Evaluation method for strip-shaped grain structure in GH4169 alloy disc forge piece

Abstract

The invention belongs to the technical field of forge piece manufacturing, and particularly relates to an evaluation method for a strip-shaped grain structure in a GH4169 alloy disc forge piece. According to the technical scheme, the method comprises the following steps that 1, a GH4169 alloy disc forging strip-shaped grain structure detection method is formulated; the method comprises the following steps: 1.1, carrying out strip-shaped grain structure detection on a high-power sample of the forge piece, wherein the strip-shaped grain structure is in a strip shape with different color shades under a 25-time microscope after the sample is corroded; 1.2, original state grain size / original state microscopic structure detection; 1.3, a heat treatment state strip-shaped grain structure / microscopic structure detection method; 2, formulating evaluation requirements of strip-shaped grain structures of the GH4169 alloy disc forgings; 2.1, evaluation requirements of the original state strip-shaped grain size / microscopic structure are met; and 2.2, evaluation requirements of strip-shaped grain size / microscopic structure in a heat treatment state are met. According to the method, the acceptance technical indexes of the GH4169 alloy disc forgings can be perfected, the structure uniformity of the forgings is improved, the metallurgical quality control requirements of the forgings are optimized, and the comprehensive mechanical property level of the forgings is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of forging manufacturing, and in particular relates to an evaluation method for a strip-shaped grain structure in a GH4169 alloy disc forging. Background Art

[0002] GH4169 alloy is used in the manufacture of various parts such as engine discs, casings, rings, and structural parts. The grain structure of GH4169 alloy forgings is determined by the quality level of raw materials, forging and heat treatment processes. Compared with casings, rings and structural parts, the existing acceptance standards for GH4169 alloy disc forgings generally require forgings to have finer grain size (at least reaching national standard grade 8), higher strength, durability, creep and fatigue performance levels. The existing standard grain size of GH4169 alloy disc forgings only determines the average grain size grade, and there is no requirement for the detection and control of banded grain structure. Existing grain size evaluation requirements: (1) Detection method: Directly perform grain size detection on the original forgings under a 100x microscope; (2) Evaluation requirements: The grain size should be national standard grade 8 or finer, and individual grains not exceeding national standard grade 2 are allowed.

[0003] Taking GH4169 alloy disc forgings as an example, the existing forging acceptance standards have the following requirements for high-magnification grains: the average grain size is national standard grade 8 or finer, and individual grains not exceeding national standard grade 2 are allowed. In actual production, the average grain size of a typical batch of forgings is grade 8 to grade 12, which meets the acceptance standard requirements; however, some batches of forgings have a banded structure with coarse and fine grains distributed side by side (national standard grade 8 to grade 9 for the coarse grain part and national standard grade 11 to grade 12 for the fine grain part). The metallographic diagram is shown in the attached figure. Figure 1 , 2 As shown in the figure, the low cycle fatigue performance of the forgings fluctuated greatly, and the test results of some positions did not meet the standards. After analysis, the unqualified mechanical properties were caused by the presence of banded structures in the forgings and the large grain size difference between the banded parts and the normal parts.

[0004] For GH4169 alloy disc forgings, acceptance is only carried out according to the lower limit of the average grain size grade and the maximum allowable grain requirements specified in the existing standards, which cannot achieve the control of the banded structure of the forgings. When the distribution of the banded structure leads to serious uneven structure, the mechanical properties of the forgings are significantly reduced or even exceed the standard. The existing technical standards for GH4169 alloy disc forgings lack banded structure evaluation and control based on the control of organizational uniformity and higher mechanical property levels, and cannot meet the high-level metallurgical quality control requirements of parts. Summary of the invention

[0005] The present invention provides an evaluation method for the banded grain structure in a GH4169 alloy disc forging, improves the technical indicators for acceptance of GH4169 alloy disc forgings, improves the uniformity of the structure of the forgings, optimizes the metallurgical quality control requirements of the GH4169 alloy disc forgings, and ensures that the forgings have a high level of comprehensive mechanical properties.

[0006] The technical solution of the present invention is as follows: A method for evaluating the banded grain structure in a GH4169 alloy disc forging comprises the following steps:

[0007] 1) Develop a method for detecting the banded grain structure of GH4169 alloy disc forgings;

[0008] 1.1) Banded grain structure detection method

[0009] The high-magnification specimens of GH4169 alloy disc forgings were tested for banded grain structure. The banded grain structure is a strip of different shades of color under a 25x microscope after the specimen is corroded.

