Homogenizing treatment method for large-specification GH4738 bar

Abstract

The invention relates to a homogenization treatment method for a large-specification GH4738 bar, and belongs to the technical field of metal material machining. The homogenizing treatment method is used for solving the problems that according to an existing homogenizing treatment method for the large-specification GH4738 bar, the heating temperature is low, the heat preservation time is short, segregation and harmful precipitated phases in a large-specification cast ingot cannot be eliminated, if the homogenizing heating temperature is increased to exceed 1200 DEG C, overburning is likely to be caused, a non-equilibrium low-melting-point eutectic phase in an alloy structure is gradually dissolved, and the quality of the large-specification GH4738 bar is influenced. The problem that the mechanical property and the plasticity of the alloy are reduced due to the fact that the grain boundary becomes sparse and the residual phase on the grain boundary is changed from continuous distribution to discontinuous distribution and the grains are coarse is solved. The homogenization treatment method for the large-specification bar containing the return scrap comprises the first-stage homogenization treatment, the second-stage homogenization treatment, the third-stage homogenization treatment and the fourth-stage homogenization treatment, and the third-stage homogenization treatment comprises the furnace cooling process. The prepared large-size bar is excellent in performance.

Description

Technical Field

[0001] The invention relates to the technical field of metal material processing, and in particular to a homogenization treatment method for large-size GH4738 bars. Background Art

[0002] GH4738 bar is a Ni-Cr-Co based precipitation hardening wrought high temperature alloy. Due to its excellent high temperature performance and corrosion resistance, it has been widely used in aerospace, energy, chemical industry and other fields.

[0003] At present, commercial aircraft engines are gradually becoming larger, and the size of key high-temperature alloy special-shaped ring forgings in the engine is also increasing. The cost of forging preparation has increased significantly. Adding return materials is an important means to achieve low-cost development of high-temperature alloy forgings in the future. Compared with alloys smelted from new materials, the high-temperature alloys smelted from a mixture of returned and new materials contain a large number of carbonitrides and large sizes, which results in reduced plasticity of the ingot and is very likely to cause cracking during the bar forming process; especially after the ingot specification is expanded, the consumable ingot diameter is expanded from Φ508mm to Φ690mm, which will lead to an increase in the degree of dendrite segregation, and the presence of γ′ phase and primary carbides in the cast structure is unevenly distributed and the size difference increases, which deteriorates its hot working plasticity; and, as the alloy ingot shape expands, the temperature drops rapidly during the blanking process, the deformation resistance increases, and hot working becomes difficult. In the preparation process of large-size GH4738 bars, coarse grains and "mixed crystal" organization problems are very likely to occur, and the coarse grains and uneven organization of the GH4738 bars are difficult to completely eliminate through subsequent hot working and heat treatment processes, thus affecting the final service performance of the forgings.

[0004] In the existing preparation method of GH4738 rods containing return materials, the homogenization process has a low heating temperature and a short holding time, which cannot eliminate the segregation and harmful precipitation phases in large-sized ingots; if the homogenization heating temperature is increased to more than 1200°C, it is easy to cause "overburning", resulting in the gradual dissolution of the non-equilibrium low-melting point eutectic phase in the alloy structure, sparse grain boundaries, and the residual phase on the grain boundaries changes from continuous distribution to discontinuous distribution, the grains are coarse, and the degree of segregation is serious, resulting in reduced mechanical properties and plasticity of the GH4738 rods. Summary of the invention

[0005] In view of the above analysis, the embodiment of the present invention aims to provide a homogenization treatment method for large-size GH4738 bars, so as to solve the problem that the homogenization process of the homogenization treatment method for large-size GH4738 bars has low heating temperature and short holding time, and cannot eliminate segregation and harmful precipitation phases in large-size ingots. If the homogenization heating temperature is increased to more than 1200°C, it is easy to cause "overburning", resulting in the gradual dissolution of the non-equilibrium low-melting eutectic phase in the GH4738 bar structure, the grain boundaries become sparse, and the residual phase on the grain boundaries changes from continuous distribution to discontinuous distribution, the grains are coarse, and the mechanical properties and plasticity of the GH4738 bars are reduced.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] The invention provides a homogenization treatment method for large-size GH4738 bars, comprising first-stage homogenization treatment, second-stage homogenization treatment, third-stage homogenization treatment and fourth-stage homogenization treatment, wherein the third-stage homogenization treatment includes a furnace cooling process.

[0008] Furthermore, the first stage homogenization treatment includes loading the consumable ingot into the furnace when the furnace temperature reaches 600-700°C, keeping it warm for 3-5 hours, and then heating the consumable ingot to 980-1020°C and keeping it warm for 6-12 hours.

[0009] Furthermore, it is characterized in that the heating rate is 20-40°C / h.

[0010] Furthermore, the second stage homogenization treatment includes heating the consumable ingot to 1140-1180° C. and keeping the temperature for 20-30 hours.

[0011] Furthermore, the heating rate is 5-10°C / h.

[0012] Furthermore, the third stage homogenization treatment includes heating the consumable ingot to 1180-1210° C., keeping the temperature for 90-120 hours, and heating up at a rate of 10-20° C. / h.

[0013] Furthermore, the third stage homogenization treatment also includes: keeping the consumable ingot at 1180-1210° C. for 90-120 hours and then cooling it to below 600° C. with the furnace.

[0014] Furthermore, the fourth stage homogenization treatment includes heating the consumable ingot to 1140-1180° C., keeping the temperature for 5-12 hours, and heating up at a rate of 10-20° C. / h.

[0015] Furthermore, the fourth stage homogenization treatment also includes jacketing the ingot after it is taken out of the furnace, returning it to the furnace for insulation for 2 to 4 hours after the jacketing is completed, and reheating the consumable ingot to 1140 to 1180°C.

