Method for improving internal quality of welding wire steel induction ingot and welding wire steel

Abstract

The invention relates to the technical field of ferrous metallurgy, and discloses a method for improving the internal quality of a welding wire steel induction ingot and welding wire steel. The method comprises the steps that a heat preservation riser is dried and subjected to heat preservation in a heating furnace at the temperature of 600-850 DEG C, the heat preservation riser is connected to an ingot mold, and the ingot mold extends from the bottom to the top and comprises a first thickness section and a second thickness section; the thickness of the first thickness section is 1-1.5 times that of the second thickness section; alloy materials are prepared according to the composition proportion and are polished, a smelting furnace is sequentially filled with materials, and a vacuum induction smelting furnace is adopted for smelting; pouring the molten steel into an ingot mold for pouring, wherein the pouring speed of an ingot body is higher than that of a riser; and the blank is subjected to heat preservation at the temperature of 600-700 DEG C, and is air-cooled to the room temperature after being discharged from the furnace. The method solves the quality problem of serious pipe shrinkage of welding wire steel produced by an ingot mold with the length-diameter ratio, solves the problem of cracking of the welding wire steel in the cold drawing process, and improves the air hole resistance of weld metal at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for improving the internal quality of a welding wire steel induction ingot and the welding wire steel. Background Art

[0002] At present, the activities of countries around the world in searching for oil and natural gas at sea are developing from shallow sea to deep sea. The investigation and exploration work of finding oil and natural gas in the ocean is constantly expanding. With the rapid development of shipbuilding and offshore 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 the requirements of 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 offshore steel welding to replace the long-term dependent flux-cored welding wire is the development trend of domestic offshore steel supporting welding materials.

[0003] At present, welding wire steel billets at home and abroad are basically produced by the process of "electric furnace steelmaking + LF refining + vacuum treatment", but for marine special equipment steel, the oxygen content requirement is ≤30PPm, and the nitrogen content requirement is ≤30PPm. The gas content of conventional processes cannot meet the user's product requirements. Therefore, the use of vacuum equipment for smelting is a good choice. However, when using a vacuum induction furnace for production, due to the large length-diameter ratio of the ingot mold (generally >4), and the fact that the riser cannot add a heating agent, after the ingot is poured, there is often a long central shrinkage hole, commonly known as "tube shrinkage", which cannot be welded in the deformation of the subsequent process, and the qualified rate is very low, which seriously affects the utilization rate of the steel ingot. Therefore, it is of great significance to study the process of producing welding wire steel with high gas content requirements in vacuum induction furnaces, reduce "tube shrinkage", and improve the internal quality of welding wire induction ingots.

[0004] Therefore, there is a need in the prior art for an improved method of improving the internal quality of welding wire steel induction ingots. Summary of the invention

[0005] In view of this, the purpose of the embodiments of the present invention is to provide a method for improving the internal quality of welding wire steel induction ingots and welding wire steel, which solves the problem of severe "tube shrinkage" and low material utilization rate in the production of low gas content welding wire steel induction ingots.

[0006] Based on the above purpose, an embodiment of the present invention provides a welding wire steel, wherein the chemical composition of the welding wire steel includes, by mass percentage: C: 0.03~0.08%, Si: 0.30~0.60%, Mn: 0.80~1.20%, P≤0.015%, S≤0.010%, Cr: 0.60%~1.20%, Mo: 0.2~0.80%, Ni: 1.0~1.50%, Ti: 0.01~0.06%, Ce: 0.02~0.08%, B: 0.002~0.008%, Al: 0.005~0.015%, [O]≤30PPm, [N]≤30PPm, and the rest are iron and impurity elements.

[0007] Another aspect of the present invention provides a method for improving the internal quality of a welding wire steel induction ingot, comprising the following steps: S1 production preparation: drying and heat-insulating the heat-insulating riser in a heating furnace at 600℃~850℃, connecting the heat-insulating riser to the ingot mold, the ingot mold extending from the bottom to the top includes a first thickness section and a second thickness section, and the thickness of the first thickness section is 1~1.5 times the thickness of the second thickness section; S2 Vacuum induction furnace smelting: prepare alloy materials according to the composition ratio and perform polishing, load the materials into the smelting furnace in sequence, and use the vacuum induction melting furnace for smelting; S3 pouring: pouring molten steel into the ingot mold for pouring, the pouring speed of the ingot body is greater than the pouring speed at the riser; S4 billet heat treatment: keep the billet at 600~700℃ and air-cool to room temperature after leaving the furnace.

