CN106756685A - A kind of method for refining nickel-based high-temperature alloy forge piece grain structure - Google Patents

Abstract

The invention discloses a method for refining the grain structure of a nickel-based high-temperature alloy forging, which is characterized in that a double-pass variable strain rate process of intermediate heat preservation is adopted to promote complete recrystallization of the material, including the following steps: (1) the nickel-based The high-temperature alloy forging billet is subjected to solid solution pretreatment, and then quenched immediately; (2) The forging billet obtained in step 1 is heated to 970 ° C ~ 1010 ° C, and after the forging billet is kept at a uniform temperature, the double-pass variable strain rate of intermediate heat preservation is adopted. The process applies deformation to the billet: the strain rate of the first pass forging billet is 0.05s ^‑1 ~ 0.1s ^‑1 , the deformation amount of the first pass forging billet is 20% to 35%, and the strain rate of the second pass forging billet The speed is 0.01s ^‑1 to 0.001s ^‑1 , the interval between two passes is 60s to 240s, and the total deformation of the two passes of the forging billet is 50% to 60%; (3) After the deformation is completed, the forging is immediately Quenching. The invention can effectively achieve the purpose of refining the grain structure of nickel-based high-temperature alloy forgings with a small total deformation amount, and provides a new technology for the quality improvement of nickel-based high-temperature alloy forgings.

Description

A method for refining the grain structure of nickel-based superalloy forgings

Technical field:

The invention belongs to the technical field of forging, and relates to a method for refining the grain structure of nickel-based superalloy forgings.

Background technique:

Nickel-based superalloys have high strength and plasticity, good corrosion resistance and oxidation resistance, and good fatigue properties. They are currently one of the most widely used alloy materials in the aviation field and are widely used in the manufacture of aero-engine turbines. Key parts such as discs, casings, compressor discs and blades.

Refining the grain structure is an important goal in the manufacturing process of forgings. The reason why hot forming processes such as forging can refine the grain structure is because the material will undergo dynamic recrystallization behavior during hot deformation. However, when the nickel-based superalloy is deformed in a single pass and under constant working conditions (temperature, strain rate), a large strain is required for complete dynamic recrystallization to occur. For example, for the GH4169 alloy, at a deformation temperature of 980°C and a strain rate of s ^-1 , the equivalent strain required for 95% dynamic recrystallization to reach 1.7 (equivalent to 82% deformation). Obviously, in the actual die forging process, such a large strain is difficult to achieve. Although increasing the deformation temperature and decreasing the strain rate can reduce the strain required for dynamic recrystallization to occur completely, it will increase the grain size of dynamic recrystallization, which obviously affects the grain refinement effect. Therefore, there is an urgent need to invent a new method, which can not only effectively reduce the strain required for the dynamic recrystallization of nickel-based superalloys to occur completely, but also make the recrystallized grain structure fine.

Invention content:

The purpose of the present invention is to provide a method for refining the grain structure of nickel-based superalloy forgings, which is characterized in that the double-pass variable strain rate process of intermediate heat preservation is used to promote the complete recrystallization of the alloy without increasing the deformation temperature or reducing the The strain rate in the final forging stage can be adjusted to achieve the purpose of refining the grain structure of nickel-based superalloy forgings with a small amount of total deformation. Difficulties in the grain structure of nickel-based superalloy forgings with fine grains.

The scheme that the present invention solves the above-mentioned difficult problem is:

Step 1: Perform solid solution pretreatment on the nickel-based superalloy forging billet, and then quench immediately; the process of solid solution pretreatment is: heating the forging billet to 1010-1040°C for 0.7-0.9 hours;

Step 2: Heat the forged billet obtained in step 1 to 970°C to 1010°C, keep it warm until the temperature of the forged billet is uniform, and apply deformation to the billet by using a double-pass variable strain rate process with intermediate heat preservation; the specific process is: the first pass The strain rate of the secondary forging blank is 0.05s ^-1 ~ 0.1s ^-1 , the deformation of the first pass forging blank is 20% ~ 35%, and the strain rate of the second pass forging blank is 0.01s ^-1 ~ 0.001s ^-1 , the interval between two passes is 60s~240s, and the total deformation of the two passes of the forging billet is 50%~60%;

Step 3: Quench the forging immediately after deformation.

