CN110499483B - A single-stage homogenization annealing process for highly alloyed GH4720Li alloy - Google Patents

Abstract

The invention discloses a single-stage homogenization annealing process of a high alloyed GH4720Li alloy. The process includes the following steps: Step 1. The high alloyed GH4720Li alloy is heated to 1120°C at a heating rate of 10°C/min to 20°C/min. Step 2: The high alloyed GH4720Li alloy heated to 1120°C in step 1 is heated to 1180°C to 1230°C at a heating rate of 1°C/min to 5°C/min, and then kept for 8h to 28h, and then furnace cooled. The invention eliminates (γ+γ′) eutectic phase and boride low melting point precipitation phase existing in high alloyed GH4720Li alloy by controlling the heating rate, temperature and holding time of single-stage homogenization, and promotes Al, Ti, W , Mo element is fully diffused, element segregation is eliminated, and no over-burning phenomenon occurs during annealing process, and high alloyed GH4720Li alloy with uniform composition is obtained.

Description

A single-stage homogenization annealing process for highly alloyed GH4720Li alloy

technical field

The invention belongs to the field of metal materials and processing thereof, in particular to a single-stage homogenization annealing process of a high-alloyed GH4720Li alloy.

Background technique

Superalloys are key hot-end materials for advanced aerospace engines, including hot-end components such as turbine disks, turbine blades, guide vanes, and combustion chambers, and their application ratio in advanced aeroengines exceeds 40%. In order to meet the needs of the rapid development of the modern aviation industry, higher content of γ' phase elements such as Al and Ti, and refractory metal elements such as W, Mo, and Nb are often added to superalloys, resulting in a higher degree of macro and micro segregation. And with the improvement of alloying degree and the expansion of ingot shape, the tendency of alloy solidification and segregation intensifies. Severe solidification segregation will lead to a very developed dendrite structure of the ingot, and a large number of harmful brittle phases will be formed between the dendrites, thereby deteriorating the hot working of the alloy. performance. The prior art adopts vacuum induction melting (VIM), protective atmosphere electroslag remelting (ESR) and vacuum consumable remelting (VAR) triple process to smelt high alloyed GH4720Li alloy with ingot shape of Φ508mm, in which there is relatively serious Al alloy. , Ti, W, Mo and other elements segregation, the formation of a large number of (γ+γ') eutectic phases between dendrites and low melting point precipitation of borides and other disadvantages. Therefore, the smelted high-alloying superalloy generally needs to undergo homogenization annealing before billet forging to dissolve the interdendritic eutectic phase, the low-melting-point precipitation phase and eliminate element segregation as much as possible, thereby improving the high-alloying superalloy. hot workability.

The research on the homogenization annealing process of highly alloyed superalloys such as GH4169 is relatively mature, and corresponding standards and databases have been formed, which has well solved the segregation problem of elements such as Nb, Al, Ti, W, Mo, etc., and improved its thermal stability. Processability. However, for the highly alloyed GH4720Li alloy with an ingot type of Φ508mm melted by vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, the low melting point precipitates are easily overburned to form pores, and Al The interaction between elements such as , Ti, W, Mo, etc., makes the diffusion law more complicated. If the homogenization annealing system is improperly selected, it is easy to cause serious structural problems in the forgings, such as the incomplete elimination of segregation, it is easy to form a strip structure in the forgings and lead to the scrapping of the forgings. At present, high-alloying superalloys often use multi-stage homogenization annealing process, which is complex and long-term, and the production cost is high. Therefore, for high-alloying superalloys, it is particularly important to formulate a reasonable homogenization annealing system.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a high-alloyed GH4720Li alloy single-stage homogenization annealing process for the deficiencies of the above-mentioned prior art. , eliminating the (γ+γ′) eutectic phase and boride low melting point precipitation phase of the highly alloyed GH4720Li alloy, and at the same time promoting the full diffusion of Al, Ti, W, Mo elements in the interdendritic and dendrite trunks, eliminating the element segregation, and no overburning phenomenon occurs during the annealing process, which solves the problem of easy overburning and element segregation residues during the homogenization annealing process of the highly alloyed GH4720Li alloy.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is: a single-stage homogenization annealing process of high alloyed GH4720Li alloy, characterized in that the process comprises the following steps:

Step 1. Heat the high-alloyed GH4720Li alloy ingot sample to 1120°C at a heating rate of 10°C/min to 20°C/min; the high-alloyed GH4720Li alloy ingot is smelted by vacuum induction and electroslag in a protective atmosphere. It is obtained by melting and vacuum consumable remelting triple process, and the ingot shape is Φ508mm;

Step 2: Heat the high-alloyed GH4720Li alloy ingot sample heated to 1120°C in step 1 to 1180°C to 1230°C at a heating rate of 1°C/min to 5°C/min, and then keep it for 8h to 28h. Cooling; the holding time decreases as the heating temperature increases.

In the present invention, the high-alloyed GH4720Li alloy is first heated to 1120°C at a heating rate of 10°C/min to 20°C/min, and then heated to 1180°C to 1230°C at a heating rate of 1°C/min to 5°C/min, and then kept at a temperature of 1180°C to 1230°C. 8h～28h. The low melting point precipitation phase of the high-alloyed GH4720Li alloy begins to dissolve back at 1120 °C, and the structure of the high-alloyed GH4720Li alloy remains stable below 1120 °C. The production efficiency is improved, and it is easy to realize in industrial production. When the temperature of the highly alloyed GH4720Li alloy is higher than 1120 °C, the elements of Al, Ti, W, and Mo begin to diffuse gradually, and the (γ+γ′) eutectic phase, boride The low-melting point precipitation phase is gradually redissolved, and the present invention adopts a heating rate of 1°C/min to 5°C/min to ensure that the (γ+γ') eutectic phase and the low-melting point precipitation phase of the high alloyed GH4720Li alloy slowly dissolve back and dendrites. The Al, Ti, Mo, and W elements in the intergranular and dendrites diffuse slowly, and the over-burning of the low-melting point precipitates and the insufficient diffusion of the Al, Ti, W, and Mo elements caused by the excessively fast heating rate are suppressed, and the heating rate is saved at the same time. Time, improve production efficiency, adopt heating to 1180 ℃ ~ 1230 ℃ and then keep for 8h ~ 28h, in the process of continuous heating and heat preservation, to eliminate the (γ+γ') eutectic phase of highly alloyed GH4720Li alloy, low boride The melting point precipitation phase dissolves back, which promotes the full diffusion of Al, Ti, W, and Mo elements between dendrites and dendrite stems, eliminates element segregation, and does not cause over-burning, which solves the problem of easy over-burning during homogenization annealing of highly alloyed GH4720Li alloy. The problem of sintering and element segregation residues is to achieve the purpose of homogenization annealing. The temperature range of this heating and heat preservation is 1180℃～1230℃. The γ′ dissolution temperature of the highly alloyed GH4720Li alloy is above 1160℃ and the initial melting temperature is below 1250℃, which meets the annealing temperature. If the temperature is close to 1180°C for a long time, the low-melting point precipitation phase can be eliminated, but the efficiency is low. When the temperature is higher than 1230°C, it is easy to cause the low-melting point precipitation phase to overburn and cause the material to be scrapped. The holding time of 8h to 28h is determined by heating The temperature is determined. The diffusion coefficients of Al, Ti, W, and Mo elements increase exponentially with the increase of temperature. At lower holding temperatures, longer holding time is required to achieve full diffusion of elements, while higher holding temperatures can shorten holding time and further Increase productivity.

In the above-mentioned single-stage homogenization annealing process of the highly alloyed GH4720Li alloy, the heating rate in step 2 is 3°C/min to 5°C/min. The heating rate used in the present invention is 3°C/min to 5°C/min to ensure that the (γ+γ') eutectic phase, the low melting point precipitation phase of boride and the Al, Ti, Mo, The W element diffuses slowly, while shortening the heating time, improving the production efficiency, and suppressing the over-sintering of the low-melting-point precipitates and the insufficient diffusion of Al, Ti, W, and Mo caused by the too fast heating rate.

