A method for solving casting deformation, large diesel engine super-long casting

Abstract

The present invention belongs to the technical field of cast iron casting, and discloses a method for solving casting deformation and an extra-long casting of a large diesel engine. The method for solving casting deformation balances the temperature field through the pouring position and the pouring system, uses the inner runner of the pouring system as a part of the process reinforcement, and disperses the inner runner reinforcement ribs, transverse reinforcement ribs, and longitudinal reinforcement ribs in the transverse and longitudinal directions of the casting to control the deformation amount in different directions of the casting state; eliminates residual stress by controlling the parameters of the casting heat treatment process, removes the process reinforcement ribs in stages, and performs vibration aging after rough machining. The present invention solves the risk of deformation of extra-long rod castings by controlling the process parameters of the casting heat treatment process to eliminate residual stress to the maximum extent, removes the process reinforcement ribs in stages, and performs vibration aging after rough machining. The present invention solves the method for solving the deformation of extra-long castings of large diesel engines, solves the quality problem of warping deformation of extra-long castings of large diesel engines, and meets production needs.

Description

Technical Field

[0001] The invention belongs to the technical field of cast iron casting, and in particular relates to a method for solving casting deformation and an extra-long casting of a large diesel engine. Background Art

[0002] At present, the A / B series machine feet are super-long parts of the bracket type, with a maximum wall thickness of 90mm and a minimum wall thickness of 40mm. The entire part is 4000mm long, 390mm wide, and 400mm high, with an aspect ratio of about 10 / 1, which is an ultra-long casting with an aspect ratio greater than 5. Due to the super-long casting and uneven wall thickness, the cooling speed of various parts of the casting is inconsistent, which hinders the normal shrinkage of the casting, resulting in uneven stress distribution inside the casting, causing deformation of the casting, affecting the yield strength of the workpiece, and also affecting the processing accuracy.

[0003] Through the above analysis, the problems and defects of the prior art are as follows: the internal stress distribution of the castings of the current super-long bracket parts is uneven, causing the castings to deform, the workpiece yield strength is low, and the processing accuracy is low.

[0004] The difficulty in solving the above problems and defects is: the casting is too long, the wall thickness varies greatly, and the inconsistent cooling of different parts of the casting causes internal stress to cause the casting to warp and deform, which is the root cause of the casting size being out of tolerance and unusable. It cannot be solved by existing methods.

[0005] The significance of solving the above problems and defects is: through the pouring position, process parameters, pouring system balance temperature field, the pouring system's endogate is used as part of the process tie rod, and different types of process tie rods are dispersed in the horizontal and vertical directions of the casting to control the deformation in different directions of the casting. The risk of warping deformation of super-long castings of large diesel engines is solved by controlling the process parameters of the casting heat treatment process to eliminate residual stress to the maximum extent, removing the process tie rods in stages and performing vibration aging after semi-finishing. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for solving casting deformation and an extra-long casting for a large diesel engine.

[0007] The present invention is achieved in this way. A method for solving the deformation of castings is provided. The method for solving the deformation of castings balances the temperature field through the pouring position and the pouring system, uses the endogate of the pouring system as a part of the process reinforcement, and disperses the endogate reinforcement ribs, transverse reinforcement ribs, and longitudinal reinforcement ribs in the transverse and longitudinal directions of the casting to control the deformation in different directions of the casting state; eliminates residual stress by controlling the parameters of the casting heat treatment process, removes the process reinforcement in stages and performs vibration aging after semi-finishing, so as to solve the risk of warping deformation of ultra-long castings of large diesel engines.

[0008] Further, the method for solving casting deformation includes:

[0009] The first step is model comparison. The machine foot casting is scanned in three dimensions by a scanner. The line laser on the scanner emits a cross laser beam to scan the surface of the object. The surface of the measured part is collected by three CCD cameras to obtain a three-dimensional model of the machine foot. The actual scanning result is compared with the three-dimensional model by software, and the size difference between the actual casting and the theoretical value is analyzed to provide a basis for process improvement.

