Manufacturing method and test evaluation method of main reducer casing hole defect sample

Abstract

The application discloses a kind of main reducer machine case air hole defect sample manufacturing method, after pouring is completed, scattering circular insoluble object, different grade air hole defect sample can be prepared in batch, it is convenient to subsequent finish machining into test piece and carry out test, to carry out evaluation to different grade air hole defect machine case, greatly shorten test cycle, reduce test cost, and reduce failure risk.The application also discloses a kind of main reducer machine case air hole defect sample testing evaluation method, by finish machining into test piece, then by testing test piece and obtaining sample data, according to test data, the static strength and fatigue strength of different grade air hole defect position on main reducer machine case can be evaluated, to quantitatively determine the tolerance of different grade air hole defect when main reducer machine case leaves factory acceptance, improve the qualified rate of machine case, save the manufacturing cost of machine case, shorten the manufacturing cycle of machine case, strong practicality, suitable for being widely promoted and applied.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gearbox defect test evaluation, in particular, relates to a manufacturing method of a main reducer gearbox gas hole defect sample. In addition, the present application also relates to a test evaluation method of a main reducer gearbox gas hole defect sample for testing and evaluating a long strip-shaped casting block sample manufactured by the manufacturing method of the main reducer gearbox gas hole defect sample. BACKGROUND

[0002] The main reducer gearbox of a helicopter is usually a magnesium alloy casting. Different levels of gas hole defects may occur in the magnesium alloy casting during the casting process, which are caused by the gas that cannot be discharged in time during the solidification of the metal liquid, such as gas, such as moisture or rust on the furnace charge, unclean surface, water vapor in the furnace gas, etc., the furnace body and the ladle after repair are not dried, the gas in the mold cavity, the gas involved during casting, poor air permeability of the mold or core, etc. may cause gas hole defects, so it is difficult to prevent. Different levels of gas hole defects have different effects on the strength and life of the magnesium alloy casting. If all the main reducer gearboxes with gas hole defects are regarded as waste products, it may cause unnecessary waste. At present, the I-class casting of the magnesium alloy gearbox has a higher requirement for the level of gas hole defects due to the high stress level in the key area. Once the defects exceed the standard range, it may cause cracks in the defective part of the gearbox, thereby failing to meet the performance requirements. Therefore, the higher the level, the larger the gas hole defect. According to the existing magnesium alloy gearbox casting acceptance standard, only level 1 gas hole defects are allowed in the key area, and levels 2-4 gas hole defects are allowed in the non-key area.

[0003] However, the existing magnesium alloy casting with gas hole defects often simply follows the relevant conversion standard when classifying defects, which lacks reliable data to determine the effect of gas hole defects of different levels on the strength and life of the gearbox. Some magnesium alloy gearbox castings may not meet the acceptance standard due to the gas hole defects, but their strength and life may meet the acceptance requirements, thereby causing unnecessary waste. If reliable data is to be obtained, a sufficient number of gearbox casting blocks containing gas hole defects of different levels are selected from the main reducer magnesium alloy gearbox casting for test evaluation. However, due to the randomness of gas hole defects in the main reducer magnesium alloy casting process, it is impossible to cut the magnesium alloy casting block containing gas hole defects of different levels from the same main reducer magnesium alloy casting, and the magnesium alloy casting block containing gas hole defects of different levels cannot be precisely machined into a typical test piece, resulting in a long test period, high cost, low test efficiency, and a high risk of failure. SUMMARY

[0004] The application provides a manufacturing method and a test evaluation method for a main reducer casing gas hole defect sample, to solve the technical problems of long test period, high cost, low test efficiency and high failure risk in the prior art when testing and evaluating main reducers of different levels of gas hole defects.

[0005] According to an aspect of the application, a manufacturing method for a main reducer casing gas hole defect sample is provided, comprising the following steps: A1, preparing a chill and heat treating the repeatedly used chills; A2, preparing a sand core from core sand and a sand mold from molding sand, and then combining the sand core, the sand mold and the chill into a sand mold mold, wherein the sand mold mold comprises a runner, a long strip-shaped casting block cavity and a riser communicating with the casting block cavity, a plurality of casting block cavities are arranged in the sand mold mold and are communicated through the runner, and the riser and the casting block cavity are arranged one by one; A3, melting the magnesium alloy block into a magnesium alloy solution, pouring the magnesium alloy solution into the sand mold mold, and after pouring is completed, a plurality of circular insoluble objects of different diameters are evenly scattered from the upper end of the riser to form a magnesium alloy casting, the magnesium alloy casting has a plurality of long strip-shaped casting blocks, and each long strip-shaped casting block has gas hole defects of different levels; A4, taking out the magnesium alloy casting from the sand mold mold, removing the molding sand and the core sand on the magnesium alloy casting, cutting the pouring riser on the magnesium alloy casting to obtain a plurality of long strip-shaped casting blocks, and then sequentially marking, surface treating and heat treating the long strip-shaped casting blocks; A5, performing gas hole defect inspection on the long strip-shaped casting blocks, marking the occupied area of gas hole defects of different levels, and processing the long strip-shaped casting blocks according to the occupied area of gas hole defects of different levels to process a single long strip-shaped casting block into a plurality of long strip-shaped casting block samples, and marking the plurality of long strip-shaped casting block samples, wherein each long strip-shaped casting block sample has only gas hole defects of the same level, and the gas hole defects are located at the center of the long strip-shaped casting block sample.

