GH738 alloy bar large-deformation semi-continuous efficient rolling device and technology

Abstract

The invention discloses a GH738 alloy bar large-deformation semi-continuous efficient rolling device and technology. The requirements for the grain size and the durability are met at the same time by optimizing the heating and deformation technology in the semi-continuous rolling process. A large-deformation semi-continuous efficient rolling device and a corresponding process are adopted, wherein the large-deformation rolling is 50%-80%; heat is supplemented in the rolling process, and the blank temperature is increased; the finish rolling temperature is increased; and the rolled blank is rapidly heated by an induction coil, and hot straightening is carried out. The method disclosed by the invention has the beneficial effects that (1) the mode of large deformation and heat compensation by using a heating furnace midway is adopted, and the standard grain size requirement of grade 3-grade 6 is met; (2) the rolled blank is heated through an induction coil to be rapidly heated, hot straightening is carried out, and the roundness and the size of the bar are improved; and after standard heat treatment, a surface stress layer cannot be generated due to straightening, so that a coarse-grain ring cannot be generated.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot processing of nickel-based deformed high-temperature alloy GH738, and specifically relates to a large-deformation semi-continuous high-efficiency rolling device and process for GH738 alloy bars, and relates to GH738 alloy bars with fine grains and the strongest high-temperature endurance performance. Technical Background

[0002] GH738 alloy is a nickel-based high-temperature alloy strengthened by γ' phase precipitation. It is resistant to high-temperature corrosion and oxidation, and has good yield strength and fatigue performance at high temperatures. Its maximum use temperature is up to 815℃. The hot-rolled bars, cold-drawn fasteners, rings, pipes, strips and forgings prepared are widely used in aviation and aerospace engines. At present, the domestic GH4738 and foreign Waspaloy American standards require that the grain size is finer than grade 3, and the high-temperature endurance performance is greater than 23h at 816℃ and 330MPa. The rolling deformation of GH738 bar is less than 40%, the dynamic recrystallization is insufficient, and there are blocky elongated crystals; although the large deformation rolling can refine the grains, even if the rolling heating temperature adopts the upper limit of the allowable heating temperature (1180℃), the grain size of the bar is still relatively fine, which is 8-10; during the rolling process, the temperature difference in the radial direction causes uneven energy storage distribution; the heat treatment adjustment cannot meet the requirements of grain size and durability at the same time, and the sub-solution treatment + stabilization + aging treatment is adopted, the grain size is too fine (8-10), and the durability is unqualified; the over-solution treatment is adopted, and the energy storage difference leads to a huge difference in grain size from the edge to the center of the bar in the radial direction, and a coarse grain ring of 00 appears on the edge, and the center is still 8-10, and the performance is still difficult to meet. In short, it is difficult for GH738 alloy bars with large deformation semi-continuous rolling to meet the requirements of grain size and durability through subsequent heat treatment. Summary of the invention

[0003] The invention discloses a large deformation semi-continuous high-efficiency rolling device and process for GH738 alloy bars, which simultaneously meet the requirements of grain size and durability performance by optimizing the heating and deformation processes in the semi-continuous rolling process.

[0004] Specific technical solutions:

[0005] 1. Billet preparation

[0006] The ingots are smelted by vacuum induction furnace + vacuum consumable furnace, vacuum induction furnace + electroslag remelting or vacuum induction furnace + electroslag remelting + vacuum consumable furnace; the ingots are subjected to high-temperature homogenization diffusion, rapid forging + radial forging combined blanking, and secondary homogenization diffusion of the blanks.