[0010] The second step is the process plan. The casting is generally in a semi-I shape, and each boss is connected to the body with a casting rib. The casting position is such that the bosses of the two castings in the A / B columns face outwards, the thick and large parts of the casting face upwards, and the side planes are arranged face to face. The upper part of the casting is cooled first to achieve a basic balance of the casting temperature field after the machine foot is poured and filled, meet the conditions for the simultaneous solidification of ductile iron, and facilitate the arrangement of process tie bars in the width direction on the large plane of the machine foot.

[0011] The third step is to draw the reinforcement. To prevent shrinkage and shrinkage defects caused by the contact heat node between the reinforcement and the casting, the thickness of the reinforcement is 40%-60% of the wall thickness at the reinforcement setting, and the width is 1.5-2 times the thickness of the reinforcement.

[0012] The fourth step is heat treatment. In order to ensure the mechanical properties of the casting and eliminate residual stress to the maximum extent, the machine feet are leveled on the trolley according to the working position. When the temperature is less than 200℃, the body is put into the furnace, heated to 500℃~550℃ at a rate of ≤50℃ / hour and kept warm for 3 hours to 4 hours. It is cooled to below 200℃ and taken out of the furnace.

[0013] The fifth step is to remove the process tie bars in the width direction after heat treatment. Before heat treatment, the tie bars bear great tensile stress or compressive stress to prevent the casting from deformation. After heat treatment, the width dimension of the machine foot casting is small, and the stress has been basically uniformed or removed. After heat treatment, the process tie bars in the width direction are removed and the casting is fully cleaned;

[0014] The sixth step is to remove the process tie bars in the length direction after rough machining. The machine foot is too long in the length direction. The clamping and extrusion during the machining process cause slight deformation of the casting. In order to eliminate the superimposed influence of the machining process on the stress, the process tie bars in the length direction are removed after rough machining of the casting.

[0015] The seventh step is vibration aging after semi-finishing. After the machine foot enters semi-finishing, the support points of the two castings in the A / B column are selected at the nodes or connections 1 / 3 away from each end for four-point support. The excitation point is first selected in the middle position, and a smaller value of dynamic stress is used. The dynamic stress is controlled at ±25-±40N / mm 2 After 5 minutes of treatment, the maximum stress peak value decreases by 20-30% and then increases to the specified value and then continues to be treated for another 5 minutes.

[0016] Furthermore, in the first step, the deformation of the side surface of the machine foot is 0mm-3mm, and the deformation of the top surface of the casting is 0mm-2mm. After scribing and checking the machine foot casting, the dimensional deviation of the machine foot in all directions is less than 3mm.

[0017] Furthermore, in the second step of pouring, the bosses of the two castings in the A / B columns are facing outward, the thick parts of the castings are facing upward, the side planes are arranged face to face, the upper part of the castings is cooled first, and the pouring system is multi-channel, dispersed, large-flow, and low-velocity. It is introduced into the mold from the middle.

[0018] Furthermore, the wall thickness of the boss part of the third step machine foot is 60, and a 30×30 / 40 longitudinal reinforcement rib is set on the side of the boss of each machine foot 1. The longitudinal reinforcement rib is fixed to the mold with a wooden strip with a draft angle and is pulled upward from the parting surface along with the mold as a whole.

[0019] Furthermore, the wall thickness of the third-step machine foot is 65, and two transverse reinforcing ribs with a diameter of ∅30 are set at 1 / 3 of the height direction of the center of each level of the machine foot from the upper part and the lower part; the transverse reinforcing ribs are made of refractory ceramic tubes with an inner diameter of ∅30, which are positioned in the model and then filled with sand around them.

[0020] Furthermore, the ingates of the third step machine foot are distributed at 1 / 2 of each level in the height direction, and the ingate reinforcement ribs are provided. The ingate reinforcement ribs use a refractory ceramic tube with a diameter of ∅30 to directly connect the cross runner and the ingate into a T-shaped channel.

