Calcium silicate type smelting flux, and preparation method and application thereof

Abstract

The present application relates to the technical field of flux, in particular to a calcium silicate type smelting flux, a preparation method and application thereof. The calcium silicate type smelting flux is composed of the following components in percentage by mass: CaF2 13%~25% and CaSiO3 75%~87%. The calcium silicate type smelting flux is composed of CaSiO3 and CaF2 in a specific ratio, and the two components synergize with each other. On the one hand, the content of oxygen in the weld after welding tends to be rationalized, so that the weld has good low-temperature toughness and deslagging performance, has excellent arc stability and weld formability, the welding process is stable, the weld metal composition and structure are uniform, the surface appearance is good, and there are no defects such as pores and cracks, so as to ensure that the weld has excellent mechanical properties. On the other hand, the content of P element in the weld after welding can be significantly reduced, so as to ensure that the weld has good mechanical properties, and in particular, the low-temperature impact toughness of the welded joint after welding is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flux, in particular to a calcium silicate type smelting flux and a preparation method and application thereof. BACKGROUND

[0002] Submerged arc welding flux has the effects of slagging, stabilizing arc and air insulation in submerged arc welding. In the welding process, the flux produces intense chemical reaction between the molten pool and the arc, which can protect the weld metal from oxidation and also can affect the microstructure and properties of the welded joint by regulating the weld metal.

[0003] Submerged arc welding flux can be divided into smelting flux and sintering flux according to the manufacturing method. The smelting flux is obtained by heating the mechanically mixed raw materials to a temperature above the melting point, uniformly melting, rapidly cooling in water, and then crushing and sieving. The smelting flux has uniform composition, and the weld metal obtained after welding also has uniform composition and microstructure. The smelting flux has small consumption during welding, strong moisture resistance and is easy to store.

[0004] However, in the prior art, the decomposition of oxides in the smelting flux forms free oxygen and oxygen gas, and the gases such as CO formed by decarburization reaction cannot be discharged in time, which can cause the formation of pores in the weld. The free oxygen can increase the brittleness of the weld metal, resulting in defects such as pores and cracks in the weld metal. At the same time, the increase in brittleness can cause the mechanical properties of the weld to decrease. In addition, P is an impurity element in steel, which can easily segregate and increase the brittle transition temperature, resulting in cold brittleness.

[0005] Therefore, it is of great significance to provide a smelting flux with excellent mechanical properties and P removal capability.

[0006] Therefore, the present application is proposed. SUMMARY

[0007] The first object of the present application is to provide a calcium silicate type smelting flux composed of CaSiO3 and CaF2 in a specific ratio, which can synergistically function in two aspects. On the one hand, the oxygen content in the weld obtained after welding tends to be rationalized, so that the weld has good low-temperature toughness and deslagging performance, excellent arc stability and weld forming property, stable welding process, uniform weld metal composition and microstructure, good surface morphology, no defects such as pores and cracks, and excellent mechanical properties of the weld. On the other hand, the P element content in the weld can be significantly reduced, ensuring good mechanical properties of the weld, especially the low-temperature impact toughness of the welded joint obtained after welding.

[0008] The second object of the present application is to provide a preparation method of the calcium silicate type smelting flux, which adopts specific operation steps, is beneficial to obtain the smelting flux with excellent performance, and has the advantages of simple operation, mild conditions and suitability for mass production.

[0009] The third object of the present application is to provide the application of the calcium silicate type smelting flux in welding HSLA steel.

[0010] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0011] The present application first provides a calcium silicate type smelting flux, which is composed of the following components in percentage by mass: CaF2 13%~25% and CaSiO3 75%~87%.

[0012] Further, the low temperature impact energy of the welding joint obtained after welding HSLA steel by using the calcium silicate type smelting flux is ≥53J at-40℃.

[0013] Further, the content of acicular ferrite in the welding joint obtained after welding HSLA steel by using the calcium silicate type smelting flux is ≥51%.

[0014] Further, the content of acicular ferrite in the welding joint obtained after welding HSLA steel by using the calcium silicate type smelting flux is ≥51%.

[0015] The present application further provides a preparation method of the above-mentioned calcium silicate type smelting flux, which comprises the following steps: mixing CaF2 and CaSiO3, then smelting and water quenching to obtain a glassy mixture; and baking, crushing and sieving the glassy mixture to obtain the calcium silicate type smelting flux.

[0016] Further, the temperature of the smelting is 1500℃~1550℃, and the time of the smelting is 35min~50min.

