Casting process for engine cylinder block

Abstract

The invention discloses an engine cylinder block casting process, which relates to the technical field of engine cylinder block casting and comprises the steps of mold pretreatment, alloy smelting, high-pressure casting and gradient cooling and post-treatment. In the high-pressure casting stage, the leading edge temperature gradient of molten aluminum is smaller than or equal to 15 DEG C through three-stage injection control, it is ensured that a cooling water channel with the wall thickness being 2 mm is completely filled, the cooling rate of a combustion chamber area reaches 2.0 mm / s through a gradient cooling system, the cooling rate of a bolt base area reaches 0.8 mm / s, and the hardness gradient is formed; the monitoring module comprises 16 thermocouples and 8 pressure sensors, the data sampling frequency is 100 Hz, the cooling flow is adjusted in real time through a fuzzy PID algorithm, the size precision of the engine cylinder body during casting is guaranteed, the shrinkage porosity defect rate is guaranteed to be reduced to 2% or below, the porosity is smaller than or equal to 0.5%, the sampling tensile strength of the engine cylinder body is larger than or equal to 320 MPa, and the ductility is larger than or equal to 3%. Therefore, the use quality and the working efficiency are effectively ensured.

Description

Technical Field

[0001] The present invention specifically relates to the technical field of engine cylinder block casting, specifically the engine cylinder block casting process. Background Technique

[0002] The engine cylinder block is the core component of the engine, undertaking key functions such as supporting moving parts, transmitting power, heat dissipation, and sealing; the material selection, casting process, processing technology, and inspection standards directly affect the performance and life of the engine; The traditional top-pouring gating system is prone to causing the molten aluminum to entrap gas, while the stepped gating improves the temperature field but does not solve the problem of incomplete filling of thin-walled water channels; due to the wide solidification temperature range of ductile iron cylinder blocks, ordinary chill blocks are difficult to achieve effective feeding, and it is necessary to rely on exothermic risers and process allowances for optimization; traditional sand casting requires multiple steps such as model making, sand mold preparation, and pouring. Especially for the green sand process, it takes time to remove slag and cool, resulting in a significant increase in cost during single-piece or small-batch production; the reaming operation destroys the blood supply of the endosteum, and the high proportion of scrap steel and return materials used leads to fluctuations in the composition of the molten iron, increasing the risk of shrinkage porosity. Summary of the Invention

[0003] The purpose of the present invention is to provide an engine cylinder block casting process. In this device, multi-stage temperature control and intelligent monitoring technology achieve the precision forming of complex-structured cylinder blocks to solve the problems in the above background technique.