In the above-mentioned single-stage homogenization annealing process of a highly alloyed GH4720Li alloy, the temperature is heated to 1230° C. for 8 hours as described in step 2. The present invention adopts heating to 1230 DEG C and then keeping for 8 hours. Higher temperature can shorten the time of keeping warm, improve production efficiency, and at the same time avoid over-burning due to long-term heat preservation at lower temperature, so as to eliminate the (γ+ γ′) eutectic phase and boride low melting point precipitation phase, which promotes the full diffusion of Al, Ti, W, and Mo elements between dendrites and dendrite stems, eliminates element segregation, and does not occur during the annealing process. Alloyed GH4720Li alloy is prone to overburning and element segregation residues during homogenization annealing.

In the above single-stage homogenization annealing process of a highly alloyed GH4720Li alloy, the heating rate is 5°C/min. The heating rate adopted in the present invention is 5°C/min, which saves heating time and improves production efficiency.

Compared with the prior art, the present invention has the following advantages:

1. The present invention performs single-stage homogenization annealing of the high-alloyed GH4720Li alloy obtained by triple smelting of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, eliminating the (γ+γ) of the high-alloying GH4720Li alloy. ') eutectic phase and boride low melting point precipitation phase, which promotes the full diffusion of Al, Ti, W, and Mo elements between dendrites and dendrite stems, eliminates element segregation, and does not cause overburning during annealing. The highly alloyed GH4720Li alloy is prone to over-sintering and residual element segregation during the homogenization annealing process, and a highly alloyed GH4720Li alloy with uniform composition is obtained.

2. The present invention realizes the single-stage homogenization annealing of the high-alloyed GH4720Li alloy by controlling the heating rate, temperature and holding time process parameters of the single-stage homogenization annealing. The heating rate increases rapidly, which improves the production efficiency. The heating rate of 1°C/min～5°C/min is used above 1120°C to avoid the overburning of the low melting point phase that is easily caused by the too fast heating rate, and at the same time save the heating time and improve the production. Efficiency, heating to 1230 ℃ for 8h, shortening the holding time and improving production efficiency.

3. The process of the present invention is simple in operation, high in production efficiency, low in production cost, and has wider applicability.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

FIG. 1a is an OM diagram of the highly alloyed GH4720Li alloy used in Example 1 of the present invention.

Figure 1b is a SEM image of the highly alloyed GH4720Li alloy used in Example 1 of the present invention.

2 is a SEM image of the highly alloyed GH4720Li alloy after single-stage homogenization annealing in Example 1 of the present invention.

FIG. 3 is a SEM image of the highly alloyed GH4720Li alloy after single-stage homogenization annealing in Comparative Example 1 of the present invention.

FIG. 4 is a SEM image of the highly alloyed GH4720Li alloy after double-stage homogenization annealing in Comparative Example 2 of the present invention.

5 is a SEM image of the highly alloyed GH4720Li alloy after single-stage homogenization annealing in Example 2 of the present invention.

Detailed ways

Example 1

This embodiment includes the following steps:

Step 1: The high alloyed GH4720Li alloy ingot of Φ508mm is smelted by the triple process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot slice with a thickness of 20mm is cut from the head, Then, a 10mm×10mm×10mm (length×width×height) high-alloyed GH4720Li alloy sample was cut from the core of the ingot, and the high-alloyed GH4720Li alloy sample was placed in a high-temperature box furnace at a temperature of 10℃/ The heating rate of min was heated to 1120 °C;

Step 2: The high-alloyed GH4720Li alloy sample heated to 1120°C in step 1 is heated to 1230°C at a heating rate of 5°C/min, then kept for 8 hours, and then cooled in the furnace.

Figure 1a is an OM image of the as-cast microstructure of the highly alloyed GH4720Li alloy used in this embodiment, and Figure 1b is a SEM image of the highly alloyed GH4720Li alloy used in this embodiment. It can be seen from Figures 1a and 1b that vacuum induction melting is adopted The as-cast structure of the highly alloyed GH4720Li alloy with the ingot type of Φ508mm smelted by the triple process of electroslag remelting and vacuum consumable remelting in protective atmosphere has (γ+γ′) eutectic phase and low melting point precipitation phase defects.

Fig. 2 is an SEM image of the high-alloyed GH4720Li alloy after single-stage homogenization annealing in this embodiment. It can be seen from Fig. 2 that carbide residues exist in the high-alloyed GH4720Li alloy after single-stage homogenization annealing. No (γ+γ′) eutectic phase and low-melting point precipitation phase defects were found around the residue, and there were no obvious pores and no over-burning phenomenon, indicating that the high-alloyed GH4720Li alloy after single-stage homogenization annealing was used in this example. The segregation of Al, Ti, W, Mo elements is fully diffused, the segregation is completely eliminated, and a good single-stage homogenization annealing effect is obtained.