[0017] Further, the temperature of the baking is 650℃~800℃, and the time of the baking is 3.5h~4h.

[0018] The present application further provides the application of the above-mentioned calcium silicate type smelting flux in welding HSLA steel, and the welding method comprises submerged arc welding.

[0019] Further, the line energy of the welding is 57kJ / cm~63kJ / cm, and the speed of the welding is 480mm / min~520mm / min.

[0020] Further, in the welding process, direct current is used in the positive electrode, and the welding current is 840A-860A, and the welding voltage is 30V-35V; and alternating current is used in the negative electrode, and the welding current is 600A-650A, and the welding voltage is 34V-38V.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] (1) The calcium silicate type smelting flux provided by the present application is composed of CaSiO3 and CaF2 in a specific ratio, and the two components synergize with each other, on the one hand, the oxygen content in the obtained weld after welding tends to be rationalized, so that the weld has good low-temperature toughness and deslagging performance, has excellent arc stability and weld forming property, the welding process is stable, the obtained weld metal after welding has uniform composition and microstructure, good surface morphology, and no defects such as pores and cracks, so that the weld has excellent mechanical properties; on the other hand, the P element content in the obtained weld after welding can be significantly reduced, so that the weld has good mechanical properties, especially the low-temperature impact toughness of the welded joint obtained after welding is good.

[0023] (2) The calcium silicate type smelting flux provided by the present application has simple composition, low melting point, no high-melting-point phase, low hygroscopicity, and the obtained weld metal after welding has uniform composition and microstructure, no segregation, stable mechanical properties, and less gas and slag generated during welding. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort.

[0025] Figure 1 The macroscopic morphology diagram of the obtained weld after welding of Example 5;

[0026] Figure 2 The macroscopic fracture morphology diagram of the obtained weld after welding of Example 5;

[0027] Figure 3 The microstructure scanning electron microscope diagram of the obtained weld after welding of Example 5; Figure 2 The enlarged view in the dashed box;

[0028] Figure 4 The picture of the welded joint of Example 5 after deslagging;

[0029] Figure 5 The microstructure scanning electron microscope diagram of the obtained weld after welding of Example 5;

[0030] Figure 6A macroscopic morphology diagram of the weld obtained after welding of Comparative Example 1;

[0031] Figure 7 A macroscopic fracture morphology diagram of the weld obtained after welding of Comparative Example 1;

[0032] Figure 8 A Figure 7 An enlarged view in the dotted box;

[0033] Figure 9 A picture of the welded joint of Comparative Example 1 after deslagging;

[0034] Figure 10 A picture of the deslagged slag of Comparative Example 1. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, rather than all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be obtained by commercial purchase.

[0036] If not specifically stated, in the present application, "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only used for description purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0037] If not specifically stated, "including" and "containing" mentioned in the present application mean open-ended, and can also be closed-ended. For example, "including" and "containing" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0038] If not specifically stated, in the present application, "one or more" or "at least one" means any one, any two or any two or more of the listed items. Among them, "several" means any two or any two or more.

[0039] In a first aspect, the present application provides a calcium silicate type smelting flux, which is composed of the following components in percentage by mass: CaF2 13%~25% and CaSiO3 75%~87%.

[0040] In the prior art, too little oxygen content in the weld will lead to difficulty in forming fine and dispersed inclusions in the weld, because oxygen is one of the necessary elements for the nucleation of inclusions in the weld, and too few inclusions lead to harmful structures in the weld, such as polygonal ferrite, grain boundary ferrite, side plate ferrite, etc. Such coarse structures are formed due to the accumulation of heat in the weld under too high heat input, which is not conducive to the improvement of the strength and toughness of the welded joint. Too high oxygen content will lead to the formation of pores, cracks and other defects in the weld, and greatly increase the brittleness of the weld, which is easy to cause the sudden fracture of the structure. Therefore, it is of great significance to strictly control the oxygen content.

[0041] The calcium silicate type smelting flux provided by the present application has a reasonable content of CaSiO3, so it can provide oxygen potential in the welding process, and the oxygen content in the weld metal tends to be more reasonable, controlled within 400ppm, which also plays a role in decarburization, and promotes the formation of inclusions with a size of less than 2 microns, which are dispersed in the weld and pinned at the austenite grain boundary and inside the grain.

