Flux-Cored Welding Strip and Welding Flux Used in Combination for Submerged Arc Welding of Duplex Stainless Steel, and Preparation Methods and Use Thereof

Abstract

Disclosed are a flux-cored welding strip and a welding flux used in combination for submerged arc welding of a duplex stainless steel, and preparation methods and use thereof. The flux-cored welding strip is composed of a stainless steel shell and a flux core powder, the flux core powder consisting of the following components: in percentages by mass, ferrochrome nitride: 0.70% to 1.0%, a chromium powder: 26% to 27%, a nickel powder: 4.5% to 5.5%, a molybdenum powder: 3.7% to 4.2%, a manganese powder: 2.55% to 2.65%, a copper powder: 1.45% to 1.55%, a ferrosilicon powder: 1.1% to 1.2%, a tungsten powder: 1.0% to 1.15%, a niobium powder: 0.25% to 0.35%, an aluminum powder: 0.35% to 0.55%, a rhenium powder: 0.35% to 0.40%, a lanthanum powder: 0.1% to 0.15%, and a balance being an iron powder.

Claims

1. A flux-cored welding strip and a welding flux used in combination for submerged arc welding of a duplex stainless steel, wherein the flux-cored welding strip is composed of a stainless steel shell and a flux core powder, the flux core powder consisting of the following components: in percentages by mass, ferrochrome nitride: 0.70% to 1.0%, a chromium powder: 26% to 27%, a nickel powder: 4.5% to 5.5%, a molybdenum powder: 3.7% to 4.2%, a manganese powder: 2.55% to 2.65%, a copper powder: 1.45% to 1.55%, a ferrosilicon powder: 1.1% to 1.2%, a tungsten powder: 1.0% to 1.15%, a niobium powder: 0.25% to 0.35%, an aluminum powder: 0.35% to 0.55%, a rhenium powder: 0.35% to 0.40%, a lanthanum powder: 0.1% to 0.15%, and a balance being an iron powder; and the welding flux consists of the following components: in percentages by mass, bauxite: 20% to 25%, a clay: 5% to 10%, a zircon sand: 10% to 15%, a magnesite clinker: 10% to 15%, fluorite: 25% to 30%, an alloying agent: 1.5% to 2%, and a balance being chromium oxide green.

2. The flux-cored welding strip and the welding flux used in combination for submerged arc welding of the duplex stainless steel as claimed in claim 1, wherein the stainless steel shell is an S32750 duplex stainless steel strip, has a thickness of 0.5 mm to 0.6 mm, and consists of: in percentages by mass, Cr: 24.0% to 26.0%, Ni: 6.0% to 8.0%, Mo: 3.0% to 5.0%, Mn: less than or equal to 1.2%, C: less than or equal to 0.03%, Si: less than or equal to 0.8%, Cu: less than or equal to 0.50%, N: 0.24% to 0.32%, S: less than or equal to 0.02%, P: less than or equal to 0.035%, and a balance being Fe.

3. A method for preparing the flux-cored welding strip and the welding flux used in combination for submerged arc welding of the duplex stainless steel as claimed in claim 1, wherein the flux-cored welding strip is prepared by a process comprising the following steps: step 1: pickling the stainless steel shell to obtain a pickled stainless steel shell; step 2: mixing powders of raw materials for the flux core powder for 1 h to 2 h under argon protection to obtain a mixed powder, and oven-drying the mixed powder to obtain the flux core powder; and step 3: bending the pickled stainless steel shell for shaping, loading the flux core powder therein, and rolling, to obtain the flux-cored welding strip for submerged arc welding of the duplex stainless steel.

4. The method as claimed in claim 3, wherein in step 1, a solution for the pickling is an aqueous solution of 30 vol % H.sub.2SO.sub.4+17 vol % HNO.sub.3+4.5 vol % HF.

5. The method as claimed in claim 3, wherein in step 2, the oven-drying is conducted at a temperature of 100 C. to 150 C. for 0.5 h to 1 h.

