A method for smelting large-size nickel and nickel alloy ingots

Abstract

The invention discloses a smelting method for large-scale nickel and nickel alloy ingots, comprising: batching according to the chemical composition of the nickel or nickel alloy ingots, and smelting, refining and casting through a vacuum induction furnace to obtain a plurality of nickel or nickel alloy ingot semi-finished products; wherein the vacuum pressure during smelting is ≤10Pa, and the vacuum pressure during refining is ≤1Pa; using a sawing fixture to saw the ends of the plurality of nickel or nickel alloy ingot semi-finished products respectively to obtain a plurality of nickel or nickel alloy ingot semi-finished products with ends presenting an inclined surface of 4° to 15°; assembling and welding the plurality of nickel or nickel alloy ingot semi-finished products after sawing through the inclined surfaces of the ends to obtain a consumable electrode; using an electroslag remelting process to perform secondary smelting on the consumable electrode to obtain a large-scale nickel or nickel alloy ingot; the fixture and the smelting process are suitable for most nickel-based ingots, and can achieve large-scale ingot unit weight and ensure product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material smelting, and in particular relates to a smelting method for large-size nickel and nickel alloy ingots. Background Art

[0002] Nickel and nickel alloys are important corrosion-resistant metal materials. They are widely used in chemical and chemical industries, and anti-wet corrosion parts of generators (such as water inlet heaters and steam pipes, etc.). Among them, wide-width (width greater than 1200mm) pure nickel strips and large-size wide thin strips are a type of market-demanding products with a wide range of uses. They need to be processed and prepared by melting large-size and large-weight (>6 tons) ingots. At present, the weight of ingots that can be produced by vacuum induction furnaces is mostly 2-4 tons, which is relatively small. Therefore, large-size nickel and nickel alloy ingots rely on multiple vacuum induction castings to prepare multiple primary electrodes, and multiple primary electrodes are welded and remelted to expand the ingot shape. The main quality problems that often occur are as follows: Figure 1~Figure 5 As shown: First, the transition is poor after remelting at the welding joint, with deep grooves and poor surface quality, which is prone to breakage during subsequent processing, especially when ultra-thin strips are rolled; second, the weld is prone to block shedding during remelting, resulting in inclusions, which leads to holes in the subsequent rolling of the strip; third, traditional electrode welding uses argon arc welding, the weld is easily contaminated with tungsten metal, and tungsten inclusions are prone to appear in the remelted ingot, resulting in cracking and failure in the prepared ultra-thin nickel strips and other products. Summary of the invention

[0003] In order to solve the above problems existing in the prior art, the present invention provides a smelting method for large-sized nickel and nickel alloy ingots. The technical problem to be solved by the present invention is achieved by the following technical solutions: A method for smelting large-size nickel and nickel alloy ingots, comprising: Step 1: preparing the nickel or nickel alloy ingot according to its chemical composition, and melting, refining and casting the ingot in a vacuum induction furnace to obtain a number of semi-finished nickel or nickel alloy ingots; wherein the vacuum pressure during melting is ≤10Pa, and the vacuum pressure during refining is ≤1Pa; Step 2: sawing the ends of the plurality of nickel or nickel alloy ingot semi-finished products respectively by using a sawing fixture to obtain a plurality of nickel or nickel alloy ingot semi-finished products with ends having an inclined surface of 4° to 15°; Step 3: Assemble and weld several semi-finished nickel or nickel alloy ingots after sawing by butting the end bevels to obtain consumable electrodes; Step 4: The consumable electrode is subjected to secondary smelting by an electroslag remelting process to obtain a large-sized nickel or nickel alloy ingot; wherein the electrode filling ratio is 0.45-0.70; the melting point of the electroslag is 1230-1350°C; the amount of electroslag is 2-4% of the weight of the consumable electrode; and the melting rate of the consumable electrode is (0.7-0.9)×the diameter of the crystallizer.

[0004] Furthermore, the sawing fixture includes a first clamping plate and a second clamping plate, the inner ends of the first clamping plate and the second clamping plate are inclined surfaces parallel to each other, and are fixed to the sawing machine by a sawing machine clamping assembly arranged on the outside of the first clamping plate and the second clamping plate, and during sawing, the nickel or nickel alloy ingot semi-finished product is clamped between the first clamping plate and the second clamping plate, so that the end of the nickel or nickel alloy ingot semi-finished product forms an angle of 4°~15° with the saw blade on the sawing machine, and then the end of the nickel or nickel alloy ingot semi-finished product is cut by the saw blade to form a 4°~15° inclined surface.

[0005] Furthermore, in step 3, the welding method of the several nickel or nickel alloy ingot semi-finished products is any one of plasma welding, laser welding, and a combination of arc welding and laser welding.

