1000MPa-grade high-strength steel welding rod for water and electricity as well as preparation method and application of high-strength steel welding rod

Abstract

The invention discloses a high-strength steel welding rod for 1000 MPa water and electricity and a preparation method and application of the high-strength steel welding rod. The invention belongs to the technical field of welding materials. The technical problems that the low-temperature impact toughness of an existing welding material for 1000 MPa-grade high-strength steel needs to be improved, and the welding cold crack sensitive index is too large are solved. The welding rod is composed of a core wire and a coating wrapping the surface of the core wire. Powder of the coating is formed by mixing marble, fluorite, rutile, silica powder, electrolytic manganese, ferrosilicon, graphite, ferromolybdenum, chromium metal, iron powder, nickel powder, sodium carbonate and sodium alginate. The welding rod has the advantages of good all-position welding process performance, stable electric arc, small flying speed, uniform coating melting, beautiful weld joint forming and good operability of welders. And weld metal has good mechanical properties. And the method is used for welding the high-strength steel for the 1000MPa-grade water

Description

Technical Field

[0001] The present invention belongs to the technical field of welding materials, and in particular relates to a 1000MPa-grade high-strength steel welding rod for hydropower, a preparation method and an application thereof. Background Art

[0002] With the development of hydropower industry, especially the construction of high-head power stations, 1000MPa high-strength steel will be used in forged and welded structures such as impact turbine volutes, water diversion pressure pipes, and bifurcated pipes in high-head, high-speed, high-efficiency, and large-capacity hydropower projects. The supporting welding technology will also be gradually widely used in the construction of hydropower projects. In various forged and welded structures of hydropower projects, the welding position is not limited to flat welding, but also vertical welding, horizontal welding, and overhead welding. Therefore, higher requirements are placed on the all-position welding performance of welding materials. In addition, due to the harsh construction environment of hydropower projects, there are also more stringent requirements on the diffusible hydrogen content of the electrode deposited metal and the moisture absorption resistance of the electrode coating.

[0003] At present, the welding materials used in 1000MPa grade high-strength steel welding generally have the problem that the impact toughness needs to be improved under low temperature (-60℃) conditions, and the welding cold crack sensitivity index is too large. Therefore, it is particularly necessary to develop a welding material with both excellent low-temperature impact toughness and low welding cold crack sensitivity index. Summary of the invention

[0004] The present invention provides a 1000MPa high-strength steel welding rod for hydropower, a preparation method and application thereof, in order to solve the technical problems that the low-temperature impact toughness of the current 1000MPa high-strength steel welding materials needs to be improved and the welding cold crack sensitivity index is too large.

[0005] One of the purposes of the present invention is to provide a 1000MPa grade high-strength steel welding rod for hydropower, the welding rod comprising a welding core and a coating coated on the surface of the welding core, the coating powder being a mixture of 35% to 45% marble, 15% to 20% fluorite, 4% to 8% rutile, 4% to 7% silicon micropowder, 4% to 6% electrolytic manganese, 3% to 6% ferrosilicon, 0.2% to 0.3% graphite, 1.5% to 3% ferromolybdenum, 2% to 4% metallic chromium, 5% to 7% iron powder, 7% to 10% nickel powder, 0.5% to 1% soda ash and 0.5% to 1% sodium alginate by mass fraction.

[0006] It is further defined that the chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

[0007] It is further defined that the welding core is H08E.

[0008] It is further defined that the coating powder is a mixture of 35% marble, 20% fluorite, 6% rutile, 7% silicon micropowder, 5% electrolytic manganese, 4.7% ferrosilicon, 0.3% graphite, 2% ferromolybdenum, 2% metallic chromium, 7% iron powder, 10% nickel powder, 0.5% soda ash and 0.5% sodium alginate by mass fraction.

[0009] It is further defined that the coating powder is a mixture of 40% marble, 18% fluorite, 8% rutile, 5.5% silicon micropowder, 6% electrolytic manganese, 3% ferrosilicon, 0.2% graphite, 1.5% ferromolybdenum, 3% metallic chromium, 6% iron powder, 7% nickel powder, 0.8% soda ash and 1% sodium alginate by mass fraction.

[0010] It is further defined that the coating powder is a mixture of 45% marble, 15% fluorite, 4% rutile, 4% silicon micropowder, 4% electrolytic manganese, 6% ferrosilicon, 0.2% graphite, 3% ferromolybdenum, 4% metallic chromium, 5% iron powder, 8% nickel powder, 1% soda ash and 0.8% sodium alginate by mass fraction.