[0016] The present invention also provides a method for preparing large-size GH4738 rods, comprising the above-mentioned homogenization treatment method.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] 1. The present invention adopts a multi-stage homogenization process to increase the homogenization temperature and holding time, promote the dissolution of the low-melting point phase, and accelerate the diffusion of alloy elements. The segregation coefficient of Ti in the ingot is significantly reduced, and there is no obvious crack on the surface of the rod during the forging process.

[0019] 2. The present invention avoids the "overburning problem" that may be caused by the heating temperature exceeding 1200° C. during the third stage of homogenization heat treatment by designing four stages of homogenization heat treatment and accurately controlling the heating temperature, holding time and heating rate during the homogenization process.

[0020] 3. The homogenization treatment method of the present invention is used for the preparation of large-sized GH4738 rods, and can be used for the preparation of large-sized homogeneous fine-grained rods of high-temperature alloys containing returned materials. The structure at the center of the prepared rod is significantly refined, and the grain size at the center and 1 / 2 of the rod reaches above level 3.5, and the structure is relatively uniform without mixed crystals. The room temperature mechanical properties and endurance properties of the center of the rod are significantly improved.

[0021] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0023] Figure 1 This is the appearance of the finished product of GH4738 bar product prepared in Example 1 of the present invention;

[0024] Figure 2 This is a low-magnification microstructure diagram of the GH4738 rod prepared in Example 1 of the present invention;

[0025] Figure 3 The grain structure diagram of each position of the head of the GH4738 rod prepared in Example 1 of the present invention;

[0026] Figure 4The grain structure diagram of each position of the tail of the GH4738 rod prepared in Example 1 of the present invention;

[0027] Figure 5 The grain structure diagram of each position of the head of the GH4738 rod prepared in Example 2 of the present invention;

[0028] Figure 6 The grain structure diagram at each position of the tail of the GH4738 rod prepared in Example 2 of the present invention;

[0029] Figure 7 The grain structure diagram at each position of the head of the GH4738 bar prepared in Comparative Example 1 of the present invention;

[0030] Figure 8 This is the grain structure diagram of each position of the tail of the GH4738 rod prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0032] The present invention provides a homogenization treatment method for large-size GH4738 bars, comprising a first-stage homogenization treatment, a second-stage homogenization treatment, a third-stage homogenization treatment and a fourth-stage homogenization treatment, wherein the third-stage homogenization treatment includes a furnace cooling process;

[0033] The first stage of homogenization treatment includes charging the consumable ingot into the furnace when the furnace temperature reaches 600-700°C (exemplarily, heating to 620°C, 640°C, 660°C, 680°C), keeping the temperature for 3-5h (exemplarily, keeping the temperature for 3.5h, 4h, 4.5h), and then heating the consumable ingot to 980-1020°C (exemplarily, heating to 985°C, 990°C, 995°C, 1000°C, 1005°C, 1010°C, 1015°C) , keep warm for 6 to 12 hours (exemplarily, keep warm for 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, and 11.5 hours), and the heating rate is 20 to 40°C / h (exemplarily, the heating rate is 22°C / h, 24°C / h, 25°C / h, 26°C / h, 28°C / h, 30°C / h, 32°C / h, 34°C / h, 35°C / h, 36°C / h, and 38°C / h);

[0034] The second stage homogenization treatment includes heating the consumable ingot to 1140-1180° C. (exemplarily, heating to 1145° C., 1150° C., 1155° C., 1160° C., 1165° C., 1170° C., 1175° C.), keeping the temperature for 20-30 hours (exemplarily, keeping the temperature for 22 hours, 24 hours, 25 hours, 26 hours, 28 hours), and the heating rate is 5-10° C. / h (exemplarily, the heating rate is 6° C. / h, 7° C. / h, 8° C. / h, 9° C. / h);

[0035] The third stage homogenization treatment includes heating the consumable ingot to 1180-1210° C. (exemplarily, heating to 1185° C., 1190° C., 1195° C., 1200° C., 1205° C.), keeping the temperature for 90-120 hours (exemplarily, keeping the temperature for 92 hours, 94 hours, 96 hours, 98 hours, 100 hours, 102 hours, 104 hours, 106 hours, 108 hours, 110 hours, 112 hours, 114 hours, 116 hours, 118 hours), Heating rate 10-20°C / h (exemplarily, the heating rate is 12°C / h, 14°C / h, 15°C / h, 16°C / h, 18°C / h); keeping warm for 90-120h (exemplarily, keeping warm for 92h, 94h, 96h, 98h, 100h, 102h, 104h, 106h, 108h, 110h, 112h, 114h, 116h, 118h) and then cooling, cooling with the furnace to below 600°C;

[0036] The fourth stage of homogenization treatment includes heating the consumable ingot to 1140-1180°C (exemplarily, heating to 1145°C, 1150°C, 1155°C, 1160°C, 1165°C, 1170°C, 1175°C), keeping it warm for 5-12h (exemplarily, keeping it warm for 6h, 7h, 8h, 9h, 10h, 11h), and heating up at a rate of 10-20°C / h (exemplarily, heating up at a rate of 12°C / h). h, 14℃ / h, 15℃ / h, 16℃ / h, 18℃ / h), after taking out the furnace, the ingot is covered, and after the covering is completed, it is returned to the furnace and kept warm for 2-4h (exemplarily, kept warm for 2.5h, 3h, 3.5h), and the consumable ingot is reheated to 1140-1180℃ (exemplarily, heated to 1145℃, 1150℃, 1155℃, 1160℃, 1165℃, 1170℃, 1175℃);