[0007] 2. Billet rolling

[0008] ⑴ The billet is heated to 1100℃~1180℃ in the box-type resistance furnace 1, and the temperature is kept for no less than 60min; after the billet is taken out of the furnace, it enters the box-type resistance furnace 2 or the continuous heating furnace 3 and is heated to 1180℃~1190℃, and the temperature is kept for 1min~5min; the billet is rolled with a large deformation through the combination 4 rolling mill. The combination 4 rolling pass may include a circle→ellipse→circle→ellipse→…circle arrangement or a circle→square→vertical ellipse→square→vertical ellipse…square, and each pass corresponding to the rolling roller includes a frame, a power device, a guide and a conveying device. The combination 4 rolling mill performs large deformation and fast rolling (roller linear speed 1m / s~15m / s), and the rolling deformation is controlled at 20%~80%, crushing coarse grains, refining the structure, and the grain size reaches level 8 or above.

[0009] (2) The square or round billet enters the gas-fired roller-hearth furnace 5, the temperature of which is set at 1180℃~1250℃, and is heated for 5s~120s. The surface of the billet is quickly heated to 1100℃~1160℃ by utilizing the high calorific value and rapid heating characteristics of the gas furnace. On the one hand, the temperature difference between the core and the surface of the billet is reduced, and the stress layer caused by the temperature drop in the rolling process is eliminated, thereby reducing the energy storage in the surface area. On the other hand, the temperature inside and outside the billet is much higher than the static recrystallization temperature (about 1050℃), and the grains from the core to the edge along the radial direction are in the range of 3 to 6.

[0010] ⑶ The blank passes through combination 6, 61 and 62 to form elliptical and circular precision hole shapes respectively, the deformation of the combination is controlled at 10% to 30%, the temperature of the blank out of the combination 6 hole shape, that is, the final rolling temperature is 920℃ to 1030℃, and the grain size is controlled at level 3 to 7.

[0011] 3. Heat treatment and finishing

[0012] (1) The blank quickly passes through the electromagnetic induction heating device 7, which is a multi-turn coil. The length of the coil is determined by the rolling speed and the insulation time. There is a high-temperature resistant non-metallic material conduit inside the coil to fix the blank in the central area of ​​the electromagnetic induction coil. The surface temperature of the blank is increased to 1100°C to 1170°C, and the insulation time is 0s to 30s, thereby improving the plasticity of the blank.

[0013] (2) The blank is subjected to high temperature plastic straightening by a hyperbolic straightening machine 8 (which may be a double-roller or multi-roller straightening machine) to improve the roundness.

[0014] ⑶ The hot-rolled solid solution delivered billet enters the box-type resistance furnace 9 for heating and insulation, and the insulation system is 1040℃~1080℃, 1h~4h or 1080℃4h, followed by water cooling; the billet is finished 10, and the finishing includes rolling straightening, peeling and fine grinding.

[0015] Or for hot-rolled and polished billets delivered, the billets that have been hot-straightened should be directly finished.

[0016] The innovative features of the present invention are as follows:

[0017] ⑴ Large deformation rolling (50% ~ 80%) makes the grains uniform, overcoming the elongated grains that are not fully dynamically recrystallized due to insufficient original deformation; during the rolling process, the surface of the billet is in contact with the roll, the cooling speed is fast, and heat is added in the middle to increase the billet temperature, which helps the billet to complete static recrystallization and promote grain growth, that is, to increase the initial grain size before the last two hole-type rolling; on the other hand, the final rolling temperature is increased to ensure that dynamic recrystallization + static recrystallization grain growth is fully completed to meet the standard requirements for grain size, level 3 to level 6; the use of large deformation + heating furnace for heating in the middle is more suitable for modern semi-continuous rapid rolling process.

[0018] (2) The rolled billet is heated quickly by an induction coil for heat straightening to improve the roundness and size of the bar; more importantly, the billet undergoes plastic deformation and the high heat straightening temperature is conducive to the timely release of compressive stress. After standard heat treatment, no coarse grain ring will be produced due to the surface stress layer generated by straightening.