[0006] As a further improvement of the above technical solution:

[0007] Further, in step A1, the specific steps of heat treatment are as follows: the chill is placed in a drying oven for drying, and after being kept at 260-300 DEG C for 3-4 h, the chill is taken out of the drying oven and naturally cooled.

[0008] Further, in step A1, when the storage time of the heat-treated chill exceeds 2 days, the chill needs to be kept at 150-180 DEG C for 30-40 min before use.

[0009] Further, the plurality of circular insoluble objects of different diameters comprises φ1mm steel balls, φ2mm steel balls and φ3mm steel balls, and the surface of the steel balls is coated with high-temperature resistant paint.

[0010] Further, the melting the magnesium alloy blocks into the magnesium alloy solution in step A3 specifically comprises the following steps: preheating the crucible to 680-720℃, adding the magnesium alloy blocks into the crucible, covering the gas protection cover, and introducing the protection gas into the crucible, wherein the gas flow rate is 15-25 L / min, the heating temperature is 760-780℃; after the magnesium alloy blocks are completely melted, a preset weight of Mg-Zr intermediate alloy is added and stirred for 8-12 min; the heating temperature is set to 765-775℃, the gas flow rate of the protection gas is increased to 25-35 L / min, then a refiner is placed in the crucible and argon is introduced for refining, the argon flow rate is 10-20 L / min, the gas flow time is 12-15 min, after the refining is completed, the crucible liquid surface slag is removed to obtain the magnesium alloy solution.

[0011] Further, the Mg-Zr intermediate alloy needs to be preheated at 100-200℃ for at least 30 min before use.

[0012] Further, the pouring the magnesium alloy solution into the sand mold in step A3 specifically comprises the following steps: controlling the temperature of the magnesium alloy solution out of the crucible to 800-830℃, so that when the magnesium alloy solution is lowered to 765-775℃, the magnesium alloy solution is poured into the sand mold, and the pouring time is controlled within 5-15 s.

[0013] Further, in step A4, the specific steps of heat treatment are as follows: heating the long strip-shaped casting block to 390-410℃ and keeping for 1.5-2.5 h, then continuously heating to 515-525℃ and keeping for 6-8 h, then quenching using a quenching medium of 60-80℃, and the quenching transfer time is not more than 20 s, and finally keeping the long strip-shaped casting block at 195-205℃ for 18-24 h.

[0014] Further, in step A4, the specific steps of surface treatment are as follows: cleaning the flash and burrs on the surface of the long strip-shaped casting block, then using a gas medium to remove the sand particles on the surface and joints of the long strip-shaped casting block, then removing the excess on the surface of the long strip-shaped casting block, and then performing chromate treatment on the long strip-shaped casting block.

[0015] According to another aspect of the present application, there is also provided a method for testing and evaluating a main reducer casing gas hole defect sample, which tests and evaluates the long strip-shaped ingot sample manufactured by the method for manufacturing a main reducer casing gas hole defect sample, comprising the following steps: B1, using sand casting and machining to obtain a plurality of standard parts without metallurgical defects, and manufacturing a plurality of batches of long strip-shaped ingot samples, each batch of long strip-shaped ingot samples having different levels of gas hole defects, and then machining the plurality of batches of long strip-shaped ingot samples into smooth round bar-shaped test pieces, and then testing the test pieces for gas hole defects to remove test pieces that do not meet the requirements in terms of gas hole defect level and position, wherein the test pieces include tensile test pieces and fatigue test pieces; B2, conducting tensile property tests on the standard parts and the tensile test pieces to obtain tensile test data including yield strength, ultimate strength, yield strength attenuation coefficient and ultimate strength attenuation coefficient of different levels of gas hole defects, and at the same time, conducting group method fatigue property tests on the standard parts and the fatigue test pieces to obtain test data for fitting a fatigue property curve, and conducting ascending and descending method fatigue property tests on the standard parts and the test pieces to obtain fatigue test data including fatigue limit and fatigue limit attenuation coefficient of different levels of gas hole defects; B3, evaluating the static strength and fatigue strength of different levels of gas hole defect positions on the main reducer casing through the tensile test data and the fatigue property data.

[0016] The present application has the following beneficial effects:

[0017] The manufacturing method of the main reducer casing gas hole defect sample of the application, by preparing a cold iron, the subsequent casting pouring is completed quickly cooling, to avoid the casting internal porosity and shrinkage cavity and other metallurgical defects, and the repeated use of the cold iron is heat treated to eliminate the residual thermal stress and thermal deformation of the cold iron, to avoid the cold iron affecting the casting quality; The core sand is prepared into a sand core, and then the molding sand is prepared into a sand mold, and then the sand core, sand mold and cold iron are combined into a sand mold mold, so that the casting can be formed by pouring through the sand mold mold; The magnesium alloy block is melted into a magnesium alloy solution, and then the magnesium alloy solution is poured into the sand mold mold, and after pouring is completed, a plurality of circular insoluble objects of different diameters are uniformly scattered from the upper end of the riser, so that the circular insoluble objects are located at the specified position of the magnesium alloy casting after the magnesium alloy solution is solidified, and a gap is formed between the circular insoluble objects and the magnesium alloy casting, then the space occupied by the circular insoluble objects can be approximately regarded as a circular gas hole defect, to form a magnesium alloy casting with a plurality of long strip castings by pouring, and each long strip casting has different levels of gas hole defects, that is, long strip castings with different levels of gas hole defects are batch prepared; The magnesium alloy casting is taken out from the sand mold mold, and the molding sand and core sand on the magnesium alloy casting are removed, and then the pouring riser on the magnesium alloy casting is cut to obtain a plurality of long strip castings, and then the long strip castings are sequentially marked, surface treated and heat treated to ensure the quality of the long strip castings; The long strip castings are subjected to gas hole defect inspection, and the occupied areas of different levels of gas hole defects are marked, and then the long strip castings are processed according to the occupied areas of different levels of gas hole defects, to process a single long strip casting into a plurality of long strip casting samples, and the plurality of long strip casting samples are marked respectively, wherein each long strip casting sample only has the same level of gas hole defects, and the gas hole defects are located at the center of the long strip casting sample, which is convenient for subsequent test evaluation; The scheme can batch prepare long strip casting samples with different levels of gas hole defects, which is convenient for subsequent fine machining into typical test pieces and testing to evaluate the main reducer casing with different levels of gas hole defects, compared with the prior art, the test cycle is greatly shortened, the test cost is reduced, and the failure risk is reduced, which has strong practicality and is suitable for wide promotion and application.