[0037] It should be noted that the ingot specifications are large, and too high a charging temperature will cause a large temperature difference between the inside and outside of the ingot, and thermal cracks are prone to appear on the surface of the ingot. If the charging temperature is low, the furnace heating time will increase and the production efficiency will decrease. Therefore, the charging temperature is set to 600-700℃; then the consumable ingot is heated to 980℃-1020℃, mainly to dissolve the coarse M in the matrix. 23C6 and γ' phases, uniform matrix alloy composition; the second stage homogenization temperature is set at 1140 ~ 1180 ℃, mainly dissolving low melting point borides in the matrix to prevent the formation of holes during the homogenization process; the third stage homogenization temperature is set at 1180 ℃ ~ 1210 ℃, continuing to dissolve the coarse MC carbides in the matrix, while accelerating the diffusion of alloying elements in the ingot, further reducing the microsegregation of alloying elements in the ingot, and reducing the risk of cracking of the ingot during the forging process, and then keeping warm for 90 ~ 120 hours After cooling, it cools down to below 600℃ with the furnace; the homogenization temperature of the fourth stage is set to 1140-1180℃; the homogenization temperature of the third stage is relatively high, the grain boundaries in the ingot matrix are in a molten state, and the plasticity of the ingot is extremely low. The ingot must be cooled to below 600℃ before the grain boundaries can recover to the equilibrium strength, and then it is reheated to 1140-1180℃ for blank forging; at the same time, the waste heat of the ingot is used for reheating, which shortens the reheating time of the ingot, saves energy and improves production efficiency.

[0038] The present invention avoids the "overburning problem" that may be caused by the heating temperature exceeding 1200° C. during the third stage of homogenization heat treatment by designing four stages of homogenization heat treatment and accurately controlling the heating temperature, holding time and heating rate during the homogenization process.

[0039] In the existing preparation method of large-size GH4738 bars, the homogenization process has a low heating temperature and a short holding time, which cannot eliminate the segregation and harmful precipitation phases in large-size ingots; increasing the homogenization heating temperature to more than 1200°C will easily cause "overburning", resulting in the gradual dissolution of the non-equilibrium low-melting-point eutectic phase in the alloy structure, sparse grain boundaries, and the residual phase on the grain boundaries changing from continuous distribution to discontinuous distribution, coarse grains, and severe segregation; the present invention adopts a multi-stage homogenization process to increase the homogenization temperature and holding time, promote the dissolution of the low-melting-point phase, and accelerate the alloy element The diffusion of elements is reduced, and the segregation coefficient of Ti in the ingot is significantly reduced. The residual segregation coefficient of the alloy element Ti at the center of the ingot head is ≤0.16, the residual segregation coefficient of the alloy element Ti at the center of the ingot tail is ≤0.17, the residual segregation coefficient of the alloy element Ti at the 1 / 2 radius of the ingot head is ≤0.21, the residual segregation coefficient of the alloy element Ti at the 1 / 2 radius of the ingot tail is ≤0.24, the residual segregation coefficient of the alloy element Ti at the edge of the ingot head is ≤0.19, and the residual segregation coefficient of the alloy element Ti at the edge of the ingot tail is ≤0.20. There is no obvious crack on the surface of the rod billet during forging.

[0040] The above homogenization treatment method is used for the preparation of large-sized GH4738 bars, and the preparation method of large-sized GH4738 bars can be optimized to prepare large-sized GH4738 bars, including the following steps:

[0041] Step 1: Raw material preparation: Select GH4738 new refined material and returned material as raw materials for preparing high-temperature alloy, and the added amount of returned material in the raw material is 40-80wt%;

[0042] Step 2: The raw materials are successively subjected to vacuum induction melting, electroslag remelting, and vacuum consumable smelting to obtain a 690mm consumable ingot;

[0043] Step 3: multi-stage homogenization heat treatment: including the first stage homogenization treatment, the second stage homogenization treatment, the third stage homogenization treatment and the fourth stage homogenization treatment, wherein the third stage homogenization treatment includes the furnace cooling process;

[0044] Step 4: Open the blank by free forging, forge it in multiple steps, and obtain a fine-grained bar blank by forging.

[0045] Specifically, in step 1, the return material is washed to obtain dry and clean return material; the amount of return material added to the raw material is 40-80wt%, and illustratively, the amount of return material added to the raw material is 45%, 50%, 55%, 60%, 65%, 70%, and 75%.

[0046] Specifically, in step 2, since the return material contains relatively high levels of harmful gas elements such as O and N, the vacuum induction melting time is 11 to 18 hours, and the remaining process parameters in the vacuum induction melting, electroslag remelting and vacuum consumable melting process can adopt conventional process parameters. Exemplarily, the vacuum induction melting time is 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours, 15 hours, 15.5 hours, 16 hours, 16.5 hours, 17 hours, 17.5 hours.

[0047] Specifically, the multi-stage homogenization heat treatment process described in step 3 is the homogenization treatment method provided by the present invention above, which will not be described in detail.

[0048] Specifically, step 4 adopts free forging to open the blank, and forging is performed in multiple fires. The blank is processed to obtain a fine-grained rod blank. The multiple fire forging can be ten forgings, which are the first fire forging, the second fire forging, the third fire forging, the fourth fire forging, the fifth fire forging, the sixth fire forging, the seventh fire forging, the eighth fire forging, the ninth fire forging and the tenth fire forging;

[0049] The first fire forging includes: using a free forging method to forge the homogenized alloy ingot to produce a first fire forging blank, in preparation for subsequent open blank forging;

[0050] The second fire forging includes: a fire forging billet is taken out of the furnace for drawing and shaping, the deformation temperature is 1150-1170°C (exemplarily, the deformation temperature is 1155°C, 1160°C, 1165°C), the deformation amount is 5-10% (exemplarily, the deformation amount is 6%, 7%, 8%, 9%), and the strain rate is 0.1-0.5s -1 (For example, the deformation is 0.2s -1 、0.3s -1 、0.4s -1 ), after the drawing is completed, it is returned to the furnace and heated to 1140-1160°C (exemplarily, to 1145°C, 1150°C, 1155°C), kept warm for 2-4h (exemplarily, kept warm for 2.5h, 3h, 3.5h) and then taken out of the furnace, and is wrapped with hot wrapping technology. After the wrapping is completed, it is returned to the furnace and kept warm for 1-3h (exemplarily, kept warm for 1.5h, 2h, 2.5h) to obtain a second-fire forging billet; this fire forging causes dynamic recrystallization on the surface of the billet, improves the hot working plasticity of the surface of the billet, and prevents cracks on the surface of large-sized bars during the open forging process.

