Welding wire steel for maritime work equipment and smelting method thereof

Abstract

The invention relates to the technical field of ferrous metallurgy, and discloses welding wire steel for maritime work equipment and a smelting method.The smelting method comprises the steps that an ingot mold and a heat preservation riser are prepared, and drying and heat preservation are conducted in a heating furnace; the method comprises the following steps: preparing materials according to the chemical components of the welding wire steel, polishing the surface, sequentially charging in a smelting furnace, carrying out vacuum induction smelting, starting to carry out power transmission smelting when the vacuum degree is less than or equal to 10Pa, sequentially adding carbon blocks, metal silicon and aluminum in batches when the vacuum degree is less than or equal to 5Pa, filling argon, adding ferrotitanium, metal manganese and metal boron, finally adding rare earth zirconium, regulating the temperature to 1590-1620 DEG C, and tapping, casting in a steel ingot mold; and carrying out heat treatment on the blank to obtain the welding wire steel cast ingot. By adding trace Ti, B and rare earth alloy elements, a bainite structure is obtained in a wide cooling range while grain structures in the steel are refined and inclusions are modified, the toughness of a welding seam is improved, the low-oxygen and low-nitrogen steel for the welding wire is prepared by adopting a vacuum induction process, and the problem of cracking in the cold drawing process of the welding wire steel is solved.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to welding wire steel for marine engineering equipment and a smelting method thereof. Background Art

[0002] With the rapid development of my country's economy, steel materials have gradually developed from ordinary grades to high-strength grades; at the same time, the market demand for high-strength welding wire steel is also increasing. Due to the rapid development of the shipbuilding and marine engineering industries, high-strength and low-temperature steel containing alloy elements such as Ni, Cr and Mo has been widely used. This type of steel needs to meet high strength, high toughness, lamellar tear resistance and corrosion resistance at the same time. This type of steel is usually welded with imported flux-cored gas shielded welding wire, which is not only expensive, but also has a long supply cycle, which restricts the development of the industry. Therefore, the development of solid welding wire suitable for high-strength marine steel welding to replace the long-term reliance on flux-cored welding wire is the development trend of domestic marine steel supporting welding materials. However, there are many problems with existing welding wire steel. There are many grain structures and inclusions in the steel, which leads to poor toughness at the rail welding point. For steel for marine special equipment, the oxygen content is required to be ≤30PPm and the nitrogen content is required to be ≤30PPm, but the gas content using conventional processes cannot meet user product requirements.

[0003] Therefore, there is a need in the prior art for improving welding wire steel for marine engineering equipment and its smelting method. Summary of the invention

[0004] In view of this, the purpose of the embodiments of the present invention is to propose a welding wire steel for marine engineering equipment and a smelting method thereof, so as to solve the problems of large grain structure and inclusions in the steel, poor toughness and easy cracking at the rail welds, and obtain products with qualified oxygen and nitrogen contents.

[0005] Based on the above purpose, an embodiment of the present invention provides a welding wire steel for marine engineering equipment. The chemical composition of the welding wire steel includes, by mass percentage: C: 0.03~0.08%, Si: 0.40~0.80%, Mn: 1.20~1.70%, P≤0.015%, S≤0.010%, Cr: 0.20%~1.00%, Mo: 0.2~1.00%, Ni: 1.5~2.00%, Ti: 0.01~0.06%, Zr: 0.002~1.00%, B: 0.002~0.008%, Al: 0.005~0.015%, [O]≤30PPm, [N]≤30PPm, and the rest are iron and impurity elements.

[0006] Another aspect of the present invention further provides a method for smelting the above-mentioned welding wire steel for marine engineering equipment, comprising: S1 prepares the ingot mold and the insulation riser and performs drying and insulation in a heating furnace; S2 prepares materials according to the chemical composition of welding wire steel and performs surface polishing, loads materials into the smelting furnace in sequence for vacuum induction melting, starts power melting when the vacuum degree is ≤10Pa, adds carbon blocks, metal silicon, and aluminum in batches in sequence when the vacuum degree is ≤5Pa, fills with argon gas and adds titanium iron, metal manganese, and metal boron, and finally adds rare earth zirconium, adjusts the temperature to 1590℃~1620℃ for steel tapping, and casts in a steel ingot mold; S3 heat treats the blank to obtain a welding wire steel ingot.

[0007] In some embodiments, in S1, the ingot mold and the insulation riser are dried in a heating furnace at 600°C to 850°C, and the insulation time is greater than 3 hours.

