Method for improving thermal cracking resistance of cupronickel alloy without adding alterant

Abstract

The invention provides a method for improving the thermal cracking resistance of a cupronickel alloy without adding an alterant, which comprises the following steps: step (1), heating and melting a cupronickel alloy raw material, fishing out the cupronickel alloy raw material, and covering charcoal and surface scum; (2) the smelting temperature is increased to 1350 + / -50 DEG C, and melt is fully stirred during heating; (3) keeping the temperature at 1350 + / -50 DEG C, standing for 8-20 minutes, and fishing out the dross after the dross in the melt fully floats upwards; step (4), covering with calcined charcoal with the thickness of 10-20 cm; (5) the temperature of the melt is reduced to 1200-1310 DEG C, casting is conducted, and the casting speed is 3.5-5.1 m / h; and (6) the round ingot obtained through casting is heated to 900-1075 DEG C, extrusion is conducted, and the cupronickel alloy pipe blank is obtained. According to the method, under the condition that no alterant is added, the cupronickel alloy which is uniform in microstructure and small in grain size is successfully prepared by controlling the smelting temperature, the standing time and the casting speed, and the high-temperature heat crack resistance and the ductility of the cupronickel alloy are remarkably improved; and meanwhile, the furnace life is effectively prevented from being influenced by alterant slagging, and the equipment maintenance cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing, and specifically relates to a method for improving the hot crack resistance of cupronickel alloys without adding modifiers. Background Technology

[0002] Cupronickel alloys possess excellent resistance to seawater corrosion and marine biofouling, as well as superior hot and cold working properties, making them widely used in shipbuilding and marine engineering, coastal power plants, and seawater pipelines and heat exchangers. However, during processes such as ingot extrusion, ingot heating forging, or ingot hot rolling, cupronickel alloys may experience high-temperature cracking due to insufficient high-temperature plasticity, thereby reducing product yield and pass rate.

[0003] Existing technologies typically employ the addition of boron or titanium as modifiers to improve the high-temperature hot crack resistance of cupronickel alloys. For example, Chinese patent application number 202510608597.6 discloses a method for improving the high-temperature crack resistance of cupronickel alloys based on the addition of modifier Ti, including the following steps: S1: heating the cupronickel alloy raw material until it is completely melted; S2: removing slag from the molten metal; S3: adding copper-magnesium alloy; S4: adding pure titanium and stirring to ensure the pure titanium fully dissolves and reacts; S5: removing slag from the molten metal; S6: after passing the pre-furnace analysis, casting is performed; S7: obtaining cupronickel alloy round or flat ingots. This method, by adding pure titanium as a modifier, can refine the grain size of the cupronickel alloy ingot, effectively improve the high-temperature plasticity of the cupronickel alloy, reduce grain boundary defects, improve the high-temperature crack resistance of the cupronickel alloy, and avoid cracking under high-temperature forging or hot rolling.

[0004] Furthermore, Chinese patent application number 202410574305.7 discloses a method for preparing a high-strength wear-resistant copper alloy, including step 1, synthesizing ferromanganese boride powder: weighing ferric nitrate nonahydrate, manganese nitrate tetrahydrate, sodium borohydride, and ammonium carbonate, mixing thoroughly, placing in a ceramic crucible, microwaving, pulverizing and sieving to obtain ferromanganese boride powder; step 2, wet grinding treatment; step 3, forming treatment; step 4, high-temperature sintering; and step 5, post-treatment: annealing and cooling the alloy green blank to obtain a high-strength wear-resistant copper alloy. In this method, iron and manganese are added to the copper alloy as ferromanganese boride, which refines the ingot grains and improves the high-temperature hot cracking resistance of the cupronickel alloy.

[0005] While adding modifiers to copper alloys can improve their performance, it can also introduce new elements and potentially create new alloys. In addition, the slag generated by the modifiers can corrode equipment, shorten its service life, and increase maintenance costs.

[0006] Therefore, there is an urgent need for a method to improve the hot crack resistance of cupronickel alloys without adding modifiers. Summary of the Invention

[0007] The purpose of this invention is to provide a method for improving the thermal crack resistance of cupronickel alloys without adding modifiers, so as to solve the problems of easy cracking of cupronickel alloys at high temperatures and the impact of slag formation on furnace life after adding modifiers in the prior art.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for improving the hot crack resistance of cupronickel alloys without adding modifiers includes the following steps:

[0010] Step (1): Heat and melt the copper alloy raw material, and skim off the charcoal covering and surface slag.