[0006] Furthermore, the electroslag slag system is selected from any one of the CaF2-CaO-Al2O3 ternary slag system, the CaF2-CaO-Al2O3-MgO quaternary slag system or the CaF2-CaO-Al2O3-MgO-TiO2 quinary slag system.

[0007] Beneficial effects of the present invention: 1. The present invention adopts a special fixture to cut the end of the consumable electrode during electroslag remelting into an inclined surface for assembly welding, and cooperates with the smelting process of the present invention to effectively eliminate the problem of poor transition at the welding joint of the consumable electrode assembly, so that the surface of the large-scale nickel and nickel alloy ingots finally prepared is smooth and consistent without partitions, which greatly improves the quality of the ingots, eliminates the risk of cracking in subsequent processing, and improves the yield rate; 2. Consumable electrode assembly welding adopts any one of plasma welding, laser welding, arc welding and laser welding combination welding, eliminating the risk of high-density tungsten inclusions caused by traditional argon arc welding cerium tungsten electrodes; 3. The fixture and smelting process are suitable for most nickel-based ingots, which can realize large-scale ingot unit weight and ensure product quality, making it possible to produce qualified wide-width (width ≥ 1000mm) strip coils through subsequent rolling; compared with traditional processing methods, the present invention can make the microstructure and properties of nickel-based alloys uniform, reduce the difficulty of subsequent processing, and is expected to be applied to various alloys other than nickel-based alloys.

[0008] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1~2 This is a photo of the appearance of an ingot obtained by electroslag remelting after welding multiple electrodes using traditional equipment and processes; Figure 3 To use Figure 1~2Photo of the cracking of the ingot after forging into a slab; Figure 4 To use Figure 1~2 The photo shows a hole in the strip caused by the weld falling off the ingot after the ingot was forged into a strip. Figure 5 The metallographic diagram of the ingot prepared by conventional equipment and process; Figure 6 It is a structural schematic diagram of the sawing fixture; Figure 7 To use Figure 6 Schematic diagram of the sawing fixture after sawing the ingot; Figure 8 This is a photo of the sawing surface after being sawed by the sawing fixture in the embodiment of the present invention after alignment; Fig. 9 A schematic diagram of welding three sawn N5 pure nickel ingot semi-finished products by combining arc welding and laser welding; Fig.10 This is a photo of the consumable electrode formed after welding is completed; Fig.11 This is a photo of the N5 pure nickel ingot obtained after electroslag remelting; Fig.12 for Fig.11 Photo of the slab after forging of N5 pure nickel ingot; Fig.13 for Fig.12 Photo of N5 pure nickel coil after hot rolling, annealing and pickling of slab; Fig.14 for Fig.13 Metallographic diagram of N5 pure nickel strip coil; Fig.15 This is a photo of the C276 alloy pure nickel ingot obtained after electroslag remelting.

[0010] Description of reference numerals: 1-first clamping plate; 2-second clamping plate; 3-sawing machine clamping assembly; 4-N5 pure nickel ingot semi-finished product; 5-hydraulic rod. DETAILED DESCRIPTION

[0011] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. Example

[0012] The embodiment of the present invention provides a method for smelting a large-scale pure nickel ingot, wherein the grade of the pure nickel is N5, and the smelting method of the N5 pure nickel ingot specifically comprises the following steps: Step: 1: According to the chemical composition of the N5 pure nickel ingot, the ingredients are prepared, and a 4-ton vacuum induction furnace is used for smelting, refining and primary casting. This is repeated three times to obtain three N5 pure nickel ingot semi-finished products with a specification of Φ700×1200mm and a weight of 4 tons; wherein the vacuum pressure during smelting is 9Pa, and the vacuum pressure during refining is 0.8Pa.

[0013] Step 2: Use a special sawing fixture on the gantry sawing machine to clamp and saw three N5 pure nickel ingot semi-finished products to obtain three N5 pure nickel ingot semi-finished products with a sawing surface of 10°. Two of the N5 pure nickel ingot semi-finished products have their heads sawed, and one N5 pure nickel ingot semi-finished product has its head and tail sawed.

[0014] Specifically, Figure 6-7 As shown, the sawing fixture includes a first clamping plate 1 and a second clamping plate 2, which are arranged opposite to each other and whose inner end faces are parallel inclined surfaces, and are fixed to the sawing machine through a sawing machine clamping assembly 3 arranged outside the first clamping plate 1 and the second clamping plate 2. The first clamping plate 1 and the second clamping plate 2 have the same structure, and their outer end faces are parallel planes; the sawing machine clamping assembly 3 is arranged parallel to the outer end faces, and the first clamping plate 1 and the second clamping plate 2 are fixedly connected to the sawing machine clamping assembly 3 by bolts, and the first clamping plate 1 and the second clamping plate 2 are fixed parallel to the sawing machine clamping assembly 3. When sawing, the nickel ingot is clamped between the first clamping plate 1 and the second clamping plate 2, and the inclination angle of the inclined surface is α, which is 10°, so that the end of the nickel ingot forms an angle α with the saw blade on the sawing machine.