[0010] 1.2) Detection method of original banded grain structure

[0011] (1) Grain size detection in the original state: After the strip-shaped microstructure sample of the GH4169 alloy disc forging was corroded, the grain size of the strip part and other normal parts were detected under a 100x microscope;

[0012] (2) Microstructure inspection of original state: After the strip-shaped structure specimen of GH4169 alloy disc forging was corroded, the microstructure of the strip part and other normal parts were inspected under a 250x microscope;

[0013] 1.3) Detection method of banded grain structure in heat treatment state

[0014] (1) Grain size detection after heat treatment: Heat treatment is performed on the strip-shaped grain structure sample: heating to 985°C, keeping the temperature for 1 hour, and air cooling; the grain size is detected after heat treatment;

[0015] (2) Microstructure detection after heat treatment: Heat treatment was performed on the banded grain structure sample: heated to 1030°C, kept at this temperature for 1 hour, and air-cooled; reheated to 900°C, kept at this temperature for 3 hours, and air-cooled; the microstructure was detected after heat treatment;

[0016] 2) Formulate the evaluation requirements for the banded grain structure of GH4169 alloy disc forgings;

[0017] 2.1) Evaluation requirements for original banded grain structure

[0018] (1) Grain size: The average grain size is national standard grade 8 or finer, and individual grains not exceeding national standard grade 2 are allowed to exist; comparing the grain size grades of the stripe part and the normal part, the grain size difference between the stripe part and the normal part should not be greater than 2 national standard grades;

[0019] (2) Microstructure: The distribution of the microstructure in the stripe area should not show a stripe-like morphology;

[0020] 2.2) Evaluation requirements for banded grain structure in heat-treated state

[0021] (1) Grain size: The grain size of the sample after heat treatment is national standard 8 or finer, and the existence of single grains not exceeding national standard 2 is allowed;

[0022] (2) Microstructure: The microstructure of the sample after heat treatment does not show a striped distribution morphology.

[0023] The beneficial effects of the present invention are as follows: the present invention establishes a method for evaluating the banded grain structure of GH4169 alloy disc forgings, improves the technical indicators for acceptance of GH4169 alloy disc forgings, improves the uniformity of the structure of forgings, optimizes the metallurgical quality control requirements of GH4169 alloy disc forgings, ensures that the forgings have a high level of comprehensive mechanical properties, and improves the mechanical properties, metallurgical quality and manufacturing technology level of disc forgings for engines and related parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the banded δ phase of GH4169 disk forging;

[0025] Figure 2 It is the banded microstructure (δ phase) of GH4169 disk forging after heat treatment;

[0026] Figure 3 This is the banded grain structure morphology under a 25x microscope;

[0027] Figure 4 This is the banded grain structure morphology under a 100x microscope;

[0028] Figure 5 The microstructures of GH4169 disc forgings with different grain size differences; (a) Batch 1: the strip part has a grain size of 12 and the normal part has a grain size of 9; (b) Batch 2: the strip part has a grain size of 10 and the normal part has a grain size of 8;

[0029] Figure 6 Microstructure of forgings after heat treatment; (a) Batch 1: banded microstructure (δ phase); (b) Batch 2: uniform microstructure (δ phase). DETAILED DESCRIPTION

[0030] An evaluation method for banded grain structure in GH4169 alloy disc forgings, the specific operation steps are as follows:

[0031] Step 1: Average grain size detection and evaluation

[0032] Cut a high-magnification sample from the GH4169 alloy disc forging, and after the high-magnification sample is corroded, the grain size is tested under a 100-times microscope. The average grain size is national standard grade 8 or finer, and a single grain not exceeding national standard grade 2 is allowed. Otherwise, the grain size is considered unqualified.

[0033] Step 2: Banded grain structure detection

[0034] After the high-power specimen of GH4169 alloy disc forging was corroded, it was tested under a 25x microscope. Figure 3 When the color is displayed in different shades, it is considered that there is a banded grain structure, where the darker the area, the grains are relatively small, belonging to the normal part; the lighter the area, the grains are relatively coarse, which is the banded grain structure area. Figure 4 The following is the high-magnification morphology of the banded grain structure under a 100x microscope, where the grains in regions A and C are relatively coarse, corresponding to Figure 3 The light-colored stripe area in the middle; the grains in areas B and D are relatively small, corresponding to Figure 3 The dark areas in the

[0035] Step 3: Original grain size evaluation requirements

[0036] The grain size of the stripe part is tested, and the grain size grade of the stripe part is compared with that of the normal part. The grain size difference between the stripe part and the normal part is no more than 2 national standard grades.