6. The flux-cored welding strip and the welding flux used in combination for submerged arc welding of the duplex stainless steel as claimed in claim 1, wherein the alloying agent in the welding flux is a WNbAlReLa alloy that comprises: W: 0.3% to 0.4%, Nb: 0.3% to 0.4%, Al: 0.3% to 0.4%, Re: 0.3% to 0.4%, and La: 0.3% to 0.4%.

7. A method for preparing the flux-cored welding strip and the welding flux used in combination for submerged arc welding of the duplex stainless steel as claimed in claim 1, wherein the welding flux is prepared by a process as follows: preliminarily screening raw materials for the welding flux, then mixing by stirring, oven-drying a resulting mixture at a low temperature, adding water glass thereto, and further stirring; and granulating a resulting wet material to obtain particles for forming the welding flux, and oven-drying and sintering the particles, to obtain the welding flux for submerged arc welding of a high-manganese low-nickel duplex stainless steel.

8. The method as claimed in claim 7, wherein the sintering is conducted at a temperature of 700 C. to 800 C.

9. Use of the flux-cored welding strip and the welding flux used in combination for submerged arc welding of the duplex stainless steel as claimed in claim 1, wherein the flux-cored welding strip and the welding flux are used in combination to conduct strip submerged arc cladding welding; and a deposited metal of a cladding layer after welding consists of the following chemical components: in percentages by mass, C: 0.15% to 0.25%, N: 0.30% to 0.50%, Cr: 26.0% to 27.0%, Ni: 4.0% to 5.0%, Mo: 3.5% to 4.0%, Mn: 2.45% to 2.55%, Cu: 1.4% to 1.5%, Si: 0.95% to 1.05%, W: 0.9% to 1.1%, Nb: 0.2% to 0.3%, Al: 0.3% to 0.5%, Re: 0.25% to 0.35%, La: 0.05% to 0.10%, S: less than or equal to 0.02%, P: less than or equal to 0.03%, and a balance being Fe.

10. The method as claimed in claim 3, wherein the stainless steel shell is an S32750 duplex stainless steel strip, has a thickness of 0.5 mm to 0.6 mm, and consists of: in percentages by mass, Cr: 24.0% to 26.0%, Ni: 6.0% to 8.0%, Mo: 3.0% to 5.0%, Mn: less than or equal to 1.2%, C: less than or equal to 0.03%, Si: less than or equal to 0.8%, Cu: less than or equal to 0.50%, N: 0.24% to 0.32%, S: less than or equal to 0.02%, P: less than or equal to 0.035%, and a balance being Fe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To describe the technical solutions in the embodiments of the present disclosure or in the prior art more clearly, the accompanying drawings required for the embodiments are briefly described below. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and those of ordinary skill in the art may still derive other accompanying drawings from these accompanying drawings without creative efforts.

[0034] FIG. 1 is a macroscopic morphology image of the cladding deposited layer obtained in Example 1.

[0035] FIG. 2 is a microscopic morphology image of the cladding deposited layer obtained in Example 1.

[0036] FIG. 3 is a macroscopic morphology image of the cladding deposited layer obtained in Example 2.

[0037] FIG. 4 is a microscopic morphology image of the cladding deposited layer obtained in Example 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To make the objects, technical solutions, and advantages of the present disclosure clearer and understandable, the present disclosure will be further described below in detail in conjunction with examples. It should be understood that the specific examples described herein are intended merely to explain the present disclosure, rather than to limit the present disclosure.

[0039] All experimental methods used in the following examples are conventional methods, unless otherwise specified. The materials, reagents, methods, and instruments used all are conventional materials, reagents, methods, and instruments in the art unless otherwise specified, and could be acquired by those skilled in the art through commercial channels.

[0040] The terms include, comprise, have, including, or any other variations thereof used in the following examples refer to non-exclusive inclusion. For example, a composition, step, method, article, or device including listed elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent elements in such a composition, step, method, article, or device.

[0041] In the text, term duplex stainless steel refers to a stainless steel that has a duplex structure of ferrite and austenite.