[0051] The third forging process includes: the second forging billet is taken out of the furnace for roughening, the deformation temperature is 1140-1160°C (exemplarily, the deformation temperature is 1145°C, 1150°C, 1155°C), the deformation amount is 30%-40% (exemplarily, the deformation amount is 32%, 34%, 36%, 38%), and the strain rate is 0.1-0.5s -1 (For example, the deformation is 0.2s -1 、0.3s -1 、0.4s -1 ), after the roughening is completed, it is returned to the furnace and heated to 1120-1140°C (exemplarily, it is heated to 1125°C, 1130°C, 1135°C), kept warm for 2-4h (exemplarily, kept warm for 2.5h, 3h, 3.5h) and then taken out of the furnace, and is wrapped with hot wrapping technology. After the wrapping is completed, it is returned to the furnace and kept warm for 1-3h (exemplarily, kept warm for 1.5h, 2h, 2.5h) to obtain a three-fire forging billet; this fire forging causes the coarse columnar crystal structure to break up and refine the rod structure.

[0052] The fourth fire forging includes: the three-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1120-1140°C (exemplarily, the deformation temperature is 1125°C, 1130°C, 1135°C), the deformation amount is 30%-40% (exemplarily, the deformation amount is 32%, 34%, 36%, 38%), and the strain rate is 0.5-1s -1 (Exemplarily, the deformation is 0.6s -1 、0.7s -1 、0.8s -1 、0.9s -1), return to the furnace and heat to 1090-1110°C (exemplarily, the deformation temperature is 1095°C, 1100°C, 1105°C), keep it warm for 2-4h (exemplarily, keep it warm for 2.5h, 3h, 3.5h) and then take it out of the furnace, use the hot packing technology to pack it out of the furnace, and return to the furnace and keep it warm for 1-3h (exemplarily, keep it warm for 1.5h, 2h, 2.5h) after the packing is completed, to obtain the four-fire casting billet;

[0053] The fifth forging process includes: the fourth forging billet is taken out of the furnace for roughening, the deformation temperature is 1090-1110°C (exemplarily, the deformation temperature is 1095°C, 1100°C, 1105°C), and the strain rate is 0.1-0.5s -1 (For example, the deformation is 0.2s -1 、0.3s -1 、0.4s -1 ), the elongation deformation is 30% to 40% (exemplarily, the deformation is 32%, 34%, 36%, and 38%), the furnace is returned to heat up to 1090 to 1110°C (exemplarily, the deformation temperature is 1095°C, 1100°C, and 1105°C), and the heat preservation is 2 to 4 hours (exemplarily, the heat preservation is 2.5 hours, 3 hours, and 3.5 hours) before being taken out of the furnace, and the furnace is wrapped with a hot wrapping technology. After the wrapping is completed, the furnace is returned to heat preservation for 1 to 3 hours (exemplarily, the heat preservation is 1.5 hours, 2 hours, and 2.5 hours) to obtain a five-fire forging billet;

[0054] The sixth fire forging includes: the five-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1090-1110°C (exemplarily, the deformation temperature is 1095°C, 1100°C, 1105°C), the deformation amount is 30%-40% (exemplarily, the deformation amount is 32%, 34%, 36%, 38%), and the strain rate is 0.5-1s -1 (Exemplarily, the deformation is 0.6s -1 、0.7s -1 、0.8s -1 、0.9s -1 ), return to the furnace and heat to 1080-1110°C (exemplarily, the deformation temperature is 1085°C, 1090°C, 1095°C, 1100°C, 1105°C), keep it warm for 2-4h (exemplarily, keep it warm for 2.5h, 3h, 3.5h) and then take it out of the furnace, use the hot bagging technology to bag it out of the furnace, and after the bagging is completed, return to the furnace and keep it warm for 1-3h (exemplarily, keep it warm for 1.5h, 2h, 2.5h) to obtain the six-fire casting billet;

[0055] The seventh forging process includes: the six-fire forging billet is taken out of the furnace for roughening, the deformation temperature is 1080-1110°C (exemplarily, the deformation temperature is 1085°C, 1090°C, 1095°C, 1100°C, 1105°C), and the strain rate is 0.1-0.5s -1(For example, the deformation is 0.2s -1 、0.3s -1 、0.4s -1 ), the elongation deformation is 30% to 40% (exemplarily, the deformation is 32%, 34%, 35%, 36%, 38%), the temperature is returned to the furnace and heated to 1060 to 1080°C (exemplarily, the deformation temperature is 1065°C, 1070°C, 1075°C), and the temperature is kept for 2 to 4 hours (exemplarily, the temperature is kept for 2.5 hours, 3 hours, 3.5 hours) before being taken out of the furnace, and the furnace is wrapped with a hot wrapping technology, and after the wrapping is completed, the furnace is returned to the furnace and kept for 1 to 3 hours (exemplarily, the temperature is kept for 1.5 hours, 2 hours, 2.5 hours) to obtain a seven-fire forging billet;

[0056] The eighth forging process includes: the seventh forging billet is taken out of the furnace for drawing, the deformation temperature is 1060-1080°C (exemplarily, the deformation temperature is 1065°C, 1070°C, 1075°C), the deformation amount is 30%-40% (exemplarily, the deformation amount is 32%, 33%, 34%, 36%, 38%), and the strain rate is 0.5-1s -1 (Exemplarily, the deformation is 0.6s -1 、0.7s -1 、0.8s -1 、0.9s -1 ), return to the furnace and heat it to 1050-1070°C (exemplarily, the deformation temperature is 1055°C, 1060°C, 1065°C), keep it warm for 2-4h (exemplarily, keep it warm for 2.5h, 3h, 3.5h) and then take it out of the furnace, use the hot packing technology to pack it out of the furnace, and return to the furnace and keep it warm for 1-3h (exemplarily, keep it warm for 1.5h, 2h, 2.5h) after the packing is completed, to obtain the eight-fire casting billet;