[0008] In some embodiments, in S2, the specific process of vacuum induction melting includes: When the vacuum degree is ≤10Pa, power is supplied for high-power melting. When the molten steel covers the bottom of the crucible, the power is switched to low power. After melting, the temperature is adjusted to 1630℃~1680℃. When the vacuum degree is ≤5Pa, carbon blocks are added, and the refining time is ≥30min under high-power stirring. Then, metal silicon and aluminum are added, and the homogenization time is ≥10min under stirring conditions. Then, argon gas is filled in, and titanium iron, metal manganese and metal boron are added. The homogenization time is ≥10min under stirring conditions. Finally, rare earth zirconium is added. The homogenization time is ≥5min under stirring conditions. The temperature is adjusted to 1590℃~1620℃ for steel casting.

[0009] In some embodiments, the melting process is controlled to have a vacuum degree of ≤5 Pa.

[0010] In some embodiments, the total refining time is ≥ 1 h.

[0011] In some embodiments, in S2, the order of loading is: first loading pure iron, and then loading metal chromium, metal molybdenum, metal nickel and other metals with the furnace.

[0012] In some embodiments, in S2, the pouring temperature is 1560°C to 1590°C, the ingot pouring speed is 80kg / s to 100kg / s, and the riser pouring speed is 2kg / s to 10kg / s.

[0013] In some embodiments, in S2, the air breaking time of the inert gas used during casting is ≥1 h, and the mold moving time is ≥6 h.

[0014] In some embodiments, in S3, the calculation method of the holding time is: T=K*D Wherein, T is the holding time; K is the correction coefficient, which is 0.1~1; D is the ingot diameter.

[0015] The present invention has at least the following beneficial technical effects: (1) The invention meets the high strength requirements of marine equipment by adding trace amounts of Cr, Mo and Ni alloy elements in the composition design, while adding trace amounts of Ti, B and rare earth alloy elements to refine the grain structure in the steel, modify the inclusions and obtain bainite structure in a wider cooling range, thereby improving the toughness of the weld; (2) The design uses a vacuum induction process to produce low-oxygen and low-nitrogen welding wire steel, where [O] + [N] ≤ 60 ppm, to solve the problem of cracking of welding wire steel during the cold drawing process and at the same time improve the weld metal's ability to resist porosity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0017] Figure 1 The present invention is a flow chart of an embodiment of a method for smelting welding wire steel for marine engineering equipment provided by the present invention. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0019] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0020] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] The purpose of the present invention is to provide a high-strength and high-toughness welding wire steel for marine engineering equipment and a smelting method thereof, so as to solve the problem that domestic high-strength and high-toughness welding wire steel for marine engineering equipment has long been dependent on imports. The chemical element percentages of high-strength and high-toughness welding wire steel for marine engineering equipment are: C: 0.03-0.08%, Si: 0.40-0.80%, Mn: 1.20-1.70%, P≤0.015%, S≤0.010%, Cr: 0.20%-1.00%, Mo: 0.2-1.00%, Ni: 1.5-2.00%, Ti: 0.01-0.06%, Zr: 0.002-1.00%, B: 0.002-0.008%, Al: 0.005-0.015%, [O]≤30PPm, [N]≤30PPm, and the rest are iron and impurity elements.

[0022] like Figure 1 The flowchart shown is an embodiment of a smelting method of welding wire steel for marine equipment provided by the present invention, comprising: S1 prepares the ingot mold and the insulation riser and performs drying and insulation in a heating furnace; S2 prepares materials according to the chemical composition of welding wire steel and performs surface polishing, loads materials into the smelting furnace in sequence for vacuum induction melting, starts power melting when the vacuum degree is ≤10Pa, adds carbon blocks, metal silicon, and aluminum in batches in sequence when the vacuum degree is ≤5Pa, fills with argon gas and adds titanium iron, metal manganese, and metal boron, and finally adds rare earth zirconium, adjusts the temperature to 1590℃~1620℃ for steel tapping, and casts in a steel ingot mold; S3 heat treats the blank to obtain a welding wire steel ingot.

[0023] Furthermore, in S1, the ingot mold and the insulating riser are dried in a heating furnace at 600°C to 850°C, and the insulation time is greater than 3h. The addition of the insulating riser can achieve the effect of sequential solidification of the ingot from bottom to top, improve the shrinkage compensation of the upper molten steel, and solve the serious quality problem of "tube shrinkage" of welding wire steel produced by ingot molds with a length-to-diameter ratio.

[0024] Further, in S2, the specific process of vacuum induction melting includes: When the vacuum degree is ≤10Pa, power is supplied for high-power melting. When the molten steel covers the bottom of the crucible, the power is switched to low power. After melting, the temperature is adjusted to 1630℃~1680℃. When the vacuum degree is ≤5Pa, carbon blocks are added, and the refining time is ≥30min under high-power stirring, then metal silicon and aluminum are added, and the homogenization time is ≥10min under stirring; then argon is filled, titanium iron, metal manganese, and metal boron are added, and the homogenization time is ≥10min under stirring, and finally rare earth zirconium is added, and the homogenization time is ≥5min under stirring, and the temperature is adjusted to 1590℃~1620℃ for steel casting. In some embodiments, the vacuum degree of the melting process is controlled to be ≤5Pa, and the total refining time is controlled to be ≥1h.

