CN104014742A - Casting process and casting mould of large propeller hub body - Google Patents

Abstract

The invention provides a casting process for a large paddle hub body and a casting mold. The pouring process for a large paddle hub body includes the following steps: the melt enters the cavity from the bottom of the casting mold, the flow direction of the melt enters the cavity and the clamping of the bottom surface of the cavity The angle is 20-80°. After the melt fills the entire mold cavity, the mold is removed after cooling to obtain the hub body. The pouring process of the large hub body of the present invention is simple and easy, can effectively reduce the degree of turbulent flow during filling of the casting, and accelerate the solidification rate of the large casting, and the precipitation and reactive pores of the large hub body cast by this process are Few defects. The invention also discloses a large propeller hub body casting mold, which has a scientific and reasonable structure and can be used to cast a large propeller hub body with less precipitation and reactive pore defects.

Description

Pouring Technology and Mold of Large Propeller Hub

technical field

The invention relates to casting technology, in particular to a pouring process and casting mold for a large propeller hub body.

Background technique

At present, the pouring of the hub body adopts conventional sand casting. When using conventional sand casting castings, the melt enters the cavity from the inrunner at the bottom of the casting mold (the inrunner is perpendicular to the runner, and the inrunner is perpendicular to the bottom of the casting mold) until the entire cavity is filled. The melt is cooled, and the casting mold is removed to obtain the hub body. Conventional sand casting can meet the casting needs of small castings, but it cannot meet the casting needs of large castings due to the defects in the process.

Taking conventional sand casting as an example to cast an adjustable-pitch propeller hub with a diameter greater than 1.7 meters, there are the following problems: (1) During pouring, the melt (copper alloy liquid) flows vertically upward from the bottom of the casting mold at a certain flow rate. The turbulence generated by the vertical upward flow of molten metal into the cavity intensifies the gas-absorbing oxidation of the high-temperature melt, which in turn leads to casting defects such as pores; (2) The solidification time of large propeller hub castings is long (up to 2-3 Days), the high-temperature melt is in contact with the sand mold (core) for a long time to cause intrusive pores and reactive pores.

Studies have found that slowing down the degree of turbulence in the filling process and accelerating the solidification rate of the melt help to solve the above problems. The existing casting technology is to reduce the flow impact of the filling process through the bottom injection method, and to strengthen the cooling effect by using sand with good thermal conductivity or adopting a cold iron process on the mold (core). However, the effects of these measures are not ideal enough for large hub body castings. Under the action of gravity, the molten metal enters the cavity through multiple ingates, and the formed multiple flows strongly interfere with each other, which aggravates the irregularity and disorder of the flow. For large castings, the heat absorption capacity of chilled iron is limited, and its continuous cooling ability is not good. Using low-pressure casting and other solutions can effectively reduce the turbulent flow phenomenon during pouring of the melt, but for large hub body castings, supporting large-scale low-pressure casting machines is not only costly, but also very difficult to implement.

Contents of the invention

The object of the present invention is to propose a pouring process for a large paddle hub body with simple steps in view of the above-mentioned conventional sand casting process in which molten metal enters the mold cavity and easily produces turbulent flow, resulting in large castings prone to casting defects such as pores , can effectively reduce the degree of turbulence during casting filling, and accelerate the solidification rate of large castings. The large hub body cast by this process has less precipitation and reactive pore defects.

In order to achieve the above object, the technical solution adopted by the present invention is: a large-scale paddle hub body pouring process, including the following steps: the melt enters the cavity from the bottom of the casting mold, and the flow direction of the melt when entering the cavity and the cavity The included angle of the bottom surface is 20-80°.

Further, the angle between the flow direction of the melt and the bottom surface of the cavity when it enters the cavity is 30-60°.

Further, when the melt enters the cavity in multiple strands, the angle between the flow direction of each strand and the bottom surface of the cavity is the same, and the angle between the flow direction of each strand and the radial direction of the melt inflow point on the bottom surface of the cavity Similarly, the preferred included angle between the melt flow direction and the radial direction of the melt inlet on the bottom surface of the cavity is 90°.

Further, a cooling system is provided in the sand core of the casting mold.

Another object of the present invention is to disclose a large hub body casting mold, including a cavity, an inner runner and a runner, and the runner is an annular channel arranged under the cavity, and the radius of the ring is the same as that of the hub The body radius is the same; the ingate is installed at the bottom of the cavity, one end is connected with the runner, and the other end is connected with the inside of the cavity; the angle between the axis of the ingate and the tangent of the runner is 20-80° .