[0008] In some embodiments, in S1, the insulation time of the insulation riser is greater than 3 hours.

[0009] In some embodiments, in S1, the first thickness section is from the bottom of the ingot mold to 1 / 2 of the height of the ingot mold, and the second thickness section is from 1 / 2 of the height of the ingot mold to the top of the ingot mold.

[0010] In some embodiments, in S2, the order of loading is to first load pure iron into the crucible, and then load metal chromium, metal molybdenum, and metal nickel into the furnace.

[0011] In some embodiments, in S2, specific requirements for vacuum induction furnace smelting include: When the vacuum degree is ≤10Pa, start to supply power, first maintain high power for melting, and switch to low power when the molten steel covers the bottom of the crucible. After melting, adjust the temperature to 1630℃~1680℃; When the vacuum degree is ≤5Pa, start adding carbon blocks, and refining time is ≥30min under high-power stirring. Then add metal silicon and aluminum, and homogenize for ≥10min under stirring. Then fill with argon, add titanium iron, metal manganese, and metal boron, and homogenize for ≥10min under stirring. Finally, add metal cerium, and homogenize for ≥5min under stirring, and pour at adjusted temperature.

[0012] In some embodiments, in S2, the vacuum degree during the melting process is ≤5 Pa, and the total refining time is ≥1 h.

[0013] In some embodiments, in S3, 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.

[0014] In some embodiments, in S3, during the pouring process, the inert gas is used with a break-through time of ≥1 h and a mold moving time of ≥6 h.

[0015] In some embodiments, in S4, 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.

[0016] The present invention has at least the following beneficial technical effects: (1) The invention changes the thickness from the bottom to 1 / 2 of the height of the induction ingot mold and adds a heat-insulating riser to achieve the effect of sequential solidification of the steel ingot from bottom to top, improve the shrinkage compensation of the upper molten steel, and solve the quality problem of serious "tube shrinkage" of welding wire steel produced by ingot molds with a length-to-diameter ratio; (2) The ingot body is cast quickly with low superheat, and the riser is cast with slow shrinkage compensation process, which is conducive to the shrinkage compensation of the ingot body and riser by the top casting method; (3) The design uses a vacuum induction process to produce low-oxygen and low-nitrogen welding wire steel, where [O] + [N] ≤ 60ppm, 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

[0017] 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.

[0018] Figure 1 A flow chart of an embodiment of a method for improving the internal quality of a welding wire steel induction ingot provided by the present invention; Figure 2 A schematic diagram of an embodiment of a stepped steel ingot provided by the present invention. DETAILED DESCRIPTION

[0019] 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.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field of the present invention; the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For example, the directions or positions indicated by the terms "length", "width", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the drawings, which are only for the convenience of description and should not be understood as limitations on the present technical solution.

[0021] 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.

[0022] 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.

[0023] At present, my country's shipbuilding and offshore engineering equipment are developing rapidly. The steel and welding wire for medium and low-end offshore engineering equipment have basically been domestically produced. However, high-strength offshore engineering steel and the corresponding welding wire steel are still heavily dependent on imports. Not only are they expensive, but the supply cycle is long, which restricts the development of the industry. Therefore, the present invention provides a welding wire steel for marine engineering equipment and a method for improving the internal quality of the welding wire steel induction ingot of this type, wherein the chemical composition of the welding wire steel includes: C: 0.03~0.08%, Si: 0.30~0.60%, Mn: 0.80~1.20%, P≤0.015%, S≤0.010%, Cr: 0.60%~1.20%, Mo: 0.2~0.80%, Ni: 1.0~1.50%, Ti: 0.01~0.06%, Ce: 0.02~0.08%, B: 0.002~0.008%, Al: 0.005~0.015%, [O]≤30PPm, [N]≤30PPm, and the rest are iron and impurity elements.