[0042] In the above-mentioned CaF2-CaSiO3 binary flux system, CaF2 can optimize the formability of the weld, reduce the oxygen potential of the flux and control the oxygen content of the weld metal, so that the oxygen content of the weld metal tends to be reasonable, which is more conducive to the growth of the structure and improves the tensile strength and low temperature toughness of the weld, and optimizes the formability of the weld. CaF2 is beneficial to the diffusion of reactants (S) and products (CaS), and can prevent the formation of high-melting-point and dense reaction layers such as 2CaO·SiO2 (dicalcium silicate) from wrapping CaO particles and thus hindering the continuation of the desulfurization reaction. At the same time, CaF2 can combine with other oxides under high temperature conditions to form fluorides with lower melting points, so it can reduce the difficulty of the preparation process of the flux, i.e. lower power and lower temperature limit of the electromagnetic induction furnace and other equipment can be used for heating during smelting. Especially for smelting flux containing CaSiO3, the melting point of CaSiO3 is above 1500℃, and adding a certain amount of CaF2 to reduce the melting point can simplify the difficulty of the smelting process. From the perspective of environmental protection, the use of flux containing less fluorine can reduce the generation of harmful gases, which is more conducive to environmental protection.

[0043] CaSiO3 is the key control component to achieve the dephosphorization of the welding flux, and the stability of CaSiO3 reduces the sharp change of the components in the welding process, so that the dephosphorization, alloy element transition and the like are more stable and predictable. The ionization potential of CaSiO3 is low during smelting, which can stabilize the arc, improve the ability of the welding flux to resist large current, and enable the welding flux to withstand large heat input welding. Meanwhile, CaSiO3 generates strong alkaline oxides during decomposition, which can improve the basicity in the welding flux, and also adjust the viscosity and high-temperature melting point. In the welding process at a high temperature of 2000℃ or above, the P element in the welding material will be transferred to the weld, and at the same time, the P in the molten pool is oxidized into P2O5 by the oxides in the slag. With the assistance of CaF2, CaSiO3 combines with the P2O5 generated by oxidation to form stable tricalcium phosphate and tetracalcium phosphate dissolved in the slag phase, so as to achieve the purpose of removing phosphorus from the weld to the welding slag shell, thereby effectively reducing the P content in the weld metal, increasing the toughness of the weld, and reducing the harm of the P element to the welded joint. The Si element transferred to the weld metal by CaSiO3 can form a network structure in the slag after welding, which can promote the post-welding deslagging performance, and also plays a role in reasonably controlling the Si in the weld, and improves the tensile strength and hardness of the welded joint and the hardenability of the molten pool during solidification.

[0044] It can be seen that the calcium silicate type smelting flux provided by the present application has specific components and specific proportions, and is a smelting flux with stable welding process, good mechanical properties of the weld metal, uniform composition and structure of the weld metal, good surface morphology, and excellent deslagging performance. The smelting flux is used for welding HSLA steel, and has good welding effect, and the obtained weld has good low-temperature toughness and deslagging performance, and has no defects such as pores and cracks, and excellent mechanical properties.

[0045] In addition, the composition of the existing conventional welding flux is relatively complex, and usually includes more than five oxides. In large heat input welding, too many oxides in the welding flux can cause the oxygen content in the weld to increase sharply, and generate high-density inclusions, which adversely affects the mechanical properties of the weld. The welding flux provided by the present application has uniform composition, no segregation, low melting point of the welding flux, low hygroscopicity (CaSiO3 is stable and does not absorb moisture), stable and predictable metallurgical effect, uniform composition of the obtained weld metal after welding, less gas and slag generated during welding, and uniform weld structure and stable mechanical properties of the weld after large heat input welding.

[0046] The calcium silicate type smelting flux provided by the present application contains CaF2 in an amount of 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25% by mass; and CaSiO3 in an amount of 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86% or 87% by mass. The specific ratio is conducive to further improving the low-temperature toughness, slag removal performance, arc stability and weld forming property of the welded joint, and is conducive to further improving the uniformity of the weld metal composition and structure.

[0047] In some specific embodiments, the welded joint obtained after welding HSLA steel by using the calcium silicate type smelting flux has a low-temperature impact energy of ≥53 J at -40℃, including but not limited to any one of 53 J, 54 J, 55 J, 56 J, 57 J, 58 J, 59 J, 60 J, 61 J, 62 J, 63 J, 64 J, 65 J, 70 J, or a range value between any two of them. The welded joint obtained after welding HSLA steel by using the calcium silicate type smelting flux provided by the present application has good low-temperature toughness.