[0019] The invention has the following benefits:

[0020] ⑴ The method of large deformation + heating in the middle with a heating furnace is more suitable for modern semi-continuous rapid rolling process; large deformation rolling makes the grain uniform; heat is added in the middle of the rolling process to increase the billet temperature and the initial grain size before the last two pass rolling; the final rolling temperature is increased to ensure that dynamic recrystallization + static recrystallization grain growth is fully completed to meet the standard requirements for grain size, level 3 to level 6;

[0021] (2) The rolled billet is heated quickly by an induction coil for heat straightening to improve the roundness and size of the bar; after standard heat treatment, no coarse grain ring will be produced due to the surface stress layer generated by straightening.

[0022] In conclusion, the GH738 alloy bars with large deformation and semi-continuous rolling can meet the requirements of grain size and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a block diagram of a large deformation semi-continuous high-efficiency rolling device.

[0024] Explanation of icons: box-type resistance heating furnace 1, resistance heating roller-hearth furnace 2, gas-heated roller-hearth furnace 3, multi-rolling mill combination 4, the rolling mill codes of the rolling mill combination 4 are 41, 42, 43, ..., 4n respectively, gas-heated roller-hearth furnace 5, last two rolling mill combination 6, elliptical rolling mill 61 with a hole type, circular rolling mill 62 with a hole type, induction heating device 7, hyperbolic straightening machine 8, box-type resistance heating furnace 9, finishing device (including peeling machine, grinder) 10, finishing 11, box-type resistance heating furnace 12.

[0025] Specific implementation measures

[0026] Example 1

[0027] The GH738 alloy φ9mm~φ80mm round products are rolled at a rolling line speed of 3m / s and a rolling deformation of 45%~80%; the initial grain size is 00 grade, and the products are heated to 1160℃~1180℃ by a box-type resistance heating furnace 1, and directly enter a multi-rolling mill combination 4 and a last two-pass rolling mill combination 6 for continuous rolling, without supplementary heat from a resistance heating roller hearth furnace 2 or a gas heating roller hearth furnace 3 and a gas heating roller hearth furnace 5, and without heating by an induction heating device 7. After the billet is cooled to room temperature, it is straightened by a hyperbolic straightening machine 8, and then subjected to standard heat treatment, finishing (straightening, peeling and polishing) is performed.

[0028] Results: The final rolling temperature was 920℃~1030℃, the billet completed dynamic recrystallization, and the grain size was 8 to 10. Due to the large deformation, the internal energy storage difference of the grain size was large, some grains grew abnormally, and there were grains of 0 and 6 at the same time; after the billet was cold straightened, there was a compressive stress layer with a thickness of 1mm to 2mm on the surface, and after standard heat treatment, a coarse grain ring of 00 was formed on the surface. The grain size did not meet the standard requirements, and the durability performance was difficult to meet the standard requirements.

[0029] Example 2

[0030] The GH738 alloy φ9mm~φ80mm round finished products are rolled at a rolling line speed of 3m / s and a rolling deformation of 20%~40%; the initial grain size is 00 grade, and the products are heated to 1160℃~1180℃ by a box-type resistance heating furnace 1, and directly enter a multi-rolling mill combination 4 and a last two-pass rolling mill combination 6 for continuous rolling, without supplementary heat from a resistance heating roller hearth furnace 2 or a gas heating roller hearth furnace 3 and a gas heating roller hearth furnace 5, and without heating by an induction heating device 7. After the billet is cooled to room temperature, it is straightened by a hyperbolic straightening machine 8, and then subjected to standard heat treatment, finishing (straightening, peeling and polishing) is performed.

[0031] Results: The final rolling temperature of the billet was 1060℃~1100℃. Due to the small deformation and insufficient dynamic recrystallization, the grain size of the rolled sample without straightening was extremely uneven, and the grain size did not meet the requirements. After standard heat treatment, the grain size still did not meet the requirements. After cold straightening of the billet, a compressive stress layer with a thickness of 1mm~2mm existed on the surface. After standard heat treatment, a coarse grain ring of grade 00 was formed on the surface, and the grain size did not meet the standard requirements.