[0004] To achieve the above purpose, the present invention provides the following technical solutions: The engine cylinder block casting process includes the following steps: a. Mold pretreatment: Preheat the combined metal mold to 180 - 220 °C, and spray a composite coating layer on the cavity surface. The coating composition is 50 - 65 wt% boron nitride, 20 - 30 wt% alumina, and 10 - 15 wt% silica sol. The coating thickness is 0.3 - 0.8 mm, and the surface roughness Ra ≤ 3.2 μm; b. Alloy melting: Use AlSi9Cu3 aluminum alloy, with a melting temperature of 720 - 750 °C. During refining, introduce an Ar + Cl2 mixed gas, with a refining time of 15 - 25 minutes. After static slag removal, the hydrogen content of the molten alloy is ≤ 0.12 ml / 100 g; c. High-pressure casting: The clamping pressure is 80 - 120 MPa, the injection speed is 3.5 - 4.5 m / s, the boosting pressure is 150 - 180 MPa, and the holding pressure time is 8 - 12 seconds; d. Gradient cooling: Control the temperature in three stages: In the first stage, pass water at 40 - 50 °C through the mold cooling water channels, with a flow rate of 5 L / min; in the second stage, switch to a coolant at 15 - 25 °C, with a flow rate of 8 L / min; in the third stage, use a low-temperature medium at -5 °C to 5 °C, with a flow rate of 3 L / min; e. Post-treatment: After the casting is demolded, it undergoes heat treatment. The steel shot used for surface shot peening has a diameter of 0.3 - 0.6 mm, and the coverage rate is ≥ 98%. As a further technical solution of the present invention, the AlSi9Cu3 aluminum alloy composition includes: Si 8.5 - 10.5 wt%, Cu 2.5 - 3.5 wt%, Mg 0.3 - 0.7 wt%, Fe ≤ 0.5 wt%, Mn 0.2 - 0.6 wt%, and the balance is Al; when melting, 0.05 - 0.15 wt% of TiB2 grain refiner is added, and the pouring temperature of the alloy liquid is controlled at 690 ± 10 °C. As a further technical solution of the present invention, the combined metal mold includes an upper mold, a lower mold, and 12 sets of adjustable core molds, and the core mold positioning accuracy is ≤ 0.02 mm; micro exhaust grooves are provided on the cavity surface, with a groove width of 0.15 - 0.25 mm, a groove depth of 0.3 - 0.5 mm, and an exhaust groove spacing of 3 - 5 mm; the mold thermal expansion coefficient is controlled at 1.05×10⁻ 5 / °C to 1.25×10⁻ 5 / °C; As a further technical solution of the present invention, the high-pressure casting stage adopts three-stage injection control: the first-stage injection speed is 0.5 - 1.0 m / s, and the stroke is 150 - 200 mm; the second-stage injection speed is 3.5 - 4.5 m / s, and the stroke is 300 - 350 mm; the third-stage boosting pressure rises to 180 MPa within 30 ms, and the boosting rate is ≥ 5 MPa / ms. As a further technical solution of the present invention, the water channel system in the gradient cooling stage includes a main cooling ring and auxiliary cooling branches. The diameter tolerance of the main cooling ring is ±0.05 mm, and the angle between the branch and the main ring is 45° - 60°; the accuracy of the coolant flow control system is ±0.5 L / min, and the temperature control accuracy is ±1 °C. As a further technical solution of the present invention, the heat treatment stage uses a nitrogen protection atmosphere, and the oxygen content is ≤ 50 ppm; the heating rate of the solution treatment is 3 - 5 °C / min, and the cooling rate of the aging stage is 1 - 2 °C / min; the Brinell hardness HB of the treated casting is 120 - 140, and the yield strength is ≥ 250 MPa. As a further technical solution of the present invention, the post-treatment of the casting includes a three-coordinate measurement process, the detection point spacing is ≤ 5 mm, and the key dimension tolerances are controlled as follows: the roundness of the cylinder hole is ≤ 0.015 mm, the coaxiality of the crankshaft hole is ≤ 0.02 mm, and the flatness is ≤ 0.03 mm / 300 mm. As a further technical solution of the present invention, the mold system includes an intelligent monitoring module, which can collect the mold temperature, pressure, and displacement data in real time, and dynamically adjust the cooling parameters through the PID algorithm to control the solidification rate gradient of the casting within 0.5 - 2.0 mm / s. Compared with the prior art, the beneficial effects of the present invention are: In the present invention, the combined metal mold is made of H13 steel, and 12 split core molds are provided for forming complex water channels and oil channels. The clearance between the core molds is ≤0.03 mm. The exhaust system includes 356 micro-exhaust grooves and 6 groups of vacuum-assisted exhaust devices, and the vacuum degree is controlled at -0.08 to -0.05 MPa; In the present invention, during the high-pressure casting stage, the temperature gradient of the aluminum liquid front is ≤15 °C through three-stage injection control, ensuring the complete filling of the cooling water channel with a wall thickness of 2 mm. The gradient cooling system enables the cooling rate in the combustion chamber area to reach 2.0 mm / s, while the cooling rate in the bolt seat area is 0.8 mm / s, forming a hardness gradient; In the present invention, the monitoring module includes 16 thermocouples and 8 pressure sensors. The data sampling frequency is 100 Hz. The cooling flow rate is adjusted in real time through the fuzzy PID algorithm to ensure the dimensional accuracy of the engine cylinder block during casting, reduce the shrinkage porosity defect rate to less than 2%, and the porosity ≤0.5%. The sampled tensile strength of this engine cylinder block is ≥320 MPa, and the elongation rate is ≥3%, thus effectively ensuring the quality and working efficiency of use. Specific embodiments