[0048] In some specific embodiments, the welded joint obtained after welding HSLA steel by using the calcium silicate type smelting flux has a needle-shaped ferrite content of ≥51%, including but not limited to any one of 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 70%, or a range value between any two of them. The calcium silicate type smelting flux provided by the present application can promote the formation of needle-shaped ferrite in the weld metal obtained after welding.

[0049] In some specific embodiments, the welded joint obtained after welding HSLA steel by using the calcium silicate type smelting flux has a number ratio of inclusions with a diameter of <2 μm of ≥82%, including but not limited to any one of 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 95%, or a range value between any two of them. The calcium silicate type smelting flux provided by the present application can promote the formation of inclusions with a size of less than 2 microns in the weld metal obtained after welding, thereby effectively promoting the nucleation of needle-shaped ferrite and more conducive to the improvement of low-temperature impact toughness.

[0050] In some specific embodiments, the calcium silicate type melting flux has a particle size of 10 mesh to 100 mesh, including but not limited to any one of 10 mesh, 20 mesh, 30 mesh, 40 mesh, 50 mesh, 60 mesh, 70 mesh, 80 mesh, 100 mesh, or a range value between any two of them.

[0051] In a second aspect, the present application provides a preparation method of the above-mentioned calcium silicate type melting flux, comprising the following steps: mixing CaF2 and CaSiO3, then melting and water quenching to obtain a glassy mixture; and baking, crushing and sieving the glassy mixture to obtain the calcium silicate type melting flux.

[0052] The preparation method can obtain a calcium silicate type melting flux with excellent performance, thereby improving the low-temperature toughness and slag removal performance of the weld after welding, and the uniformity and surface morphology of the weld metal.

[0053] In addition, the preparation method also has the advantages of simple operation, short process, and suitability for batch production.

[0054] In some specific embodiments, the melting temperature is 1500℃ to 1550℃, including but not limited to any one of 1500℃, 1510℃, 1520℃, 1530℃, 1540℃, 1550℃, or a range value between any two of them.

[0055] In some specific embodiments, the melting time is 35 min to 50 min, including but not limited to any one of 35 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, or a range value between any two of them.

[0056] Using the above-mentioned melting temperature and melting time is conducive to further improving the low-temperature toughness and slag removal performance of the welded joint after welding, and the uniformity and surface morphology of the weld metal.

[0057] In some specific embodiments, the device used for melting includes but is not limited to a graphite crucible.

[0058] In some specific embodiments, the baking temperature is 650℃ to 800℃, including but not limited to any one of 650℃, 660℃, 680℃, 700℃, 720℃, 740℃, 750℃, 760℃, 780℃, 800℃, or a range value between any two of them.

[0059] In some specific embodiments, the baking time is 3.5h to 4h.

[0060] Calcination helps remove residual impurities from the flux, such as carbon powder impurities remaining on the surface when a graphite crucible is used as the melting device.

[0061] Using the above-mentioned calcination temperature and time is beneficial to further improve the low-temperature toughness, slag removal performance, uniformity and surface morphology of the weld joint.

[0062] In some specific implementations, the roasting apparatus includes, but is not limited to, a muffle furnace.

[0063] Thirdly, the present invention provides the application of the above-mentioned calcium silicate-type fused flux in welding HSLA steel, wherein the welding method includes submerged arc welding. That is, HSLA steel is welded using the above-mentioned calcium silicate-type fused flux via submerged arc welding.

[0064] Among them, HSLA steel refers to high-strength low-alloy structural steel, also known as "micro-alloyed steel", which is a type of steel used in marine engineering.

[0065] The aforementioned calcium silicate-based fusion flux meets the welding process requirements for HSLA steel as the base material. Using this calcium silicate-based fusion flux for welding HSLA steel significantly improves the low-temperature toughness, slag removal performance, arc stability, weld formation, and the uniformity of weld metal composition and microstructure.

[0066] In some specific embodiments, the calcium silicate-type molten flux is dried before welding. The drying method includes baking, which can be carried out in a tube furnace or oven; the drying temperature can be, for example, 250°C to 350°C, and the drying time can be 2 hours to 4 hours.

[0067] In some specific embodiments, the welding line energy is 57kJ / cm to 63kJ / cm, including but not limited to any one of 57kJ / cm, 58kJ / cm, 59kJ / cm, 60kJ / cm, 61kJ / cm, 62kJ / cm, and 63kJ / cm, or any range between two of them.

[0068] Welding parameters are an important means of controlling and improving welding performance. The welding heat input described above in this invention can improve the low-temperature toughness and slag removal performance of the weld, as well as improve the uniformity and morphology of the weld.

