A method for preparing a small-size GH4105 alloy rod

Abstract

The present application belongs to the technical field of high-temperature alloy processing, and discloses a preparation method of GH4105 alloy small-size rod, which comprises the following steps: performing one-time high-temperature homogenization treatment on a GH4105 ingot, then performing seven-time open-die forging to obtain a rod with a diameter of Φ120mm-Φ200mm; performing one-time high-temperature homogenization treatment on the rod with a diameter of Φ120mm-Φ200mm, then performing one-time rolling to obtain a rod with a diameter of Φ45mm-Φ75mm; performing one-time or two-time rolling on the rod with a diameter of Φ45mm-Φ75mm to obtain a rod with a diameter of Φ8mm-Φ33mm, and after straightening and grinding, a finished rod with a diameter of Φ5mm-Φ30mm meeting the standard requirements is obtained. The present application makes the carbide distribution more uniform and improves the mixed crystal problem, and improves the consistency and stability of the structure and performance of the rod.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy processing technology, specifically relating to a method for preparing small-diameter bars of GH4105 alloy. Background Technology

[0002] GH4105 alloy is a nickel-based age-hardening superalloy. This alloy is strengthened through solid solution treatment and age precipitation hardening by adding large amounts of Co, Mo, Al, and Ti. With the development of my country's aerospace, power, and petrochemical industries, the demand for superalloys is increasing year by year. GH4105 possesses good room temperature and high temperature strength, excellent corrosion resistance, structural stability, good creep resistance, and oxidation resistance, allowing it to be used at temperatures ranging from 750 to 950℃. It is widely used in the manufacture of various components such as turbine blades, turbine disks, annular parts, bolts, and fasteners.

[0003] Due to its high degree of alloying, GH4105 has a combined Al and Ti mass fraction greater than 6%, and contains relatively high levels of Co (18%–22%) and Mo (4.5%–5.5%), resulting in severe elemental segregation. Furthermore, its C content is as high as 0.12%–0.17%, and if the C composition is uneven, carbide banding is highly likely to occur. In addition, the γ' phase precipitation can reach 45% (mass fraction), which easily generates precipitation stress and thermal stress. Combined with the influence of grain boundary carbide banding, this further increases the likelihood of cracking during deformation and heat treatment, causing significant difficulties in production. It is a typical example of a difficult-to-deform and easily cracked alloy with a narrow hot-working window. Although GH4105 is a coarse-grained alloy with relatively low grain size requirements, controlling the uniformity, consistency, and stability of its composition, microstructure, and mechanical properties is extremely difficult. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing small-diameter bars of GH4105 alloy, which makes the carbide distribution more uniform and improves the mixed crystal problem, thereby improving the consistency and stability of the microstructure and properties of the bars.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing small-diameter bars of GH4105 alloy includes the following steps:

[0007] Step 1: The GH4105 ingot is subjected to a high-temperature homogenization treatment, and then subjected to seven-stage forging to obtain bars with diameters of Φ120mm to Φ200mm.

[0008] Step 2: The Φ120mm~Φ200mm bars are subjected to another high-temperature homogenization treatment, and then rolled in one pass to obtain Φ45mm~Φ75mm bars.

[0009] Step 3: Roll the Φ45mm~Φ75mm bars in one or two passes to obtain Φ8mm~Φ33mm bars. After straightening and grinding, obtain finished bars of Φ5mm~Φ30mm that meet the standard requirements.

[0010] Preferably, in step 1, the high-temperature homogenization treatment involves maintaining the temperature at 1110–1200°C for at least 50 hours.

[0011] Preferably, in step 1, the seven-stage forging process includes four stages of upsetting and drawing, two stages of drawing and elongation, and one stage of rounding.

[0012] Preferably, in step 1, the ingot is forged on a high-speed forging machine of 4500T or above.