[0018] The test evaluation method of the main reducer casing pore defect sample of the application, by manufacturing standard parts and long strip-shaped ingot samples, then machining the long strip-shaped ingot samples into smooth round bar-shaped test pieces, to truly simulate the real internal hole defects existing in the main reducer casing, and according to the requirements of tensile property test and fatigue property test, respectively obtain tensile test pieces and fatigue test pieces during machining, then carry out pore defect test on the test pieces, to remove the test pieces whose pore defect grade and position do not meet the requirements, to improve the reliability of the test results, by carrying out tensile property test of the standard parts and the tensile test pieces, by comparing the test data of the standard parts and the tensile test pieces, to obtain the tensile test data of the yield strength, the ultimate strength, the yield strength attenuation coefficient and the ultimate strength attenuation coefficient containing different grades of pore defects, at the same time, carry out the fatigue property test of the standard parts and the fatigue test pieces by the group method, to obtain the test data for fitting the fatigue property curve, and carry out the fatigue property test of the standard parts and the test pieces by the ascending and descending method, by comparing the test data of the standard parts and the fatigue test pieces, to obtain the fatigue test data of the fatigue limit and the fatigue limit attenuation coefficient containing different grades of pore defects, by the tensile test data and the fatigue property data, the static strength and the fatigue strength of the different grade pore defect positions on the main reducer casing can be evaluated, to quantitatively determine the tolerance of different grade pore defects when the main reducer casing is delivered and accepted, improve the qualified rate of the casing, save the manufacturing cost of the casing, shorten the manufacturing cycle of the casing, have strong practicality, and are suitable for being widely popularized and applied.

[0019] In addition to the objects, features, and advantages described above, the present application has other objects, features, and advantages. The present application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, illustrate the preferred embodiments of the application, and assist in the explanation of the application. In the drawings, the same reference numbers represent the same elements throughout the several views of the drawings:

[0021] Figure 1 is a step block diagram of the manufacturing method of the main reducer casing pore defect sample of the preferred embodiment of the application;

[0022] Figure 2 is a structural schematic diagram of the magnesium alloy casting in the manufacturing method of the main reducer casing pore defect sample of the preferred embodiment of the application;

[0023] Figure 3 is a structural schematic diagram of the long strip-shaped ingot in the manufacturing method of the main reducer casing pore defect sample of the preferred embodiment of the application;

[0024] Figure 4is a structure schematic diagram of the long strip-shaped casting block sample in the manufacturing method of the main reducer casing gas hole defect sample of the preferred embodiment of the present application;

[0025] Figure 5 is a step block diagram of the test evaluation method of the main reducer casing gas hole defect sample of the preferred embodiment of the present application;

[0026] Figure 6 is a structure schematic diagram of the tensile test piece in the test evaluation method of the main reducer casing gas hole defect sample of the preferred embodiment of the present application;

[0027] Figure 7 is a structure schematic diagram of the fatigue test piece in the test evaluation method of the main reducer casing gas hole defect sample of the preferred embodiment of the present application. DETAILED DESCRIPTION

[0028] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as defined and covered by the following.

[0029] As Figures 1-4As shown, the manufacturing method of the main reducer casing porosity defect sample of the embodiment includes the following steps: A1, preparing a chill and heat treating the repeatedly used chill; A2, preparing a sand core from core sand and a sand mold from molding sand, and then combining the sand core, the sand mold and the chill into a sand mold mold, wherein the sand mold mold includes a sprue, a long strip-shaped casting block cavity and a riser communicating with the casting block cavity, a plurality of casting block cavities are arranged in the sand mold mold in intervals and are communicated through the sprue, and the riser and the casting block cavity are arranged one by one; A3, melting the magnesium alloy block into a magnesium alloy solution, pouring the magnesium alloy solution into the sand mold mold, and after pouring is completed, a plurality of circular insoluble objects of different diameter sizes are evenly scattered from the upper end of the riser to pour and form a magnesium alloy casting, the magnesium alloy casting has a plurality of long strip-shaped casting blocks, and each long strip-shaped casting block has different levels of porosity defects; A4, taking out the magnesium alloy casting from the sand mold mold, removing the molding sand and core sand on the magnesium alloy casting, cutting the pouring riser on the magnesium alloy casting to obtain a plurality of long strip-shaped casting blocks, and then sequentially marking, surface treating and heat treating the long strip-shaped casting blocks; A5, performing porosity defect inspection on the long strip-shaped casting blocks, marking the area occupied by porosity defects of different levels, and processing the long strip-shaped casting blocks according to the area occupied by porosity defects of different levels to process a single long strip-shaped casting block into a plurality of long strip-shaped casting block samples, and marking each long strip-shaped casting block sample, wherein each long strip-shaped casting block sample has only the same level of porosity defects, and the porosity defects are located at the center of the long strip-shaped casting block sample. Optionally, in step A4, the specific steps of marking are using a vibrating pen to mark the blank number, the solution batch number and the sequence number on the long strip-shaped casting block. Optionally, in step A5, the specific steps of marking are using a vibrating pen to impact mark the blank number, the solution batch number and the porosity defect level at the specified position of the long strip-shaped casting block sample. It should be understood that the main reducer casing is a magnesium alloy casting, so by manufacturing long strip-shaped casting block samples of different levels of porosity defects of magnesium alloy, the strength of different levels of porosity defect parts on the main reducer casing is truly simulated. Optionally, the sand mold mold further includes a straight gate for pouring of the magnesium alloy solution, which is communicated with the sprue.