[0021] Furthermore, in the fourth step, when the temperature is less than 200°C, the body is put into the furnace, heated to 500°C-550°C at a speed of ≤50°C / hour, kept at that temperature for 3-4 hours, and then cooled to below 200°C before being taken out of the furnace.

[0022] Furthermore, in the seventh step, the maximum stress peak value is reduced by 20-30% and then increased to the specified value and processed for another 5 minutes; the excitation point is moved to the two ends and processed again respectively, and the total vibration time of each casting is controlled within 30 minutes.

[0023] Another object of the present invention is to provide an extra-long casting for a large diesel engine cast by the method for solving casting deformation.

[0024] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: In terms of casting process, the present invention balances the temperature field through the pouring position and the pouring system, uses the inner runner of the pouring system as part of the process tie rod, and arranges different types of process tie rods in a dispersed manner in the horizontal and vertical directions of the casting to control the deformation in different directions of the casting. The risk of deformation of super-long rod castings is solved by controlling the process parameters of the casting heat treatment process to eliminate residual stress to the maximum extent, removing the process tie rods in stages, and performing vibration aging after semi-finishing.

[0025] The invention solves the problem of deformation of overlong castings of large diesel engines by means of casting process parameters, process reinforcement setting, heat treatment, vibration aging and the like; it solves the problem of warping deformation quality of overlong castings of large diesel engines and meets production needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a method for solving casting deformation provided by an embodiment of the present invention.

[0027] Figure 2 Schematic diagram of the process of drawing reinforcement of the ingrown provided by an embodiment of the present invention;

[0028] In the figure: 1. Machine foot; 2. Ingate; 3. Horizontal reinforcement ribs; 4. Longitudinal reinforcement ribs.

[0029] Figure 3 The method for solving casting deformation provided by the embodiment of the present invention is effective Figure 1 .

[0030] Figure 4 The method for solving casting deformation provided by the embodiment of the present invention is effective Figure 2 .

[0031] Figure 5 The method for solving casting deformation provided by the embodiment of the present invention is effective Figure 3 .

[0032] Figure 6 The method for solving casting deformation provided by the embodiment of the present invention is effective Figure 4 . DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] In view of the problems existing in the prior art, the present invention provides a method for solving casting deformation and an extra-long casting for a large diesel engine. The present invention is described in detail below in conjunction with the accompanying drawings.

[0035] like Figure 1 As shown, the method for solving casting deformation provided by the present invention comprises the following steps:

[0036] S101: A method for performing a three-dimensional scan of the machine foot casting using a high-precision scanner, and comparing the actual scan result with the three-dimensional model using software to analyze the difference in size between the actual casting and the theoretical value;

[0037] S102: The casting is generally in a semi-I shape, and each boss is connected to the body with a casting rib; the casting position is such that the bosses of the two castings in the A / B row face outwards, the thick parts of the casting face upwards, and the side planes are arranged face to face, and the upper part of the casting is cooled first;

[0038] S103: The setting of process tie bars in the length and width directions is evenly arranged in a dispersed manner, reducing heat nodes, and making a smooth transition with the wall thickness in terms of distribution position, shape and size, and casting processability; the thickness of the process tie bars is 40%-60% of the wall thickness at the setting of the tie bars, and the width is 1.5 times-2 times the thickness of the process tie bars;

[0039] S104: The machine feet are leveled on the trolley according to the working position. When the temperature is less than 200°C, the machine body is put into the furnace, heated to 500°C~550°C at a speed of ≤50°C / hour, and kept at this temperature for 3 hours to 4 hours. The machine body is cooled to below 200°C and taken out of the furnace.

