阅读说明：本技术 一种高强镍钴基合金管材的制备成型工艺 (Preparation and forming process of high-strength nickel-cobalt-based alloy pipe ) 是由 严靖博 杨征 张醒兴 谷月峰 袁勇 黄锦阳 于 2020-05-08 设计创作，主要内容包括：一种高强镍钴基合金管材的制备成型工艺,按质量百分比计包括：Cr：17～20％,Co：27～30％,Ti：1.5～3.5％,Al：3.0～4.5％,W：3.0～9.0％,Mo：≤1.0％,Nb：0.5～1.0％,Ta：≤1.0％,Si：≤0.5％,Mn：≤0.5％,C：0.04～0.07％,B：≤0.003％,Zr：0.01～0.03％,Hf：0.05～0.15％,余量为Ni；合金熔炼后均匀化处理,热轧,最后进行热处理。本发明的合金具备极高的高温强度性能,其铸态合金经固溶处理后在1160℃及1180℃压缩屈服强度分别不低于110MPa及100MPa。(A preparation forming process of a high-strength nickel-cobalt-based alloy pipe comprises the following steps of: cr: 17-20%, Co: 27-30%, Ti: 1.5-3.5%, Al: 3.0-4.5%, W: 3.0-9.0%, Mo: less than or equal to 1.0 percent, Nb: 0.5 to 1.0%, Ta: less than or equal to 1.0 percent, Si: less than or equal to 0.5 percent, Mn: less than or equal to 0.5 percent, C: 0.04-0.07%, B: less than or equal to 0.003 percent, Zr: 0.01-0.03%, Hf: 0.05-0.15% and the balance of Ni; homogenizing after alloy smelting, hot rolling and finally heat treatment. The alloy of the invention has extremely high-temperature strength performance, and the compression yield strength of the as-cast alloy after solution treatment at 1160 ℃ and 1180 ℃ is not lower than 110MPa and 100MPa respectively.)

1. A preparation forming process of a high-strength nickel-cobalt-based alloy pipe is characterized by comprising the following steps:

1) alloy smelting: taking Cr: 17-20%, Co: 27-30%, Ti: 1.5-3.5%, Al: 3.0-4.5%, W: 3.0-9.0%, Mo: less than or equal to 1.0 percent, Nb: 0.5 to 1.0%, Ta: less than or equal to 1.0 percent, Si: less than or equal to 0.5 percent, Mn: less than or equal to 0.5 percent, C: 0.04-0.07%, B: less than or equal to 0.003 percent, Zr: 0.01-0.03%, Hf: 0.05-0.15% and the balance of Ni;

adding Cr, Co, Ni, W, Nb, Mo, Ta, Si and Mn into an induction arc furnace, refining for 0.5-1h after melting, and then adding Al, Ti, B, Zr and C under the protection of argon to obtain an alloy ingot;

2) homogenizing: the alloy ingot is kept at 950-1050 ℃ for 0.5-1.0 h and then is subjected to Ni treatment₃Homogenizing at 10-50 deg.C above Al solid solution temperature for 24-72 hr, and air cooling to room temperature;

3) high-temperature hot rolling: the alloy after the homogenization treatment is insulated for 2 to 3 hours at the temperature of 1140-1180 ℃, and then high-temperature rolling is carried out;

4) and (6) heat treatment.

2. The process of claim 1, wherein in step 2), the temperature is raised from room temperature to 950-1050 ℃ at a rate of 10-20 ℃/min.

3. The process for preparing and forming a high-strength nickel-cobalt-based alloy pipe according to claim 1, wherein before the step 3), the homogenized alloy is drilled inside, then the surfaces of the inner wall and the outer wall are turned to form a pipe blank, and finally a 304 stainless steel plate is used for respectively coating the inner wall and the outer wall of the pipe blank.

4. The process for preparing and forming a high-strength nickel-cobalt-based alloy pipe according to claim 3, wherein the outer wall of the pipe blank is coated with a 304 stainless steel plate with the thickness of 2.5-3.5mm, and the inner wall of the pipe blank is coated with a 304 stainless steel plate with the thickness of 1.0-1.5 mm.

5. The process of claim 1, wherein in step 3), the temperature is raised from room temperature to 1140-1180 ℃ at a rate of 10-20 ℃/min.

6. The process for preparing and forming a high-strength nickel-cobalt-based alloy pipe as claimed in claim 1, wherein in the step 3), the extrusion ratio of the high-temperature rolling is 7-9.