[0069] The welding speed is 480 mm / min to 520 mm / min, including but not limited to any one of 480 mm / min, 485 mm / min, 490 mm / min, 495 mm / min, 500 mm / min, 505 mm / min, 510 mm / min, 515 mm / min, 520 mm / min or a range value between any two of them. With the above welding speed, the low-temperature toughness and deslagging performance of the weld can be further improved, and the uniformity and morphology of the weld can be improved.

[0070] In some specific embodiments, during the welding process: the electrode positive direction adopts direct current, and the welding current is 840 A to 860 A, including but not limited to any one of 845 A, 850 A, 855 A, 858 A or a range value between any two of them, and the welding voltage is 30 V to 35 V, including but not limited to any one of 31 V, 32 V, 33 V, 34 V, 35 V or a range value between any two of them. The electrode reverse direction adopts alternating current, and the welding current is 600 A to 650 A, including but not limited to any one of 605 A, 610 A, 615 A, 620 A, 625 A, 630 A, 635 A, 640 A, 645 A or a range value between any two of them, and the welding voltage is 34 V to 38 V, including but not limited to any one of 35 V, 36 V, 37 V or a range value between any two of them. With the above welding current and welding voltage, the low-temperature toughness and deslagging performance of the weld can be further improved, and the uniformity and morphology of the weld can be improved.

[0071] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. The specific conditions are not specified in the examples, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained by purchase.

[0072] Example 1

[0073] The calcium silicate type smelting flux provided in this example is composed of the following components in terms of mass percentage: CaF2 13% and CaSiO3 87%.

[0074] The preparation method of the calcium silicate type smelting flux provided in this example includes the following steps:

[0075] (1) Put 156 g of CaF2 and 1044 g of CaSiO3 into a mixing device and stir to mix uniformly; then place the uniformly mixed material in a graphite crucible, smelt at a temperature of 1500 °C for 35 min to obtain a smelted product; then water quench the smelted product to obtain a glassy mixed material.

[0076] (2) Place the glassy mixed material above into a muffle furnace and bake at 660 °C for 4 h to remove carbon powder and other impurities; then crush and sieve the product obtained after baking to obtain a calcium silicate type smelting flux with a particle size of 10-100 mesh (i.e. the particle size distribution range of the calcium silicate type smelting flux is within the range of 10-100 mesh).

[0077] Place the calcium silicate type smelting flux prepared in this embodiment 1 in a drying oven at a temperature of 300 °C and dry for 2 h, then use the dried calcium silicate type smelting flux to weld HSLA steel by the submerged arc welding method. The welding parameters are as follows: welding line energy is 60 kJ / cm, welding speed is 500 mm / min; electrode positive is direct current, and welding current is 850 A, welding voltage is 32 V; electrode reverse is alternating current, and welding current is 620 A, welding voltage is 36 V.

[0078] Embodiment 2

[0079] The calcium silicate type smelting flux provided in this embodiment is composed of the following components in terms of mass percentage: CaF2 15% and CaSiO3 85%.

[0080] The preparation method of the calcium silicate type smelting flux provided in this embodiment includes the following steps:

[0081] (1) Put 180 g of CaF2 and 1020 g of CaSiO3 into a mixing device and stir to mix uniformly; then place the uniformly mixed material in a graphite crucible, smelt at a temperature of 1510 °C for 38 min to obtain a smelted product; then water quench the smelted product to obtain a glassy mixed material.

[0082] (2) Place the glassy mixed material above into a muffle furnace and bake at 680 °C for 4 h to remove carbon powder and other impurities; then crush and sieve the product obtained after baking to obtain a calcium silicate type smelting flux with a particle size of 10-100 mesh.

[0083] The calcium silicate type smelting flux prepared in this embodiment 2 is dried in a drying oven at 350 ℃ for 2 h, and then is used to weld HSLA steel by using the submerged arc welding method. The welding parameters are as follows: the welding line energy is 57 kJ / cm, the welding speed is 480 mm / min; the electrode positive direction uses direct current, and the welding current is 840 A, and the welding voltage is 30 V; the electrode reverse direction uses alternating current, and the welding current is 600 A, and the welding voltage is 34 V.

[0084] Embodiment 3

[0085] The calcium silicate type smelting flux provided in this embodiment is composed of the following components in percentage by mass: CaF2 16% and CaSiO3 84%.