[0013] Preferably, in step 1, the first heating temperature is 1090℃~1190℃, held for 4~6 hours, the upsetting deformation is 10%~25%, and the final forging temperature is not lower than 900℃. The heating temperature of the second to fourth heating processes gradually decreases to 1090℃~1170℃ with each heating process, held for 4~6 hours, the upsetting deformation is 15%~45%, of which the upsetting deformation is not less than 30%, and the deformation increases with each heating process, and the final forging temperature is not lower than 900℃. The heating temperature of the fifth to sixth heating processes is 1090℃~1150℃, held for 4~6 hours, the deformation further increases to 30%~50%, and the final forging temperature is not lower than 750℃. The heating temperature of the seventh heating process is 1090℃~1150℃, held for 4~6 hours, the deformation is 3%~10%, and the final forging temperature is not lower than 750℃.

[0014] Preferably, in step 2, the high-temperature homogenization treatment involves maintaining the temperature at 1110–1200℃ for at least 30 hours.

[0015] Preferably, in step 2, the bar is rolled in one pass on a 650 reversible rolling mill or a 550 three-roll tandem rolling mill, with a heating temperature of 1100℃~1200℃ and a holding time of 3.5~5 hours.

[0016] Preferably, in step 2, the single-pass rolling includes multiple passes, the deformation of each pass is controlled at 10% to 25%, and the interval between each pass is 5s to 20s, and the surface temperature of the bar after rolling is greater than 900℃.

[0017] Preferably, in step 3, the bar is rolled once or twice on a 350 three-roll tandem mill, with a heating temperature of 1100℃~1200℃ and a holding time of 1~2 hours.

[0018] Preferably, in step 3, the single-pass rolling includes multiple passes, the deformation per pass is controlled at 12% to 25%, and the interval between each pass is 0s to 10s, and the surface temperature of the bar after rolling is greater than 900℃.

[0019] The present invention has the following beneficial effects: The present invention eliminates the carbide band structure of the bar by means of two high-temperature homogenization treatments and reasonable fast forging mill billet opening and rolling process, so that the carbide distribution is more uniform. By precisely controlling the various factors affecting the temperature during the deformation process, the surface cracking and edge-core structure difference of the bar are avoided, which improves the consistency and stability of the bar structure and properties. The low magnification transverse and longitudinal structure and carbides of small-diameter bars of Φ5mm to Φ30mm are uniformly distributed. The structure after solution treatment is uniform and free of mixed crystals, and the grain size reaches 3.0 to 4.0 grade, which breaks through the ≥0 grade grain size requirement of the relevant aero-engine standards. At the same time, the performance of the heat-treated bar meets the corresponding standard requirements. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention.

[0021] Figure 2 The images show the carbide distribution in the as-cast microstructure of the Φ460mm ingot of this invention. In the images, Figure a represents the carbides in the core of the ingot, Figure b represents the carbides in the R / 2 area of ​​the ingot, and Figure c represents the carbides in the edge area of ​​the ingot.

[0022] Figure 3 This is a high-magnification microstructure diagram of the Φ460mm ingot of the present invention in the as-cast state, wherein Figure a represents the high-magnification microstructure of the ingot core, Figure b represents the high-magnification microstructure of the ingot R / 2, and Figure c represents the high-magnification microstructure of the ingot edge.

[0023] Figure 4 The images show the actual distribution of transverse and longitudinal carbides in the Φ150mm bar after high-temperature homogenization according to the present invention. In the images, Figure a represents longitudinal core carbides, Figure b represents longitudinal R / 2 carbides, Figure c represents longitudinal edge carbides, Figure d represents transverse core carbides, Figure e represents transverse R / 2 carbides, and Figure f represents transverse edge carbides.

[0024] Figure 5 The diagram shows the high-magnification microstructure of the transverse and longitudinal sections of the Φ150mm bar after high-temperature homogenization according to the present invention. In the diagram, Figure a represents the high-magnification group of the longitudinal core, Figure b represents the high-magnification group of the longitudinal R / 2 section, Figure c represents the high-magnification group of the longitudinal edge section, Figure d represents the high-magnification group of the transverse core section, Figure e represents the high-magnification group of the transverse R / 2 section, and Figure f represents the high-magnification group of the transverse edge section.

[0025] Figure 6 The figures shown are actual images of the carbide distribution in the Φ53mm rolled bar of the present invention. In the figures, a represents the transverse edge, b represents the transverse center, c represents the longitudinal edge, and d represents the longitudinal center.