7. The preparation and forming process of the high-strength nickel-cobalt-based alloy pipe material according to claim 1, wherein the specific process of the step 4) is as follows: keeping the temperature of the rolled alloy at the temperature of more than 30 ℃ of the gamma' solid solution temperature for 0.5 to 2.0 hours, and cooling the alloy to room temperature in air after the heat preservation is finished; then air cooling is carried out after heat preservation is carried out for 3-9 hours in the range of 300-350 ℃ below the gamma 'solid solution temperature, and finally air cooling is carried out after heat preservation is carried out for 1-3 hours in the range of 200-250 ℃ below the gamma' solid solution temperature.

8. The process for preparing and forming a high-strength nickel-cobalt-based alloy pipe as recited in claim 7, wherein the temperature is raised to a temperature above the γ' solution temperature by 30 ℃ at a rate of 50-90 ℃/min.

Technical Field

The invention belongs to the field of high-temperature alloy, and particularly relates to a preparation and forming process of a high-strength nickel-cobalt-based alloy pipe, which is particularly suitable for high-temperature key parts such as a fire power advanced ultra-supercritical unit filter/reheater pipe and the like.

Background

With the increasing demand of electricity in China, the problems of energy shortage and environmental pollution are increasingly highlighted, and the demand for developing efficient, energy-saving and environment-friendly power generation modes is more urgent. Thermal power generation is the most important power generation technology in China for a long time, and the improvement of steam parameters of a unit is considered to be the most effective way for solving the problems. A great deal of past practice shows that the service performance of key component materials is the most main reason for restricting the improvement of steam parameters of a boiler unit, and as one of the key components with the severest service working conditions in the boiler of a thermal power unit, components such as an over/reheater pipe and the like have extremely high requirements on the service performance of the materials. With the great improvement of main steam parameters of the thermal power generating unit, the development of high-temperature alloy materials which can meet the performance requirements of key components of the advanced ultra-supercritical unit and have excellent processing performance is a problem to be solved urgently in the thermal power generation industry.

The pass/reheater and the like are used as parts with the severest service working conditions in the boiler of the thermal power generating unit, and have high requirements on the lasting strength and the corrosion resistance of candidate materials. Currently, a series of nickel-based wrought superalloy materials have been developed abroad, such as Inconel 740H developed by U.S. special metals, Haynes 282 developed by U.S. hastella, CCA617 developed by dergarton corp, Nimonic 263 developed by Rolls-Royce, uk, FENIX700 developed by hitachi, TOS1X developed by toshiba, and LTESR700 developed by mitsubishi. To ensure excellent long-term strength of the alloy, current candidate materials tend to have a lower Al/Ti ratio. Meanwhile, the higher Cr element content in the alloy ensures the oxidation resistance and corrosion resistance of the alloy. However, with the continuous increase of steam parameters of the thermal power generating unit, the test of alloy performance is more severe.

In order to obtain a good high-temperature strength, a large amount of solid-solution strengthening elements such as W, Mo and precipitation strengthening elements such as Al, Ti, Nb, and Ta are often added to the alloy. Meanwhile, enough Al and Cr element contents need to be ensured in the alloy so as to ensure that the alloy has excellent corrosion/oxidation resistance during high-temperature service. However, the addition of the above elements has a serious influence on the alloy workability, and for example, the addition of W increases the red hardness of the alloy, and the addition of Nb easily promotes the precipitation of a harmful phase such as grain boundary CrNbN.

Disclosure of Invention

The invention aims to develop a preparation and forming process of a high-strength nickel-cobalt-based alloy pipe, which guarantees the good high-temperature strength and corrosion resistance of the alloy and also considers the processing and forming performance of the alloy. Precipitation strengthening elements such as Al, Ta and the like and solid solution strengthening elements such as W and the like are added to ensure the excellent high-temperature strength performance of the alloy, and meanwhile, the content of Al and Cr is increased on the premise of structural stability to improve the corrosion/oxidation resistance of the alloy. In addition, the contents of Mo, Ti, Nb and other elements in the alloy are adjusted to weaken the adverse effect on the corrosion resistance and the processability of the alloy.