The beneficial effects of the present invention are: the method makes full use of the interaction mechanism of deformation-dislocation-double-pass heat preservation-metadynamic and dynamic recrystallization, and finally realizes the refinement of nickel-based high temperature with relatively small total deformation The purpose of the grain structure of alloy forgings provides a new technology for the quality improvement of nickel-based superalloy forgings.

Description of drawings:

Fig. 1 Microstructure of GH4169 alloy forging blank after solid solution pretreatment;

The strain rate-strain curve of Fig. 2 embodiment 1;

Fig. 3 Example 1 adopts the grain structure of the GH4169 alloy forging obtained by the double-pass variable strain rate process of intermediate heat preservation;

Figure 4 The grain structure of the GH4169 alloy forging obtained in the comparative experiment of Example 1: (a) constant strain rate is 0.1s ^-1 ; (b) constant strain rate is 0.01s ^-1 ; (c ⁾ variable strain rate is 0.1s -1 1-0.01s ^{-1 ;}

The strain rate-strain curve of Fig. 5 embodiment 2;

Fig. 6 Example 2 adopts the grain structure of the GH4169 alloy forging obtained by the double-pass variable strain rate process of intermediate heat preservation;

Fig. 7 The grain structure of the GH4169 alloy forging obtained in the comparative experiment of Example 2: (a) constant strain rate is 0.1s ^-1 ; (b) constant strain rate is 0.001s ^-1 ; (c ⁾ variable strain rate is 0.1s -1 ¹ -0.001s ^-1 .

detailed description:

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention is a method for refining the grain structure of a nickel-based superalloy forging. In all the following examples, a typical nickel-based superalloy—GH4169 alloy forging is selected as the object, and its chemical composition is shown in Table 1.

The GH4169 alloy composition (wt.%) of material used in the example of the present invention in table 1

Example 1

Step 1: Perform solid solution pretreatment on the GH4169 alloy forging billet, and then quench immediately; the process of solid solution pretreatment is: heat the forging billet to 1040°C for 0.75 hours; The structure after treatment is shown in Figure 1. Through solution treatment, a uniform grain structure is obtained, and the average grain size can be measured by the intercept method to be about 75 μm.

Step 2: Heat the forging billet obtained in step 1 to 1010°C, keep it warm until the temperature of the forging billet is uniform, and apply deformation to the billet by adopting the double-pass variable strain rate process of intermediate heat preservation: the strain rate of the first pass forging billet is 0.1 s ^-1 , the deformation of the first pass forging blank is 30% (true strain 0.35), the strain rate of the second pass forging blank is 0.01s ^-1 , the interval between two passes is 60s, the forging blank has experienced The total deformation after the two-stage deformation is 60% (true strain 0.92); the relationship between the strain rate and the strain in Example 1 is shown in Figure 2.

Step 3: Immediately after the deformation, the forging billet is quenched.

The metallographic observation of the GH4169 alloy forging is shown in Figure 3. Comparing Fig. 3 and Fig. 1, it can be seen that the method of the present invention can achieve the purpose of promoting the dynamic recrystallization of GH4169 alloy completely and refining the grain structure. In order to prove the superiority of the method of the present invention, a comparative experiment has been carried out. The selected deformation temperature and the total deformation of the forging blank in the comparative experiment are the same as in Example 1 of the present invention. The difference is that the comparative experiment adopts constant strain rate and variable strain without heat preservation. Velocity mode for deformation. Figure 4(a) shows the metallographic structure obtained when the strain is deformed at a constant strain rate of 0.1s ^-1 to a total deformation of 60% (true strain 0.92 ⁾ ; The metallographic structure is obtained when the deformation reaches 60% of the total deformation (true strain 0.92). Figure 4(c) shows that the deformation is first performed at a constant strain rate of 0.1s ^-1 to a total deformation of 30% (true strain 0.35), then the strain rate is rapidly reduced to 0.01s ^-1 , and then compressed to a total deformation of 60% ( The metallographic structure obtained when the true strain is 0.92). It can be seen from Fig. 4(a) that only a small amount of dynamic recrystallized grains are found around the original large grain boundaries at a constant strain rate of 0.1s ^-1 to 60% deformation, and the metal structure is dominated by the original large grains. In Figure 4(b) and (c), only part of the dynamic recrystallization occurred, and the metallographic structure was mixed crystal, which did not achieve the effect of grain refinement. Therefore, comparative experiments have proved that the method proposed by the present invention has superiority.