[0011] The second object of the present invention is to provide a method for preparing a 1000MPa grade high-strength steel welding rod for hydropower, the method being carried out according to the following steps:

[0012] Step 1: subjecting fluorite, rutile and silicon powder to high temperature baking treatment;

[0013] Step 2: Sieve the powders and mix them evenly, then add the binder, continue mixing, and then press-coat and coat the binder on the welding core;

[0014] Step 3: Dry the coated welding rod at low temperature first, and then at high temperature to obtain 1000MPa grade high-strength steel welding rod for hydropower.

[0015] It is further defined that the high temperature baking temperature in step 1 is 800-900°C.

[0016] It is further defined that the binder in step 2 is potassium-sodium water glass with a potassium-sodium ratio of 3:1, a modulus of 2.8-2.85M, a concentration of 44.5-45.5°Be', and an addition amount of 15-25% of the mass of the coating powder.

[0017] It is further defined that the coating pressure in step 2 is 10 to 16 MPa.

[0018] It is further defined that in step 3, the low-temperature drying temperature is 130-150° C., the time is 2-4 hours, and the high-temperature drying temperature is 350-380° C., the time is 1-3 hours.

[0019] The third object of the present invention is to provide an application of the above-mentioned welding rod in welding 1000MPa grade high-strength steel for hydropower.

[0020] The fourth object of the present invention is to provide a deposited metal obtained by the above-mentioned application, wherein the deposited metal has a tensile strength ≥950MPa, a yield strength ≥870MPa, an impact absorption energy at -40°C ≥60J, an impact absorption energy at -60°C ≥47J, and a cold crack sensitivity index Pcm<0.3.

[0021] The advantages of the present invention compared to the prior art are:

[0022] The functions of each component in the present invention are as follows:

[0023] Marble, the main component of which is CaCO3, decomposes into CaO and CO2 gas under the action of arc heat during the use of welding rods, playing the role of slag and gasification. CaO is an alkaline oxide, which can increase the basicity of slag, increase the surface tension of slag, and improve the slag removal performance. Too high a content will make slag removal difficult, and due to the increase in melting point, the welding rod coating will melt unevenly, resulting in unstable arc; too low a content will result in insufficient arc blowing force, poor protection, and unstable arc. In the present invention, the marble is controlled at 35% to 45%.

[0024] Fluorite, the main component of which is CaF2, can improve the viscosity and fluidity of the slag and increase dehydrogenation; when the content is too high, the slag is too thin and the coverage is deteriorated; when the content is too low, the slag viscosity is too high, resulting in deterioration of the weld bead forming. The present invention controls the fluorite to 15% to 20%.

[0025] Rutile mainly plays the role of arc stabilization and slag formation, and can adjust the melting point, viscosity and fluidity of slag, improve molding and reduce splashing. In the present invention, the rutile content is controlled at 4% to 8%.

[0026] Ferrosilicon is mainly used as a deoxidizer and also added as an alloy. An appropriate amount of silicon can reduce the oxygen content of the weld metal and improve the impact toughness of the weld metal, but too high a content will reduce the impact toughness. The present invention controls the ferrosilicon content to 3% to 6%.

[0027] Electrolytic manganese plays a role in desulfurization, and plays a role in combined deoxidation with ferrosilicon, transition welding seam alloy, and improve welding seam strength. The present invention controls the electrolytic manganese to 4% to 6%.

[0028] The addition of nickel powder and ferromolybdenum is mainly to transition alloy elements into the weld. The addition of Ni is beneficial to improving the impact toughness of the weld metal, and the addition of Mo is beneficial to improving the strength of the weld metal.

[0029] Soda ash and sodium alginate can increase the plasticity and smoothness of the coating and improve the coating properties of the electrode. At the same time, potassium alginate can be immediately ashed during the welding process, which can reduce spatter and increase arc stability.

[0030] The present invention pre-bakes fluorite, rutile, silicon powder and other powders at high temperature before powder mixing, so as to further reduce the content of diffusible hydrogen in the weld.

[0031] The present invention adds marble, fluorite, rutile and silicon powder to the coating components, and adjusts the proportion of each component to ensure that the welding rod obtains excellent welding process performance, adds ferrosilicon, electrolytic manganese, graphite, ferromolybdenum, nickel powder and other components to ensure that the welding rod obtains excellent mechanical properties, and adds soda ash, sodium alginate and other components to improve the pressure coating performance of the welding rod.