[0011] Step (2): Increase the melting temperature to 1350±50℃, and stir the melt thoroughly while heating;

[0012] Step (3): Keep the temperature at 1350±50℃ and let it stand for 8 to 20 minutes to allow the scum in the melt to float to the surface, then remove all the scum.

[0013] Step (4): Cover with calcined charcoal to a thickness of 10-20 cm;

[0014] Step (5): Reduce the melt temperature to 1200-1310℃ and carry out casting at a speed of 3.5-5.1 m / h;

[0015] Step (6): Heat the cast ingot to 900-1075℃ and extrude it to obtain a cupronickel alloy tube blank.

[0016] By controlling the melting temperature, settling time, and casting speed, this invention successfully prepared a cupronickel alloy with uniform microstructure and small grain size, significantly improving the alloy's resistance to hot cracking at high temperatures. The cast ingots did not exhibit cracks or fissures during hot extrusion into tube blanks, demonstrating excellent product quality. Both the ingots and tube blanks produced by this invention exhibit excellent high-temperature resistance to hot cracking and elongation.

[0017] Step (1) of the present invention: heat and melt the white copper alloy raw material, and skim off the covering charcoal and surface slag.

[0018] Furthermore, the cupronickel alloy raw materials in step (1) include copper, nickel, iron, manganese, and recycled materials of this alloy.

[0019] In this invention, the first type of return material of this alloy refers to ingots with substandard surface and internal structure, ingot heads and tails produced by sawing ingots, extruded tube blank heads and tails, stretched substandard tubes, and heads and tails produced by cut to length. This invention re-inputs substandard or excess products into smelting, which can shorten the smelting cycle and improve furnace efficiency.

[0020] In step (2) of this invention, the melting temperature is increased to 1350±50℃, and the melt is stirred thoroughly during the heating process.

[0021] Furthermore, in step (2), the melt is thoroughly stirred using a stirring rod or an electromagnetic stirrer.

[0022] In this invention, the stirring rod is preferably made of graphite; by using a stirring rod or electromagnetic stirring to fully stir the melt, the fluidity of the melt can be enhanced, the dissolution and diffusion of the metal block can be effectively promoted, the metal elements can be evenly distributed in the melt, and the uniformity of the melt temperature can also be ensured.

[0023] In step (3) of this invention, the slag in the melt is kept at 1350±50℃ for 8 to 20 minutes to allow the slag to float to the surface. Then, the slag is removed.

[0024] This invention controls the melting temperature to 1350±50℃ and the settling time to 8–20 minutes to prevent grain boundary melting due to excessively high temperature or time, poor melt fluidity due to low temperature, or insufficient settling time that hinders inclusion floating and affects subsequent processing. This setting allows slag in the melt to float effectively, thereby purifying the melt and preventing slag from becoming a crack initiation point.

[0025] Furthermore, in step (3), the temperature is kept at 1340-1400℃ and left to stand for 10-20 minutes.

[0026] Furthermore, in step (3), the temperature is kept at 1340-1370℃ and left to stand for 15-20 minutes.

[0027] Furthermore, in step (3), a slag-removing spoon is used to remove slag from the melt.

[0028] Step (4) of the present invention: Cover with calcined charcoal 10-20cm thick.

[0029] This invention uses calcined charcoal to cover the surface of the melt, forming a dense isolation layer that effectively isolates the air from contact with the melt; at the same time, as a porous material, the large specific surface area of ​​calcined charcoal can also enhance the reduction function.

[0030] In step (5) of this invention, the melt temperature is reduced to 1200-1310℃ and casting is carried out at a casting speed of 3.5-5.1m / h.

[0031] This invention refines grain size by slightly lowering the temperature before casting; at the same time, controlling the casting speed to 3.5–5.1 m / h ensures both uniform grain size and production efficiency.

[0032] Furthermore, the casting speed in step (5) is 4.5 to 5.1 m / h.

[0033] Step (6) of the present invention: heating the cast round ingot to 900-1075°C and extruding it to obtain a cupronickel alloy tube blank.

[0034] The round ingots or cupronickel alloy tube blanks prepared by the preparation method described in this invention have excellent high-temperature thermal crack resistance and will not crack or split during subsequent processing.

[0035] The present invention also provides a cupronickel alloy without the addition of a modifier, which is prepared by the preparation method described in claim 1.

[0036] Furthermore, the cupronickel alloy exhibits an elongation of over 80% at 1000℃, and no cracks or fissures appear during hot forging, hot rolling, or welding.

