A test method for analyzing abnormal grain growth
By using plane strain testing, rapidly cooling metal samples heated by induction coils and pressed by indenters, and combining this with numerical simulation analysis, the problem of testing abnormal grain growth during the hot forming process of metal forgings was solved. This approach enables low-cost and effective analysis of abnormal grain growth behavior, thereby reducing production risks.
Patent Information
- Application Number
- CN202210860036.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-20
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2042-07-20
AI Technical Summary
During the hot forming process of metal forgings, uneven thermal deformation in different parts leads to inconsistent grain size and structure, with some grains growing abnormally, resulting in non-uniform microstructure. Existing technologies lack effective testing methods, leading to high trial-and-error costs in production.
By employing the plane strain test method, metal samples of a specific shape are prepared, and induction coil heating, indenter pressing and rapid cooling are used. Combined with numerical simulation analysis of the microstructure, the process parameter window for abnormal grain growth is determined.
This paper presents a simple and low-cost testing method that can effectively analyze abnormal grain growth behavior, reduce the risk of product defects caused by grain inhomogeneity in production, and lower testing costs.
Smart Images
Figure CN115326536B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application is a test method for analyzing abnormal grain growth, belonging to the field of measurement testing. BACKGROUND
[0002] Grain growth refers to the phenomenon that the system average grain size of a strain-free polycrystalline material gradually increases during annealing. After the completion of recrystallization, the microstructure of the polycrystalline material will undergo coarsening phenomenon driven by the release of grain boundary energy, that is, larger grains grow by swallowing smaller grains. Therefore, grain growth can be a subsequent process of primary recrystallization. Although the deformation storage energy has been completely released after the completion of primary recrystallization, the material has not yet reached the most stable state. Due to the presence of a large number of grain boundaries in the structure, in order to reduce the total interfacial energy, the grains have a large tendency to grow.
[0003] Many metal forgings currently being developed in China are subjected to actual thermal deformation parameters that are not consistent at different parts of the forgings during hot forming. Therefore, it is easy to cause the microstructure of the alloy forgings to have inconsistent grain sizes and structures. After standard heat treatment, some grains even abnormally grow, causing the uniformity of the structure, that is, abnormal grain growth, resulting in unqualified products. Therefore, tests need to be conducted in advance, but the cost of such trial and error is very high. Therefore, it is urgent and realistic for the production to test the abnormal grain growth behavior that may occur in metal forgings. SUMMARY
[0004] The application is designed to solve the problems in the prior art and provides a test method for analyzing abnormal grain growth. The purpose is to provide a plane strain test method for analyzing abnormal grain growth, which tests the abnormal grain growth behavior that may occur in metal forgings.
[0005] The purpose of the application is achieved by the following technical solutions:
[0006] The test method for analyzing abnormal grain growth comprises the following steps:
[0007] Step 1, preparing a metal sample
[0008] The metal sample is a cuboid shape, and a blind hole 7 is symmetrically processed on the center points of the two side surfaces of the metal sample along the length direction;
[0009] Step 2, preparing a test tool
[0010] The test fixture includes two pressure heads 6, sliders 3, ejector pins 4, and induction coils 2. The pressure heads 6 are made of high-temperature alloy mold material. The two pressure heads 6 are symmetrically arranged at the center of the upper and lower parts of the metal sample along the height direction, and together apply pressure to the deformation zone 1 in the middle of the metal sample. The sliders 3 are respectively arranged at the left and right ends of the metal sample. The end faces of the sliders are machined with blind holes 7 that are the same as and corresponding to the metal sample. The ejector pins 4 are inserted between the blind holes 7 on both sides. When the center of the metal sample is pressed, the sliders 3 can slide to both sides with a near-zero resistance state under the push of the free extension force on both sides of the metal sample. The induction coils 2 surround the non-deformation zone 5 outside the deformation zone 1 of the metal sample to heat the metal sample. The induction coils 2 are arranged outside the deformation zone 1 of the metal sample to prevent the induction coils (2) from affecting the movement trajectory of the pressure heads (6).
[0011] Step 3: Planar Deformation Test
[0012] Start the induction coil 2, and move the upper and lower pressure heads 6 to contact the plane of the deformation zone 1 of the metal sample. At this time, the pressure is zero. The heating temperature is 500℃~1200℃, and the holding time is 5min~15min. The pressure heads 6 apply pressure to the deformation zone 1 in the middle of the metal sample together, with a moving speed of 0.001s. -1 ~10s -1 The moving distance is 5mm to 15mm. Then the metal sample is rapidly cooled. After the metal sample is cooled to room temperature, the metal sample is removed to complete the deformation test.