[0040] S105: After heat treatment, remove the process tie bars in the height direction and clean the casting thoroughly;

[0041] S106: Remove the process reinforcement in the length direction after rough machining of the casting;

[0042] S107: After semi-finishing, the support points of the two castings in the A / B column are selected at the nodes or connections 1 / 3 away from each end for four-point support. The excitation point is first selected in the middle position, and a smaller dynamic stress is used. The dynamic stress is controlled at ±25-±40N / mm 2 After 5 minutes of treatment, the highest stress peak value drops by 20-30% and then increases to the specified value and then treats for another 5 minutes; move the excitation point to both ends and treat them again. The total vibration time of each casting is controlled at about 30 minutes.

[0043] like Figure 2 As shown, the process reinforcement of the ingrown provided in the embodiment of the present invention includes: a machine foot 1, an ingrown reinforcement rib 2, a transverse reinforcement rib 3, and a longitudinal reinforcement rib 4.

[0044] The wall thickness of the boss of the machine foot 1 is 60, and a longitudinal reinforcing rib 4 of 30×30 / 40 (30 away from the casting, 30×40) is set on the side of the boss of each machine foot 1. The longitudinal reinforcing rib 4 is fixed on the mold with a draft wood strip and pulled upward from the parting surface with the mold as a whole. The wall thickness of the machine foot 1 is 65, and 32 transverse reinforcing ribs with a diameter of ∅30 are set at 1 / 3 of the height direction of the center of each machine foot. The transverse reinforcing rib 3 is a refractory ceramic tube with an inner diameter of ∅30, which is positioned in the model and then filled with sand to compact it.

[0045] The ingates of the machine foot 1 are distributed at 1 / 2 of each level in the height direction, and the ingates reinforcement ribs 2 are arranged. The ingates reinforcement ribs 2 use a refractory ceramic tube with a diameter of ∅30 to directly connect the cross runner and the ingates into a "T-shaped" channel, so that after the ingates complete the filling function, the cooling process can also play the role of process tensioning.

[0046] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0047] The method for solving casting deformation provided by the present invention uses the inner runner of the pouring system as part of the process tie rod, and evenly arranges different types of process tie rods in the horizontal and vertical directions to control the amount of cast deformation. In the heat treatment process of the casting, the process parameters are controlled to eliminate the residual stress to the maximum extent, and the process tie rods are removed in stages and vibration aging is performed after rough processing to solve the deformation of super-long rod castings; specifically, the following steps are included:

[0048] The first step is to detect and analyze the structure and deformation of the casting. The deformation of the casting is detected by the three-dimensional scanning fitting method, that is, the machine foot casting is scanned in three dimensions by a high-precision scanner, and the actual scanning results are compared with the three-dimensional model by software to analyze the difference between the actual casting and the theoretical value. From the three-dimensional scanning fitting, the deformation of the side of the machine foot (length direction) is between 0mm and 3mm, and the deformation of the top surface of the casting (height direction) is between 0mm and 2mm. After checking the machine foot casting, the dimensional deviation of the machine foot in all directions is less than 3mm, which is consistent with the scanning fitting.

[0049] The second step is casting process design. The deformation of the casting is closely related to the inconsistent cooling speed of each part. The casting is generally in a "semi-I" shape, and each boss is connected to the body with a cast rib.

[0050] The pouring position is to have the bosses of the two castings in the A / B columns facing outward, the thick and large parts of the casting facing upward, and the side planes facing each other. The upper part of the casting is cooled first, which is also conducive to the use of riser shrinkage compensation. The gating system is multi-channel, dispersed, with large flow and low flow rate introduced from the middle of the casting mold, which is conducive to the consistent cooling speed of various parts of the casting. However, the upper part of the entire casting is thicker and is subject to tensile stress, while the lower part is thinner and is subject to compressive stress. The length-to-width ratio of the casting is about 10 / 1. The cooling speed at both ends is faster and is subject to tensile stress, while the cooling speed in the middle is slower and is subject to compressive stress. There is still a risk of deformation in the length and height direction of the casting.