[0032] The welding rod of the present invention has good all-position welding process performance, stable arc, small splash, uniform coating melting, beautiful weld formation, good welder operability. The weld metal has good mechanical properties, tensile strength ≥950MPa, yield strength ≥870MPa, elongation ≥14%, -40℃ impact absorption energy ≥47J. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0035] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0036] When equivalent, concentration or other value or parameter is represented by the range limited by range, preferred range or a series of upper preferred value and lower preferred value, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the scope is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the scope is intended to include its end value and all integers and fractions within the scope. In the present application specification and claims, range limitation can be combined and / or interchanged, if these ranges are not otherwise stated, include all sub-ranges contained therein.

[0037] The indefinite articles "a" and "an" before the elements or components of the present invention have no limitation on the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity obviously refers to the singular form only.

[0038] The "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure or characteristic that can be included in at least one implementation of the present invention. The "in one embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0039] The endpoints and any values ​​of the ranges disclosed in the invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

[0040] Embodiment 1:

[0041] The 1000MPa grade high-strength steel welding rod for hydropower in this embodiment is composed of a welding core and a coating wrapped on the surface of the welding core;

[0042] The coating powder is prepared by mixing 35% of marble, 20% of fluorite, 6% of rutile, 7% of silicon micropowder, 5% of electrolytic manganese, 4.7% of ferrosilicon, 0.3% of graphite, 2% of ferromolybdenum, 2% of metallic chromium, 7% of iron powder, 10% of nickel powder, 0.5% of soda ash and 0.5% of sodium alginate by mass fraction.

[0043] The welding core is H08E welding core, and the chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

[0044] The preparation method of the welding rod is carried out according to the following steps:

[0045] Step 1: bake fluorite, rutile and silica powder at 850°C for 120 minutes;

[0046] Step 2: Sieve and mix the powders to obtain coating powders, then add 20% of the total mass of the coating powders with potassium-sodium water glass (potassium-sodium ratio of 3:1, modulus of 2.8M, concentration of 45°Be'), continue to mix, and then, pressure-coat and coat the coating on the welding core at a pressure of 12-15MPa;

[0047] Step 3: First, dry the pressed electrode at 150°C for 3 hours, and then dry it at 380°C for 2 hours to obtain a 1000MPa grade high-strength steel electrode for hydropower.

[0048] The welding rod prepared by the above process has stable arc, small splash, uniform melting of the coating, beautiful weld formation and good welder operability.

[0049] Embodiment 2:

[0050] The 1000MPa grade high-strength steel welding rod for hydropower in this embodiment is composed of a welding core and a coating wrapped on the surface of the welding core;

[0051] The coating powder is prepared by mixing 40% of marble, 18% of fluorite, 8% of rutile, 5.5% of silicon micropowder, 6% of electrolytic manganese, 3% of ferrosilicon, 0.2% of graphite, 1.5% of ferromolybdenum, 3% of metallic chromium, 6% of iron powder, 7% of nickel powder, 0.8% of soda ash and 1% of sodium alginate by mass fraction.

[0052] The welding core is H08E welding core, and the chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

[0053] The preparation method of the welding rod is carried out according to the following steps:

[0054] Step 1: bake fluorite, rutile and silica powder at 850°C for 120 minutes;

[0055] Step 2: Sieve and mix the powders to obtain coating powders, then add 20% of the total mass of the coating powders with potassium-sodium water glass (potassium-sodium ratio of 3:1, modulus of 2.8M, concentration of 45°Be'), continue to mix, and then, pressure-coat and coat the coating on the welding core at a pressure of 12-15MPa;

[0056] Step 3: First, dry the pressed electrode at 150°C for 3 hours, and then dry it at 380°C for 2 hours to obtain a 1000MPa grade high-strength steel electrode for hydropower.

[0057] The welding rod prepared by the above process has stable arc, small splash, uniform melting of the coating, beautiful weld formation and good welder operability.

[0058] Embodiment 3:

[0059] The 1000MPa grade high-strength steel welding rod for hydropower in this embodiment is composed of a welding core and a coating wrapped on the surface of the welding core;

[0060] The coating powder is prepared by mixing 45% of marble, 15% of fluorite, 4% of rutile, 4% of silicon micropowder, 4% of electrolytic manganese, 6% of ferrosilicon, 0.2% of graphite, 3% of ferromolybdenum, 4% of metallic chromium, 5% of iron powder, 8% of nickel powder, 1% of soda ash and 0.8% of sodium alginate by mass fraction.