[0037] Compared with existing technologies, the method for improving the high-temperature crack resistance of cupronickel alloys without adding modifiers, as described in this invention, has the following advantages:

[0038] The cupronickel alloy tube blank prepared by this invention has a uniform microstructure and small grain size. It has an elongation of over 80% at 1000℃ and excellent high-temperature thermal crack resistance. No cracks or fissures were observed under hot rolling and other conditions. At the same time, this invention significantly improves the high-temperature thermal crack resistance and elongation of cupronickel alloy without the need to add modifiers. It effectively avoids the impact of modifier slagging on furnace life and reduces equipment maintenance costs. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the described embodiments are only some, not all, of the embodiments of this invention. The specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0040] The present invention will be described in detail below through embodiments.

[0041] The processing steps described in the embodiments of the present invention include hot forging, hot rolling, and welding.

[0042] Example 1:

[0043] This invention has been applied to the preparation of Ф100×10 tube blanks from Ф310 cupronickel alloy BFe10-1.6-1 ingots, as detailed below:

[0044] 1. The cupronickel alloying smelting process completes the melting of copper, nickel, iron and manganese raw materials, as well as a certain proportion of the alloy's first-class recycled material.

[0045] 2. Remove all the charcoal covering the surface and any surface scum.

[0046] 3. Increase the melting temperature to 1300-1320℃. During the temperature increase, use stirring tools such as stirring rods to stir the melt thoroughly, enhance the fluidity of the melt, and ensure that metals such as copper, nickel, and iron are fully melted.

[0047] 4. Keep the temperature at 1300-1320℃ and let it stand for 10-15 minutes to allow the slag in the melt to float to the surface.

[0048] 5. Use tools such as a slag ladle to remove all floating slag.

[0049] 6. Then cover with 10-15cm thick calcined charcoal.

[0050] 7. Casting should be carried out at a melt temperature of 1280℃~1310℃ to avoid excessive heat absorption of gas by the melt. The casting speed should be in the range of 4.0~5.1m / h.

[0051] 8. The cast round ingots are heated to 900-960℃ and extruded to obtain Ф100×10 cupronickel alloy tube blanks.

[0052] The Ф100×10 cupronickel alloy BFe10-1.6-1 tube blank has an elongation of not less than 50% at 800℃ and excellent high-temperature thermal crack resistance. No cracks or fissures were observed during subsequent processing.

[0053] Example 2:

[0054] This invention has been applied to the preparation of Ф76×8 tube blanks from Ф195 cupronickel alloy BFe10-1-1 ingots, as detailed below:

[0055] 1. The cupronickel alloying smelting process completes the melting of copper, nickel, iron and manganese raw materials, as well as a certain proportion of the alloy's first-class recycled material.

[0056] 2. Remove all the charcoal covering the surface and any surface scum.

[0057] 3. Increase the melting temperature to 1310-1340℃. During the temperature increase, use stirring tools such as stirring rods to fully stir the melt, enhance the fluidity of the melt, and ensure that metals such as copper, nickel, and iron are fully melted.

[0058] 4. Keep the temperature at 1310-1340℃ and let it stand for 8-10 minutes to allow the slag in the melt to float to the surface.

[0059] 5. Use tools such as a slag ladle to remove all floating slag.

[0060] 6. Then cover with calcined charcoal to a thickness of 12-20cm.

[0061] 7. Casting should be carried out at a melt temperature of 1250–1300℃ to avoid excessive heat causing gas absorption in the melt. The casting speed should be within the range of 4.0–4.3 m / h.

[0062] 8. The cast round ingots are heated to 920-1000℃ and extruded to obtain Ф76×8 cupronickel alloy tube blanks.

[0063] The Ф76×8 cupronickel alloy BFe10-1-1 tube blank has an elongation of not less than 50% at 900℃, exhibits excellent high-temperature thermal crack resistance, and no cracks or fissures were observed during subsequent processing.

[0064] Example 3:

[0065] This invention has been applied to the preparation of Ф85×7.5 tube blanks from Ф245 cupronickel alloy BFe10-1-1 ingots, as detailed below:

[0066] 1. The cupronickel alloying smelting process completes the melting of copper, nickel, iron and manganese raw materials, as well as a certain proportion of the alloy's first-class recycled material.

[0067] 2. Remove all the charcoal covering the surface and any surface scum.

[0068] 3. Increase the melting temperature to 1340-1370℃. During the temperature increase, use stirring tools such as stirring rods to fully stir the melt, enhance the fluidity of the melt, and allow metals such as copper, nickel, and iron to melt completely.

[0069] 4. Keep the temperature at 1340-1370℃ and let it stand for 10-15 minutes to allow the slag in the melt to float to the surface.

[0070] 5. Use tools such as a slag ladle to remove all floating slag.