Further, the angle between the axis of the ingate and the tangent of the runner is 30-60°, more preferably the angle between the axis of the ingate and the tangent of the runner is 60°.

Further, when there are multiple inrunners, the angle between each inrunner and runner is the same, and the included angle between the axis of each inrunner and the radial direction of the inrunner on the bottom surface of the cavity is the same.

Further, the cross-sections in the longitudinal direction of the runner and the inrunner are both rectangular, preferably square.

Further, a cooling water channel is arranged in the sand core of the casting mold.

Further, the water inlet of the cooling channel is set at the bottom of the mold, and the water outlet is set at the top of the mold.

The pouring process of the large propeller hub body of the present invention is simple and easy, and the casting mold structure is scientific and reasonable. Compared with the prior art, it has at least the following advantages:

1. The pouring process of the large propeller hub body of the present invention reduces the flow impact of the filling process through the bottom injection method; at the same time, when the melt enters the cavity, the angle between the flow direction and the bottom surface of the cavity is 20-80°, and the gravitational field or external force Under the action, the melt pouring obtains the initial speed, and the melt obtains the same direction of rotating filling flow in the cavity; the same direction of rotating filling flow makes the flow of the melt in the cavity in a laminar flow mode, which can avoid the melt (such as copper alloy melt) flow interference with each other when they enter the cavity vertically from multiple inflow runners, thereby reducing the occurrence of suction slag entrainment, which is beneficial to improving the quality of castings;

2. The circumferential melt rotation flow obtained in the cavity can improve the heat transfer coefficient between the casting/mold, thereby improving the cooling efficiency, accelerating the solidification rate, and reducing the solidification time by 1/10-3/10;

3. The sand core of the casting mold described in the present invention is provided with a cooling system, and the cooling system in the sand core can take away the heat of the sand core in time to cool the inside of the casting mold. The mutual cooperation of internal and external heat exchange accelerates the solidification rate of large hub body castings and reduces precipitation and reactive pore defects.

Description of drawings

Fig. 1 is the structural schematic diagram of embodiment 1 large propeller hub body mold;

Fig. 2 is the schematic diagram of the flow of the melt in the large propeller hub body casting mold of embodiment 1;

Figure 3 is a comparison between the hub body obtained in Example 1 and the hub body obtained by using the existing casting method, a is the hub body obtained by the existing casting method; b is the hub body obtained in Example 1;

Fig. 4 is an axial sectional view of the casting core of Example 2.

Detailed ways

The invention discloses a pouring process suitable for large castings whose basic outline is circular, and is especially suitable for the casting process of the propeller hub body of a large marine adjustable-pitch propeller.

The pouring process of the large hub body includes the following steps: the melt forms an initial velocity under the action of external force or gravity field, enters the cavity from the bottom of the casting mold, and the flow direction of the melt when entering the cavity is the same as that of the bottom surface of the cavity. The included angle is 20-80°. The angle between the flow direction of the melt and the bottom surface of the cavity when it enters the cavity is 30-60°, more preferably 60°. Under this angle, the swirling effect of the melt in the cavity is the best. When the melt enters the cavity in multiple strands, the angle between the flow direction of each strand and the bottom surface of the cavity is the same, and the angle between the flow direction of each strand and the radial direction of the melt inflow on the bottom surface of the cavity is the same, that is When the multi-strand melt enters the cavity, the flow direction of the melt is consistent along the circumferential flow direction of the cavity, so that the multi-strand melt does not interfere with each other. The melt enters the mold cavity at the above-mentioned pouring angle, which can make the melt flow in the same direction in the mold cavity. When they enter the cavity vertically, they generate flow interference with each other, thereby reducing the occurrence of suction slag entrainment. The circumferential melt rotation flow obtained in the cavity can improve the heat transfer coefficient between the casting/mold, thereby improving the cooling efficiency and accelerating the solidification rate.

The melt enters the cavity at the above pouring angle until it fills the entire cavity, and after cooling, the casting mold is removed to obtain the hub body. In order to increase the cooling rate of the melt, reduce the cooling time, and alleviate the precipitation and reactive pore defects, a cooling system is also arranged in the sand core of the casting mold of the present invention. The cooling system includes air cooling or water cooling, preferably the cooling system is water cooling.

The casting mold in the present invention can be selected from sand mold, metal mold or ceramic mold, preferably sand mold. It can be understood that the pouring process described in the present invention is also applicable to the pouring of other large castings whose basic outline is circular.