[0051] The third step is the design of the process tie bars. The setting of the process tie bars in the length and width directions should be comprehensively considered from the aspects of distribution position, shape and size, and casting processability. They should be evenly arranged step by step to reduce hot spots and have a smooth transition with the wall thickness. The thickness of the process tie bars is 40%-60% of the wall thickness at the setting of the tie bars, and the width is 1.5-2 times the thickness of the process tie bars.

[0052] (1) Length direction: The wall thickness of the boss of the A / B column machine feet is 60, and a 30×30 / 40 (30 away from the casting, 30×40) longitudinal process tie rod is set on the side of each boss. The tie rod is fixed to the mold with a draft angle wooden strip and pulled upward from the parting surface along with the mold as a whole.

[0053] (2) Width direction: The wall thickness of the A / B column machine feet is 65, and two transverse process tie bars with a diameter of ∅30 are set at the height direction of the center of each gear, 1 / 3 of the distance from the upper part and the lower part. The tie bars are made of refractory ceramic tubes with an inner diameter of ∅30, which are positioned in the mold and then filled with sand to compact them.

[0054] (3) The process reinforcement function of the ingates: The ingates of the A / B series machine feet are distributed at 1 / 2 of the height direction of each gear. A refractory ceramic tube with a diameter of ∅30 is used to directly connect the cross runner and the ingates into a "T-shaped" channel, so that after the ingates complete the filling function, the cooling process can also play the role of process reinforcement.

[0055] The fourth step is to select heat treatment parameters: When the casting is subjected to stress relief annealing at 550℃-650℃, the strength and hardness of the casting will decrease while the stress is eliminated. When the yield stress decreases and plastic deformation occurs, the residual stress will decrease rapidly, but the rate of decrease of the residual stress will slow down significantly after 2 hours.

[0056] In order to ensure the mechanical properties of the casting and eliminate the residual stress to the maximum extent, 500℃-550℃ is selected for insulation for 3-4 hours. At this time, the residual stress is lower than the yield stress at this temperature. The specific heat treatment process is: the machine feet are leveled on the trolley according to the working position, the body is put into the furnace when it is less than 200℃, heated to 500℃~550℃ at a speed of ≤50℃ / hour, and kept for 3-4 hours, and then cooled to below 200℃ and taken out of the furnace.

[0057] The fifth step is to remove the process reinforcement in the height direction after heat treatment and thoroughly clean the casting.

[0058] The sixth step is to remove the process reinforcement in the length direction after rough machining of the casting.

[0059] The seventh step is vibration aging treatment: vibration aging eliminates stress by superimposing the alternating stress of vibration and the residual stress. When the energy absorbed by the friction inside the material reaches or exceeds a certain threshold of the material, the workpiece undergoes microscopic or macroscopic viscoelastic mechanical changes, reducing or homogenizing the residual stress inside the workpiece, which is also called the Bauschinger effect.

[0060] Select the support points of the two castings in the A / B column at the nodes or connections 1 / 3 away from each end for four-point support. The excitation point is first selected in the middle position, and a smaller dynamic stress is used. The dynamic stress is controlled at ±25-±40N / mm 2After 5 minutes of treatment, the highest stress peak value drops by 20-30% and then increases to the specified value and then treats for another 5 minutes to avoid fatigue of the casting. In order to make each section of the workpiece under high influence, the excitation point is moved to the two ends and treated again. The change of the excitation point will arouse a new vibration mode, which plays an important role in the homogenization of residual stress. The total vibration time of each casting is controlled at about 30 minutes. Through this method, the residual stress inside the machine foot is effectively eliminated or homogenized.

[0061] The technical effects of the present invention are described in detail below in conjunction with experiments.

[0062] The residual stress test plan of the impact-resistant machine feet of columns A and B in this experiment

[0063] (1) The purpose is to explore the residual stress state of the impact-resistant engine foot castings in series A and B before, after and after heat treatment, and to decide to conduct residual stress testing on the rear air intake box.