[0032] Example 3

[0033] The GH738 alloy φ9mm~φ80mm round products are rolled at a rolling line speed of 3m / s and a rolling deformation of 45%~80%; the initial grain size is 00 grade, and the products are heated to 1160℃~1180℃ by a box-type resistance heating furnace 1, and directly enter a multi-rolling mill combination 4 and a last two-pass rolling mill combination 6 for continuous rolling, and supplementary heat is carried out by a resistance heating roller hearth furnace 2 or a gas heating roller hearth furnace 3 and a gas heating roller hearth furnace 5 in the middle, and no induction heating device 7 is used for heating. After the billet is cooled to room temperature, it is straightened by a hyperbolic straightening machine 8, and then subjected to standard heat treatment, finishing (straightening, peeling and polishing) is carried out.

[0034] Results: The grain size of the rolled sample without straightening is uniform (grade 3 to 6), which meets the requirement of finer than grade 3. After standard heat treatment, the average grain size is grade 3 to 6, and the durability meets the requirements. After cold straightening, there is a compressive stress layer with a thickness of 1mm to 2mm on the surface of the billet. After standard heat treatment, a coarse grain ring of grade 00 is formed on the surface, and the grain size does not meet the standard requirements.

[0035] Example 4

[0036] Rolling GH738 alloy φ9mm~φ80mm round finished products, rolling line speed 3m / s, rolling deformation of 50%~80%; initial grain size is 00 grade, heated to 1160℃~1180℃ by box-type resistance heating furnace 1, directly into multi-rolling mill combination 4 and last two-pass rolling mill combination 6 for continuous rolling, supplementary heat by resistance heating roller hearth furnace 2 or gas heating roller hearth furnace 3 and gas heating roller hearth furnace 5 in the middle; heating by induction heating device 7, the surface temperature of the billet is raised to 1170℃, the holding time is 5s, the billet is directly straightened by hyperbolic straightening machine 8, then heat treated according to standard, and then finished (straightening, peeling and polishing).

[0037] Results: The grain size of the rolled sample without straightening is uniform (grade 3 to 6) and meets the requirement of finer than grade 3. After standard heat treatment, the average grain size is grade 3 to 6, and the endurance performance meets the requirements. After the blank is hot straightened, there is no stress layer on the surface of the blank. After standard heat treatment, the average grain size is grade 3 to 6, there is no coarse grain ring on the surface, and the endurance performance meets the requirements; after finishing, the grain size and endurance performance are still qualified.

Claims

1. A GH738 alloy bar large deformation semi-continuous high-efficiency rolling device, characterized in that: The device is constructed as follows: a box-type resistance heating furnace (1) is connected to a resistance heating roller hearth furnace (2) and a gas-heating roller hearth furnace (3), and then connected to a multi-rolling mill assembly (4), wherein the rolling mill codes of the multi-rolling mill assembly (4) are (41), (42), (43), ..., (4n), respectively; the multi-rolling mill assembly (4) is connected to a gas-heating roller hearth furnace (5), and the gas-heating roller hearth furnace (5) is connected to the last two rolling mill assemblies (6), wherein the pass types are an elliptical rolling mill (61) and a circular rolling mill (62), respectively; the last two rolling mill assemblies (6) are connected to an induction heating device (7) and a hyperbolic straightening machine (8), and the hyperbolic straightening machine (8) is connected to a box-type resistance heating furnace (9), a finishing device (10), and a finishing device (11), and then to a box-type resistance heating furnace (12); The rolling pass of the multi-mill combination (4) may include a circle → ellipse → circle → ellipse → ... circle arrangement or a circle → square → cubic ellipse → square → cubic ellipse ... square, and each roll corresponding to the pass includes a frame, a power device, a guide and a transmission device; The electromagnetic induction device (7) is a multi-turn coil, the length of which is determined by the rolling speed and the holding time, and there is a high-temperature resistant non-metallic material conduit inside the coil to fix the blank in the central area of ​​the electromagnetic induction coil; The finishing device ⑽ and finishing ⑾ both include a peeling machine and a grinder.

