A high return ratio GH4099 alloy large bar fine grain forging process

Abstract

The present invention discloses a fine-grain forging process for large GH4099 alloy bars with a high return ratio, comprising the following steps: A) heating a prepared bar blank to 1330°C, holding the temperature for 5 hours, and then cooling the temperature to 650°C at a cooling rate of 15°C / min; B) heating the bar blank to 1160°C and performing octagonal forging with a forging deformation of 30% to 35%; C) cooling the bar blank to 1150°C and performing a first upset forging with a forging deformation of 45% to 50%; D) cooling the bar blank to 1130°C and performing a second upset forging with a forging deformation of 40% to 45%; and E) cooling the bar blank to 950°C at a rate of 60°C / min, then cooling the bar blank to 500°C at a rate of 20°C / s, and performing a light forging finish. This invention can overcome the shortcomings of existing technologies, refine the core grains, and improve the overall microstructure uniformity of the bar.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy forging, in particular to a fine-grain forging process for a large bar of a GH4099 alloy with a high return ratio. Background Art

[0002] GH4099 is a Ni-Cr-based, age-hardened high-temperature alloy capable of long-term service below 900°C, with a short-term maximum temperature of 1000°C. This alloy boasts a stable microstructure, excellent comprehensive mechanical properties, and excellent hot and cold working, forming, and welding performance. It is primarily used in high-temperature, load-bearing, welded plate components, such as combustion chambers and afterburners in aircraft engines. This alloy has a complex phase composition, and traditional forging processes can easily lead to coarse grains in the core and radius of the bar, resulting in poor overall microstructure uniformity and impacting final performance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a fine-grain forging process for large GH4099 alloy bars with a high return ratio, thereby refining the core grains and improving the overall structural uniformity of the bars.

[0004] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0005] A high return ratio GH4099 alloy large bar fine grain forging process comprises the following steps:

[0006] A. The prepared bar blank was heated to 1330°C, kept at this temperature for 5 hours, and then cooled to 650°C at a cooling rate of 15°C / min. The bar blank contained 0.08 wt% C and 0.01 wt% Fe.

[0007] B. Heat the bar billet to 1160℃ and perform octagonal forging with a forging deformation of 30% to 35%;

[0008] C. Lower the temperature of the bar billet to 1150℃ and perform the first upsetting forging with a forging deformation of 45% to 50%;

[0009] D. Lower the temperature of the bar billet to 1130℃ and perform the second upsetting forging with a forging deformation of 40% to 45%;

[0010] E. Reduce the temperature of the bar blank to 950℃ at a rate of 60℃ / min, then reduce the temperature of the bar blank to 500℃ at a rate of 20℃ / s, perform light forging and trimming, and then naturally cool to room temperature.

[0011] Preferably, the bar stock comprises,

[0012] 0.08wt% C, 18.42wt% Cr, 6wt% W, 4.02wt% Mo, 2.19wt% Al, 1.22wt% Ti, 6.52wt% Co, 0.004wt% B, 0.005wt% Ce, 0.01wt% Mn, 0.05wt% Si, 0.006wt% P, 0.001wt% S, 0.01wt% Fe, and the balance is Ni.

[0013] Preferably, the proportion of returned material in the bar blank is ≥65%.

[0014] Preferably, the reduction amount of a single hammer during forging is 20% of the current bar blank size.

[0015] Preferably, nitrogen is used for gas protection during the forging process.

[0016] The beneficial effects brought about by the above technical solution are: the present invention refines the grains and reduces structural defects by heat treating the bar blank before forging. Since the Cr and Fe elements in the GH4099 alloy easily precipitate σ phase in a specific temperature range, the brittleness of the bar increases and the performance decreases. In order to solve this problem, the present invention increases the content of the C element in the alloy while reducing the content of the Fe element, and reasonably optimizes the ratio of other elements, effectively inhibiting the precipitation of σ phase in the bar during the heat treatment process. During the forging process, the present invention adopts the "octagonal forging + two piers and two pulls" forging process, which effectively improves the forging deformation amount and deformation uniformity, and refines the core grains by repeatedly kneading the core of the ingot, while also reducing the risk of cracking. At the same time, the temperature is gradually reduced with the forging fire, and the final fire heating temperature is stabilized at 1130°C, ensuring that the 1 / 2 radius of the bar and the core grains will not grow due to excessively high heating temperature. By increasing the single hammer reduction, the desired deformation at both the 1 / 2 radius and the core of the forging blank can be achieved during longitudinal drawing, thus ensuring the uniformity of the bar's structure. Heat treatment after forging optimizes the cooling rate in different temperature ranges to reduce the bar's residence time in the temperature range prone to σ phase precipitation, while further optimizing the bar's overall mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a low-magnification metallographic photograph of the GH4099 alloy bar treated by the present invention.