[0071] 6. Then cover with 15-20cm thick calcined charcoal.

[0072] 7. Casting should be carried out at a melt temperature of 1200–1300℃ to avoid excessive heat causing gas absorption in the melt. The casting speed should be in the range of 4.5–5.1 m / h.

[0073] 8. The cast round ingots are heated to 950-1075℃ and extruded to obtain Ф85×7.5 cupronickel alloy tube blanks.

[0074] The Ф85×7.5 cupronickel alloy BFe10-1-1 tube blank has an elongation of over 80% at 1000℃ and excellent high-temperature thermal crack resistance. No cracks or fissures were observed during subsequent processing.

[0075] Example 4:

[0076] This invention has been applied to the preparation of Ф125×5 tube blanks from Ф245 cupronickel alloy BFe10-1-1 ingots, as detailed below:

[0077] 1. The cupronickel alloying smelting process involves melting copper, nickel, iron, and manganese raw materials, as well as a certain proportion of Class I recycled material from this alloy. Class I recycled material refers to ingots with surface and internal defects, ingot heads and tails from ingot sawing, extruded tube blank heads and tails, stretched substandard tubes, and heads and tails from fixed-length sawing.

[0078] 2. Remove all the charcoal covering the surface and any surface scum.

[0079] 3. Increase the melting temperature to 1370-1400℃. During the temperature increase, use stirring tools such as stirring rods to stir the melt thoroughly, enhance the fluidity of the melt, and ensure that metals such as copper, nickel, and iron are fully melted.

[0080] 4. Keep the temperature at 1370-1400℃ and let it stand for 20 minutes to allow the slag in the melt to float to the surface.

[0081] 5. Use tools such as a slag ladle to remove all floating slag.

[0082] 6. Then cover with 15-20cm thick calcined charcoal.

[0083] 7. Casting should be carried out at a melt temperature of 1250–1300℃ to avoid excessive heat causing gas absorption in the melt. The casting speed should be in the range of 4.7–5.1 m / h.

[0084] 8. The cast round ingots are heated to 920-1025℃ and extruded to obtain Ф125×5 cupronickel alloy tube blanks.

[0085] The Ф125×5 cupronickel alloy BFe10-1-1 tube blank has an elongation of over 70% at 1000℃, exhibits excellent high-temperature resistance to hot cracking, and has not cracked under conditions such as hot rolling.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the hot crack resistance of cupronickel alloys without adding modifiers, characterized in that, Includes the following steps: Step (1): Heat and melt the copper alloy raw material, and skim off the charcoal covering and surface slag. Step (2): Increase the melting temperature to 1350±50℃, and stir the melt thoroughly while heating; Step (3): Keep the temperature at 1350±50℃ and let it stand for 8 to 20 minutes to allow the scum in the melt to float to the surface, then remove all the scum. Step (4): Cover with calcined charcoal to a thickness of 10-20 cm; Step (5): Reduce the melt temperature to 1200-1310℃ and carry out casting at a speed of 3.5-5.1 m / h; Step (6): Heat the cast ingot to 900-1075℃ and extrude it to obtain a cupronickel alloy tube blank.

2. The method for improving the crack resistance of cupronickel alloys without adding modifiers according to claim 1, characterized in that, The cupronickel alloy raw materials in step (1) include copper, nickel, iron, manganese, and recycled materials of this alloy.

3. A method for improving the crack resistance of cupronickel alloys without adding modifiers, as described in claim 1 or 2, characterized in that, In step (3), the temperature is kept at 1340-1400℃ and left to stand for 10-20 minutes.

4. The method for improving the crack resistance of cupronickel alloys without adding modifiers according to claim 3, characterized in that, In step (3), the temperature is kept at 1340-1370℃ and left to stand for 15-20 minutes.

5. The method for improving the crack resistance of cupronickel alloys without adding modifiers according to claim 3, characterized in that, The casting speed in step (5) is 4.5 to 5.1 m / h.

6. The method for improving the crack resistance of cupronickel alloys without adding modifiers according to claim 1, characterized in that, In step (2), the melt is thoroughly stirred using a stirring rod or an electromagnetic stirrer.

7. The method for improving the crack resistance of cupronickel alloys without adding modifiers according to claim 1, characterized in that, In step (3), a slag scoop is used to remove the slag from the melt.

8. A cupronickel alloy without added modifiers, characterized in that, It was prepared using the preparation method described in claim 1.

9. A cupronickel alloy without added modifiers according to claim 8, characterized in that, The cupronickel alloy exhibits an elongation of over 80% at 1000℃, and no cracks or fissures appear during hot forging, hot rolling, or welding.