns of the amorphous melting fluxes of examples 1 to 3 have only one dispersion peak at 20 to 40 °, which indicates that the fluxes prepared in examples 1 to 3 are all in an amorphous state.

As can be seen from FIG. 2, the X-ray diffraction patterns of comparative example 2 and comparative example 4 each exhibited a plurality of sharp crystal peaks, and the main crystal phase was CaF₂，CaTiO₃And TiO₂This indicates that the fluxes prepared in comparative examples 2 and 4 are both crystalline.

Then, the welding is performed by using the fluxes prepared in examples 1 to 3 and comparative example 5 according to the welding parameters in example 4, and the macro photographs of the welding seams of examples 1 to 3 are shown in fig. 3, and the macro photograph of the welding seam of comparative example 5 is shown in fig. 4. It can be seen that the weld joints of examples 1 to 3 have good formability and are easy to deslag. The slag particles adhered to the surface of the weld joint of the comparative example 5 are obvious, which shows that the slag detachability is poor, and the method is not suitable for large-heat-input rapid welding.

Experimental example 2

The welds obtained after welding in each set of example 4 and EH36 steel were each tested for chemical composition. The O and N of each set of welds was tested by an oxygen nitrogen analyzer (ONH 836, LECO, USA); the C of the weld was tested by an infrared carbon sulfur analyzer (CS 230, LECO, USA); the remaining elements were tested by inductively coupled plasma emission spectrometer (Optima 8300DV, PE company, usa); specific test results are shown in table 2.

TABLE 2 chemical composition (mass fraction) of each set of weld heads

Ingredient (wt.%)	C	Si	Mn	Cu	Cr	Ni	Nb	Ti	O	P	S
												EH36 steel	0.133	0.310	1.320	0.070	0.046	0.017	0.018	0.010	0.003	0.018	0.013
Example 1	0.085	0.466	1.310	0.061	0.045	0.016	0.034	0.013	0.026	0.009	0.008
												Example 2	0.084	0.478	1.260	0.059	0.043	0.015	0.033	0.015	0.028	0.010	0.008
Example 3	0.081	0.507	1.240	0.058	0.042	0.015	0.033	0.018	0.030	0.011	0.007

As can be seen from Table 2, the weld beads produced in examples 1-3 each had lower P and S contents than the base material EH36 steel; the contents of Ti and Si in the welding seam are improved compared with the content of the base metal, which shows that certain Si and Ti can be added to the welding seam through alloy transition, thereby achieving the microalloying treatment of the welding seam. The two points are beneficial to improving the strength and the low-temperature impact toughness of the welding seam.

Experimental example 3

The mechanical properties of the welds obtained after welding of the various groups of solder in example 4 were tested and the results are shown in table 3.

The tensile strength, elongation and reduction of area test were carried out according to the requirements of GB/T2652-2008, and the instrument used for the test was an Instron5982 type tensile tester (INSTRON, USA).

The method for testing the content of acicular ferrite is as follows: the weld joint was sampled and magnified by 200 times under a metallographic microscope (GX 51, olympus, japan), and measured by taking an average value after measuring 50 fields a plurality of times by a line intercept method.

The test of low-temperature impact energy (-40 ℃) refers to GB/T2650-.

Scanning Electron Microscope (SEM) tests were performed on the welds obtained after welding with the flux of example 3 in example 4, and the results are shown in fig. 5 to 7.

TABLE 3 mechanical Properties of the weld lines

Group of	Example 1	Example 2	Example 3	GB/T5293 Standard of F5A2-H10Mn2 in 2018
					Radiographic inspection (grade)	Ⅰ	Ⅰ	Ⅰ	Ⅰ
Tensile strength Rm (mpa)	689	693	711	≥480
					Yield strength ReL (mpa)	492	496	508	≥400
Elongation A (%)	31	32	32	≥22
					Volume fraction of acicular ferrite (%)	60	60	62	-
-40 ℃ impact absorption energy KV2(J)	82	83	85	≥27

As can be seen from Table 3, the weld joint obtained after welding by the welding flux provided by the invention has no defects in radiographic detection, and the mechanical properties of weld joint metal are all higher than the specifications of F5A2-H10Mn2 in GB/T5293-2018.

Compared with the national standard, the low-temperature toughness index of the welding seam obtained by welding with the welding flux of the invention at-40 ℃ is 3.15 times of that of the relevant national standard, and the main reason is that Si and Ti in the welding flux are effectively transferred into the welding seam to refine welding seam grains.

FIGS. 5 to 7 are SEM images of the weld joints obtained in examples 1 to 3, in which Inclusion represents inclusions; AF represents acicular ferrite; PF represents polygonal ferrite.

As can be seen from fig. 5 to 7, the formation of the composite inclusion containing Ti and Si in the weld seam effectively promotes the formation of acicular ferrite in the weld seam, and the volume percentage of acicular ferrite is 60% or more. This contributes to further improvement in the strength and low-temperature impact toughness of the weld.

In conclusion, the welding flux provided by the invention has the advantages of low melting temperature, smooth weld surface, good formability and excellent slag removal performance, and solves the problems of high cost, high energy consumption, unstable performance, need of drying before use and the like of the traditional product. Therefore, the welding flux provided by the invention can be effectively applied to welding of the high-strength marine steel thick plate.

While particular embodiments of the present invention have been illustrated and described, it will be appreciated that the above embodiments are merely illustrative of the technical solution of the present invention and are not restrictive; those of ordinary skill in the art will understand that: modifications may be made to the above-described embodiments, or equivalents may be substituted for some or all of the features thereof without departing from the spirit and scope of the present invention; the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention; it is therefore intended to cover in the appended claims all such alternatives and modifications that are within the scope of the invention.

Claims

1. Amorphous meltThe smelting flux is characterized by being prepared from the following components in percentage by mass: CaF₂ 20%~25%，CaO 30%~35%，SiO₂30-35% and TiO₂ 5%~15%；

The slagging temperature of the amorphous state smelting flux is 1250-1350 ℃;

the viscosity of the amorphous melting welding flux at 1400 ℃ is 0.15-0.25 Pa.s.

2. The method of preparing amorphous melting flux of claim 1, comprising the steps of:

3. The method of claim 2, further comprising, before the crushing, a step of drying; the drying temperature is 250-300 ℃, and the drying time is 1.5-2 h.

4. The preparation method according to claim 2, wherein during the mixing, the particle size of each raw material is 80-120 meshes;

and/or the granularity of the amorphous smelting welding flux is 8-30 meshes.

5. The preparation method of claim 2, wherein in the smelting process, the smelting temperature is 1450-1500 ℃, and the holding time is 15-20 min.

6. The welding method of structural steel for ships and oceanographic engineering, which is characterized in that the structural steel for ships and oceanographic engineering is welded by using the amorphous melting flux of claim 1 or the amorphous melting flux prepared by the preparation method of any one of claims 2 to 5;

wherein the welding method comprises double-wire submerged arc welding;

7. The welding method according to claim 6, wherein a stacking height of the flux is 35 to 40mm during the welding;

and/or the welding speed is 23-30 cm/min;

and/or the welding line energy is 50-70 kJ/cm.

8. The welding method according to claim 6, characterized in that, in the welding process, a front wire and a rear wire with a distance of 20-25 mm are used;

the front wire adopts direct current, the welding current of the direct current is 450-500A, and the welding voltage is 25-30V; and/or the rear wire adopts alternating current, the welding current of the alternating current is 350-400A, and the welding voltage is 30-35V.