[0086] The preparation method of the calcium silicate type smelting flux provided in this embodiment comprises the following steps:

[0087] (1) 192 g of CaF2 and 1008 g of CaSiO3 are put into a mixing device for stirring to make them uniformly mixed; then the uniformly mixed mixture is placed in a graphite crucible, and is smelted at a temperature of 1520 ℃ for 40 min to obtain a smelting product; and then the smelting product is water quenched to obtain a glassy mixture.

[0088] (2) The glassy mixture is placed in a muffle furnace and calcined at 700 ℃ for 3.5 h to remove carbon powder and other impurities; then the product obtained after calcination is crushed and sieved to obtain a calcium silicate type smelting flux with a particle size of 10-100 mesh.

[0089] The calcium silicate type smelting flux prepared in this embodiment 3 is dried in a drying oven at 330 ℃ for 2.5 h, and then is used to weld HSLA steel by using the submerged arc welding method. The welding parameters are as follows: the welding line energy is 63 kJ / cm, the welding speed is 520 mm / min; the electrode positive direction uses direct current, and the welding current is 860 A, and the welding voltage is 35 V; the electrode reverse direction uses alternating current, and the welding current is 650 A, and the welding voltage is 38 V.

[0090] Embodiment 4

[0091] The calcium silicate type smelting flux provided in this embodiment is composed of the following components in percentage by mass: CaF2 16% and CaSiO3 84%.

[0092] The preparation method of the calcium silicate type smelting flux provided in this embodiment comprises the following steps:

[0093] (1) Put 216 g of CaF2 and 984 g of CaSiO3 into a mixing device and stir to mix uniformly; then place the uniformly mixed material in a graphite crucible, smelt at a temperature of 1530 °C for 40 min to obtain a smelted product; then water quench the smelted product to obtain a glassy mixed material.

[0094] (2) Place the glassy mixed material in a muffle furnace and bake at 750 °C for 4 h to remove carbon powder and other impurities; then crush and sieve the product obtained after baking to obtain a calcium silicate type smelting flux with a particle size of 10-100 mesh.

[0095] Place the calcium silicate type smelting flux prepared in this example 4 in a drying oven at a temperature of 290 °C for 3.5 h, then use the dried calcium silicate type smelting flux to weld HSLA steel by submerged arc welding. The welding parameters are as follows: welding line energy is 58 kJ / cm, welding speed is 490 mm / min; the electrode is positive direct current, and the welding current is 850 A, the welding voltage is 33 V; the electrode is negative alternating current, and the welding current is 630 A, the welding voltage is 35 V.

[0096] Example 5

[0097] The calcium silicate type smelting flux provided in this example is composed of the following components in terms of mass percentage: CaF2 20% and CaSiO3 80%.

[0098] The preparation method of the calcium silicate type smelting flux provided in this example includes the following steps:

[0099] (1) Put 240 g of CaF2 and 960 g of CaSiO3 into a mixing device and stir to mix uniformly; then place the uniformly mixed material in a graphite crucible, smelt at a temperature of 1550 °C for 40 min to obtain a smelted product; then water quench the smelted product to obtain a glassy mixed material.

[0100] (2) Place the glassy mixed material in a muffle furnace and bake at 800 °C for 4 h to remove carbon powder and other impurities in the smelting flux; then crush and sieve the product obtained after baking to obtain a calcium silicate type smelting flux with a particle size of 10-100 mesh.

[0101] The calcium silicate-type fused flux prepared in Example 5 was dried in a drying oven at 350°C for 2 hours. Then, HSLA steel was welded using submerged arc welding with the dried calcium silicate-type fused flux. The welding parameters were as follows: welding heat input of 60 kJ / cm, welding speed of 500 mm / min; direct current was used for the forward electrode, with a welding current of 850 A and a welding voltage of 32 V; alternating current was used for the reverse electrode, with a welding current of 625 A and a welding voltage of 36 V.

[0102] The macroscopic morphology of the weld obtained after welding in Example 5 is as follows: Figure 1 As shown, from Figure 1 It can be seen that the weld has a uniform composition, good surface morphology, and good slag removal properties after welding.

[0103] The macroscopic fracture morphology of the weld obtained after welding in Example 5 is as follows: Figure 2 As shown, and Figure 3 for Figure 2 The enlarged view within the dashed box is a microscopic fracture morphology diagram. From Figure 2 and Figure 3 It can be seen that the impact fracture morphology of the weld is ductile fracture, with small dimple diameter and high density, which can absorb a large amount of energy released during fracture, effectively preventing sudden fracture during use and avoiding various accidents.