[0042] Particularly, the present disclosure provides use of the flux-cored welding strip and the welding flux used in combination for strip submerged arc cladding welding. The process parameters could be set according to conventional strip submerged arc cladding welding processes. In some embodiments, the use includes [0043] covering a surface of a base material with the welding flux as described above; [0044] inserting the flux-cored welding strip as described above as an electrode into the welding flux, and generating an arc between the base material and the electrode after powering; and [0045] in the action of arc heat, simultaneously melting the flux-cored welding strip and the welding flux, and then cooling, thereby forming a deposited metal.

[0046] When an amount, concentration, or other value or parameter is expressed in a range, a preferred range, or a range defined by a series of upper and lower preferred values, it should be understood that all ranges formed by any pair of an upper limit or preferred value of any range with a lower limit or preferred value of any range are specifically disclosed, regardless of whether the ranges are independently disclosed. For example, when a range of 1 to 5 is disclosed, the described range should be interpreted as including the ranges of 1 to 4, 1 to 3, 1 to 2, 1 to 2 and 4 to 5, 1 to 3 and 5, or the like. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range. In the description and claims of the present disclosure, these ranges may be combined and/or interchangeable, and unless otherwise stated, these ranges include all sub-ranges included in these ranges.

[0047] Indefinite articles a and an before an element or component of the present disclosure have no restriction on a quantity (namely, an occurrence frequency) of the elements or components. Therefore, a or an shall be construed to include one or at least one, and an element or a component in a singular form also includes a plural form, unless it clearly refers merely to a singular form.

Example 1

[0048] In this example, a flux-cored welding strip for submerged arc welding of a duplex stainless steel was provided, consisting of a stainless steel shell and a flux core powder, wherein the flux core powder was composed of the following components: in percentages by mass, ferrochrome nitride: 0.70%, a chromium powder: 26%, a nickel powder: 4.5%, a molybdenum powder: 3.7%, a manganese powder: 2.55%, a copper powder: 1.45%, a ferrosilicon powder: 1.1%, a tungsten powder: 1.0%, a niobium powder: 0.25%, an aluminum powder: 0.35%, a rhenium powder: 0.35%, a lanthanum powder: 0.1%, and the balance being an iron powder.

[0049] The stainless steel shell was an S32750 duplex stainless steel strip, had a thickness of 0.5 mm, and was composed of the following elements: in percentages by mass, Cr: 24%, Ni: 6.0%, Mo: 3.0%, Mn: 1.0%, C: 0.15%, Si: 0.6%, Cu: 0.30%, N: 0.24%, S: 0.01%, P: 0.03%, and a balance being Fe.

[0050] The chromium powder, the nickel powder, the molybdenum powder, the manganese powder, the copper powder, and the iron powder each have a granularity of 100 mesh, and the ferrochrome nitride, the ferrosilicon powder, the tungsten powder, the niobium powder, the aluminum powder, the rhenium powder, and the lanthanum powder each have a granularity of 50 mesh.

[0051] The flux-cored welding strip for submerged arc welding of a duplex stainless steel was prepared according to the following procedures:

[0052] Step 1: the stainless steel shell was pickled with an aqueous solution of 30 vol % H.sub.2SO.sub.4+17 vol % HNO.sub.3+4.5 vol % HF, obtaining a pickled stainless steel shell.

[0053] Step 2: powders of raw materials for the flux-cored welding strip were mixed for 1 h under argon protection, and then oven-dried at 100 C. for 0.5 h, obtaining the flux core powder.

[0054] Step 3: the pickled stainless steel shell was bent for shaping, the flux core powder was loaded therein, and rolling was then conducted, obtaining the flux-cored welding strip with a width of 29.5 mm and a thickness of 1.5 mm for submerged arc welding of a duplex stainless steel.

[0055] A welding flux used in combination with the flux-cored welding strip for submerged arc welding of a duplex stainless steel was provided, being composed of the following components: in percentages by mass, bauxite: 20%, a clay: 5%, a zircon sand: 10%, a magnesite clinker: 10%, fluorite: 25%, an alloying agent: 1.7%, and the balance being chromium oxide green, wherein the alloying agent was a WNbAlReLa alloy that included: W: 0.3%, Nb: 0.4%, Al: 0.3%, Re: 0.4%, and La: 0.3%.