[0064] (2) Detection method

[0065] The small hole method is used for stress measurement. A small hole (diameter φ2, depth 2mm) is drilled with a drilling tool at the location where the residual stress is to be tested. The metal at that location and the residual stress therein are released, and the original residual stress loses balance. At this time, a certain amount of release strain will be generated around the small hole, and its size is corresponding to the released stress. The strain release caused by the small hole processing near the small hole is measured, and the original residual stress value of the small hole can be converted through elastic mechanics calculation.

[0066] (3) Testing location: A total of 27 points were selected on the top, bottom and side of the impact-resistant machine foot castings in columns A and B for residual stress testing.

[0067] (4) Number of tests: once before heat treatment, once after heat treatment (without shot peening), and once after semi-finishing.

[0068] Experiment 1: Residual stress test report of impact-resistant machine feet in column A (before annealing)

[0069] In this experiment, the blind hole method was used to test and compare the residual stress of the impact-resistant machine feet of column A. The main conclusions are as follows: the tested machine feet have not undergone stress relief treatment, and the residual principal stress in the test area of ​​the machine feet is mainly compressive stress. The residual compressive stress is maintained within 185MPa, and the residual tensile stress values ​​are all within 130MPa.

[0070] Table 1 A: Test data and calculation results of residual stress of impact-resistant machine feet

[0071]

[0072] Experiment 2: Residual stress test report of impact-resistant machine feet in column A (after annealing)

[0073] The present invention uses the blind hole method to test and compare the residual stress of the impact-resistant machine feet of column A, and the main conclusions are as follows: after the stress relief treatment of the tested machine feet, the residual principal stress in the test area of ​​the machine feet is mainly compressive stress, the residual compressive stress is maintained within 80MPa, and the residual tensile stress values ​​are all within 70MPa.

[0074] Table 2 A column of residual stress test data and calculation results of impact-resistant machine feet

[0075]

[0076] Experiment 3: Residual stress test report of impact-resistant machine feet in column A (after semi-finishing)

[0077] The present invention uses the blind hole method to test and compare the residual stress of the impact-resistant machine feet of column A, and the main conclusions are as follows: the machine feet under test have been semi-finished, and the residual principal stress in the test area of ​​the machine feet is mainly compressive stress. The residual compressive stress is maintained within 70MPa, and the residual tensile stress values ​​are all within 65MPa.

[0078] Table 3 A column of residual stress test data and calculation results of impact-resistant machine feet

[0079]

[0080] Experiment 4: Residual stress test report of impact-resistant machine feet in row B (before annealing)

[0081] In this experiment, the blind hole method was used to test and compare the residual stress of the B-row impact-resistant machine feet. The main conclusions are as follows: the tested machine feet have not undergone stress relief treatment, and the residual principal stress in the test area of ​​the machine feet is mainly compressive stress. The residual compressive stress is maintained within 180MPa, and the residual tensile stress values ​​are all within 130MPa.

[0082] Table 4. Test data and calculation results of residual stress of impact-resistant machine feet in column B

[0083]

[0084] Experiment 5: Residual stress test report of impact-resistant machine feet in row B (after annealing)

[0085] In this experiment, the blind hole method was used to test and compare the residual stress of the B-row impact-resistant machine feet. The main conclusions are as follows: after the stress relief treatment of the tested machine feet, the residual principal stress in the test area of ​​the machine feet was mainly compressive stress, the residual compressive stress was maintained within 80MPa, and the residual tensile stress values ​​were all within 60MPa.

[0086] Table 5. Test data and calculation results of residual stress of impact-resistant machine feet in column B

[0087]

[0088] Experiment 6: Residual stress test report of impact-resistant machine feet in column B (after semi-finishing)

[0089] In this experiment, the blind hole method was used to test and compare the residual stress of the B-row impact-resistant machine feet. The main conclusions are as follows: the machine feet underwent semi-finishing processing, and the residual principal stress in the test area of ​​the machine feet was mainly compressive stress. The residual compressive stress was maintained within 70MPa, and the residual tensile stress values ​​were all within 65MPa.