[0005] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0006] In the embodiments of the present invention, the casting process of the engine cylinder block includes the following steps: a. Mold pretreatment: Preheat the combined metal mold to 180 - 220 °C, and spray a composite coating layer on the cavity surface. The coating composition is 50 - 65 wt% boron nitride, 20 - 30 wt% alumina, and 10 - 15 wt% silica sol. The coating thickness is 0.3 - 0.8 mm, and the surface roughness Ra ≤ 3.2 μm; b. Alloy melting: Use AlSi9Cu3 aluminum alloy, the melting temperature is 720 - 750 °C. When refining, introduce a mixed gas of Ar + Cl2, the refining time is 15 - 25 minutes, and the hydrogen content in the alloy liquid after standing and slag removal is ≤0.12 ml / 100 g; c. High-pressure casting: The clamping pressure is 80 - 120 MPa, the injection speed is 3.5 - 4.5 m / s, the boosting pressure is 150 - 180 MPa, and the holding pressure time is 8 - 12 seconds; d. Gradient cooling: Control the temperature in three stages: In the first stage, water at 40 - 50 °C is passed through the cooling water channel of the mold, and the flow rate is 5 L / min; in the second stage, it is switched to a coolant at 15 - 25 °C, and the flow rate is 8 L / min; in the third stage, a low-temperature medium at -5 °C to 5 °C is used, and the flow rate is 3 L / min; e. Post-treatment: After the casting is demolded, it is heat-treated, and the steel shot used for surface shot peening has a diameter of 0.3 - 0.6 mm, and the coverage rate is ≥ 98%; The composition of the AlSi9Cu3 aluminum alloy includes: Si 8.5 - 10.5 wt%, Cu 2.5 - 3.5 wt%, Mg 0.3 - 0.7 wt%, Fe ≤ 0.5 wt%, Mn 0.2 - 0.6 wt%, and the balance is Al; 0.05 - 0.15 wt% of TiB2 grain refiner is added during melting, and the pouring temperature of the alloy liquid is controlled at 690 ± 10 °C By adopting the above technical solution, the combined metal mold is made of H13 steel (hardness HRC 48 - 52), 12 split core molds are provided for forming complex water channels and oil channels, the core mold fitting clearance is ≤ 0.03 mm, the exhaust system includes 356 micro-exhaust grooves and 6 groups of vacuum-assisted exhaust devices, and the vacuum degree is controlled at -0.08 to -0.05 MPa; In this embodiment, the combined metal mold includes an upper mold, a lower mold and 12 groups of adjustable core molds, and the core mold positioning accuracy is ≤ 0.02 mm; micro-exhaust grooves are arranged on the cavity surface, the groove width is 0.15 - 0.25 mm, the groove depth is 0.3 - 0.5 mm, and the exhaust groove spacing is 3 - 5 mm; the mold thermal expansion coefficient is controlled at 1.05×10⁻ 5 / °C to 1.25×10⁻ 5 / °C; In this embodiment, the high-pressure casting stage adopts three-stage injection control: the first-stage injection speed is 0.5 - 1.0 m / s, and the stroke is 150 - 200 mm; the second-stage injection speed is 3.5 - 4.5 m / s, and the stroke is 300 - 350 mm; the third-stage boosting pressure rises to 180 MPa within 30 ms, and the boosting rate is ≥ 5 MPa / ms; The water channel system in the gradient cooling stage includes a main cooling ring and auxiliary cooling branches. The diameter tolerance of the main cooling ring is ±0.05 mm, and the included angle between the branch and the main ring is 45° - 60°; the accuracy of the coolant flow control system is ±0.5 L / min, and the temperature control accuracy is ±1 °C; By adopting the above technical solution, in the high-pressure casting stage, the temperature gradient of the aluminum liquid front is ≤ 15 °C through three-stage injection control, ensuring the complete filling of the cooling water channel with a wall thickness of 2 mm. The gradient cooling system enables the cooling rate in the combustion chamber area to reach 2.0 mm / s, while the cooling rate in the bolt seat area is 0.8 mm / s, forming a hardness gradient (HB 140 vs HB 125); Furthermore, the heat treatment stage adopts a nitrogen protection atmosphere, and the oxygen content is ≤ 50 ppm; the heating rate during solution treatment is 3 - 5 °C / min, and the cooling rate during the aging stage is 1 - 2 °C / min; the Brinell hardness of the castings after treatment is HB 120 - 140, and the yield strength is ≥ 250 MPa; In this embodiment, the post-treatment of the casting includes a three-coordinate measurement process, with the distance between measurement points ≤ 5 mm. For the control of key dimension tolerances: the roundness of the cylinder hole ≤ 0.015 mm, the coaxiality of the crankshaft hole ≤ 0.02 mm, and the flatness ≤ 0.03 mm / 300 mm; The mold system includes an intelligent monitoring module that collects data on mold temperature, pressure, and displacement in real time and dynamically adjusts the cooling parameters through the PID algorithm to control the solidification rate gradient of the casting within 0.5 - 2.0 mm / s; By adopting the above technical solution, the monitoring module includes 16 thermocouples and 8 pressure sensors, with a data sampling frequency of 100 Hz. The cooling flow rate is adjusted in real time through the fuzzy PID algorithm to ensure the dimensional accuracy of the engine cylinder block during casting, ensure that the shrinkage porosity defect rate is reduced to less than 2%, the porosity ≤ 0.5%, the tensile strength of the sampled engine cylinder block ≥ 320 MPa, and the elongation ≥ 3%, thus effectively ensuring the quality and working efficiency of use.