[0026] Figure 7This is a high-magnification schematic diagram of the transverse and longitudinal microstructure of the Φ53mm rolled bar of the present invention, wherein Figure a represents the transverse core, Figure b represents the transverse edge, Figure c represents the longitudinal edge, and Figure d represents the longitudinal core.

[0027] Figure 8 The image shows the actual distribution of carbides in the hot-rolled state of the Φ21.5mm bar of the present invention, where Figure a represents transverse carbides and Figure b represents longitudinal carbides.

[0028] Figure 9 This is a schematic diagram of the high-magnification microstructure of the Φ21.5mm bar in the hot-rolled state according to the present invention, wherein Figure a represents the transverse high-magnification microstructure and Figure b represents the longitudinal high-magnification microstructure.

[0029] Figure 10 The images show the distribution of carbides in the solid solution aged state of the Φ20mm bar of this invention. In Figure a, carbides are represented by transverse carbides, and carbides are represented by longitudinal carbides.

[0030] Figure 11 This is a schematic diagram of the high-magnification microstructure of the Φ20mm bar material in the solution-treated and aged state according to the present invention. In the diagram, Figure a represents the transverse high-magnification microstructure and Figure b represents the longitudinal high-magnification microstructure. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments.

[0032] like Figure 1 As shown, a method for preparing small-diameter GH4105 alloy bars includes the following steps:

[0033] Step 1: The GH4105 ingot is subjected to a high-temperature homogenization treatment, and then subjected to seven-stage forging to obtain bars with diameters of Φ120mm to Φ200mm.

[0034] Before forging, the ingot needs to undergo a high-temperature homogenization heat treatment. This is achieved by controlling the furnace charging temperature, heating rate, and multi-stage heating and holding process, maintaining the temperature at 1110–1200℃ for no less than 50 hours. This is to eliminate low-melting-point phases, segregation, and eutectic phases, and to prevent the formation of banded structures during subsequent processing, thus preventing cracking of the bar during forging.

[0035] The seven-stage forging process includes four stages of upsetting and drawing, two stages of drawing for chamfering, and one stage of rounding. These multiple stages of upsetting and drawing ensure the refinement, uniformity, and surface quality of the bar stock while reducing carbide banding, thus ensuring smooth operation of the subsequent rolling process. The ingot is forged on a 4500T (ensuring sufficient forging force) or higher high-speed forging mill. The forging method is axial upsetting deformation. The first stage heating temperature is 1090℃~1190℃, held for 4~6 hours. Upsetting and drawing uses a relatively small deformation amount, 10%~25%, to improve the as-cast microstructure while preventing surface cracking. The final forging temperature is not lower than 900℃, and the forged material is air-cooled. The heating temperature for the second to fourth forging processes gradually decreases to 1090℃–1170℃, and is held for 4–6 hours. A larger deformation amount is used in the upsetting and drawing, ranging from 15% to 45% (of which the upsetting deformation is not less than 30%), and this deformation increases with each forging. This large deformation process effectively and thoroughly breaks down and homogenizes the microstructure, thereby reducing the banded distribution of carbides and further refining the grains to improve the microstructure and properties. The final forging temperature is not lower than 900℃, and the forged material is air-cooled. The fifth and sixth forging processes are mainly for drawing and shaping, with a heating temperature of 1090℃–1150℃ and a holding time of 4–6 hours. The deformation amount is further increased to 30%–50%. While extending the compressed cross-section of the bar stock (from square to octagonal), the microstructure is further broken down, refined, and homogenized, and properties are improved. The final forging temperature is not lower than 750℃, and the forged material is air-cooled. The seventh forging process is mainly a shaping and rounding process. The heating temperature is 1090℃~1150℃, and the holding time is 4~6 hours. The deformation amount is 3%~10%. The main purpose is to round the cross-section of the bar from an octagon to Φ120mm~Φ200mm. The final forging temperature is not lower than 750℃, and the bar is air-cooled after forging.