[0104] Therefore, it can be seen that by using a specific amount of CaSiO3 and working synergistically with CaF2, the present invention has excellent arc stability and weld formation, stable welding process, uniform weld metal composition and structure, good surface morphology, and no defects such as porosity and cracks.

[0105] Example 6

[0106] The calcium silicate type fused flux provided in this embodiment is composed of the following components by mass percentage: 22% CaF2 and 78% CaSiO3.

[0107] The preparation method of calcium silicate type molten flux provided in this embodiment is basically the same as that in embodiment 5, except that: the raw materials in step (1) are 264g of CaF2 and 936g of CaSiO3, and the calcination temperature in step (2) is 750℃.

[0108] Using the calcium silicate type molten flux prepared in Example 6, HSLA steel was welded according to the drying method and parameters, as well as the welding method and parameters in Example 5.

[0109] Example 7

[0110] The calcium silicate type smelting flux provided in the embodiment is composed of the following components in percentage by mass: CaF2 24% and CaSiO3 76%.

[0111] The preparation method of the calcium silicate type smelting flux provided in the embodiment is basically the same as that in Embodiment 5, except that the raw materials in step (1) are 288 g of CaF2 and 912 g of CaSiO3.

[0112] The calcium silicate type smelting flux prepared in Embodiment 7 is used to weld HSLA steel according to the drying method and parameters and the welding method and parameters in Embodiment 5.

[0113] Comparative Example 1

[0114] The calcium silicate type smelting flux provided in the comparative example is composed of the following components in percentage by mass: CaF2 40% and CaSiO3 60%.

[0115] The preparation method of the calcium silicate type smelting flux provided in the comparative example is basically the same as that in Embodiment 5, except that the raw materials in step (1) are 480 g of CaF2 and 720 g of CaSiO3.

[0116] The calcium silicate type smelting flux prepared in Comparative Example 1 is used to weld HSLA steel according to the drying method and parameters and the welding method and parameters in Embodiment 5.

[0117] Comparative Example 2

[0118] The calcium silicate type smelting flux provided in the comparative example is composed of the following components in percentage by mass: CaF2 60% and CaSiO3 40%.

[0119] The preparation method of the calcium silicate type smelting flux provided in the comparative example is basically the same as that in Embodiment 5, except that the raw materials in step (1) are 720 g of CaF2 and 480 g of CaSiO3.

[0120] The calcium silicate type smelting flux prepared in Comparative Example 1 is used to weld HSLA steel according to the drying method and parameters and the welding method and parameters in Embodiment 5.

[0121] Comparative Example 3

[0122] The calcium silicate type smelting flux provided in the comparative example is composed of the following components in percentage by mass: CaF2 80% and CaSiO3 20%.

[0123] The preparation method of the calcium silicate type smelting flux provided in the comparative example is basically the same as that in Embodiment 5, except that the raw materials in step (1) are 960 g of CaF2 and 240 g of CaSiO3.

[0124] The calcium silicate type smelting flux prepared in the present comparative example 1 was used to weld HSLA steel according to the drying method and parameters, and the welding method and parameters of example 5.

[0125] Experimental example

[0126] The acicular ferrite content, inclusion number density, inclusion diameter <2 μm ratio (number ratio), and low temperature impact energy (-40℃) of the welded joints obtained after welding of each example and each comparative example were tested, and the test results are shown in Table 1 below.

[0127] The acicular ferrite content was measured by taking a sample of the welded joint under an OLYMPUS GX51 metallographic microscope at 200 times magnification, and using the intercept method.

[0128] The test method of inclusion number density is as follows: a sample of the welded joint was taken and photographed under 5000 times magnification using a TESCAN MIRA3 field emission scanning electron microscope.

[0129] The low temperature impact energy (-40℃) was tested in accordance with GB / T 2650-2008, and the instrument used was a SANS-ZBC2452-C impact testing machine.

[0130] Table 1 Performance test results of each welded joint

[0131]

[0132] As can be seen from Table 1, the low temperature toughness of the welded joints obtained from each example is good, especially the low temperature impact energy (-40℃) of example 5 is 65J, which is much greater than the national standard of 34J, and the acicular ferrite content is 68%.

[0133] The low temperature toughness of the welded joints obtained from each comparative example is poor, and the acicular ferrite content is low.