[0030] As Figures 1-4As shown, specifically, the manufacturing method of the main reducer casing porosity defect sample of the present application prepares a chill to quickly cool the subsequent casting after pouring and casting is completed, to avoid the formation of internal porosity and shrinkage and other metallurgical defects in the casting, and heat treats the repeatedly used chills to eliminate the residual thermal stress and thermal deformation of the chills, to avoid the influence of the chills on the quality of the casting; prepares the core sand into a sand core, and then prepares the molding sand into a sand mold, and then combines the sand core, the sand mold and the chills into a sand mold mold, to form the casting by pouring through the sand mold mold; melts the magnesium alloy block into a magnesium alloy solution, and then pours the magnesium alloy solution into the sand mold mold, and after pouring is completed, evenly and uniformly sprinkles multiple circular insoluble objects of different diameters from the upper end of the riser, to ensure that the circular insoluble objects are located at the specified positions of the magnesium alloy casting after the magnesium alloy solution solidifies, and a gap is formed between the circular insoluble objects and the magnesium alloy casting, so that the space occupied by the circular insoluble objects can be approximately regarded as a circular porosity defect, to pour and form a magnesium alloy casting with multiple long strip-shaped casting blocks, and each long strip-shaped casting block has different levels of porosity defects, that is, long strip-shaped casting blocks with different levels of porosity defects are prepared in batches; the magnesium alloy casting is taken out of the sand mold mold, and the molding sand and the core sand on the magnesium alloy casting are removed, and then the pouring riser on the magnesium alloy casting is cut, to obtain multiple long strip-shaped casting blocks, and then the long strip-shaped casting blocks are sequentially marked, surface treated and heat treated, to ensure the quality of the long strip-shaped casting blocks; the long strip-shaped casting blocks are inspected for porosity defects, and the occupied areas of different levels of porosity defects are marked, and then the long strip-shaped casting blocks are processed according to the occupied areas of different levels of porosity defects, to process a single long strip-shaped casting block into multiple long strip-shaped casting block samples, and the multiple long strip-shaped casting block samples are respectively marked, wherein each long strip-shaped casting block sample only has the same level of porosity defects, and the porosity defects are located at the center of the long strip-shaped casting block sample, to facilitate subsequent testing and evaluation; the present scheme can prepare long strip-shaped casting block samples with different levels of porosity defects in batches, which are convenient for subsequent fine processing into typical test pieces and testing, to evaluate the main reducer casing with different levels of porosity defects, compared with the prior art, the testing period is greatly shortened, the testing cost is reduced, and the failure risk is reduced, which has strong practicality and is suitable for wide promotion and application.

[0031] In the present embodiment, in step A1, the specific steps of heat treatment are as follows: the chill is placed in a drying oven for drying, and after being kept at 260-300°C for 3-4h, the chill is taken out of the drying oven and naturally cooled. Specifically, by keeping the chill at 260-300°C for 3-4h, the residual thermal stress and thermal deformation in the chill are eliminated to the maximum extent. Optionally, after heat treatment is completed, whether there is oil stain, rust, water droplets and other dirt on the working surface of the chill is checked, and if so, it should be thoroughly cleaned; the appearance quality of the chill is checked, the surface should be dense, and there should be no defects such as slag inclusion and sand inclusion, and the chill should not be used if the deformation affects positioning.

[0032] In the embodiment, when the storage time of the cold iron after heat treatment exceeds 2 days, the cold iron needs to be kept at 150-180°C for 30-40 min before use. Specifically, when the storage time of the cold iron after heat treatment exceeds 2 days, the heat conduction performance will change, and by keeping the cold iron at 150-180°C for 30-40 min, the thermal stress caused by the too large temperature difference between the cold iron and the pouring temperature of the magnesium alloy casting is reduced, and the heat of the magnesium alloy casting can be better absorbed, the cooling efficiency is improved, which helps the casting to solidify quickly and obtain good microstructure and trans energy, avoids the generation of metallurgical defects such as porosity and shrinkage hole in the casting, and prolongs the service life of the cold iron. It should be understood that once the magnesium alloy casting has internal porosity and shrinkage hole and other metallurgical defects, it is difficult to accurately judge the influence of the gas hole defect on the strength of the casing during subsequent test evaluation, and it cannot be used. Therefore, during the manufacturing process of the magnesium alloy casting, metallurgical defects other than gas hole defects should be avoided in the long strip-shaped casting block on the magnesium alloy casting.