[0036] GH4105 alloy billet forging is highly temperature-sensitive, exhibiting a strong tendency to crack during the forging process. The forging temperature cannot be too low, but excessively high forging temperatures may result in a coarse microstructure, affecting subsequent processing. Therefore, strict control of deformation and temperature is necessary during forging. Intermediate reheating can be performed during the forging process based on the actual temperature drop. The upper and lower hammers, anvils, and other related tools and dies of the high-speed forging mill must be preheated to a temperature not lower than 400℃. If the forging interval exceeds 30 minutes, the relevant tools and dies must be reheated. The transfer speed and time of the bar stock should be controlled within 90 seconds. The bar stock must be covered with a soft sheath to prevent surface temperature drop. A combination of square and octagonal forging methods should be used to minimize dendritic structures and prevent deformation dead zones, improving microstructure uniformity and providing qualified bars for subsequent rolling processing.

[0037] Step 2: The Φ120mm~Φ200mm bars are subjected to another high-temperature homogenization treatment, and then rolled in one pass to obtain Φ45mm~Φ75mm bars.

[0038] Bars with diameters of 120mm to 200mm require a second high-temperature homogenization heat treatment before rolling. This is achieved by controlling the furnace charging temperature, heating rate, and a two-stage heating and holding process, holding at 1110–1200℃ for at least 30 hours to further reduce and eliminate microsegregation in the bars. The 120mm–200mm bars are then rolled in a single pass on a 650 reversible mill or a 550 three-roll tandem mill to produce bars with diameters of 45mm to 75mm. The heating temperature is 1100℃–1200℃, and the holding time is 3.5–5 hours. To reduce cracking and ensure uniform microstructure, a uniformly deformed box-elliptical-round hole system is used. To prevent excessive edge-center temperature differences that could lead to poor microstructure uniformity, the deformation per pass is controlled at 10%–25%, with an interval of 5–20 seconds between passes. After rolling, the surface temperature of the bars exceeds 900℃.

[0039] Step 3: Roll the Φ45mm~Φ75mm bars in one or two passes to obtain Φ8mm~Φ33mm bars. After straightening and grinding, obtain finished bars of Φ5mm~Φ30mm that meet the standard requirements.

[0040] Bars with diameters of 45mm to 75mm are rolled in one or two passes on a 350mm three-roll tandem mill to achieve a final size of 8mm to 33mm before grinding. To prevent excessive passes and long rolling cycles that could lead to surface cracking due to low temperatures and increased differences in microstructure between the edges and center, two passes are used for diameters below 15mm, while one pass is used for diameters above 15mm. The heating temperature is 1100℃ to 1200℃, with a holding time of 1 to 2 hours. To reduce surface cracking and differences in microstructure between the edges and center caused by rapid temperature drops in smaller diameter bars, an elliptical-square hole rolling system with large elongation and corner changes is used to achieve greater elongation deformation (making the surface temperature drop of the rolled piece more uniform). The bars are then rolled to the final size before grinding using an elliptical-round hole rolling system. The deformation per pass is controlled at 12% to 25%, with an interval of 0s to 10s between each pass. The surface temperature of the rolled bar is greater than 900℃.

[0041] In steps 2 and 3, preheating before rolling should be carried out slowly, with stepped heat preservation before rising to the rolling temperature to avoid surface cracking caused by excessive thermal stress. The rolling process should be carried out at a relatively high temperature, and the rolls should be preheated to a temperature of not less than 100°C to avoid surface cracking and microstructure differences in the finished bar due to temperature drop.

[0042] The present invention will be further described in detail through the following embodiments.

[0043] Example 1

[0044] A method for preparing small-diameter bars of GH4105 alloy, specifically including the following:

[0045] Step 1: The GH4105 alloy ingot with a diameter of Φ510mm undergoes a high-temperature homogenization treatment, held at 1190℃ for 55 hours. The initial three heating cycles for the initial forging are at 1160℃, and the subsequent four heating cycles are at 1130℃, held for 4-5 hours. The initial forging is performed using an 8000T high-speed forging mill, followed by seven heating cycles to an ingot with a diameter of Φ160mm. The deformation process consists of four heating cycles and two heating cycles for lengthening followed by one heating cycle for rounding. The deformation during the lengthening cycle is 20%-50% (with the upsetting deformation not less than 30%), gradually increasing with each heating cycle. The deformation during the rounding cycle is 7%. After the first four heating cycles, the surface temperature of the ingot is above 930℃, and after the subsequent three heating cycles, the surface temperature is above 820℃. After forging, the ingot is air-cooled and 100% of its defects are removed.