By comparing Fig. 1a, Fig. 1b and Fig. 2, it can be seen that the (γ+γ') eutectic phase and low melting point precipitation phase of the highly alloyed GH4720Li alloy after single-stage homogenization annealing in this example are eliminated, and there is no The existence of obvious voids indicates that the (γ+γ′) eutectic phase and the boride low-melting precipitation phase of the high-alloyed GH4720Li alloy after the single-stage homogenization annealing are more thoroughly re-dissolved, no overburning phenomenon occurs, and a good single-stage annealing is obtained. Homogenizing the annealing effect.

Comparative Example 1

This comparative example includes the following steps:

Step 1: The high alloyed GH4720Li alloy ingot of Φ508mm is smelted by the triple process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot slice with a thickness of 20mm is cut from the head, Then, a 10mm×10mm×10mm (length×width×height) high-alloyed GH4720Li alloy sample was cut from the core of the ingot, and the high-alloyed GH4720Li alloy sample was placed in a high-temperature box furnace at a temperature of 10℃/ The heating rate of min was heated to 1120 °C;

Step 2: The high-alloyed GH4720Li alloy sample heated to 1120°C in step 1 is heated to 1230°C at a heating rate of 10°C/min, then kept for 8 hours, and then cooled in the furnace.

Figure 3 is the SEM image of the high-alloyed GH4720Li alloy after single-stage homogenization annealing in the comparative example. It can be seen from Figure 3 that the high-alloyed GH4720Li alloy after single-stage homogenization annealing has obvious carbide residues. Pores formed by overburning of the low melting point phase appear around the residue.

It can be seen from the comparison between Fig. 2 and Fig. 3 that the highly alloyed GH4720Li alloy after single-stage homogenization annealing in this comparative example has obvious pores formed by over-burning, which indicates that the heating rate used in this comparative example is too fast, resulting in high alloying. The low melting point precipitation phase of the alloyed GH4720Li alloy is over-burned to produce pores, which leads to the scrapping of the high-alloyed GH4720Li alloy.

Comparative Example 2

This comparative example includes the following steps:

Step 1: The high alloyed GH4720Li alloy ingot of Φ508mm is smelted by the triple process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot slice with a thickness of 20mm is cut from the head, Then, a 10mm×10mm×10mm (length×width×height) high-alloyed GH4720Li alloy sample was cut from the core of the ingot, and the high-alloyed GH4720Li alloy sample was placed in a high-temperature box furnace at a temperature of 10℃/ The heating rate of min was heated to 1120 °C;

Step 2: Heat the high-alloyed GH4720Li alloy sample heated to 1120°C in step 1 to 1180°C for 24h at a heating rate of 10°C/min, then heat to 1230°C for 28h at a heating rate of 10°C/min, and then Cool in the oven.

Fig. 4 is the SEM image of the high-alloyed GH4720Li alloy obtained by the double-stage homogenization annealing in the comparative example. It can be seen from Fig. 4 that the high-alloyed GH4720Li obtained by the double-stage homogenization annealing in the prior art is used in the comparative example. There are carbide residues in the alloy, and holes formed by the overburning of the low-melting-point precipitates appear around the carbide residues.

It can be seen from the comparison between Fig. 2 and Fig. 4 that the high-alloyed GH4720Li alloy obtained by the double-stage homogenization annealing in the prior art obviously has pores formed by over-burning, indicating that the high-alloyed GH4720Li alloy has It is said that the double-stage homogenization annealing still has low melting point precipitation phase overburning and produces pores, which leads to the scrapping of the highly alloyed GH4720Li alloy.

Example 2

This embodiment includes the following steps:

Step 1: The high alloyed GH4720Li alloy ingot of Φ508mm is smelted by the triple process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot slice with a thickness of 20mm is cut from the head, Then, a 10mm×10mm×10mm (length×width×height) high-alloyed GH4720Li alloy sample was cut from the core of the ingot, and the high-alloyed GH4720Li alloy sample was placed in a high-temperature box furnace at 15°C/ The heating rate of min was heated to 1120 °C;

Step 2: The high-alloyed GH4720Li alloy sample heated to 1120°C in step 1 was heated to 1180°C at a heating rate of 1°C/min for 28 hours, and then cooled in the furnace.