In order to achieve the above purpose, the invention adopts the technical scheme that:

a preparation and forming process of a high-strength nickel-cobalt-based alloy pipe comprises the following steps:

1) alloy smelting: taking Cr: 17-20%, Co: 27-30%, Ti: 1.5-3.5%, Al: 3.0-4.5%, W: 3.0-9.0%, Mo: less than or equal to 1.0 percent, Nb: 0.5 to 1.0%, Ta: less than or equal to 1.0 percent, Si: less than or equal to 0.5 percent, Mn: less than or equal to 0.5 percent, C: 0.04-0.07%, B: less than or equal to 0.003 percent, Zr: 0.01-0.03%, Hf: 0.05-0.15% and the balance of Ni;

adding Cr, Co, Ni, W, Nb, Mo, Ta, Si and Mn into an induction arc furnace, refining for 0.5-1h after melting, and then adding Al, Ti, B, Zr and C under the protection of argon to obtain an alloy ingot;

2) homogenizing: the alloy ingot is kept at 950-1050 ℃ for 0.5-1.0 h and then is subjected to Ni treatment₃AlHomogenizing at 10-50 deg.C above the solid solution temperature for 24-72 hr, and air cooling to room temperature;

3) high-temperature hot rolling: the alloy after the homogenization treatment is insulated for 2 to 3 hours at the temperature of 1140-1180 ℃, and then high-temperature rolling is carried out;

4) and (6) heat treatment.

The invention is further improved in that in the step 2), the temperature is increased from room temperature to 950-1050 ℃ at the speed of 10-20 ℃/min.

The further improvement of the invention is that before the step 3), the interior of the homogenized alloy is drilled, then the surfaces of the inner wall and the outer wall are turned to form a tube blank, and finally, a 304 stainless steel plate is adopted to respectively coat the inner wall and the outer wall of the tube blank.

The invention is further improved in that the outer wall of the tube blank is coated by a 304 stainless steel plate with the thickness of 2.5-3.5mm, and the inner wall of the tube blank is coated by a 304 stainless steel plate with the thickness of 1.0-1.5 mm.

The invention is further improved in that in the step 3), the temperature is increased from room temperature to 1140-1180 ℃ at the speed of 10-20 ℃/min.

The invention is further improved in that in the step 3), the extrusion ratio of high-temperature rolling is 7-9.

The further improvement of the invention is that the specific process of the step 4) is as follows: keeping the temperature of the rolled alloy at the temperature of more than 30 ℃ of the gamma' solid solution temperature for 0.5 to 2.0 hours, and cooling the alloy to room temperature in air after the heat preservation is finished; then air cooling is carried out after heat preservation is carried out for 3-9 hours in the range of 300-350 ℃ below the gamma 'solid solution temperature, and finally air cooling is carried out after heat preservation is carried out for 1-3 hours in the range of 200-250 ℃ below the gamma' solid solution temperature.

The invention is further improved in that the temperature is raised to be within 30 ℃ above the gamma' solid solution temperature at the speed of 50-90 ℃/min.

Compared with the prior art, the invention has the beneficial effects that: the processing performance of the alloy is greatly challenged by higher contents of strengthening elements such as W, Al, Ti and the like in the alloy, so the processing of the alloy generally needs to be carried out at higher temperature. However, excessive processing temperature easily causes the grain boundary overtemperature, and particularly easily causes the workpiece to crack when the deformation amount is large. Therefore, the invention not only ensures the good high-temperature strength and corrosion resistance of the alloy, but also gives consideration to the processing and forming performance of the alloy. Precipitation strengthening elements such as Al, Ta and the like and solid solution strengthening elements such as W and the like are added to ensure the excellent high-temperature strength performance of the alloy, and meanwhile, the content of Al and Cr is increased on the premise of structural stability to improve the corrosion/oxidation resistance of the alloy. In addition, the contents of Mo, Ti, Nb and other elements in the alloy are adjusted to weaken the adverse effect on the corrosion resistance and the processability of the alloy.

Furthermore, the mode of inner and outer wall sheathing is adopted in the processing process to avoid overlarge temperature drop amplitude, the alloy deformation temperature range is strictly controlled to avoid the initiation and the expansion of cracks, and finally, a finished pipe is obtained through single-pass large deformation processing, so that the processing technology of the alloy is greatly simplified. Meanwhile, the alloy has larger strain energy storage, so that the grain size and the like of the alloy can be effectively regulated and controlled, and the mechanical property of the alloy is further improved.