[0033] In the embodiment, the plurality of circular insoluble objects of different diameters includes φ1 mm steel balls, φ2 mm steel balls and φ3 mm steel balls, and the surfaces of the steel balls are coated with high-temperature resistant paint. Specifically, by adding φ1 mm steel balls, φ2 mm steel balls and φ3 mm steel balls, and coating the surfaces of the steel balls with high-temperature resistant paint, the steel balls and the magnesium alloy solution are separated to avoid fusion, so that the gas hole defect morphology in the long strip-shaped casting block on the magnesium alloy casting is consistent with the real gas hole defect morphology, thereby forming three different levels of gas hole defects in the long strip-shaped casting block on the magnesium alloy casting, which facilitates the subsequent test evaluation of the long strip-shaped casting block sample with three different levels of gas hole defects.

[0034] In the embodiment, the melting of the magnesium alloy block into the magnesium alloy solution in step A3 specifically comprises the following steps: preheating the crucible to 680-720°C, adding the magnesium alloy block into the crucible, covering the gas protection cover, and introducing the protective gas into the crucible, wherein the gas flow rate is 15-25 L / min, and the heating temperature is 760-780°C; after the magnesium alloy block is completely melted, a preset weight of Mg-Zr intermediate alloy is added and stirred for 8-12 min; the heating temperature is set to 765-775°C, the gas flow rate of the protective gas is increased to 25-35 L / min, then a refiner is placed in the crucible and argon is introduced for refining, the argon gas flow rate is 10-20 L / min, the gas flow time is 12-15 min, after the refining is completed, the surface slag of the crucible is removed to obtain the magnesium alloy solution. Specifically, by preheating the crucible to 680-720°C, the temperature difference is reduced, the heat transfer is promoted, the thermal stress is reduced, the stability is maintained, the magnesium alloy block is uniformly heated, the impurities are reduced, and the pouring quality is improved. The protective gas with a gas flow rate of 15-25 L / min is introduced to prevent the metal from being oxidized and improve the pouring quality. The heating temperature is controlled at 760-780°C to quickly melt the magnesium alloy block. After the magnesium alloy block is completely melted, a preset weight of Mg-Zr intermediate alloy is added and stirred for 8-12 min to refine the grains, improve the mechanical properties of the magnesium alloy solution, improve the organizational structure of the magnesium alloy casting, and improve the process performance of the magnesium alloy casting. By setting the heating temperature to 765-775°C, increasing the gas flow rate of the protective gas to 25-35 L / min, then placing a refiner in the crucible and introducing argon for refining, the argon gas flow rate is 10-20 L / min, and the gas flow time is 12-15 min, the impurities in the magnesium alloy solution are further removed, the defects are reduced, and the metal properties are improved to improve the quality of the magnesium alloy casting. It should be understood that the temperature parameters, gas flow rate, and time parameters in the embodiment can maximize the guarantee of the magnesium alloy solution after the magnesium alloy block is melted, with less impurities, high melting efficiency, and favorable for improving the quality of the casting. Alternatively, the volume content of the protective gas is 98% CO2 and 2% SF6.

[0035] In the embodiment, the Mg-Zr intermediate alloy is preheated at 100-200°C for at least 30 min before use. Specifically, by preheating the Mg-Zr intermediate alloy at 100-200°C for at least 30 min before use, the utilization rate and effect of the intermediate alloy are improved, the preheated intermediate alloy can better play its role in refining the grains, further improve the organizational structure and performance of the magnesium alloy casting, improve the quality and yield of the magnesium alloy casting, and also improve the production efficiency, while preventing adverse reactions and safety problems.

[0036] In the embodiment, the pouring the magnesium alloy solution into the sand mold in step A3 specifically comprises the following steps: controlling the temperature of the magnesium alloy solution at the outlet of the ladle at 800-830°C, so that the magnesium alloy solution is poured into the sand mold when the temperature of the magnesium alloy solution drops to 765-775°C, and the pouring time is controlled within 5-15s. Specifically, by controlling the temperature of the magnesium alloy solution at the outlet of the ladle at 800-830°C, the pouring temperature is ensured to be appropriate to avoid the magnesium alloy castings from generating metallurgical defects such as shrinkage, porosity and cracks, and also helps the magnesium alloy solution to maintain stable fluidity and filling property during pouring, so that the castings have dense structure and fine grains, thereby improving the mechanical properties and surface quality of the magnesium alloy castings, and also reducing energy consumption and cost; when the pouring time is controlled within 5-15s, the magnesium alloy solution can quickly fill the cavity, reducing defects such as cold shut, insufficient pouring and the like caused by insufficient fluidity, and also being conducive to the discharge of gas in the cavity and the uniform solidification of the magnesium alloy castings, and also improving the production efficiency, reducing the production cycle and cost; when the pouring time is less than 5s, the scouring effect of the magnesium alloy solution on the cavity wall is enhanced, which may generate defects such as sand swelling and sand washing, and is not conducive to the discharge of gas in the cavity and the uniform solidification of the magnesium alloy castings; when the pouring time is greater than 15s, the magnesium alloy solution cannot quickly fill the cavity, which may generate defects such as cold shut and insufficient pouring, and also relatively low production efficiency, increasing the production cycle and cost.