[0015] When in use, the N5 pure nickel ingot semi-finished product 4 to be sawed is placed between the first clamping plate 1 and the second clamping plate 2, and pressure is applied to clamp the semi-finished product 4 by the hydraulic rod 5 on one side of the sawing machine clamping assembly 3, so that the N5 pure nickel ingot semi-finished product 4 is in an inclined state, and the angle between it and the saw blade on the sawing machine is 10°. After the end of the semi-finished product 4 is cut by using the saw blade, the end of the semi-finished product has a 10° bevel.

[0016] Step 3: The three N5 pure nickel ingot semi-finished products after sawing are assembled end to end by connecting the end bevels, and a straight consumable electrode weighing 11 tons is obtained by welding. Figures 8-10 shown.

[0017] Specifically, the welding method is any one of plasma welding, laser welding, and a combination of arc welding and laser welding. In the embodiment of the present invention, a combination of arc welding and laser welding is selected.

[0018] This welding method abandons the commonly used tungsten inert gas welding, avoids the contamination of the weld by the metal tungsten in the welding gun during the welding process, and ensures that the final N5 pure nickel ingot will not have the problem of tungsten inclusions.

[0019] Step 4: The consumable electrode is subjected to secondary smelting by electroslag remelting process to obtain a large-sized N5 pure nickel ingot, such as Fig.11 As shown, the surface of the ingot is smooth without partition grooves; wherein, the diameter of the crystallizer is 800 / 840 mm, and the electrode filling ratio is 0.65; the CaF2-CaO-Al2O3-MgO quaternary slag system is adopted, and the melting point of the electroslag is 1330°C; the amount of electroslag is 2.5% of the weight of the consumable electrode; the melting rate of the consumable electrode is 560 kg / h, and finally an N5 pure nickel ingot weighing about 11 tons is obtained, and the N5 pure nickel ingot is sawed off the head and tail before the next step.

[0020] The N5 pure nickel ingot semi-finished product 3 with 10° bevels at three ends is welded to each other through the bevels, so that when the welded electrodes are placed vertically, the weld has a bevel angle of 10° with the ground. During smelting, the weld can be melted smoothly and gradually enter the slag pool, rather than all welds being melted in the slag pool at the same time, thereby ensuring the stability of the weld during the smelting process; ultimately, the ingot will not be caused to have metallurgical defects and cold shuts, effectively eliminating the problem of poor transition at the welding joint of the electrode group, making the final ingot surface smooth and consistent, greatly improving the ingot quality, eliminating the risk of cracking in subsequent processing, and improving the yield rate.

[0021] In addition, the N5 pure nickel ingot is heated to 900-1050°C and forged into a nickel slab of 180 mm × 1450 mm × 4700 mm on a free forging hydraulic press; the slab is milled on a milling machine and then polished to obtain a billet with a smooth surface suitable for rolling, such as Fig.12 As shown; and then through hot rolling, pickling and annealing, a white surface N5 pure nickel strip coil 3.2mm×1410mm×C is obtained, as shown Fig.13 As shown. And the metallographic analysis of the coil is carried out, as shown Fig.14 It can be seen that the structure of the coil is uniform and good, without any undesirable inclusions. Example

[0022] The embodiment of the present invention provides a method for smelting a large-size nickel alloy ingot, wherein the grade of the nickel alloy is C276 alloy, and the smelting method of the C276 alloy ingot specifically comprises the following steps: Step 1: According to the chemical composition of the C276 alloy ingot, the ingredients are prepared, and a 3-ton vacuum induction furnace is used for smelting, refining and primary casting. This is repeated twice to obtain two C276 alloy ingot semi-finished products with a specification of Φ560×1500mm and a weight of 3 tons; wherein the vacuum pressure during smelting is 6Pa, and the vacuum pressure during refining is 0.5Pa.

[0023] Step 2: Use the following method on the gantry saw: Figure 6The special sawing fixture shown is used to clamp and saw the heads of three C276 alloy ingot semi-finished products to obtain two C276 alloy ingot semi-finished products with sawing surfaces having a 15° inclined surface.

[0024] Specifically, the sawing fixture has the same structure as the sawing fixture in Example 1, and the embodiment of the present invention will not be described in detail here.