[0090] Table 6 B: Test data and calculation results of residual stress of impact-resistant machine feet

[0091]

[0092] Conclusions of this experiment:

[0093] 1. Before annealing of column A

[0094] The machine feet of column A under inspection have not undergone stress relief treatment. The residual principal stress in the test area of ​​the machine feet is mainly compressive stress. The residual compressive stress is maintained within 185MPa, and the residual tensile stress values ​​are all within 130MPa.

[0095] 2. After annealing of column A

[0096] After annealing and stress relief treatment of the inspected A-series machine feet, the residual principal stress in the test area of ​​the machine feet is mainly compressive stress, the residual compressive stress is maintained within 80MPa, and the residual tensile stress values ​​are all within 70MPa.

[0097] 3. Semi-finishing of row A

[0098] The machine feet of the tested A series have undergone semi-finishing processing. The residual principal stress in the test area of ​​the machine feet is mainly compressive stress. The residual compressive stress is maintained within 70MPa, and the residual tensile stress values ​​are all within 65MPa.

[0099] 4. Before annealing of row B

[0100] Before annealing, the machine feet of column B under inspection had not undergone stress relief treatment. The residual principal stress in the test area of ​​the machine feet was mainly compressive stress, and the residual compressive stress was maintained within 180MPa, and the residual tensile stress values ​​were all within 130MPa.

[0101] 5. After annealing of row B

[0102] After annealing and stress relief treatment of the inspected B column machine feet, the residual principal stress in the machine foot test area is mainly compressive stress, the residual compressive stress is maintained within 80MPa, and the residual tensile stress values ​​are all within 60MPa.

[0103] 6. Semi-finishing of row B

[0104] After semi-finishing of the machine feet in column B under inspection, the residual principal stress in the test area of ​​the machine feet was mainly compressive stress, the residual compressive stress was maintained within 70MPa, and the residual tensile stress values ​​were all within 65MPa.

[0105] The stress tests in the above stages indicate that the residual stress inside the machine foot is effectively eliminated or homogenized by this method.

[0106] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for solving casting deformation, characterized in that: The method for solving casting deformation balances the temperature field through the pouring position and the pouring system, uses the ingates of the pouring system as part of the process reinforcement, and disperses the ingates, transverse reinforcements, and longitudinal reinforcements in the transverse and longitudinal directions of the casting to control the deformation in different directions of the casting state; eliminates residual stress by controlling the parameters of the casting heat treatment process, removes the process reinforcement in stages, and performs vibration aging after semi-finishing, thereby solving the risk of warping deformation of the super-long casting of the large diesel engine; The method for solving casting deformation includes: The first step is model comparison. The machine foot casting is scanned in three dimensions by a scanner. The line laser on the scanner emits a cross laser beam to scan the surface of the object. The surface of the measured part is collected by three CCD cameras to obtain a three-dimensional model of the machine foot. The actual scanning result is compared with the three-dimensional model by software, and the size difference between the actual casting and the theoretical value is analyzed to provide a basis for process improvement. The second step is the process plan. The casting is generally in a semi-I shape, and each boss is connected to the body with a casting rib. The casting position is such that the bosses of the two castings in the A / B columns face outwards, the thick and large parts of the casting face upwards, and the side planes are arranged face to face. The upper part of the casting is cooled first to achieve a basic balance of the casting temperature field after the machine foot is poured and filled, meet the conditions for the simultaneous solidification of ductile iron, and facilitate the arrangement of process tie bars in the width direction on the large plane of the machine foot. The third step is to draw the reinforcement. To prevent shrinkage and shrinkage defects caused by the contact heat node between the reinforcement and the casting, the thickness of the reinforcement is 40%-60% of the wall thickness at the reinforcement, and the width is 1.5-2 times the thickness of the reinforcement. The fourth step is heat treatment. To ensure the mechanical properties of the casting and eliminate the residual stress to the maximum extent, the machine feet are leveled on the trolley according to the working position. When the temperature is less than 200℃, the casting is put into the furnace, heated to 500℃~550℃ at a rate of ≤50℃ / hour, and kept at this temperature for 3~4 hours. The casting is cooled to below 200℃ and then taken out of the furnace. The fifth step is to remove the process tie bars in the width direction after heat treatment. Before heat treatment, the tie bars are subjected to large tensile stress or compressive stress to prevent the casting from deformation. After heat treatment, the width dimension of the machine foot casting is small, and the stress has been basically uniformed or removed. After heat treatment, the process tie bars in the width direction are removed and the casting is fully cleaned. The sixth step is to remove the process tie bars in the length direction after rough machining. The machine foot is too long in the length direction. The clamping and extrusion during the machining process cause slight deformation of the casting. In order to eliminate the superimposed influence of the machining process on the stress, the process tie bars in the length direction are removed after rough machining of the casting. The seventh step is vibration aging after semi-finishing. After the machine foot enters semi-finishing, the support points of the two castings in the A / B column are selected at the nodes or connections 1 / 3 away from each end for four-point support. The excitation point is first selected in the middle position, and a smaller value of dynamic stress is used. The dynamic stress is controlled at ±25-±40N / mm 2 After 5 minutes of treatment, the maximum stress peak value decreases by 20-30% and then increases to the specified value and then continues to be treated for another 5 minutes.