[0025] Furthermore, in S2, the order of loading is: first loading pure iron, and then loading metal chromium, metal molybdenum, metal nickel and other metals into the furnace.

[0026] Furthermore, in S2, the pouring temperature is 1560°C~1590°C, the pouring speed of the ingot body is 80kg / s~100kg / s, the pouring speed of the riser is 2kg / s~10kg / s, the ingot body is quickly poured with low superheat, and the riser is poured with a slow shrinkage compensation process, which is conducive to the shrinkage compensation of the ingot body and the riser by the upper pouring method.

[0027] Furthermore, in S2, the air-breaking time of the inert gas used during casting is ≥1h, and the mold moving time is ≥6h.

[0028] Furthermore, in S3, the calculation method of the holding time is: T=K*D Wherein, T is the holding time; K is the correction coefficient, which is 0.1~1; D is the ingot diameter.

[0029] The beneficial effects of the present invention include: in the composition design, the present invention meets the high strength requirements of marine equipment by adding trace amounts of Cr, Mo and Ni alloy elements, while adding trace amounts of Ti, B and rare earth alloy elements, refining the grain structure in the steel, modifying the inclusions while obtaining bainite structure in a wider cooling range, and improving the toughness of the weld. In addition, the present invention adopts a vacuum induction process to produce low-oxygen and low-nitrogen welding wire steel, wherein [O]+[N]≤60ppm, thereby solving the problem of cracking of welding wire steel during cold drawing and improving the ability of the weld metal to resist pores.

[0030] Example 1 This embodiment uses a 6t vacuum induction furnace to produce Φ360mm H08MnNi high-strength and high-toughness welding wire steel, specifically: Step 1: Preparation First, only the materials are prepared, and the pure iron, metal chromium, metal molybdenum, and metal nickel are sandblasted, and then the materials are divided according to the chemical composition: C 0.03% per furnace, Si: 0.70%, Mn: 1.50%, Cr: 0.80%, Mo: 0.60%, Ni: 1.75%, Ti: 0.45%, B: 0.006%, Al: 0.01%, Zr: 0.008%, and the rest are pure iron bars; Next, carry out pre-production preparation.

[0031] (1) Dry the ingot mold and insulation riser in a heating furnace at 600℃~850℃, and the insulation time is more than 3h; (2) Charging of the crucible: small pieces of pure iron are placed on the bottom, pure iron rods are placed around the crucible, and metal chromium, molybdenum and nickel are placed loosely in the middle.

[0032] Step 2: Vacuum Induction Melting (1) Evacuate the vacuum and start supplying power after the vacuum degree is ≤10pa; (2) Melt at high power first, and then switch to low power after the molten steel covers the bottom of the crucible. After the molten steel is completely melted, adjust the temperature to 1630℃~1680℃.

[0033] (3) When the vacuum degree is ≤5Pa, carbon blocks are added and the refining time is 45 minutes under high-power stirring. Then metal silicon and aluminum are added and the homogenization time is 12 minutes under stirring conditions. (4) Fill with argon gas, add ferrotitanium, metallic manganese and metallic boron, and homogenize for 12 minutes under stirring conditions; (5) Add rare earth zirconium and homogenize for 8 minutes under stirring; (6) Adjust the temperature to 1590℃~1620℃ and cast the steel; (7) Breaking time: 150 minutes, moving mold after 450 minutes.

[0034] Step 3: Heat treatment process (1) Annealing process: heat up to 650℃ at a heating rate of ≤120℃ / hour, keep at this temperature for 3h, and then air cool out of the furnace.

[0035] (2) The composition was tested, and the [O] content was 18 ppm and the [N] content was 23 ppm.

[0036] Example 2 This embodiment uses a 12t vacuum induction furnace to produce Φ600mm H08MnNi high-strength and high-toughness welding wire steel, specifically: Step 1: Preparation First, prepare the materials, sandblast pure iron, metal chromium, metal molybdenum, and metal nickel, and then mix the materials according to the chemical composition: C 0.04% per furnace, Si: 0.8%, Mn: 1.65%, Cr: 0.70%, Mo: 0.75%, Ni: 1.8%, Ti: 0.50%, B: 0.005%, Al: 0.01%, Zr: 0.005%, and the rest are pure iron bars; Next, carry out pre-production preparation.

[0037] (1) Dry the ingot mold and insulation riser in a heating furnace at 600℃~850℃, and the insulation time is more than 5h; (2) Charging of the crucible: small pieces of pure iron are placed on the bottom, pure iron rods are placed around the crucible, and metal chromium, molybdenum and nickel are placed loosely in the middle.