[0061] The welding core is H08E welding core, and the chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

[0062] The preparation method of the welding rod is carried out according to the following steps:

[0063] Step 1: bake fluorite, rutile and silica powder at 850°C for 120 minutes;

[0064] Step 2: Sieve and mix the powders to obtain coating powders, then add 20% of the total mass of the coating powders with potassium-sodium water glass (potassium-sodium ratio of 3:1, modulus of 2.8M, concentration of 45°Be'), continue to mix, and then, pressure-coat and coat the coating on the welding core at a pressure of 12-15MPa;

[0065] Step 3: First, dry the pressed electrode at 150°C for 3 hours, and then dry it at 380°C for 2 hours to obtain a 1000MPa grade high-strength steel electrode for hydropower.

[0066] The welding rod prepared by the above process has stable arc, small splash, uniform melting of the coating, beautiful weld formation and good welder operability.

[0067] Comparative Example 1:

[0068] The welding rod of this comparative example is composed of a welding core and a coating wrapped on the surface of the welding core;

[0069] The coating powder is prepared by mixing 45% of marble, 17% of fluorite, 4% of rutile, 4% of silicon micropowder, 6% of electrolytic manganese, 5% of ferrosilicon, 0.2% of graphite, 3% of ferromolybdenum, 4% of metallic chromium, 5% of iron powder, 5% of nickel powder, 1% of soda ash and 0.8% of sodium alginate by mass fraction.

[0070] The welding core is H08E welding core, and the chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

[0071] The preparation method of the welding rod is carried out according to the following steps:

[0072] Step 1: bake fluorite, rutile and silica powder at 850°C for 120 minutes;

[0073] Step 2: Sieve and mix the powders to obtain coating powders, then add 20% of the total mass of the coating powders with potassium-sodium water glass (potassium-sodium ratio of 3:1, modulus of 2.8M, concentration of 45°Be'), continue to mix, and then, pressure-coat and coat the coating on the welding core at a pressure of 12-15MPa;

[0074] Step 3: First, dry the pressed electrode at 150°C for 3 hours, and then dry it at 380°C for 2 hours to obtain the electrode.

[0075] Comparative Example 2:

[0076] The welding rod of this comparative example is composed of a welding core and a coating wrapped on the surface of the welding core;

[0077] The coating powder is prepared by mixing 40% of marble, 15% of fluorite, 4% of rutile, 4% of silicon micropowder, 6% of electrolytic manganese, 5% of ferrosilicon, 0.2% of graphite, 3% of ferromolybdenum, 4% of metallic chromium, 3% of iron powder, 14% of nickel powder, 1% of soda ash and 0.8% of sodium alginate by mass fraction.

[0078] The welding core is H08E welding core, and the chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

[0079] The preparation method of the welding rod is carried out according to the following steps:

[0080] Step 1: bake fluorite, rutile and silica powder at 850°C for 120 minutes;

[0081] Step 2: Sieve and mix the powders to obtain coating powders, then add 20% of the total mass of the coating powders with potassium-sodium water glass (potassium-sodium ratio of 3:1, modulus of 2.8M, concentration of 45°Be'), continue to mix, and then, pressure-coat and coat the coating on the welding core at a pressure of 12-15MPa;

[0082] Step 3: First, dry the pressed electrode at 150°C for 3 hours, and then dry it at 380°C for 2 hours to obtain the electrode.

[0083] The above embodiments and comparative examples are used in conjunction with 1000MPa grade high-strength steel for hydropower, and the welding process parameters of the deposited metal test plate are shown in Table 1, the chemical composition of the deposited metal is shown in Table 2, and the mechanical properties of the weld metal are shown in Table 3. The cold crack sensitivity index Pcm is calculated according to the following formula.

[0084]

[0085] Table 1 Welding process parameters

[0086]

[0087] Table 2 Chemical composition of deposited metal (wt%)

[0088] Serial number C Si Mn S P Cr Ni Mo Cu V B Pc Example 1 0.070 0.22 1.42 0.003 0.007 0.60 3.35 0.52 0.02 0.01 0.001 0.276 Example 2 0.063 0.17 1.58 0.003 0.006 0.73 2.98 0.47 0.02 0.01 0.001 0.272 Example 3 0.060 0.26 1.33 0.003 0.007 0.98 3.17 0.65 0.03 0.01 0.001 0.287 Comparative Example 1 0.061 0.20 1.55 0.003 0.006 0.95 2.54 0.61 0.02 0.01 0.001 0.283 Comparative Example 2 0.061 0.19 1.50 0.003 0.007 0.92 4.38 0.60 0.03 0.01 0.001 0.309

[0089] Table 3 Mechanical properties of weld metal

[0090]

[0091]

[0092] The Ni content of comparative example 1 is too low, and the impact toughness does not meet the assessment requirements. The Ni content of comparative example 2 is too high, and the elongation does not meet the assessment requirements, and the cold crack sensitivity index is >0.3.