[0057] The ninth fire forging includes: the eight-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1050-1070°C (exemplarily, the deformation temperature is 1055°C, 1060°C, 1065°C), the deformation amount is 20%-30% (exemplarily, the deformation amount is 22%, 23%, 24%, 25%, 26%, 28%), and the strain rate is 0.5-1s -1 (Exemplarily, the deformation is 0.6s -1 、0.7s -1 、0.8s -1 、0.9s -1 ), return to the furnace and heat it to 1040-1060°C (exemplarily, the deformation temperature is 1045°C, 1050°C, 1055°C), keep it warm for 2-4h (exemplarily, keep it warm for 2.5h, 3h, 3.5h), then take it out of the furnace and wrap it with a hot wrapping technology. After wrapping, return to the furnace and keep it warm for 1-3h (exemplarily, keep it warm for 1.5h, 2h, 2.5h) to obtain a nine-fire casting billet;

[0058] The tenth forging process includes: the nine-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1040-1070°C (exemplarily, the deformation temperature is 1045°C, 1050°C, 1055°C, 1060°C, 1065°C), the deformation amount is 5%-10% (exemplarily, the deformation amount is 6%, 7%, 8%, 9%), and the strain rate is 0.5-1s -1 (Exemplarily, the deformation is 0.6s -1 、0.7s -1 、0.8s -1 、0.9s -1 ), then air-cooled to room temperature and polished to obtain fine-grained rods.

[0059] It should be noted that the deformation temperature range of the first to fourth fires is 1120-1170℃. If the deformation temperature is less than 1120℃, the deformation resistance is significantly larger, and the coarse columnar crystals in the core of large-sized bars are difficult to fully recrystallize; if the deformation temperature is higher than 1170℃, the grain size of the bars increases significantly, the thermoplasticity of the bars deteriorates, and cracks are easily generated during forging; the deformation amount of the second fire is 5%-10%, so that the surface of the bar billet recrystallizes, improves the plasticity of the bar surface, avoids cracks on the surface of the bar billet, and prepares for the subsequent upsetting process. The upsetting deformation amount of the third and fourth fires is 30%-40%. If the deformation amount is less than 30%, the dynamic recrystallization of the bar is insufficient, and it is difficult to break the coarse columnar crystal structure; if the deformation amount exceeds 40%, the deformation resistance increases, and the bar is prone to cracks.

[0060] The deformation temperature used in the fifth to eighth fires is 1060-1110℃. After repeated upsetting and drawing from the first to fourth fires, the grain size of the bar is significantly refined, the plasticity of the bar is improved, the forging temperature is reduced, and the structure of the large-size bar is further refined; the deformation amount used in the fifth to eighth fires is higher than 30%, which can improve the dynamic recrystallization ratio and structural uniformity of the bar matrix structure.

[0061] From the ninth to the tenth fire, the deformation temperature range used is 1040 ~ 1070 ℃, the forging temperature of the bar is further reduced, the bar structure is further refined, and the bar is shaped at the same time; the dissolution temperature of the γ' phase of the bar is about 1040 ℃. If the forging temperature is lower than 1040 ℃, a large amount of γ' phase will be produced, the deformation resistance of the bar will increase significantly, and the load of the fast forging machine will increase rapidly, which cannot meet the requirements of the bar size accuracy control. At the same time, the surface temperature of the bar is reduced, which is prone to cracks. Therefore, the bar blank forging temperature should be higher than 1040 ℃.

[0062] The preparation method adopts the multi-stage homogenization process provided by the present invention, improves the homogenization temperature and the holding time, promotes the dissolution of the low melting point phase, accelerates the diffusion of the alloying elements, and significantly reduces the segregation coefficient of Ti in the ingot. There are no obvious cracks on the surface of the bar during the forging process. By optimizing the forging temperature, reasonably matching the deformation amount of the fire times, reducing the upsetting fire times in the high temperature stage, and performing large deformation in the low temperature stage, the structure at the center of the bar is significantly refined, and the grain size at the center and 1 / 2 of the bar reaches 3.5 or above, and the structure is relatively uniform, without mixed crystals, and the room temperature tensile properties and endurance properties of the center of the bar are significantly improved.

[0063] The large-size GH4738 rod prepared by the preparation method including the multi-stage homogenization process of the present invention has a significantly reduced segregation coefficient of Ti in the ingot, a residual segregation coefficient of the alloy element Ti at the center of the ingot head ≤0.16 (such as 0.145-0.152), a residual segregation coefficient of the alloy element Ti at the center of the ingot tail ≤0.17 (such as 0.155-0.164), a residual segregation coefficient of the alloy element Ti at 1 / 2 radius of the ingot head ≤0.21 (such as 0.191-0.209), a residual segregation coefficient of the alloy element Ti at 1 / 2 radius of the ingot tail ≤0.24 (such as 0.217-0.233), a residual segregation coefficient of the alloy element Ti at the edge of the ingot head ≤0.19 (such as 0.183-0.187), and a residual segregation coefficient of the alloy element Ti at the edge of the ingot tail ≤0.20 (such as 0.176-0.198).