[0018] Figure 2 This is a high-magnification metallographic structure photograph of the GH4099 alloy rod processed by the present invention at 1 / 2 radius.

[0019] Figure 3 This is a high-magnification metallographic photograph of the core of the GH4099 alloy bar processed by the present invention. DETAILED DESCRIPTION Example

[0020] A high return ratio GH4099 alloy large bar fine grain forging process comprises the following steps:

[0021] A. Heat the prepared bar blank to 1330°C, keep it at that temperature for 5 hours, and then reduce the temperature to 650°C at a cooling rate of 15°C / min;

[0022] Bar stock includes,

[0023] 0.08wt% C, 18.42wt% Cr, 6wt% W, 4.02wt% Mo, 2.19wt% Al, 1.22wt% Ti, 6.52wt% Co, 0.004wt% B, 0.005wt% Ce, 0.01wt% Mn, 0.05wt% Si, 0.006wt% P, 0.001wt% S, 0.01wt% Fe, and the balance is Ni;

[0024] The proportion of returned materials in the blank is ≥65%;

[0025] B. Heat the bar billet to 1160℃ and perform octagonal forging with a forging deformation of 30% to 35%;

[0026] C. Lower the temperature of the bar billet to 1150℃ and perform the first upsetting forging with a forging deformation of 45% to 50%;

[0027] D. Lower the temperature of the bar billet to 1130℃ and perform the second upsetting forging with a forging deformation of 40% to 45%;

[0028] E. Reduce the temperature of the bar blank to 950℃ at a rate of 60℃ / min, then reduce the temperature of the bar blank to 500℃ at a rate of 20℃ / s, perform light forging and trimming, and then naturally cool to room temperature;

[0029] During the forging process, the single hammer reduction is 20% of the current bar blank size, and nitrogen is used for gas protection during the forging process.

[0030] project Tensile strength (MPa) Yield strength (MPa) Elongation (%) Sectional shrinkage (%) result 1615 1460 22 39

[0031] The process of the present invention was used to trial-produce multiple batches of bars with specifications of φ190mm and φ250mm, and the results of microstructure and performance were stable.

[0032] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A high return ratio GH4099 alloy large bar fine grain forging process, characterized by The following steps are involved: A. Heat the prepared bar blank to 1330°C, keep it at that temperature for 5 hours, and then reduce the temperature to 650°C at a cooling rate of 15°C / min. The bar blank includes: 0.08wt% C, 18.42wt% Cr, 6wt% W, 4.02wt% Mo, 2.19wt% Al, 1.22wt% Ti, 6.52wt% Co, 0.004wt% B, 0.005wt% Ce, 0.01wt% Mn, 0.05wt% Si, 0.006wt% P, 0.001wt% S, 0.01wt% Fe, and the balance is Ni; B. Heat the bar blank to 1160℃ and perform octagonal forging with a forging deformation of 30% to 35%; C. Lower the temperature of the bar billet to 1150℃ and perform the first upsetting forging with a forging deformation of 45% to 50%; D. Lower the temperature of the bar billet to 1130℃ and perform the second upsetting forging with a forging deformation of 40% to 45%; E. Reduce the temperature of the bar blank to 950℃ at a rate of 60℃ / min, then reduce the temperature of the bar blank to 500℃ at a rate of 20℃ / s, perform light forging and trimming, and then naturally cool to room temperature; The single hammer reduction during forging is 20% of the current bar stock size.

2. The high return ratio GH4099 alloy large bar fine grain forging process according to claim 1 is characterized in that: The proportion of returned material in the bar billet is ≥65%.

3. The high return ratio GH4099 alloy large bar fine grain forging process according to claim 1 is characterized in that: Nitrogen is used for gas protection during the forging process.

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