[0013] Step 4: Post-treatment of metal samples
[0014] The metal specimens that have completed the deformation test are analyzed. The specimens are cut along the center lines in three directions and subjected to solution heat treatment according to the technical standards of the metal itself. The microstructure of the specimens is then observed. Combined with numerical simulation, the process parameter window for abnormal grain growth in the metal specimens is determined.
[0015] In practice, the rectangular metal sample has a length, width, and height of 50mm × 20mm × 10mm. The upper and lower pressure heads 6 have trapezoidal cross-sections along their length, with the angle of the hypotenuse being 10° to 20°. The length and width of the smallest plane at the bottom of the pressure head 6 are 15mm × 20mm. The upper and lower pressure heads 6 can move up and down in the vertical direction.
[0016] In practice, slider 3 is made of high-strength steel.
[0017] In practice, the surface roughness of the six faces of the rectangular metal sample is not less than 1.6.
[0018] In implementation, the size of the blind hole 7 is Φ2mm*5mm.
[0019] In implementation, the distance between the blind hole 7 and the center point of the plane is 5mm.
[0020] In implementation, the ejector pin 4 is made of high-temperature alloy mold material, and the length of the ejector pin 4 can be used to control heat conduction.
[0021] In implementation, in step three, the metal sample is rapidly cooled by helium.
[0022] The characteristics and beneficial effects of the technical solution of the present application are as follows:
[0023] 1. Compared with the traditional double-cone sample or wedge-shaped sample, the present application provides a brand-new metal sample, which has a simple structure and is easy to process, and has low processing difficulty.
[0024] 2. The plane deformation test does not require a large plane die and a heating furnace, and can be completed by using ordinary vacuum boxes and induction heating equipment.
[0025] 3. The metal sample obtained according to the technical solution of the present application can be directly processed into a tensile sample, which is convenient for in-situ performance testing, wherein the deformation area is used as the processing area of the metal tensile sample, and the non-deformation area is used as the non-processing area of the metal tensile sample. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 is a schematic view of a metal sample;
[0027] Figure 2 is a schematic view of a test tool.
[0028] Figure 3 is a photo of the metal sample before and after deformation test DETAILED DESCRIPTION
[0029] The technical solution of the present application will be further described in detail below in combination with the drawings and examples:
[0030] Referring to the drawings, Figure 1 , 2 the steps of the test method for analyzing abnormal grain growth according to the technical solution of the present application are as follows:
[0031] Step 1: Metal sample preparation
[0032] Prepare a metal sample with a size of 50mm x 20mm x 10mm or 50mm x 20mm x 20mm, and the surface roughness of the six surfaces of the metal sample is not less than 1.6. Two blind holes with a size of Φ2mm x 5mm are machined on the left and right ends of the metal sample, and the center of the blind hole 7 is located on the center line of the plane, and the center of the blind hole 7 is 5mm away from the center;
[0033] Step two, test tool preparation
[0034] The test tool mainly consists of a pressure head 6, a sliding block 3, a top pin 4 and an induction coil 2. The pressure head 6 is made of high-temperature alloy mold material. Two pressure heads 6 are symmetrically arranged at the center positions of the upper and lower sides of the metal sample in the height direction, and jointly apply pressure to the deformation zone 1 in the middle of the metal sample. The length and width of the deformation zone 1 are 50mm x 20mm at the center position. The cross section of the pressure head 6 along the length direction is trapezoidal, and the angle of the trapezoidal inclined edge is 10°-20°. The length and width of the minimum plane at the bottom of the pressure head 6 are 15mm x 20mm. The upper and lower pressure heads 6 can move up and down along the vertical direction.