[0093] It can be concluded from the above-mentioned Examples 1-3 and Comparative Examples 1-2 that the welding rod for 1000MPa high-strength steel for hydropower according to the present invention has a tensile strength that meets the requirements of ≥950MPa, a yield strength that meets the requirements of ≥870MPa, and an elongation that meets the requirements of ≥14%. At the same time, it has good impact toughness at -40°C and -60°C, and a cold crack sensitivity index of <0.3, and is suitable for welding 1000MPa high-strength steel for hydropower.

[0094] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A 1000MPa grade high-strength steel welding rod for hydropower, characterized in that: The welding rod consists of a welding core and a coating wrapped on the surface of the welding core. The coating powder is mixed by mass fraction with 35% to 45% of marble, 15% to 20% of fluorite, 4% to 8% of rutile, 4% to 7% of silicon micropowder, 4% to 6% of electrolytic manganese, 3% to 6% of ferrosilicon, 0.2% to 0.3% of graphite, 1.5% to 3% of ferromolybdenum, 2% to 4% of metallic chromium, 5% to 7% of iron powder, 7% to 10% of nickel powder, 0.5% to 1% of soda ash and 0.5% to 1% of sodium alginate.

2. The welding rod according to claim 1, characterized in that The chemical composition and mass percentage of the welding core are C≤0.06%, Si≤0.15%, Mn≤0.55%, S≤0.006%, P≤0.012% and the balance Fe.

3. The welding rod according to claim 1, characterized in that The coating powder is prepared by mixing 35% of marble, 20% of fluorite, 6% of rutile, 7% of silicon micropowder, 5% of electrolytic manganese, 4.7% of ferrosilicon, 0.3% of graphite, 2% of ferromolybdenum, 2% of metallic chromium, 7% of iron powder, 10% of nickel powder, 0.5% of soda ash and 0.5% of sodium alginate by mass fraction.

4. The welding rod according to claim 1, characterized in that The coating powder is prepared by mixing 40% of marble, 18% of fluorite, 8% of rutile, 5.5% of silicon micropowder, 6% of electrolytic manganese, 3% of ferrosilicon, 0.2% of graphite, 1.5% of ferromolybdenum, 3% of metallic chromium, 6% of iron powder, 7% of nickel powder, 0.8% of soda ash and 1% of sodium alginate by mass fraction.

5. The welding rod according to claim 1, characterized in that The coating powder is prepared by mixing 45% of marble, 15% of fluorite, 4% of rutile, 4% of silicon micropowder, 4% of electrolytic manganese, 6% of ferrosilicon, 0.2% of graphite, 3% of ferromolybdenum, 4% of metallic chromium, 5% of iron powder, 8% of nickel powder, 1% of soda ash and 0.8% of sodium alginate by mass fraction.

6. The method for preparing the welding rod according to any one of claims 1 to 5, characterized in that: The method: Step 1: subjecting fluorite, rutile and silicon powder to high temperature baking treatment; Step 2: Sieve the powders and mix them evenly, then add the binder, continue mixing, and then press-coat and coat the binder on the welding core; Step 3: Dry the coated welding rod at low temperature first, and then at high temperature to obtain 1000MPa grade high-strength steel welding rod for hydropower.

7. The method according to claim 6, characterized in that The high temperature baking temperature in step 1 is 800-900°C.

8. The method according to claim 6, characterized in that In step 3, the low-temperature drying temperature is 130-150° C., the time is 2-4 hours, and the high-temperature drying temperature is 350-380° C., the time is 1-3 hours.

9. Use of the welding rod according to any one of claims 1 to 5 in welding 1000MPa grade high-strength steel for hydropower.

10. The deposited metal obtained by the application of claim 9, characterized in that: The deposited metal has a tensile strength of ≥950MPa, a yield strength of ≥870MPa, an impact absorption energy of -40°C of ≥60J, an impact absorption energy of -60°C of ≥47J, and a cold crack sensitivity index Pcm<0.3.

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