2. The process of the large deformation semi-continuous high-efficiency rolling device for GH738 alloy bars according to claim 1, characterized in that: The specific technical process of large deformation semi-continuous high-efficiency rolling is as follows: ⑴ Billet preparation The ingots are smelted by vacuum induction furnace + vacuum consumable furnace, vacuum induction furnace + electroslag remelting or vacuum induction furnace + electroslag remelting + vacuum consumable furnace. The ingots are subjected to high-temperature homogenization diffusion, rapid forging + radial forging combined blanking, and secondary homogenization diffusion of the blanks. ⑵ Billet rolling ① The billet is heated to 1100℃~1180℃ in box-type resistance furnace 1 and kept warm for no less than 60min; after the billet is taken out of the furnace, it enters box-type resistance furnace 2 or continuous heating furnace 3 and is heated to 1180℃~1190℃, and kept warm for 1min~5min; the billet is rolled with large deformation through combination 4 rolling mill. Combination 4 rolling mill performs large deformation and rapid rolling, with the linear speed of the rollers at 1m / s~15m / s, and the rolling deformation is controlled at 20%~80%, crushing coarse grains, refining the structure, and the grain size reaches level 8 or above; ② The square or round billet enters the gas-fired roller hearth furnace 5, the temperature of which is set at 1180°C to 1250°C, and is heated for 5s to 120s, so that the surface temperature of the billet is quickly raised to 1100°C to 1160°C; ③ The blank passes through combination 6, 61 and 62, respectively, with elliptical and circular precision holes, and the deformation of the combination is controlled at 10% to 30%. The temperature of the blank out of the combination 6 hole, i.e., the final rolling temperature, is 920℃ to 1030℃; ⑶Heat treatment and finishing ① The blank quickly passes through the electromagnetic induction heating device 7, the surface temperature of the blank rises to 1100°C to 1170°C, and the holding time is 0s to 30s; ② The blank passes through a hyperbolic straightening machine 8, which can be a double-roller or multi-roller straightening machine, for high-temperature plastic straightening; ③ The hot-rolled solid solution delivery billet enters the box-type resistance furnace 9 for heating and heat preservation, the heat preservation system is 1040℃~1080℃, 1h~4h or 1080℃4h, and then water-cooled; the billet is finished 10, and the finishing includes roller straightening, peeling and fine grinding; Or for hot-rolled and polished billets delivered, the billets that have been hot-straightened should be directly finished.

3. The process of the GH738 alloy bar large deformation semi-continuous high-efficiency rolling device according to claim 2, characterized in that: Rolling GH738 alloy φ9mm~φ80mm round finished products, rolling line speed 3m / s, rolling deformation 50%~80%; initial grain size is 00 grade, heated to 1160℃~1180℃ by box-type resistance heating furnace 1, directly into multi-mill combination 4 and last two-pass rolling mill combination 6 for continuous rolling, supplementary heat by resistance heating roller hearth furnace 2 or gas heating roller hearth furnace 3 and gas heating roller hearth furnace 5 in the middle; heating by induction heating device 7, the surface temperature of the billet is raised to 1170℃, the holding time is 5s, the billet is directly straightened by hyperbolic straightening machine 8, then heat treated according to standard, and then finishing, i.e. straightening, peeling and polishing; Results: The grain size of the rolled sample without straightening is uniform, ranging from grade 3 to grade 6, meeting the requirement of being finer than grade 3. After standard heat treatment, the average grain size is grade 3 to grade 6, and the endurance performance meets the requirements. After the billet is hot straightened, there is no stress layer on the surface of the billet. After standard heat treatment, the average grain size is grade 3 to grade 6, there is no coarse grain ring on the surface, and the endurance performance meets the requirements. After finishing, the grain size and durability are still qualified after inspection.

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