[0035] The sliding block 3 is arranged at the left and right ends of the metal sample respectively, and the end face is machined with the same blind hole 7 as the metal sample and corresponding to the blind hole 7. The top pin 4 is inserted between the two blind holes 7. The top pin 4 is made of high-temperature alloy mold material. When the center of the metal sample is pressed, the sliding block 3 can slide to both sides under the pushing force of the free extension of the metal sample, and the sliding block 3 can slide to both sides under the pushing force of the top pin 4 in a state close to zero resistance;
[0036] The induction coil 2 surrounds the non-deformation zone 5 outside the deformation zone 1 of the metal sample to heat the metal sample;
[0037] Step three, plane deformation test
[0038] Start the induction coil 2, move the pressure head 6 up and down respectively, and contact the plane of the metal sample, but ensure that the pressure is zero. The heating temperature is 500℃-1200℃, the holding time is 5min-15min, the pressure head 6 is moved up and down respectively, the moving rate is 0.001s-1-10s-1, the moving distance is 5mm-15mm, and after the moving is completed, the metal sample is rapidly cooled by helium;
[0039] Step four, post-processing
[0040] After the metal sample is cooled to room temperature, the metal sample is taken out, and the plane deformation test is completed.
[0041] The metal sample after deformation test is analyzed, the center line of the sample in three directions is cut, solid solution heat treatment is carried out according to the technical standard of the metal itself, then the microstructure of the sample is observed, and the process parameter window of abnormal grain growth of the metal sample can be judged by combining numerical simulation.
Claims
1. A test method for analyzing abnormal grain growth, characterized by: The steps of the test method are as follows: Step one, preparing a metal sample The metal sample is a cuboid, and a blind hole (7) is symmetrically processed on the center point of the two side faces of the metal sample along the length direction. Step two, preparing a test tool The test tool includes two pressure heads (6), a sliding block (3), a top pin (4), and an induction coil (2). The pressure heads (6) are made of high-temperature alloy mold material, and are symmetrically arranged at the center positions of the upper and lower sides of the metal sample along the height direction, and jointly apply pressure to the deformation zone (1) of the metal sample. The sliding block (3) is arranged at the left and right ends of the metal sample, and the end face is processed with the same blind hole (7) as the metal sample. The blind holes (7) on both sides are inserted with the top pin (4). When the center of the metal sample is pressed, the sliding block (3) can slide to both sides with nearly zero resistance under the pushing force of the top pin (4). The induction coil (2) surrounds the non-deformation zone (5) outside the deformation zone (1) of the metal sample to heat the metal sample. Step three, plane deformation test The start induction coil (2) moves the upper and lower pressure heads (6) to be in contact with the plane of the deformation zone (1) of the metal sample, at this time the pressure is zero, the heating temperature is 500-1200 DEG C, the holding time is 5-15 min, the pressure heads (6) jointly apply pressure to the center of the deformation zone (1) of the metal sample, the moving speed is 0.001-10 s -1 , the moving distance is 5-15 mm, then the metal sample is rapidly cooled, after the metal sample is cooled to room temperature, the metal sample is taken out, and the deformation test is completed. -1 Step four, post-processing of the metal sample The metal sample after the deformation test is analyzed, cut along the center line of the three directions of the sample, and then subjected to solid solution heat treatment according to the technical standard of the metal itself. Then, the microstructure of the sample is observed, and the process parameter window of the abnormal grain growth of the metal sample is determined by combining numerical simulation.
2. The test method for analyzing abnormal grain growth according to claim 1, characterized by: The length, width, and height of the cuboid-shaped metal sample are 50mm×20mm×10mm. The cross section of the pressure head (6) on the upper and lower sides along the length direction is trapezoidal, the angle of the trapezoidal inclined edge is 10°-20°, and the length and width of the bottom minimum plane of the pressure head (6) are 15mm×20mm. The upper and lower pressure heads (6) can move up and down along the vertical direction.
3. The test method for analyzing abnormal grain growth according to claim 1, characterized by: The sliding block (3) is made of high-strength steel material.
4. The test method for analyzing abnormal grain growth according to claim 1, characterized by: The surface roughness of the six faces of the cuboid-shaped metal sample is not less than 1.
6.
5. The test method for analyzing abnormal grain growth according to claim 1, characterized by: The size specification of the blind hole (7) is Φ2mm×5mm.
6. The test method for analyzing abnormal grain growth according to claim 1, characterized by: The distance between the blind hole (7) and the center point of the plane is 5mm.
7. The test method for analyzing abnormal grain growth according to claim 1, characterized by: The top pin (4) is made of high-temperature alloy mold material.
8. The test method for analyzing abnormal grain growth according to claim 1, characterized by: In step three, the metal sample is rapidly cooled by helium gas.