[0037] Step 4: Original state organization evaluation requirements

[0038] Microstructure (δ phase) detection was performed on the stripe area, and no stripe-like distribution morphology was found.

[0039] Step 5: Grain size evaluation requirements after heat treatment

[0040] Heat treatment was performed on the sample with banded grain structure: heating to 985°C, keeping at this temperature for 1 hour, and air cooling. After heat treatment, the grain size was evaluated, and the grain size was national standard grade 8, and there were individual grains not exceeding national standard grade 2.

[0041] Step 6: Requirements for organization evaluation after heat treatment

[0042] Heat treatment was performed on the sample with banded grain structure: heating to 1030°C, keeping at this temperature for 1 hour, air cooling; reheating to 900°C, keeping at this temperature for 3 hours, air cooling. After heat treatment, the microstructure (δ phase) was evaluated and no banded distribution morphology was shown.

[0043] Step 7: Comprehensive evaluation of forging banded grain structure

[0044] According to the above steps, the original grain size, microstructure of the forging with banded grains, as well as the grain size and microstructure evaluation after heat treatment all meet the control requirements, and the banded grain structure of the GH4169 alloy disc forging meets the requirements.

[0045] Example

[0046] For two batches of GH4169 alloy disc forgings (Batch 1 and Batch 2), strip microstructure testing was carried out; the grain size difference between the strip part and the normal part of Batch 1 was about 3 levels, and the grain size difference between the strip part and the normal part of Batch 2 was about 2 levels. Figure 5 After heat treatment, the microstructure (δ phase) of batch 1 showed a striped distribution, and the microstructure (δ phase) of batch 2 showed a uniform distribution, as shown in Figure 2. Figure 6 shown.

[0047] After mechanical property testing, the low-cycle fatigue performance (cycle times) of Batch 1 did not meet the acceptance technical requirements and was significantly lower than that of Batch 2, as shown in Table 1.

[0048] Table 1 Low cycle fatigue properties of GH4169 forgings with different grain size differences

[0049]

Claims

1. A method for evaluating the banded grain structure in a GH4169 alloy disc forging, characterized in that: The following steps are involved: 1) Develop a method for detecting the banded grain structure of GH4169 alloy disc forgings; 1.1) Banded grain structure detection method The high-magnification specimens of GH4169 alloy disc forgings were tested for banded grain structure. The banded grain structure is a strip of different shades of color under a 25x microscope after the specimen is corroded. 1.2) Detection method of original banded grain structure (1) Grain size detection in the original state: After the strip-shaped microstructure sample of the GH4169 alloy disc forging was corroded, the grain size of the strip part and other normal parts were detected under a 100x microscope; (2) Microstructure inspection of original state: After the strip-shaped structure specimen of GH4169 alloy disc forging was corroded, the microstructure of the strip part and other normal parts were inspected under a 250x microscope; 1.3) Detection method of banded grain structure in heat treatment state (1) Grain size detection after heat treatment: Heat treatment is performed on the strip-shaped grain structure sample: heating to 985°C, keeping the temperature for 1 hour, and air cooling; the grain size is detected after heat treatment; (2) Microstructure detection after heat treatment: Heat treatment was performed on the banded grain structure sample: heated to 1030°C, kept at this temperature for 1 hour, and air-cooled; reheated to 900°C, kept at this temperature for 3 hours, and air-cooled; the microstructure was detected after heat treatment; 2) Formulate the evaluation requirements for the banded grain structure of GH4169 alloy disc forgings; 2.1) Evaluation requirements for original banded grain structure (1) Grain size: The average grain size is national standard grade 8 or finer, and individual grains not exceeding national standard grade 2 are allowed to exist; comparing the grain size grades of the stripe part and the normal part, the grain size difference between the stripe part and the normal part should not be greater than 2 national standard grades; (2) Microstructure: The distribution of the microstructure in the stripe area should not show a stripe-like morphology; 2.2) Evaluation requirements for banded grain structure in heat-treated state (1) Grain size: The grain size of the sample after heat treatment is national standard 8 or finer, and the existence of single grains not exceeding national standard 2 is allowed; (2) Microstructure: The microstructure of the sample after heat treatment does not show a striped distribution morphology.

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