[0064] The large-size GH4738 rod prepared by the preparation method including the multi-stage homogenization process of the present invention has a tensile strength of ≥1300MPa (e.g. 1313-1329MPa) at the head of the ingot, a yield strength of ≥915MPa (e.g. 917-925MPa) at the head of the ingot, an elongation after fracture of ≥23% (e.g. 23-29%) at the head of the ingot, a cross-sectional shrinkage of ≥24% (e.g. 23-29%), and a high temperature endurance of 732°C / 517MPa. The tensile strength of the ingot tail is ≥1300MPa (for example, 1321-1324MPa), the yield strength of the ingot head is ≥880MPa (for example, 885-916MPa), the elongation after fracture of the ingot head is ≥22% (for example, 22.5-25%), the cross-sectional shrinkage is ≥20% (for example, 22-25%), and the high temperature endurance time at 732°C / 517MPa is ≥140h (for example, 142-146h).

[0065] Example 1

[0066] This embodiment provides a homogenization treatment method for large-size GH4738 bars, including a first-stage homogenization treatment, a second-stage homogenization treatment, a third-stage homogenization treatment, and a fourth-stage homogenization treatment, wherein the third-stage homogenization treatment includes a furnace cooling process:

[0067] The first stage of homogenization treatment includes loading the consumable ingot into the furnace when the furnace temperature reaches 600°C, keeping it at that temperature for 3 hours, and then heating the consumable ingot to 1010°C, keeping it at that temperature for 10 hours, and the heating rate is 25°C / h;

[0068] The second stage homogenization treatment includes heating the consumable ingot to 1160°C, keeping it at this temperature for 25h, and heating rate of 8°C / h;

[0069] The third stage of homogenization treatment includes heating the consumable ingot to 1210°C, keeping it at this temperature for 98 hours, and heating up at a rate of 15°C / h; cooling it after keeping it at this temperature for 98 hours, and cooling it to 600°C with the furnace;

[0070] The fourth stage of homogenization treatment includes heating the consumable ingot to 1160°C, keeping it warm for 12 hours, and heating at a rate of 10°C / h. After taking out the furnace, the ingot is wrapped. After wrapping, it is returned to the furnace and kept warm for 3 hours, and the consumable ingot is heated to 1160°C again.

[0071] The homogenization method of this embodiment is used to prepare large-size GH4738 bars, comprising the following steps:

[0072] Step 1: Raw material preparation: GH4738 new refined material and returned material are selected as raw materials for preparing high-temperature alloy, and the added amount of returned material in the raw materials is 40wt%;

[0073] Step 2: The raw materials are successively subjected to vacuum induction melting, electroslag remelting, and vacuum consumable smelting to obtain a 690 mm consumable ingot. The vacuum induction melting time is 12 hours.

[0074] Step 3: multi-stage homogenization heat treatment: for specific parameters, see the homogenization treatment method of this embodiment;

[0075] Step 4: Use free forging to forge the blank, forge it in multiple steps, and process the blank to obtain a fine-grained billet:

[0076] The first fire forging includes: using free forging to forge the homogenized alloy ingot to produce a first-fire forging blank, in preparation for the subsequent open blank forging;

[0077] The second forging process includes: the first forging billet is taken out of the furnace for drawing and shaping, the deformation temperature is 1160℃, the deformation amount is 7%, and the strain rate is 0.1s -1After the drawing is completed, the furnace is returned to heat up to 1140℃, kept at this temperature for 4 hours before being taken out of the furnace. The furnace is wrapped with hot-packing technology. After the wrapping is completed, the furnace is returned to heat for 3 hours to obtain the second-fire forging billet;

[0078] The third forging process includes: the second forging billet is taken out of the furnace for roughening, the deformation temperature is 1155℃, the deformation amount is 32%, and the strain rate is 0.2s -1 , return to the furnace and heat it to 1130℃, keep it warm for 4 hours before taking it out of the furnace, use the hot packing technology to pack it out of the furnace, and after the packing is completed, return to the furnace and keep it warm for 3 hours to obtain the three-fire forging billet;

[0079] The fourth forging process includes: the third forging billet is taken out of the furnace for drawing, the deformation temperature is 1130℃, the deformation amount is 38%, and the strain rate is 0.5s -1 , return to the furnace and heat it to 1110℃, keep it warm for 3 hours before taking it out of the furnace, use the hot packing technology to pack it out of the furnace, and after the packing is completed, return to the furnace and keep it warm for 3 hours to obtain the four-fire casting billet;

[0080] The fifth forging process includes: the billet forged in the fourth forging process is taken out of the furnace for roughening, the deformation temperature is 1110℃, and the strain rate is 0.4s -1 , the elongation deformation is 30%, and the furnace is returned to heat up, and the temperature is raised to 1110℃ with the furnace, and it is kept warm for 3 hours before being taken out of the furnace. The hot-packing technology is used to pack it out of the furnace. After the packing is completed, it is returned to the furnace and kept warm for 2 hours to obtain the five-fire forging billet;

[0081] The sixth forging process includes: the five-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1110℃, the deformation amount is 36%, and the strain rate is 0.6s -1 , return to the furnace and heat it to 1090℃, keep it warm for 3 hours before taking it out of the furnace, use the hot packing technology to pack it out of the furnace, and return to the furnace and keep it warm for 2 hours after the packing is completed to obtain the six-fire casting billet;

[0082] The seventh forging process includes: the billet for forging is taken out of the furnace for roughening, the deformation temperature is 1090℃, and the strain rate is 0.3s -1 , the elongation deformation is 32%, and the furnace is returned to heat up, and the temperature is raised to 1080℃ with the furnace, and it is kept warm for 3 hours before being taken out of the furnace. The hot packing technology is used to pack it out of the furnace. After the packing is completed, the furnace is returned to heat preservation for 3 hours to obtain the seven-fire forging billet;

[0083] The eighth forging process includes: the seventh forging billet is taken out of the furnace for drawing, the deformation temperature is 1070℃, the deformation amount is 30%, and the strain rate is 0.6s -1 , return to the furnace and heat it to 1060℃, keep it warm for 3 hours before taking it out of the furnace, and use the hot packing technology to pack it out of the furnace. After the packing is completed, return to the furnace and keep it warm for 2 hours to obtain the eight-fire casting billet;

[0084] The ninth forging process includes: the eight-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1060℃, the deformation amount is 25%, and the strain rate is 0.8s -1, return to the furnace and heat it to 1050℃, keep it warm for 2 hours before taking it out of the furnace, and use the hot packing technology to pack it out of the furnace. After the packing is completed, return to the furnace and keep it warm for 2 hours to obtain the nine-fire casting billet;

[0085] The tenth forging process includes: the nine-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1050℃, the deformation amount is 6%, and the strain rate is 0.5s -1 , then air-cooled to room temperature, and polished to obtain Ф550mm fine-grained bars.