[0056] The welding flux was prepared according to the following procedures:

[0057] Firstly, powders of above raw materials for the welding flux were preliminarily screened separately to obtain those having a granularity of 30 mesh, and then mixed by stirring. The resulting mixture was oven-dried at 150 C. for 30 min, obtaining a dry material.

[0058] Secondly, water glass was added to the dry material, and the resulting mixture was further stirred, obtaining a wet material.

[0059] Thirdly, the wet material was granulated, obtaining welding flux particles, and the welding flux particles were oven-dried at 150 C. and then sintered at 700 C. for 40 min, obtaining the welding flux for submerged arc welding of a duplex stainless steel.

[0060] Use Example 1: The flux-cored welding strip for submerged arc welding of a duplex stainless steel and the welding flux for submerged arc welding of a duplex stainless steel in Example 1 were used in combination for strip submerged arc cladding welding with welding process parameters shown in Table 1.

TABLE-US-00001 TABLE 1 Welding process parameters Cladding Cladding Cladding speed/mm/ Interpass Power polarity current/A voltage/V min temperature/ C. Direct current 800 32 300 150 reverse polarity

[0061] Results: A deposited metal of a cladding layer formed after cladding had the following chemical components: in percentages by mass, C: 0.15%, N: 0.30%, Cr: 26%, Ni: 4.0%, Mo: 3.5%, Mn: 2.45%, Cu: 1.4%, Si: 0.95%, W: 0.9%, Nb: 0.2%, Al: 0.3%, Re: 0.25%, La: 0.05%, S: 0.015%, P: 0.02%, and the balance being Fe.

[0062] A macroscopic morphology of the cladding deposited layer is shown in FIG. 1, a microscopic morphology of the cladding deposited layer is shown in FIG. 2, and stress-corrosion resistance of the deposited metal is shown in Table 2.

TABLE-US-00002 TABLE 2 Stress-corrosion resistance of the deposited metal Tensile Yield strength, strength, Corrosive environment Rp0.2/MPa Rm/MPa Example 1 0.1 mol/L S.sub.2O.sub.3.sup.2 + 20 wt % 720 850 NaCl, pH = 4

[0063] It can be seen from FIG. 1 that the cladding layer is beautifully formed, and has no defects such as pores, cracks, incomplete fusion, and oxidation. It can be seen from FIG. 2 that a ferrite and an austenite are distributed in equal proportions, and weld seam grains are significantly refined.

Example 2

[0064] In this example, a flux-cored welding strip for submerged arc welding of a duplex stainless steel was provided, consisting of a stainless steel shell and a flux core powder, wherein the flux core powder was composed of the following components: in percentages by mass, ferrochrome nitride: 1.0%, a chromium powder: 27%, a nickel powder: 5.5%, a molybdenum powder: 4.2%, a manganese powder: 2.65%, a copper powder: 1.55%, a silicon powder: 1.2%, a tungsten powder: 1.15%, a niobium powder: 0.35%, an aluminum powder: 0.50%, a rhenium powder: 0.40%, a lanthanum powder: 0.15%, and the balance being an iron powder.

[0065] The stainless steel shell was an S32750 duplex stainless steel strip, had a thickness of 0.6 mm, and was composed of the following elements: in percentages by mass, Cr: 26%, Ni: 8.0%, Mo: 5.0%, Mn: 0.8%, C: 0.015%, Si: 0.75%, Cu: 0.45%, N: 0.32%, S: 0.01%, P: 0.02%, and the balance being Fe.

[0066] The chromium powder, the nickel powder, the molybdenum powder, the manganese powder, the copper powder, and the iron powder each have an average granularity of 120 mesh; and the ferrochrome nitride, the ferrosilicon powder, the tungsten powder, the niobium powder, the aluminum powder, the rhenium powder, and the lanthanum powder each have an average granularity of 60 mesh.