[0007] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

[0008] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only includes an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Engine block casting process, characterized in that: It includes the following steps: a. Mold pretreatment: Preheat the combined metal mold to 180 - 220 °C, and spray a composite coating layer on the cavity surface. The coating composition is 50 - 65 wt% boron nitride, 20 - 30 wt% alumina, and 10 - 15 wt% silica sol. The coating thickness is 0.3 - 0.8 mm, and the surface roughness Ra ≤ 3.2 μm; b. Alloy melting: Use AlSi9Cu3 aluminum alloy, with a melting temperature of 720 - 750 °C. When refining, introduce an Ar + Cl2 mixed gas, and the refining time is 15 - 25 minutes. After standing and removing slag, the hydrogen content in the molten alloy is ≤ 0.12 ml / 100 g; c. High-pressure casting: The clamping pressure is 80 - 120 MPa, the injection speed is 3.5 - 4.5 m / s, the boosting pressure is 150 - 180 MPa, and the holding pressure time is 8 - 12 seconds; d. Gradient cooling: Control the temperature in three stages: In the first stage, pass water at 40 - 50 °C through the mold cooling water channels, with a flow rate of 5 L / min; in the second stage, switch to a coolant at 15 - 25 °C, with a flow rate of 8 L / min; in the third stage, use a low-temperature medium at -5 °C to 5 °C, with a flow rate of 3 L / min; e. Post-treatment: After the casting is demolded, it undergoes heat treatment, and the steel shot for surface shot peening treatment has a diameter of 0.3 - 0.6 mm, and the coverage rate ≥ 98%.

2. The engine block casting process according to claim 1, characterized in that: The composition of the AlSi9Cu3 aluminum alloy includes: Si 8.5 - 10.5 wt%, Cu 2.5 - 3.5 wt%, Mg 0.3 - 0.7 wt%, Fe ≤ 0.5 wt%, Mn 0.2 - 0.6 wt%, and the balance is Al; When melting, add 0.05 - 0.15 wt% of TiB2 grain refiner, and control the pouring temperature of the molten alloy at 690 ± 10 °C.

3. The engine block casting process according to claim 1, characterized in that: The combined metal mold includes an upper mold, a lower mold and 12 sets of adjustable core molds, and the positioning accuracy of the core molds is ≤ 0.02 mm; micro exhaust grooves are arranged on the cavity surface, the groove width is 0.15 - 0.25 mm, the groove depth is 0.3 - 0.5 mm, and the exhaust groove spacing is 3 - 5 mm; the thermal expansion coefficient of the mold is controlled at 1.05×10⁻ 5 / °C to 1.25×10⁻ 5 / °C.

4. The engine block casting process according to claim 1, wherein: The high-pressure casting stage adopts three-stage injection control: The first-stage injection speed is 0.5 - 1.0 m / s, and the stroke is 150 - 200 mm; the second-stage injection speed is 3.5 - 4.5 m / s, and the stroke is 300 - 350 mm; the third-stage boosting pressure rises to 180 MPa within 30 ms, and the boosting rate ≥ 5 MPa / ms.

5. The engine block casting process according to claim 1, wherein: The water channel system in the gradient cooling stage includes a main cooling ring and auxiliary cooling branches. The diameter tolerance of the main cooling ring is ± 0.05 mm, and the angle between the branch and the main ring is 45° - 60°; The accuracy of the coolant flow control system is ± 0.5 L / min, and the temperature control accuracy is ± 1 °C.

6. The engine block casting process according to claim 1, wherein: The heat treatment stage uses a nitrogen protection atmosphere, with an oxygen content ≤ 50 ppm; The heating rate for solution treatment is 3 - 5 °C / min, and the cooling rate in the aging stage is 1 - 2 °C / min; After treatment, the Brinell hardness HB of the casting is 120 - 140, and the yield strength ≥ 250 MPa.

7. The engine block casting process according to claim 1, characterized in that: The post-treatment of the casting includes a three-coordinate measurement process, the distance between measurement points ≤ 5 mm, and the control of key dimension tolerances: The roundness of the cylinder hole ≤ 0.015 mm, the coaxiality of the crankshaft hole ≤ 0.02 mm, and the flatness ≤ 0.03 mm / 300 mm.

8. The engine block casting process according to claim 1, characterized in that: The mold system includes an intelligent monitoring module, which collects mold temperature, pressure, and displacement data in real time, and dynamically adjusts the cooling parameters through the PID algorithm to control the solidification rate gradient of the casting at 0.5 - 2.0 mm / s.