[0037] In the embodiment, the specific steps of the heat treatment in step A4 are as follows: the long strip-shaped casting block is heated to 390-410°C and kept for 1.5-2.5 hours, then heated to 515-525°C and kept for 6-8 hours, then quenched by using a quenching medium at 60-80°C, and the quenching transfer time is not more than 20 seconds, and finally the long strip-shaped casting block is kept at 195-205°C for 18-24 hours. Specifically, the long strip-shaped casting block is heated to 390-410°C and kept for 1.5-2.5 hours, then heated to 515-525°C and kept for 6-8 hours, and then quenched by using a quenching medium at 60-80°C, so as to realize the solid solution treatment of the long strip-shaped casting block. The second phase in the long strip-shaped casting block is dissolved into the solid solution by the solid solution treatment, and the re-precipitation of these phases is inhibited in the subsequent rapid cooling, so as to obtain a refined grain structure, which helps to improve the mechanical properties and corrosion resistance of the long strip-shaped casting block, and at the same time, the composition segregation in the long strip-shaped casting block can be eliminated, the alloying elements are more uniformly distributed in the solid solution, and the strength and hardness of the casting are improved, and the plasticity and toughness are improved. Finally, the long strip-shaped casting block is kept at 195-205°C for 18-24 hours to realize the aging treatment of the casting. The residual stress of the long strip-shaped casting block is eliminated by the aging treatment, the strength and hardness of the long strip-shaped casting block are further improved, the toughness and impact toughness of the long strip-shaped casting block are improved, the fatigue performance is improved, the corrosion resistance is improved, the material structure is stabilized, and the processing performance is improved. Alternatively, the quenching medium is an aqueous solution.

[0038] In the embodiment, the specific steps of the surface treatment in step A4 are as follows: the flash and burrs on the surface of the long strip-shaped casting block are cleaned, then the sand particles on the surface and the joint gap of the long strip-shaped casting block are removed by using a gas medium, then the excess substances on the surface of the long strip-shaped casting block are removed, and then the long strip-shaped casting block is subjected to chromate treatment. Specifically, the flash and burrs on the surface of the long strip-shaped casting block are cleaned, then the sand particles on the surface and the joint gap of the long strip-shaped casting block are removed by using a gas medium, so as to improve the surface quality of the long strip-shaped casting block, then the excess substances on the surface of the long strip-shaped casting block are removed, and then the long strip-shaped casting block is subjected to chromate treatment, so as to form a chromium oxide film on the surface of the long strip-shaped casting block, improve the corrosion resistance of the long strip-shaped casting block, enhance the adhesion, improve the gloss and color of the surface of the long strip-shaped casting block, and improve the surface hardness of the long strip-shaped casting block, and further clean the dirt and grease on the surface of the long strip-shaped casting block.

[0039] As Figures 5-7As shown, the test evaluation method of the main reducer casing pore defect sample of the embodiment is used to test and evaluate the long strip-shaped ingot sample manufactured by the manufacturing method of the main reducer casing pore defect sample, and includes the following steps: B1, a plurality of standard parts without metallurgical defects are obtained by sand casting and machining, and a plurality of batches of long strip-shaped ingot samples are manufactured, each batch of long strip-shaped ingot samples has different pore defect levels, then the long strip-shaped ingot samples are finished into smooth round bar-shaped test pieces, and then the test pieces are subjected to pore defect inspection to remove the test pieces whose pore defect levels and positions do not meet the requirements, wherein the test pieces include tensile test pieces and fatigue test pieces; B2, tensile performance tests of the standard parts and the tensile test pieces are carried out to obtain tensile test data of yield strength, ultimate strength, yield strength attenuation coefficient and ultimate strength containing different levels of pore defects, at the same time, group method fatigue performance tests of the standard parts and the fatigue test pieces are carried out to obtain test data for fitting fatigue performance curves, and ascending and descending method fatigue performance tests of the standard parts and the test pieces are carried out to obtain fatigue test data of fatigue limit and fatigue limit attenuation coefficient containing different levels of pore defects; B3, the static strength and fatigue strength of different levels of pore defect positions on the main reducer casing are evaluated through the tensile test data and the fatigue performance data.

[0040] As shown, specifically, the test evaluation method of the main reducer casing pore defect sample of the embodiment is used to test and evaluate the long strip-shaped ingot sample manufactured by the manufacturing method of the main reducer casing pore defect sample, and includes the following steps: B1, a plurality of standard parts without metallurgical defects are obtained by sand casting and machining, and a plurality of batches of long strip-shaped ingot samples are manufactured, each batch of long strip-shaped ingot samples has different pore defect levels, then the long strip-shaped ingot samples are finished into smooth round bar-shaped test pieces, and then the test pieces are subjected to pore defect inspection to remove the test pieces whose pore defect levels and positions do not meet the requirements, wherein the test pieces include tensile test pieces and fatigue test pieces; B2, tensile performance tests of the standard parts and the tensile test pieces are carried out to obtain tensile test data of yield strength, ultimate strength, yield strength attenuation coefficient and ultimate strength containing different levels of pore defects, at the same time, group method fatigue performance tests of the standard parts and the fatigue test pieces are carried out to obtain test data for fitting fatigue performance curves, and ascending and descending method fatigue performance tests of the standard parts and the test pieces are carried out to obtain fatigue test data of fatigue limit and fatigue limit attenuation coefficient containing different levels of pore defects; B3, the static strength and fatigue strength of different levels of pore defect positions on the main reducer casing are evaluated through the tensile test data and the fatigue performance data. Figures 5-7 As shown, specifically, the test evaluation method of the main reducer casing pore defect sample of the embodiment is used to test and evaluate the long strip-shaped ingot sample manufactured by the manufacturing method of the main reducer casing pore defect sample, and includes the following steps: B1, a plurality of standard parts without metallurgical defects are obtained by sand casting and machining, and a plurality of batches of long strip-shaped ingot samples are manufactured, each batch of long strip-shaped ingot samples has different pore defect levels, then the long strip-shaped ingot samples are finished into smooth round bar-shaped test pieces, and then the test pieces are subjected to pore defect inspection to remove the test pieces whose pore defect levels and positions do not meet the requirements, wherein the test pieces include tensile test pieces and fatigue test pieces; B2, tensile performance tests of the standard parts and the tensile test pieces are carried out to obtain tensile test data of yield strength, ultimate strength, yield strength attenuation coefficient and ultimate strength containing different levels of pore defects, at the same time, group method fatigue performance tests of the standard parts and the fatigue test pieces are carried out to obtain test data for fitting fatigue performance curves, and ascending and descending method fatigue performance tests of the standard parts and the test pieces are carried out to obtain fatigue test data of fatigue limit and fatigue limit attenuation coefficient containing different levels of pore defects; B3, the static strength and fatigue strength of different levels of pore defect positions on the main reducer casing are evaluated through the tensile test data and the fatigue performance data.