[0025] When the sawing fixture is in use, the C276 alloy ingot semi-finished product to be sawed is placed between the first clamping plate and the second clamping plate, and pressure is applied to clamp the semi-finished product through the hydraulic rod on one side of the sawing machine clamping assembly, so that the C276 alloy ingot semi-finished product is in an inclined state, and the angle between the semi-finished product and the saw blade on the sawing machine is 15°. After the end of the ingot is cut by using the saw blade, the end of the ingot has a 15° bevel.

[0026] Step 3: Assemble the two C276 alloy ingot semi-finished products after sawing by connecting the end bevels, and obtain a straight consumable electrode weighing 6 tons by welding.

[0027] Specifically, the welding method is any one of plasma welding, laser welding, and a combination of arc welding and laser welding. In the embodiment of the present invention, plasma welding is selected.

[0028] This welding method abandons the commonly used tungsten inert gas welding, avoids the contamination of the weld by the metal tungsten in the welding gun during the welding process, and ensures that the final C276 alloy ingot does not have the problem of tungsten inclusions.

[0029] Step 4: The consumable electrode is subjected to secondary smelting by electroslag remelting process to obtain a large-sized C276 alloy ingot, such as Fig.15 As shown, the surface of the ingot is smooth without partition grooves; wherein, the diameter of the crystallizer is 650 / 690 mm, and the electrode filling ratio is 0.6; the CaF2-CaO-Al2O3-MgO-TiO2 quaternary slag system is adopted, and the melting point of the electroslag is 1250°C; the amount of electroslag is 4% of the weight of the consumable electrode; the melting rate of the consumable electrode is 460 kg / h, and finally a C276 alloy ingot weighing about 6 tons is obtained, and the C276 alloy ingot is sawed off from the head to the tail before the next step.

[0030] The C276 alloy ingot semi-finished product 3 with 15° bevels at both ends is welded to each other through the bevels, so that when the welded electrodes are placed vertically, the weld has a bevel angle of 15° with the ground. During smelting, the weld can be melted smoothly and gradually enter the slag pool, rather than all welds being melted in the slag pool at the same time, thereby ensuring the stability of the weld during the smelting process; ultimately, the ingot will not be caused to have metallurgical defects and cold shuts, effectively eliminating the problem of poor transition at the welding joint of the electrode group, making the final ingot surface smooth and consistent, greatly improving the ingot quality, eliminating the risk of cracking in subsequent processing, and improving the yield rate.

[0031] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for smelting large-sized nickel and nickel alloy ingots, characterized in that: include: Step 1: preparing the nickel or nickel alloy ingot according to its chemical composition, and melting, refining and casting the ingot in a vacuum induction furnace to obtain a number of semi-finished nickel or nickel alloy ingots; wherein the vacuum pressure during melting is ≤10Pa, and the vacuum pressure during refining is ≤1Pa; Step 2: sawing the ends of the plurality of nickel or nickel alloy ingot semi-finished products respectively by using a sawing fixture to obtain a plurality of nickel or nickel alloy ingot semi-finished products with ends having an inclined surface of 4° to 15°; Step 3: Assemble and weld several semi-finished nickel or nickel alloy ingots after sawing by butting the end bevels to obtain consumable electrodes; Step 4: The consumable electrode is subjected to secondary smelting by an electroslag remelting process to obtain a large-sized nickel or nickel alloy ingot; wherein the electrode filling ratio is 0.45-0.70; the melting point of the electroslag is 1230-1350°C; the amount of electroslag is 2-4% of the weight of the consumable electrode; and the melting rate of the consumable electrode is (0.7-0.9)×the diameter of the crystallizer.

2. The method for smelting large-sized nickel and nickel alloy ingots according to claim 1, characterized in that: The sawing fixture includes a first clamping plate and a second clamping plate, the inner ends of which are inclined surfaces parallel to each other, and are fixed to a sawing machine by a sawing machine clamping assembly arranged on the outside of the first clamping plate and the second clamping plate. During sawing, the semi-finished nickel or nickel alloy ingot is clamped between the first clamping plate and the second clamping plate, so that the end of the semi-finished nickel or nickel alloy ingot forms an angle of 4° to 15° with the saw blade on the sawing machine, and then the end of the semi-finished nickel or nickel alloy ingot is cut by the saw blade to form an inclined surface of 4° to 15°.

3. The smelting method of large-sized nickel and nickel alloy ingots according to claim 1, characterized in that: In the step 3, the welding method of the several nickel or nickel alloy ingot semi-finished products is any one of plasma welding, laser welding, and a combination of arc welding and laser welding.

4. The method for smelting large-sized nickel and nickel alloy ingots according to claim 1, characterized in that: The electroslag slag system is selected from any one of the CaF2-CaO-Al2O3 ternary slag system, the CaF2-CaO-Al2O3-MgO quaternary slag system or the CaF2-CaO-Al2O3-MgO-TiO2 quinary slag system.

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