[0134] Further, pictures of the welded joints of example 5 and comparative example 1 after welding, and pictures after deslagging were taken respectively, and the results are shown in Figures 4-10 As can be seen from Table 1, the low temperature toughness of the welded joints obtained from each example is good, especially the low temperature impact energy (-40℃) of example 5 is 65J, which is much greater than the national standard of 34J, and the acicular ferrite content is 68%. Figure 4 is the picture of the welded joint of example 5 after deslagging. Figure 5 is the microstructure scanning electron microscope image of the weld obtained after welding of example 5. Figure 6 is the macroscopic morphology image of the weld after welding of comparative example 1. Figure 7 is the macroscopic fracture morphology image of the weld after welding of comparative example 1; Figure 8 is Figure 7 is the enlarged view in the dashed box, i.e. the micro-fracture morphology. Figure 9 is the picture of the welded joint of comparative example 1 after deslagging.Figure 10 Picture of the slag shell fallen from Comparative Example 1.

[0135] From Figure 4 It can be seen that the weld of Example 5 is defect-free, the slag shell has excellent protection effect on the weld, and the deslagging performance is good. Figure 5 It can be seen that the weld structure of Example 5 after welding is mainly cross-interlocking acicular ferrite structure, which takes inclusions as nucleation cores, and can effectively improve the low-temperature impact toughness of the weld.

[0136] From Figure 7 And Figure 8 It can be seen that the impact fracture morphology of the weld of Comparative Example 1 is brittle fracture, there are a large number of river pattern cleavage planes, and the impact performance is poor. Figure 9 And Figure 10 It can be seen that the slag shell of Comparative Example 1 is adhered to the surface of the welded joint, cannot be completely deslagged, and has many pores, that is, the deslagging performance of Comparative Example 1 is poor.

[0137] It can be seen that the calcium silicate type smelting flux provided by the present application is composed of CaSiO3 and CaF2 in a specific ratio, and the two components synergize with each other. On the one hand, the oxygen content in the obtained weld after welding tends to be rationalized, so that the weld has good low-temperature toughness and deslagging performance, has excellent arc stability and weld forming property, the welding process is stable, the composition and structure of the obtained weld metal after welding are uniform, the surface morphology is good, and there are no pores, cracks and other defects, so as to ensure that the weld has excellent mechanical properties. On the other hand, the P element content in the obtained weld after welding can be significantly reduced, so as to ensure that the weld has good mechanical properties, and in particular, the low-temperature impact toughness of the welded joint obtained after welding is good.

[0138] Although the present application has been illustrated and described with reference to specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limiting thereof; it should be understood by those skilled in the art that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and scope of the present application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; therefore, this means that all these replacements and modifications within the scope of the present application are included in the appended claims.

Claims

1. A calcium silicate type smelting flux, characterized in that, It is composed of the following components by mass percentage: CaF2 13%~25% and CaSiO3 75%~87%; The welded joint obtained by welding HSLA steel using the calcium silicate-type molten flux has a low-temperature impact energy of ≥53J at -40℃. The acicular ferrite content in the weld joint obtained by welding HSLA steel using the calcium silicate-type flux is ≥51%; The proportion of inclusions with a diameter <2μm in the weld joint obtained after welding HSLA steel using the calcium silicate type fusion flux is ≥82%.

2. A method for preparing the calcium silicate-type smelting flux according to claim 1, characterized in that, Includes the following steps: CaF2 and CaSiO3 are mixed and then smelted and water-quenched to obtain a glassy mixture. The glassy mixture is calcined, crushed, and sieved to obtain the calcium silicate type smelting flux.

3. The method for preparing calcium silicate-type smelting flux according to claim 2, characterized in that, The melting temperature is 1500℃~1550℃, and the melting time is 35min~50min.

4. The method for preparing calcium silicate-type smelting flux according to claim 2, characterized in that, The roasting temperature is 650℃~800℃, and the roasting time is 3.5h~4h.

5. The application of the calcium silicate-type flux of claim 1 in welding HSLA steel, characterized in that, The welding method includes submerged arc welding.

6. The application of the calcium silicate-type fusion flux according to claim 5 in welding HSLA steel, characterized in that, The welding line energy is 57kJ / cm~63kJ / cm, and the welding speed is 480mm / min~520mm / min.

7. The application of the calcium silicate-type smelting flux according to claim 5 in welding HSLA steel, characterized in that, During the welding process, direct current is used for the forward electrode, with a welding current of 840A~860A and a welding voltage of 30V~35V. Alternating current is used for the reverse electrode, with a welding current of 600A~650A and a welding voltage of 34V~38V.

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