[0041] Optionally, when the long strip-shaped ingot sample is finished into a tensile test piece, the surface roughness of the tensile test piece is ensured to be Ra0.8 by turning processing, and then the reliability of the test results in the subsequent tensile performance test is ensured. Optionally, when the long strip-shaped ingot sample is finished into a fatigue test piece, the surface roughness of the fatigue test piece is ensured to be Ra0.8 by turning processing, and then the surface roughness of the fatigue test piece is ensured to be Ra0.2 by manual polishing or polishing machine polishing, and then the reliability of the test results in the subsequent fatigue performance test is ensured.

[0042] The specific calculation process of the static strength and fatigue strength attenuation coefficient of the different grade pore defect parts on the main reducer casing is as follows through the tensile test data and the fatigue performance data:

[0043] Static strength checking standard

[0044] The yield strength reserve coefficient and the ultimate strength reserve coefficient calculation formula is as follows:

[0045]

[0046] Among them, K s is the yield strength reserve coefficient, K b is the ultimate strength reserve coefficient, σ lim is the maximum equivalent stress of the pore defect part of the main reducer casing, σ b is the ultimate strength of the magnesium alloy, σ s is the yield strength of the magnesium alloy, S b is the ultimate strength attenuation coefficient of the magnesium alloy of different grade pore defects, S s is the yield strength attenuation coefficient of the magnesium alloy of different grade pore defects, σ bw is the median ultimate strength of the standard piece, σ sw is the median yield strength of the standard piece, σ bq is the median ultimate strength of the tensile test piece, σ sq is the median yield strength of the tensile test piece.

[0047] Fatigue strength checking standard

[0048] The fatigue equivalent stress is converted according to the Soderberg conversion formula corresponding to the stress cycle, and the calculation formula is as follows:

[0049] σ eq = σ a / (1- σ m / σ s )

[0050] Among them, σ eq is the dynamic value of the equivalent stress of the pore defect area of the main reducer casing under symmetric cycle, σa Dynamic value of stress cycle of the gas hole elastic area of the main reducer case m Static value of stress cycle of the gas hole defect area of the main reducer case

[0051] The calculation formula of the low cycle fatigue strength reserve coefficient is as follows:

[0052]

[0053] Wherein, K F低周 ≥0 is the low cycle fatigue strength reserve coefficient, σ eq低周 is the low cycle fatigue equivalent stress of the main reducer case, S L is the fatigue limit of magnesium alloy, Fq is the low cycle fatigue limit attenuation coefficient of magnesium alloy with different grades of gas hole defects, σ -1w is the median fatigue case of the standard part, σ -1q is the low cycle fatigue limit of the fatigue test piece.

[0054] If K F低周 ≥0, the low cycle fatigue safety cycle number is 100,000 times. Otherwise, the low cycle fatigue life is determined through the low cycle safety fatigue S-N curve, and the basic equation of the low cycle safety fatigue S-N curve is:

[0055] S=F q ×S L [H+A×(10*N 低周 +C) -B ]

[0056] Wherein, S is the dynamic stress of the gas hole defect area of the main reducer case, N 低周 is the low cycle life cycle number, A, B, C, H are fatigue performance constants.

[0057] The calculation formula of the high cycle fatigue strength reserve coefficient is as follows:

[0058]

[0059] Wherein, K F高周 is the high cycle fatigue strength reserve coefficient, σ eq高周 is the high cycle fatigue equivalent stress of the main reducer case, k F is the fatigue strength reduction coefficient, if the part does not perform fatigue test, k F =3, if the fatigue test is performed, k F =2,

[0060] If K F高周 ≥0, the high cycle fatigue life is infinite. Otherwise, the high cycle fatigue life is determined through the high cycle safety fatigue S-N curve, and the basic equation of the high cycle safety fatigue S-N curve is:

[0061] S = F q x S L [H + A x (N + C) -B ]

[0062] wherein N is the number of high cycle life cycles.

[0063] The above description is merely that of the preferred embodiments of the application and is not intended to limit the application. One skilled in the art can make various modifications and variations without departing from the spirit and scope of the application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the application shall be included in the scope of the protection of the application.