[0086] Example 2

[0087] This embodiment provides a homogenization treatment method for large-size GH4738 bars, including a first-stage homogenization treatment, a second-stage homogenization treatment, a third-stage homogenization treatment, and a fourth-stage homogenization treatment, wherein the third-stage homogenization treatment includes a furnace cooling process:

[0088] The first stage of homogenization treatment includes loading the consumable ingot into the furnace when the furnace temperature reaches 700°C, keeping it at that temperature for 4 hours, and then heating the consumable ingot to 1000°C, keeping it at that temperature for 10 hours, with a heating rate of 35°C / h;

[0089] The second stage homogenization treatment includes heating the consumable ingot to 1170°C, holding it for 22 hours, and heating up at a rate of 10°C / h;

[0090] The third stage of homogenization treatment includes heating the consumable ingot to 1190°C, keeping it at this temperature for 120 hours, and heating it at a rate of 18°C / h; cooling it after keeping it at this temperature for 120 hours, and cooling it to 550°C with the furnace;

[0091] The fourth stage of homogenization treatment includes heating the consumable ingot to 1180°C, keeping it warm for 10 hours, and heating at a rate of 15°C / h. After taking out the furnace, the ingot is wrapped. After wrapping, it is returned to the furnace and kept warm for 3 hours, and the consumable ingot is heated to 1180°C again.

[0092] The homogenization method of this embodiment is used to prepare large-size GH4738 bars, comprising the following steps:

[0093] Step 1: Raw material preparation: GH4738 new refined material and returned material are selected as raw materials for preparing high-temperature alloy, and the added amount of returned material in the raw material is 60wt%;

[0094] Step 2: The raw materials are successively subjected to vacuum induction melting, electroslag remelting, and vacuum consumable smelting to obtain a 690 mm consumable ingot. The vacuum induction melting time is 16 hours.

[0095] Step 3: multi-stage homogenization heat treatment: for specific parameters, see the homogenization treatment method of this embodiment;

[0096] Step 4: Use free forging to forge the blank, forge it in multiple steps, and process the blank to obtain a fine-grained billet:

[0097] The first fire forging includes: using free forging to forge the homogenized alloy ingot to produce a first-fire forging blank, in preparation for the subsequent open blank forging;

[0098] The second fire forging includes: heating the first fire forging billet to 1155℃ for stretching and shaping, with a deformation of 9% and a strain rate of 0.2s -1 After the drawing is completed, the furnace is returned to heat up to 1155℃, kept at this temperature for 4 hours before being taken out of the furnace. The furnace is wrapped with hot-packing technology. After the wrapping is completed, the furnace is returned to heat for 2 hours to obtain the second-fire forging billet;

[0099] The third forging process includes: the second forging billet is taken out of the furnace for roughening, the deformation temperature is 1150℃, the deformation amount is 34%, and the strain rate is 0.3s -1 , return to the furnace and heat it to 1140℃, keep it warm for 4 hours before taking it out of the furnace, use the hot packing technology to pack it out of the furnace, and return to the furnace and keep it warm for 3 hours after the packing is completed to obtain the three-fire forging billet;

[0100] The fourth forging process includes: the third forging billet is taken out of the furnace for drawing, the deformation temperature is 1130℃, the deformation amount is 36%, and the strain rate is 0.7s -1 , return to the furnace and heat it to 1110℃, keep it warm for 4 hours before taking it out of the furnace, use the hot packing technology to pack it out of the furnace, and return to the furnace and keep it warm for 3 hours after the packing is completed to obtain the four-fire casting billet;

[0101] The fifth forging process includes: the billet forged from the fourth forging process is taken out of the furnace for roughening, the deformation temperature is 1100℃, and the strain rate is 0.3s -1 , the elongation deformation is 34%, the furnace is heated to 1100℃, and it is kept warm for 3 hours before being taken out of the furnace. The furnace is wrapped with hot jacketing technology, and after the wrapping is completed, the furnace is returned to the furnace and kept warm for 3 hours to obtain the five-fire forging billet;

[0102] The sixth forging process includes: the five-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1100℃, the deformation amount is 32%, and the strain rate is 0.7s -1 , the temperature is raised to 1090℃, kept at this temperature for 3 hours, and then returned to the furnace. After being taken out of the furnace, the heat-wrapped technology is used for wrapping. After wrapping, the furnace is returned to the furnace and kept at this temperature for 2 hours to obtain the six-fire casting billet;

[0103] The seventh forging process includes: the billet for forging is taken out of the furnace for roughening, the deformation temperature is 1090℃, and the strain rate is 0.5s -1 , the elongation deformation is 35%, the temperature is raised to 1080℃, and it is kept warm for 3 hours before being taken out of the furnace. After being taken out of the furnace, it is covered with hot-packing technology. After the covering is completed, it is returned to the furnace and kept warm for 2 hours to obtain the seven-fire forging billet;

[0104] The eighth forging process includes: the seventh forging billet is taken out of the furnace for drawing, the deformation temperature is 1080℃, the deformation amount is 33%, and the strain rate is 0.6s -1 , return to the furnace and heat it to 1060℃, keep it warm for 3 hours before taking it out of the furnace, use the hot packing technology to pack it out of the furnace, and after the packing is completed, return to the furnace and keep it warm for 3 hours to obtain the eight-fire casting billet;

[0105] The ninth forging process includes: the eight-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1070℃, the deformation amount is 23%, and the strain rate is 0.9s -1 , the temperature is raised to 1050℃, kept at this temperature for 2 hours, and then returned to the furnace. After being taken out of the furnace, the hot-packing technology is used for packing. After the packing is completed, the furnace is returned to the furnace and kept at this temperature for 2 hours to obtain the nine-fire casting billet;

[0106] The tenth forging process includes: the nine-fire forging billet is taken out of the furnace for drawing, the deformation temperature is 1050℃, the deformation amount is 5%, and the strain rate is 0.6s -1 , then air-cooled to room temperature, and polished to obtain Ф550mm fine-grained bars.