[0024] A method for improving the internal quality of welding wire steel induction ingots, such as Figure 1 As shown, the following steps are included: S1 production preparation: drying and heat-insulating the heat-insulating riser in a heating furnace at 600℃~850℃, connecting the heat-insulating riser to the ingot mold, the ingot mold extending from the bottom to the top includes a first thickness section and a second thickness section, and the thickness of the first thickness section is 1~1.5 times the thickness of the second thickness section; S2 Vacuum induction furnace smelting: prepare alloy materials according to the composition ratio and perform polishing, load the materials into the smelting furnace in sequence, and use the vacuum induction melting furnace for smelting; S3 pouring: pouring molten steel into the ingot mold for pouring, the pouring speed of the ingot body is greater than the pouring speed at the riser; S4 billet heat treatment: keep the billet at 600~700℃ and air-cool to room temperature after leaving the furnace.

[0025] Furthermore, in S1, the insulation time of the insulation riser is greater than 3 hours. Figure 2 As shown, the ingot mold is a stepped ingot mold, the first thickness section is from the bottom of the ingot mold to 1 / 2 of the height of the ingot mold, and the second thickness section is from 1 / 2 of the height of the ingot mold to the top of the ingot mold. Specifically, the thickness of the ingot mold from the bottom to 1 / 2 of the height of the ingot mold is 1 to 1.5 times the thickness of the remaining ingot molds, and at the same time, a heat preservation riser is added to the ingot mold to achieve the effect of sequential solidification of the induction ingot from bottom to top.

[0026] Furthermore, in S2, the order of loading is to first load pure iron into the crucible, and then load metal chromium, metal molybdenum, and metal nickel into the furnace.

[0027] After the loading is completed, vacuum induction furnace smelting is carried out. The specific requirements include: When the vacuum degree is ≤10Pa, start to supply power, first maintain high power for melting, and switch to low power when the molten steel covers the bottom of the crucible. After melting, adjust the temperature to 1630℃~1680℃; When the vacuum degree is ≤5Pa, start adding carbon blocks, and refining time is ≥30min under high-power stirring. Then add metal silicon and aluminum, and homogenize for ≥10min under stirring. Then fill with argon, add titanium iron, metal manganese, and metal boron, and homogenize for ≥10min under stirring. Finally, add metal cerium, and homogenize for ≥5min under stirring, and pour at adjusted temperature.

[0028] In some embodiments, the vacuum degree during the melting process is ≤5 Pa, and the total refining time is ≥1 h.

[0029] Further, in S3, the pouring temperature is 1560°C to 1590°C, the pouring speed of the ingot body is 80kg / s to 100kg / s, and the pouring speed of the riser is 2kg / s to 10kg / s. During the pouring process, the inert gas is used with a breaking time of ≥1h and a moving mold time of ≥6h.

[0030] Furthermore, in S4, 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.

[0031] After annealing, a qualified welding wire steel ingot can be obtained, wherein the [O] content is ≤30PPm and the [N] content is ≤30PPm.

[0032] The present invention provides a method for improving the internal quality of welding wire steel induction ingots, and its advantages are mainly as follows: (1) The invention changes the thickness from the bottom to 1 / 2 of the height of the induction ingot mold, and at the same time adds a heat-insulating riser to achieve the effect of sequential solidification of the steel ingot from bottom to top, improve the shrinkage compensation of the upper molten steel, and solve the quality problem of serious "tube shrinkage" of welding wire steel produced by the length-to-diameter ratio ingot mold. (2) The ingot body adopts low superheat rapid casting, and the riser adopts a slow shrinkage compensation process, which is conducive to the shrinkage compensation of the ingot body and riser of the upper casting method induction ingot; (3) The design adopts a vacuum induction process to produce low-oxygen and low-nitrogen welding wire steel, whose [O]+[N]≤60ppm, which solves the problem of cracking of welding wire steel during cold drawing, and improves the ability of weld metal to resist pores.

[0033] The present invention will be further explained below in conjunction with specific embodiments.

[0034] Example 1 The method of the present invention is used to prepare Φ360mm H08MnNi high-strength and high-toughness welding wire steel.

[0035] 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, 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: 0.45%, Mn: 0.9%, Cr: 0.70%, Mo: 0.50%, Ni: 1.25%, Ti: 0.02%, B: 0.006%, Al: 0.01%, Ce: 0.005%, and the rest are pure iron bars; (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.