Claims

1. A method for manufacturing a sample with porosity defects in a main reducer casing, characterized in that, Includes the following steps: A1. Prepare chills and heat-treat the reusable chills. A2, core sand is prepared into sand core, molding sand is prepared into sand mold, and then sand core, sand mold and chill are combined into sand mold. The sand mold includes a horizontal sprue, a casting cavity arranged in a long strip and a riser connected to the casting cavity. Multiple casting cavities are arranged at intervals in the sand mold and connected by the horizontal sprue. The riser and the casting cavity are arranged in a one-to-one correspondence. A3, melt the magnesium alloy block into a magnesium alloy solution, then pour the magnesium alloy solution into a sand mold, and after pouring, evenly sprinkle multiple round insoluble materials of different diameters from the top of the riser to form a magnesium alloy casting. The magnesium alloy block has multiple long strip-shaped blocks, and each long strip-shaped block has different levels of porosity defects. A4. Remove the magnesium alloy casting from the sand mold, remove the molding sand and core sand from the magnesium alloy casting, and then cut the gating and riser on the magnesium alloy casting to obtain multiple long strip-shaped castings. Then, mark, surface treat and heat treat the long strip-shaped castings in sequence. A5. Perform porosity defect inspection on the elongated casting and mark the area occupied by different grades of porosity defects. Then, process the elongated casting according to the area occupied by different grades of porosity defects to process a single elongated casting into multiple elongated casting sample. Mark the multiple elongated casting sample separately. Each elongated casting sample has only the same grade of porosity defect, and the porosity defect is located at the center of the elongated casting sample.

2. The method for manufacturing a test sample with porosity defects in the main reducer casing according to claim 1, characterized in that, In step A1, the specific steps of the heat treatment are as follows: The cold iron is placed in a drying oven and dried at 260℃-300℃ for 3-4 hours. After that, the cold iron is removed from the drying oven and allowed to cool naturally.

3. The method for manufacturing a test sample with porosity defects in the main reducer casing according to claim 1, characterized in that, In step A1, if the storage time of the heat-treated chill exceeds 2 days, the chill needs to be kept at 150℃-180℃ for 30min-40min before use.

4. The method for manufacturing a test sample for a main reducer casing with porosity defects according to claim 1, characterized in that, Multiple round, insoluble objects of different diameters include steel balls with diameters of φ1mm, φ2mm, and φ3mm, with a high-temperature resistant coating on their surface.

5. The method for manufacturing a test specimen for a main reducer casing with porosity defects according to any one of claims 1-4, characterized in that, In step A3, melting the magnesium alloy block into a magnesium alloy solution specifically includes the following steps: Preheat the crucible to 680℃-720℃, add the magnesium alloy block into the crucible, and cover it with a gas protection cap to introduce protective gas into the crucible. The gas flow rate is 15L / min-25L / min, and the heating temperature is 760℃-780℃. After the magnesium alloy block has completely melted, add the preset weight of Mg-Zr master alloy and stir for 8-12 minutes. The heating temperature was set to 765℃-775℃, and the ventilation rate of the protective gas was increased to 25L / min-35L / min. Then, a refiner was placed in the crucible and argon gas was introduced for refining. The argon gas ventilation rate was 10L / min-20L / min, and the ventilation time was 12min-15min. After refining, the inclusions on the surface of the crucible were removed to obtain a magnesium alloy solution.

6. The method for manufacturing a test sample with porosity defects in the main reducer casing according to claim 5, characterized in that, Before using Mg-Zr master alloy, it needs to be preheated at 100℃-200℃ for at least 30 minutes.

7. The method for manufacturing a test specimen for a main reducer casing with porosity defects according to any one of claims 1-4, characterized in that, Step A3, which involves pouring the magnesium alloy solution into the sand mold, specifically includes the following steps: The temperature of the magnesium alloy solution exiting the crucible is controlled at 800℃-830℃, so that when the temperature of the magnesium alloy solution drops to 765℃-775℃, the magnesium alloy solution is poured into the sand mold, and the pouring time is controlled within 5s-15s.

8. The method for manufacturing a test specimen for a main reducer casing with porosity defects according to any one of claims 1-4, characterized in that, In step A4, the specific steps of the heat treatment are as follows: The elongated casting block is heated to 390℃-410℃ and held for 1.5h-2.5h, then heated to 515℃-525℃ and held for 6h-8h. It is then quenched using a quenching medium at 60℃-80℃, with the quenching transfer time not exceeding 20s. Finally, the elongated casting block is held at 195℃-205℃ for 18h-24h.

9. The method for manufacturing a test specimen for a main reducer casing with porosity defects according to any one of claims 1-4, characterized in that, In step A4, the specific steps for surface treatment are as follows: Clean the burrs and flash from the surface of the elongated ingot, then use a gaseous medium to remove sand particles from the surface and crevices of the elongated ingot, then remove excess material from the surface of the elongated ingot, and finally perform chromate treatment on the elongated ingot.

10. A method for testing and evaluating a sample with porosity defects in a main reducer casing, characterized in that, The testing and evaluation of the elongated cast ingot specimen manufactured using the manufacturing method for the main reducer casing porosity defect specimen according to any one of claims 1-9 includes the following steps: B1. Multiple standard parts free of metallurgical defects are obtained by sand casting and machining, and multiple batches of long strip-shaped ingot samples are manufactured. The porosity defect level of each batch of long strip-shaped ingot samples is different. The multiple batches of long strip-shaped ingot samples are then precision machined into smooth round bar-shaped test pieces. The test pieces are then inspected for porosity defects to remove test pieces that do not meet the requirements for porosity defect level and location. The test pieces include tensile test pieces and fatigue test pieces. B2. Conduct tensile property tests on standard parts and tensile test specimens to obtain tensile test data including yield strength, ultimate strength, yield strength attenuation coefficient, and ultimate strength attenuation coefficient with different levels of porosity defects. At the same time, conduct group fatigue property tests on standard parts and fatigue test specimens to obtain test data for fitting fatigue performance curves. Conduct rise and fall fatigue property tests on standard parts and test specimens to obtain fatigue test data including fatigue limit and fatigue limit attenuation coefficient with different levels of porosity defects. B3, using tensile test data and fatigue performance data, evaluates the static strength and fatigue strength of different levels of porosity defects on the main reducer casing.

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