2. The method for solving casting deformation according to claim 1, characterized in that: In the first step, the deformation of the side surface of the machine foot is 0mm-3mm, and the deformation of the top surface of the casting is 0mm-2mm. After scribing and checking the machine foot casting, the dimensional deviation of the machine foot in all directions is less than 3mm.

3. The method for solving casting deformation according to claim 1, characterized in that: In the second step, the casting position is such that the bosses of the two castings in the A / B row face outward, the thick parts of the casting face upward, and the side planes are arranged face to face. The upper part of the casting is cooled first, and the pouring system is multi-channel, dispersed, large-flow, and low-speed. It is introduced into the mold from the middle.

4. The method for solving casting deformation according to claim 1, characterized in that: The wall thickness of the boss part of the third step machine foot is 60, and a 30×30 / 40 longitudinal reinforcement rib is set on the side of the boss of each machine foot 1. The longitudinal reinforcement rib is fixed to the mold with a wooden strip with a draft angle and is pulled upward from the parting surface along with the mold as a whole.

5. The method for solving casting deformation according to claim 1, characterized in that: The wall thickness of the third step machine foot is 65, and the diameter is set at 1 / 3 of the height direction of the center of each step machine foot from the upper part and the lower part. There are 2 transverse reinforcement ribs; the transverse reinforcement ribs are made of inner diameter After the refractory ceramic tube is positioned in the model, the surrounding sand is filled tightly.

6. The method for solving casting deformation according to claim 1, characterized in that: The third step is to set the inner runner reinforcement ribs at 1 / 2 of the height direction of each level. The inner runner reinforcement ribs are made of 1 diameter The refractory ceramic tube directly connects the runner and the ingates into a T-shaped channel.

7. The method for solving casting deformation according to claim 1, characterized in that: In the fourth step, when the temperature is less than 200°C, the body is put into the furnace, heated to 500°C-550°C at a speed of ≤50°C / hour, kept at that temperature for 3-4 hours, and then cooled to below 200°C and taken out of the furnace.

8. The method for solving casting deformation according to claim 1, characterized in that: In the seventh step, after the peak value of the highest stress decreases by 20-30%, it is increased to the specified value and then processed for another 5 minutes; the exciting point is moved to the two ends and processed again respectively, and the total vibration time of each casting is 30 minutes.

9. An extra-long casting for a large diesel engine cast by the method for solving casting deformation according to any one of claims 1 to 8.

Images