FIG. 5 is a SEM image of the high-alloyed GH4720Li alloy after single-stage homogenization annealing in this embodiment. It can be seen from FIG. 5 that there are carbide residues in the high-alloyed GH4720Li alloy after single-stage homogenization annealing. No (γ+γ′) eutectic phase and low melting point precipitation phase defects were found around the residue, and there were no obvious pores and no overburning phenomenon, indicating that the high-alloyed GH4720Li alloy after single-stage homogenization annealing was adopted in this example. The segregation of Al, Ti, W, Mo elements is fully diffused, the segregation is completely eliminated, and a good single-stage homogenization annealing effect is obtained.

Example 3

This embodiment includes the following steps:

Step 1: The high alloyed GH4720Li alloy ingot of Φ508mm is smelted by the triple process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot slice with a thickness of 20mm is cut from the head, Then, a 10mm×10mm×10mm (length×width×height) high-alloyed GH4720Li alloy sample was cut from the core of the ingot, and the high-alloyed GH4720Li alloy sample was placed in a high-temperature box furnace at 20℃/ The heating rate of min was heated to 1120 °C;

Step 2: The high-alloyed GH4720Li alloy sample heated to 1120°C in step 1 was heated to 1200°C at a heating rate of 3°C/min for 16 hours, and then cooled with the furnace.

After testing, it was found that the (γ+γ′) eutectic phase and the boride low melting point precipitation phase of the highly alloyed GH4720Li alloy after single-stage homogenization annealing in this example were completely re-dissolved, and there were no obvious holes and no overburning. The phenomenon occurs, the segregation of Al, Ti, W, Mo elements is fully diffused, the segregation is completely eliminated, and a good homogenization annealing effect is obtained.

Example 4

This embodiment includes the following steps:

Step 1: The high alloyed GH4720Li alloy ingot of Φ508mm is smelted by the triple process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot slice with a thickness of 20mm is cut from the head, Then, a 10mm×10mm×10mm (length×width×height) high-alloyed GH4720Li alloy sample was cut from the core of the ingot, and the high-alloyed GH4720Li alloy sample was placed in a high-temperature box furnace at a temperature of 10℃/ The heating rate of min was heated to 1120 °C;

Step 2: The high-alloyed GH4720Li alloy sample heated to 1120°C in step 1 was heated to 1230°C at a heating rate of 4°C/min for 8 hours, and then cooled in the furnace.

After testing, it was found that the (γ+γ′) eutectic phase and the boride low melting point precipitation phase of the highly alloyed GH4720Li alloy after single-stage homogenization annealing in this example were completely re-dissolved, and there were no obvious holes and no overburning. The phenomenon occurs, the segregation of Al, Ti, W, Mo elements is fully diffused, the segregation is completely eliminated, and a good homogenization annealing effect is obtained.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any way. Any simple modifications, changes and equivalent changes made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solutions of the present invention.

Claims (4)

1. A high-alloying GH4720Li alloy single-stage homogenization annealing process is characterized by comprising the following steps:

step one, heating a high-alloying GH4720Li alloy ingot casting sample to 1120 ℃ at a heating rate of 10-20 ℃/min; the high-alloying GH4720Li alloy cast ingot is obtained by smelting through a triple process of vacuum induction smelting, protective atmosphere electroslag remelting and vacuum consumable remelting, and the ingot shape is phi 508 mm;

step two, heating the high-alloying GH4720Li alloy ingot casting sample heated to 1120 ℃ in the step one to 1180-1230 ℃ at a heating rate of 1-5 ℃/min, preserving heat for 8-28 h, and then cooling along with the furnace; the time of the heat preservation is reduced along with the increase of the heating temperature.

2. The process according to claim 1, wherein the temperature increase rate in the second step is 3 ℃/min to 5 ℃/min.

3. The process according to claim 2, wherein in step two, the temperature is maintained for 8h after heating to 1230 ℃.

4. The process of claim 2, wherein the temperature increase rate in step two is 5 ℃/min.

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