[0107] Comparative Example 1

[0108] This comparative example provides a homogenization treatment method for large-size GH4738 bars. Different from the embodiment, the homogenization treatment method of this comparative example includes a first-stage homogenization treatment, a second-stage homogenization treatment, and a third-stage homogenization treatment:

[0109] The first stage of homogenization treatment includes loading the consumable ingot into the furnace when the furnace temperature reaches 700°C, keeping it at that temperature for 3 hours, and then heating the consumable ingot to 1160°C, keeping it at that temperature for 20 hours, and the heating rate is 25°C / h;

[0110] The second stage of homogenization treatment includes heating the consumable ingot to 1190°C, keeping it at this temperature for 72 hours, with a heating rate of 10°C / h, cooling it to 1000°C with the furnace, and air cooling it after it leaves the furnace;

[0111] The third stage of homogenization treatment includes heating the consumable ingot to 1160°C, keeping it warm for 12 hours, and heating up at a rate of 15°C / h. After it is taken out of the furnace, the ingot is wrapped and then returned to the furnace for insulation for 3 hours.

[0112] The homogenization treatment method of this embodiment is used to prepare a large-scale homogeneous fine-grained high-temperature alloy bar containing a return material, comprising the following steps:

[0113] Step 1: Raw material preparation: GH4738 new refined material and returned material are selected as raw materials for preparing high-temperature alloy, and the added amount of returned material in the raw material is 60wt%;

[0114] Step 2: The raw materials are successively subjected to vacuum induction melting, electroslag remelting, and vacuum consumable smelting to obtain a 690 mm consumable ingot. The vacuum induction melting time is 16 hours.

[0115] Step 3: Multi-stage homogenization heat treatment: for specific parameters, see the homogenization treatment method of this comparative example;

[0116] Step 4: Open the blank by free forging, forge it in multiple steps, and process the blank to obtain a fine-grained rod blank: the same as Example 2.

[0117] Comparative Example 2

[0118] The homogenization treatment method of the large-size GH4738 bar in this comparative example is similar to that of Example 1, except that: the third stage homogenization treatment includes heating the consumable ingot to 1160°C;

[0119] The homogenization treatment method of the comparative example is used to prepare large-size GH4738 rods. The preparation method is similar to that of Example 1, except that:

[0120] 1. The multi-stage heat treatment stage adopts the homogenization treatment method of this comparative example;

[0121] 2. In the free forging stage, the roughing deformation of the third forging is 22%, and the roughing deformation of the fifth forging is 24%.

[0122] The dynamic recrystallization of the matrix in this comparative example is insufficient, resulting in an uneven matrix structure.

[0123] Table 1 shows the residual segregation coefficient of Ti element at different positions of the rods of the embodiment and the comparative example; Table 2 shows the grain size test results at different positions of the rods of the embodiment and the comparative example; Table 3 shows the mechanical properties at different positions of the rods of the embodiment and the comparative example.

[0124] Table 1 Residual segregation coefficient of Ti element at different positions in the bar

[0125]

[0126]

[0127] Table 2 Test results of grain size at different positions of rods

[0128]

[0129] Table 3 Mechanical properties of bars at different positions

[0130]

[0131]

[0132] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A homogenization treatment method for large-size GH4738 bars, characterized in that: The method comprises a first stage homogenization treatment, a second stage homogenization treatment, a third stage homogenization treatment and a fourth stage homogenization treatment, wherein the third stage homogenization treatment comprises a furnace cooling process.

2. The homogenization method according to claim 1, characterized in that: The first stage of homogenization treatment includes loading the consumable ingot into the furnace when the furnace temperature reaches 600-700°C, keeping it warm for 3-5 hours, and then heating the consumable ingot to 980-1020°C and keeping it warm for 6-12 hours.

3. The homogenization method according to claim 2, characterized in that: The heating rate is 20-40°C / h.

4. The homogenization method according to claim 3, characterized in that: The second stage homogenization treatment includes heating the consumable ingot to 1140-1180° C. and keeping the temperature for 20-30 hours.

5. The uniform processing method according to claim 4, characterized in that: The heating rate is 5-10°C / h.

6. The homogenization method according to claim 5, characterized in that: The third stage homogenization treatment includes heating the consumable ingot to 1180-1210° C., keeping the temperature for 90-120 hours, and heating up at a rate of 10-20° C. / h.

7. The homogenization method according to claim 6, characterized in that: The third stage homogenization treatment also includes: keeping the consumable ingot at 1180-1210° C. for 90-120 hours and then cooling it to below 600° C. with the furnace.

8. The homogenization method according to claim 7, characterized in that: The fourth stage homogenization treatment includes heating the consumable ingot to 1140-1180° C., keeping the temperature for 5-12 hours, and heating up at a rate of 10-20° C. / h.

9. The homogenization method according to claim 8, characterized in that: The fourth stage homogenization treatment also includes jacketing the ingot after it is taken out of the furnace, returning it to the furnace for insulation for 2 to 4 hours, and reheating the consumable ingot to 1140 to 1180°C.

10. A method for preparing large-size GH4738 rods, comprising the homogenization treatment method according to any one of claims 1 to 9.

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