[0038] Step 2: Vacuum Induction Melting (1) Evacuate the vacuum and start supplying power after the vacuum degree is ≤10pa; (2) Melt at high power first, and then switch to low power after the molten steel covers the bottom of the crucible. After the molten steel is completely melted, adjust the temperature to 1630℃~1680℃.

[0039] (3) When the vacuum degree is ≤5Pa, carbon blocks are added and the refining time is 60 minutes under high-power stirring. Then metal silicon and aluminum are added and homogenization time is 20 minutes under stirring conditions. (4) Fill with argon gas, add ferrotitanium, metallic manganese and metallic boron, and homogenize for 18 minutes under stirring conditions; (5) Add rare earth zirconium and homogenize for 15 minutes under stirring; (6) Adjust the temperature to 1590℃~1620℃ and cast the steel; (7) Breaking time: 180 minutes, moving mold after 600 minutes.

[0040] Step 3: Annealing (1) Annealing process: Heat to 680℃ at a heating rate of ≤120℃ / hour, keep at this temperature for 5h, and then air cool after leaving the furnace.

[0041] (2) Samples were taken for testing of composition, of which the [O] content was 22 ppm and the [N] content was 25 ppm.

[0042] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0043] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0044] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0045] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A welding wire steel for marine engineering equipment, characterized in that: The chemical composition of the welding wire steel includes, by mass percentage, C: 0.03-0.08%, Si: 0.40-0.80%, Mn: 1.20-1.70%, P≤0.015%, S≤0.010%, Cr: 0.20%-1.00%, Mo: 0.2-1.00%, Ni: 1.5-2.00%, Ti: 0.01-0.06%, Zr: 0.002-1.00%, B: 0.002-0.008%, Al: 0.005-0.015%, [O]≤30PPm, [N]≤30PPm, and the rest are iron and impurity elements.

2. A smelting method for welding wire steel for offshore equipment as claimed in claim 1, characterized in that: include: S1 prepares the ingot mold and the insulation riser and performs drying and insulation in a heating furnace; S2 prepares materials according to the chemical composition of the welding wire steel and performs surface polishing, loads materials into the smelting furnace in sequence for vacuum induction melting, starts power smelting when the vacuum degree is ≤10Pa, adds carbon blocks, metal silicon, and aluminum in batches in sequence when the vacuum degree is ≤5Pa, fills with argon gas and adds titanium iron, metal manganese, and metal boron, and finally adds rare earth zirconium, adjusts the temperature to 1590°C~1620°C for steel production, and casts in the ingot mold; S3 heat treats the blank to obtain a welding wire steel ingot.

3. The smelting method of welding wire steel for offshore equipment according to claim 2, characterized in that: In S1, the steel ingot mold and the heat-insulating riser are dried in a heating furnace at 600° C. to 850° C., and the heat-insulating time is greater than 3 hours.

4. The smelting method of welding wire steel for offshore equipment according to claim 2, characterized in that: In S2, the specific process of vacuum induction melting includes: When the vacuum degree is ≤10Pa, power is supplied for high-power melting. When the molten steel covers the bottom of the crucible, the power is switched to low power. After melting, the temperature is adjusted to 1630℃~1680℃. When the vacuum degree is ≤5Pa, carbon blocks are added, and the refining time is ≥30min under high-power stirring. Then, metal silicon and aluminum are added, and the homogenization time is ≥10min under stirring conditions. Then, argon gas is filled in, and titanium iron, metal manganese and metal boron are added. The homogenization time is ≥10min under stirring conditions. Finally, rare earth zirconium is added. The homogenization time is ≥5min under stirring conditions. The temperature is adjusted to 1590℃~1620℃ for steel casting.

5. The smelting method of welding wire steel for offshore equipment according to claim 4, characterized in that: The vacuum degree during melting process is controlled at ≤5Pa.

6. The smelting method of welding wire steel for offshore equipment according to claim 4, characterized in that: The total refining time is ≥1h.

7. The smelting method of welding wire steel for offshore equipment according to claim 2, characterized in that: In S2, the order of loading is: first load pure iron, then load metal chromium, metal molybdenum, metal nickel and other metals with the furnace.

8. The smelting method of welding wire steel for offshore equipment according to claim 2, characterized in that: In S2, the pouring temperature is 1560℃~1590℃, the ingot pouring speed is 80kg / s~100kg / s, and the riser pouring speed is 2kg / s~10kg / s.

9. The smelting method of welding wire steel for offshore equipment according to claim 2, characterized in that: In S2, the air breaking time of the inert gas used during casting is ≥1h, and the mold moving time is ≥6h.

10. The smelting method of welding wire steel for offshore equipment according to claim 2, characterized in that: In S3, the calculation method of holding time is: T=K*D Wherein, T is the holding time, unit; K is the correction coefficient, which is 0.1~1; D is the ingot diameter, unit.

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