[0046] Step 2: Perform a high-temperature homogenization heat treatment on the Φ160mm GH4105 alloy bar, holding at 1170℃ for 32 hours. Roll the Φ160mm bar to Φ65mm bar on a 650 reversible rolling mill or a 550 tandem rolling mill, heating at 1120℃ and holding for 3.5 hours. Control the deformation per pass to 15%–25%, with an average interval of 11 seconds between passes. The surface temperature of the rolled bar is 1023℃. After rolling, air cool and 100% clean any defects.

[0047] Step 3: Roll the Φ65mm bar to Φ33mm on a transverse rolling mill. The heating temperature is 1100℃, and the holding time is 1.5 hours. The deformation per pass is controlled at 15%–25%, with an average interval of 5 seconds between passes. The surface temperature of the rolled bar is 1053℃. After rolling, the bar is air-cooled. It is then straightened and ground to Φ30mm.

[0048] Example 2

[0049] A method for preparing small-diameter bars of GH4105 alloy, specifically including the following:

[0050] Step 1: The GH4105 alloy ingot with a diameter of Φ460mm undergoes a high-temperature homogenization treatment, held at 1180℃ for 50 hours. The first three heating cycles for the initial forging are at 1150℃, and the subsequent four heating cycles are at 1120℃, held for 4-5 hours. The initial forging is performed using a 4500T high-speed forging mill, followed by seven heating cycles to an ingot with a diameter of Φ150mm. The deformation process consists of four heating cycles and two heating cycles for lengthening followed by one heating cycle for rounding. The deformation during the lengthening cycle is 20%-45% (of which the upsetting deformation is not less than 30%), gradually increasing with each heating cycle. The deformation during the rounding cycle is 6%. After the first four heating cycles, the surface temperature of the ingot is above 935℃, and after the subsequent three heating cycles, the surface temperature is above 830℃. After forging, the ingot is air-cooled and 100% of its defects are removed.

[0051] Step 2: Perform a high-temperature homogenization heat treatment on the Φ150mm GH4105 alloy bar, holding at 1170℃ for 30 hours. Roll the Φ150mm bar to Φ53mm bar on a 650 reversible rolling mill or a 550 tandem rolling mill, heating at 1150℃ and holding for 3.5 hours. Control the deformation per pass to 14%–24%, with an average interval of 7 seconds between passes. The surface temperature of the rolled bar is 1026℃. After rolling, air cool and 100% clean any defects.

[0052] Step 3: Roll the Φ53mm bar to Φ21.5mm on a transverse rolling mill. The heating temperature is 1100℃, and the holding time is 1 hour. The deformation per pass is controlled at 16%–25%, with an average interval of 4 seconds between passes. The surface temperature of the rolled bar is 1022℃. After rolling, the bar is air-cooled. It is then straightened and ground to Φ20mm.

[0053] Example 3

[0054] A method for preparing small-diameter bars of GH4105 alloy, specifically including the following:

[0055] Steps 1 and 2 are the same as in Example 2, and will not be repeated here.

[0056] Step 3: Roll the Φ53mm bar to Φ9.5mm in two passes on a transverse rolling mill. The first pass rolls to a Φ26.5mm intermediate billet. The first pass is heated to 1100℃ and held for 1 hour, with the deformation per pass controlled at 16%–25%, and an average interval of 6 seconds between passes. The surface temperature of the rolled bar is 1032℃. The second pass is heated to 1150℃ and held for 1 hour, with the deformation per pass controlled at 10%–24%, and an average interval of no more than 1 second between passes. The surface temperature of the rolled bar is 1005℃ (the length of the Φ26.5mm intermediate billet should not exceed 1500mm; otherwise, the final rolling temperature will be less than 1000℃). After rolling to Φ9.5mm, air cooling is performed. Subsequent straightening and grinding to Φ8.0mm are then carried out.

[0057] Performance testing of small-diameter GH4105 alloy bars prepared by the method of this invention:

[0058] Multiple batches of production were carried out using the method of the present invention, and the high-temperature creep performance data of GH4105 alloy small-diameter bars with a specification of Φ20mm are shown in Table 1, and the room temperature tensile and high temperature tensile mechanical property data are shown in Table 2.