[0067] The flux-cored welding strip for submerged arc welding of a duplex stainless steel was prepared according to the following procedures:

[0068] Step 1: the stainless steel shell was pickled with an aqueous solution of 30 vol % H.sub.2SO.sub.4+17 vol % HNO.sub.4+4.5 vol % HF, obtaining a pickled stainless steel shell.

[0069] Step 2: powders of raw materials for the flux-cored welding strip were mixed for 2 h under argon protection, and then oven-dried at 150 C. for 1 h, obtaining the flux core powder.

[0070] Step 3: the pickled stainless steel shell was bent for shaping, the flux core powder was loaded, and rolling was then conducted, obtaining the flux-cored welding strip with a width of 30.5 mm and a thickness of 2 mm.

[0071] A welding flux used in combination with the flux-cored welding strip for submerged arc welding of a duplex stainless steel was provided, having the following components: in percentages by mass, bauxite: 25%, a clay: 10%, a zircon sand: 15%, a magnesite clinker: 15%, fluorite: 30%, an alloying agent: 1.9%, and the balance being chromium oxide green. The alloying agent was a WNbAlReLa alloy that included: W: 0.5%, Nb: 0.3%, Al: 0.4%, Re: 0.3%, and La: 0.4%.

[0072] The welding flux was prepared according to the following procedures:

[0073] Firstly: powders of above raw materials for the welding flux were preliminarily screened to obtain those having a granularity of 40 mesh, and then mixed by stirring. The resulting mixture was oven-dried at 200 C. for 40 min, obtaining a dry material.

[0074] Secondly: water glass was added to the dry material, and the resulting mixture was further stirred, obtaining a wet material.

[0075] Thirdly: the wet material was granulated, obtaining welding flux particles, and the welding flux particles were oven-dried at 200 C. and then sintered at 800 C. for 50 min, obtaining the welding flux for submerged arc welding of a duplex stainless steel.

[0076] Use Example 2: The flux-cored welding strip for submerged arc welding of a duplex stainless steel and the welding flux for submerged arc welding of a duplex stainless steel in Example 2 were used in combination for strip submerged arc cladding welding with welding process parameters shown in Table 3.

TABLE-US-00003 TABLE 3 Welding process parameters Cladding Cladding Cladding speed/mm/ Interpass Power polarity current/A voltage/V min temperature/ C. Direct current 700 30 350 100 reverse polarity

[0077] Results: a deposited metal of a cladding layer formed after cladding has the following chemical components: in percentages by mass, C: 0.25%, N: 0.50%, Cr: 27%, Ni: 5%, Mo: 4.0%, Mn: 2.55%, Cu: 1.5%, Si: 1.05%, W: 1.1%, Nb: 0.3%, Al: 0.5%, Re: 0.35%, La: 0.1%, S: 0.01%, P: 0.015%, and the balance being Fe.

[0078] A macroscopic morphology of the cladding deposited layer is shown in FIG. 3, a microscopic morphology of the cladding deposited layer is shown in FIG. 4, and stress-corrosion resistance of the deposited metal is shown in Table 4.

TABLE-US-00004 TABLE 4 Stress-corrosion resistance of the deposited metal Tensile Yield strength, strength, Corrosive environment Rp0.2/MPa Rm/MPa Example 1 0.1 mol/L S.sub.2O.sub.3.sup.2 + 20 wt % 740 875 NaCl, pH = 4

[0079] It can be seen from FIG. 3 that the cladding layer is beautifully formed, and has no defects such as pores, cracks, incomplete fusion, and oxidation. It can be seen from FIG. 4 that a ferrite and an austenite are distributed in equal proportions, and weld seam grains are significantly refined.

[0080] Specific examples are used for illustration of the principles and embodiments of the present disclosure. The description of the examples is intended to help understand illustrate the method and its core concept of the present disclosure. In addition, those skilled in the art could make various modifications in terms of specific embodiments and scope of application according to the concept of the present disclosure. In conclusion, the content of the present specification shall not be construed as limitations to the present disclosure.