Example 2

Step 1: Perform solid solution pretreatment on the GH4169 alloy forging billet, and then quench immediately; the process of solid solution pretreatment is: heat the forging billet to 1040°C for 0.75 hours; The structure after treatment is shown in Figure 1. Through solution treatment, a uniform grain structure is obtained, and the average grain size can be measured by the intercept method to be about 75 μm.

Step 2: Heat the forging billet obtained in step 1 to 980°C, keep it warm until the temperature of the forging billet is uniform, and apply deformation to the billet by using the double-pass variable strain rate process of intermediate heat preservation: the strain rate of the forging billet in the first pass is 0.1 s ^-1 , the deformation of the first pass forging blank is 30% (true strain 0.35), the strain rate of the second pass forging blank is 0.001s ^-1 , the interval between two passes is 120s, the forging blank has experienced The total deformation after the two-stage deformation is 60% (true strain 0.92); the relationship between the strain rate and the strain in Example 1 is shown in Figure 5.

Step 3: Immediately after the deformation, the forging billet is quenched.

The metallographic observation of the GH4169 alloy forging is shown in Figure 6. Comparing Figure 6 and Figure 1, it can be seen that the method of the present invention can achieve the purpose of promoting the dynamic recrystallization of GH4169 alloy completely and refining the grain structure of GH4169 alloy. In order to prove the superiority of the method of the present invention, a comparative experiment has been carried out. The selected deformation temperature and the total deformation of the forging blank in the comparative experiment are the same as in Example 1 of the present invention. The difference is that the comparative experiment adopts constant strain rate and variable strain without heat preservation. Velocity mode for deformation. Figure 7(a) shows the metallographic structure obtained when the strain is deformed at a constant strain rate of 0.1s ^-1 to a total deformation of 60% (true strain 0.92 ⁾ ; The metallographic structure is obtained when the deformation reaches 60% of the total deformation (true strain 0.92). Figure 7(c) shows that the deformation is first performed at a constant strain rate of 0.1s ^-1 to a total deformation of 30% (true strain 0.35), then the strain rate is rapidly reduced to 0.001s ^-1 , and then compressed to a total deformation of 60% ( The metallographic structure obtained when the true strain is 0.92). It can be seen from Fig. 7(a) that only a small amount of dynamic recrystallization grains are found around the original large grain boundaries when the deformation is carried out at a constant strain rate of 0.1s ^-1 to 60%, and the metal structure is dominated by the original large grains. In Figure 7(b), due to the deformation at a constant strain rate of 0.1s ^-1 to 60% deformation, the degree of dynamic recrystallization is relatively high, but there are still a small amount of original large grains in the metallographic structure, and dynamic recrystallization Not quite enough. Figure 7(c) is similar to the results in Figure 7(b). Therefore, comparative experiments have proved that the method proposed by the present invention has superiority.

Claims (2)

1. it is a kind of refine nickel-based high-temperature alloy forge piece grain structure new method, it is characterised in that：The method uses moderate soak Two pass time become strain rate technique and promote nickel base superalloy that complete recrystallization occurs, it comprises the following steps：

Step 1：Nickel base superalloy forging stock is carried out into solid solution pretreatment, is quenched immediately after；

Step 2：The forging stock that step 1 is obtained is heated to 970 DEG C~1010 DEG C, insulation to forging stock temperature it is uniform after, using centre The two pass time of insulation becomes strain rate technique and blank is applied to deform；Its concrete technology is：The strain rate of the first passage forging stock It is 0.05s^-1~0.1s^-1, the deflection of the first passage forging stock is 20%~30%, and the strain rate of the second passage forging stock is 0.01s^-1~0.001s^-1, the interval time between two passages is 60s~240s, the total deformation of the passage of forging stock two for 50%~ 60%；

Step 3：After deformation terminates, forging is quenched immediately.

2. the method for claim 1, it is characterised in that the forging stock solid solution pretreating process described in step 1 is：By forging stock 1010~1040 DEG C of insulations are heated to, soaking time is 0.7 hour~0.9 hour.