[0059] As can be seen from Tables 1 and 2, the performance meets the standard requirements, and the high-temperature creep performance margin is over 100%. (Based on Tables 1 and 2...) Figures 2-11The results show that the GH4105 high-temperature alloy small-diameter bars produced using the high-temperature homogenization treatment and reasonable deformation processing technology of this invention have a uniform microstructure. The transverse microstructure is uniformly blurred at low magnification, without metallurgical defects such as shrinkage cavities, cracks, and inclusions. The high-magnification transverse and longitudinal microstructures are relatively uniform and fine, with uniform distribution of carbides at both the edge and center. The microstructure after solution treatment is uniform and consistent without mixed crystals, with an average grain size of 3.0 to 4.0. The performance test results fully meet the standard requirements.

[0060] Table 1 Mechanical properties of GH4105 high-temperature alloy bars

[0061]

[0062]

[0063] Table 2 High-Tension Mechanical Properties of GH4105 High-Temperature Alloy Bars

[0064]

Claims

1. A method for preparing small-diameter bars of GH4105 alloy, characterized in that, Includes the following steps: Step 1: The GH4105 ingot is subjected to a high-temperature homogenization treatment, and then subjected to seven-stage forging to obtain bars with diameters of Φ120mm to Φ200mm. In step 1, the high-temperature homogenization treatment is to keep the temperature at 1110-1200℃ for no less than 50 hours. In step 1, the seven-fire forging process includes four-fire upsetting and drawing, two-fire drawing and elongation, and one-fire rounding. In step 1, the first heating temperature is 1090℃~1190℃, held for 4~6 hours, the upsetting deformation is 10%~25%, and the final forging temperature is not lower than 900℃. The heating temperature of the second to fourth heating processes gradually decreases to 1090℃~1170℃ with each heating process, held for 4~6 hours, the upsetting deformation is 15%~45%, of which the upsetting deformation is not less than 30%, and the deformation increases with each heating process, and the final forging temperature is not lower than 900℃. The heating temperature of the fifth to sixth heating processes is 1090℃~1150℃, held for 4~6 hours, the deformation further increases to 30%~50%, and the final forging temperature is not lower than 750℃. The heating temperature of the seventh heating process is 1090℃~1150℃, held for 4~6 hours, the deformation is 3%~10%, and the final forging temperature is not lower than 750℃. Step 2: The Φ120mm~Φ200mm bars are subjected to another high-temperature homogenization treatment, and then rolled in one pass to obtain Φ45mm~Φ75mm bars. In step 2, the high-temperature homogenization treatment involves holding the temperature at 1110–1200℃ for at least 30 hours. In step 2, the single-pass rolling includes multiple passes, the deformation of each pass is controlled at 10% to 25%, and the interval between each pass is 5s to 20s. After rolling, the surface temperature of the bar is greater than 900℃. Step 3: Roll the Φ45mm~Φ75mm bars in one or two passes to obtain Φ8mm~Φ33mm bars. After straightening and grinding, obtain finished bars of Φ5mm~Φ30mm that meet the standard requirements. In step 3, two-fire rolling is used for specifications below Φ15mm, and one-fire rolling is used for specifications above Φ15mm. In step 3, the single-pass rolling includes multiple passes, with the deformation amount per pass controlled at 12% to 25%, and the interval between each pass being 0s to 10s. After rolling, the surface temperature of the bar is greater than 900℃.

2. The method for preparing small-diameter GH4105 alloy bars according to claim 1, characterized in that, In step 1, the ingot is forged on a high-speed forging machine of 4500T or above.

3. The method for preparing small-diameter GH4105 alloy bars according to claim 1, characterized in that, In step 2, the bar is rolled in one pass on a 650 reversible rolling mill or a 550 three-roll tandem rolling mill, with a heating temperature of 1100℃~1200℃ and a holding time of 3.5~5 hours.

4. The method for preparing small-diameter GH4105 alloy bars according to claim 1, characterized in that, In step 3, the bar is rolled once or twice on a 350 three-roll tandem mill, with a heating temperature of 1100℃~1200℃ and a holding time of 1~2 hours.

Images