Drawings

FIG. 1 is a photograph of the jacketed pipe blanks of examples 1 to 4 and comparative example 1;

FIG. 2 is a view showing the outer wall of a pipe blank coated with a heat insulating agent before hot rolling in example 1;

FIG. 3 is a photograph of hot rolled pipes of examples 1-4;

FIG. 4 is a photograph of a hot-rolled pipe of comparative example 1.

Detailed Description

The present invention will be described in further detail with reference to examples.

The invention is developed aiming at the requirements of advanced ultra-supercritical thermal power generating units, and can meet the service performance requirements of high-temperature parts such as a superheater/reheater and the like.

The alloy has extremely high-temperature strength performance, and the compression yield strengths of the as-cast alloy at 1160 ℃ and 1180 ℃ are not lower than 110MPa and 100MPa respectively after solution treatment. After rolling and forming, a small-caliber pipe with the outer diameter of 44mm and the wall thickness of 10mm can be prepared, and the extrusion ratio is 7-9.

A preparation forming process of a high-strength nickel-cobalt-based alloy pipe comprises five steps of alloy smelting, homogenization treatment, rolling pretreatment, high-temperature hot rolling and heat treatment, and specifically comprises the following steps:

1) alloy smelting: taking Cr: 17-20%, Co: 27-30%, Ti: 1.5-3.5%, Al: 3.0-4.5%, W: 3.0-9.0%, Mo: less than or equal to 1.0 percent, Nb: 0.5 to 1.0%, Ta: less than or equal to 1.0 percent, Si: less than or equal to 0.5 percent, Mn: less than or equal to 0.5 percent, C: 0.04-0.07%, B: less than or equal to 0.003 percent, Zr: 0.01-0.03%, Hf: 0.05-0.15% and the balance of Ni;

smelting in an induction arc furnace, controlling the vacuum degree within the range of 0.3-0.5Pa, refining for 0.5-1h after Cr, Co, Ni, W, Nb and other elements are completely melted, and adding Al, Ti, B, Zr and C under the protection of high-purity argon to obtain an alloy ingot; wherein, when the alloy is smelted, a magnesia alkaline furnace lining is adopted, a pure nickel washing furnace is adopted before smelting, and shot blasting treatment is carried out before adding the alloy raw material;

2) homogenizing: heating the alloy ingot from room temperature to 950 ℃ and 1050 ℃ at the speed of 10-20 ℃/min, preserving the heat for 0.5-1.0 h, then continuing to heat and adding Ni₃Homogenizing at 10-50 deg.C above Al (gamma') solid solution temperature for 24-72 hr, and air cooling to room temperature;

after the alloy is subjected to homogenization treatment, the compressive yield strengths of the alloy at 1160 ℃ and 1180 ℃ are not lower than 110MPa and 100MPa respectively;

3) pretreatment before rolling: drilling the interior of the alloy, turning the surfaces of the inner wall and the outer wall of the alloy to form a tube blank, and respectively coating the surfaces of the inner wall and the outer wall of the tube blank by using 304 stainless steel plates to avoid the problems of over-high temperature, transverse shear stress and the like in the rolling process; specifically, the thickness of the 304 alloy used for the outer wall sheath of the alloy tube blank is 2.5-3.5mm, and the thickness of the 304 alloy used for the inner wall sheath is 1.0-1.5 mm.

4) High-temperature hot rolling: before rolling, the surfaces of a core rod and a die need to be coated with lubricating oil, and the surface of a pipe blank needs to be coated with a heat preservation agent; then heating the sheathed alloy pipe blank from room temperature to 1140-1180 ℃ at the speed of 10-20 ℃/min, preserving the heat for 2-3 hours, and then carrying out high-temperature rolling on the alloy pipe blank, wherein the extrusion ratio is 7-9;

5) and (3) heat treatment: heating the rolled alloy from room temperature to a temperature which is 30 ℃ above the gamma' solid solution temperature at a speed of 50-90 ℃/min, preserving the heat for 0.5-2.0 hours, and cooling the alloy to room temperature in air after the completion; then heating the alloy to the temperature of 300-350 ℃ below the gamma 'solid solution temperature, then carrying out air cooling after the heat preservation is carried out for 3-9 hours, and finally heating to the temperature of 200-250 ℃ below the gamma' solid solution temperature, then carrying out air cooling after the heat preservation is carried out for 1-3 hours.

After alloy rolling is finished, the outer diameter is 44-46mm, and the wall thickness is 10-11 mm. The length of the processed and formed pipe can reach 1.5-2.0 meters.