[0036] 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℃.

[0037] (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 metallic cerium, homogenize for 8 minutes under stirring conditions, and then adjust the temperature for pouring.

[0038] Step 3: Pouring (1) 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.

[0039] (2) Breaking time: 150 minutes, moving mold after 450 minutes.

[0040] Step 4: Heat treatment of blank (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.

[0041] (2) The composition was tested, and the [O] content was 20 ppm and the [N] content was 26 ppm.

[0042] Example 2 The method of the present invention is used to prepare Φ600mm H08MnNi high-strength and high-toughness welding wire steel.

[0043] 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, pure iron, metal chromium, metal molybdenum and metal nickel are sandblasted, and then the materials are divided according to the chemical composition: C 0.02% per furnace, Si: 0.40%, Mn: 1.00%, Cr: 1.00%, Mo: 0.50%, Ni: 1.20%, Ti: 0.04%, B: 0.005%, Al: 0.01%, Ce: 0.008%, and the rest are pure iron bars; (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.

[0044] 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℃.

[0045] (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 metallic cerium and homogenize for 15 minutes under stirring conditions Step 3: Pouring (1) 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.

[0046] (2) Breaking time: 180 minutes, moving mold after 600 minutes.

[0047] Step 4: Heat treatment of blank (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.

[0048] (2) Samples were taken for testing of composition, of which the [O] content was 21 ppm and the [N] content was 25 ppm.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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: 0.30-0.60%, Mn: 0.80-1.20%, P≤0.015%, S≤0.010%, Cr: 0.60%-1.20%, Mo: 0.2-0.80%, Ni: 1.0-1.50%, Ti: 0.01-0.06%, Ce: 0.02-0.08%, B: 0.002-0.008%, Al: 0.005-0.015%, [O]≤30PPm, [N]≤30PPm, and the rest are iron and impurity elements.

2. A method for improving the internal quality of welding wire steel induction ingots, using the composition ratio as claimed in claim 1, characterized in that: include: S1 production preparation: drying and heat-insulating the heat-insulating riser in a heating furnace at 600°C to 850°C, and connecting the heat-insulating riser to an ingot mold, wherein the ingot mold extends from the bottom to the top and includes a first thickness section and a second thickness section, and the thickness of the first thickness section is 1 to 1.5 times the thickness of the second thickness section; S2 Vacuum induction furnace smelting: prepare alloy materials according to the composition ratio and perform polishing treatment, load the materials into the smelting furnace in sequence, and use a vacuum induction melting furnace for smelting; S3 pouring: pouring molten steel into the ingot mold for pouring, and the pouring speed of the ingot body is greater than the pouring speed at the riser; S4 billet heat treatment: keep the billet at 600~700℃ and air-cool to room temperature after leaving the furnace.

3. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S1, the insulation time of the insulation riser is greater than 3 hours.

4. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S1, the first thickness section is from the bottom of the ingot mold to 1 / 2 of the height of the ingot mold, and the second thickness section is from 1 / 2 of the height of the ingot mold to the top of the ingot mold.

5. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S2, the order of loading is to first load pure iron into the crucible, and then load metal chromium, metal molybdenum and metal nickel into the furnace.

6. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S2, the specific requirements for vacuum induction furnace melting include: When the vacuum degree is ≤10Pa, start to supply power, first maintain high power for melting, and switch to low power when the molten steel covers the bottom of the crucible. After melting, adjust the temperature to 1630℃~1680℃; When the vacuum degree is ≤5Pa, start adding carbon blocks, and refining time is ≥30min under high-power stirring. Then add metal silicon and aluminum, and homogenize for ≥10min under stirring. Then fill with argon, add titanium iron, metal manganese, and metal boron, and homogenize for ≥10min under stirring. Finally, add metal cerium, and homogenize for ≥5min under stirring, and pour at adjusted temperature.

7. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S2, the vacuum degree during the melting process is ≤5 Pa, and the total refining time is ≥1 h.

8. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S3, 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 method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S3, during the pouring process, the inert gas is used with a breaking time of ≥1h and a mold moving time of ≥6h.

10. The method for improving the internal quality of welding wire steel induction ingot according to claim 2, characterized in that: In S4, 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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