The invention also discloses a large hub body casting mold, which includes a cavity, an inner runner and a runner, the runner is an annular channel arranged under the cavity, and the radius of the ring is the same as that of the hub body (the The outer contour of the hub body is cylindrical, and the bottom surface of the casting mold used for casting is also circular); the inner sprue is installed at the bottom of the cavity, one end is connected with the runner, and the other end is connected with the inside of the cavity; The included angle between the axis of the runner and the tangent of the runner is 20-80°. The included angle between the axis of the ingate and the tangent of the runner is 30-60°, more preferably the angle between the axis of the ingate and the tangent of the runner is 60°, and the swirl effect generated at this time is the best. Unless otherwise specified, the included angle between the straight line and the plane in the present invention = the included angle between the straight line and its projection in the plane.

When the melt flows under the action of the gravity field (gravity casting), the large hub body mold also includes a vertical runner connected with the runner.

When there are multiple inrunners, the included angles between each inrunner and the runner are the same, and the included angles between the axis of each inrunner and the radial direction of the inner runner on the bottom of the cavity are the same, so that the melt enters The motion trajectories behind the cavity are the same without interference with each other. The number of inrunners is selected according to the size of the hub body, for example, there are 4-6 inrunners with a diameter of 1.7 meters in the hub body, preferably 5, and the inrunners are evenly arranged on the runner.

The cross-sections of the runner and the inner runner in the length direction of the present invention are both rectangular, preferably square.

A cooling water channel is arranged in the sand core of the casting mold, and the cooling water channel is fixed on the bottom of the sand box through a rigid base. In order to enhance the cooling water effect, the water inlet of the cooling channel is arranged at the bottom of the mold, and the water outlet is arranged at the top of the mold. The cooling water channel is made of a material with excellent thermal conductivity, preferably made of red copper. When the casting mold is used to cast a large propeller hub body casting, the cooling water in the cooling water channel can take away the heat of the sand core in time to realize the internal cooling of the casting. The mutual cooperation of internal and external heat exchange accelerates the solidification rate of large hub body castings and reduces the precipitation and reactive pore defects.

The present invention is further described below in conjunction with embodiment:

Example 1

Fig. 1 is a schematic structural view of the large-scale hub body mold of embodiment 1; Fig. 2 is a schematic diagram of the flow of melt in the large-scale hub body mold of embodiment 1; Fig. 3 is the hub body obtained in embodiment 1 and the existing Comparison of the hub body obtained by the casting method, a is the hub body obtained by the existing casting method; b is the hub body obtained in Example 1;

This embodiment discloses a large propeller hub body casting mold, which is used for casting the propeller hub body of a large marine adjustable pitch propeller with a diameter of 1.7 meters and a weight of about 8 tons. The casting mold of the large propeller hub body adopts the side bottom pouring type pouring system as a whole. For the lower annular channel, the radius of the ring is the same as the radius of the hub body, and the cross-section of the runner is square, with a side length of 60 mm; five ingates 2 are evenly arranged on the runner 1 around the entire circumference, and the inrunner 2 is pierced At the bottom of the cavity 3, one end is connected to the runner 1, and the other end is connected to the inside of the cavity 3. The cross section of the runner 2 is square, with a side length of 40 mm. In this embodiment, the large-scale paddle hub body casting mold also includes a vertical sprue 4 , and the lower end of the vertical sprue 4 communicates with the runner 1 .

The included angle between the axis of the runner 2 and the tangent of the runner 1 is 60°. The inrunner 2 intersects with the runner 1 in an unconventional perpendicular manner, but at a certain angle (along the downstream direction of pouring). After computer numerical simulation analysis and optimization, the swirl effect generated at 60 degrees is the best.

The process of casting the hub body with the above-mentioned large hub body mold includes the following steps: the melt flows through the vertical runner 4, the runner 1 and the inner runner 2 in sequence under the action of the gravity field, and then enters from the bottom of the casting mold Cavity 3, the melt enters cavity 3 in five strands, and the angle between the flow direction of each strand and the bottom surface of cavity 3 is the same as 60°, and the flow direction of each strand of melt is the same as that of the bottom surface of cavity 3. The included angles in the radial direction are the same. The swirling flow of the melt entering the cavity 3 is in a stable laminar flow mode as shown in Figure 2 .

In this embodiment, the included angle between the axis of the runner and the tangent of the runner is 60°, which can effectively reduce the degree of turbulence during filling of the casting and accelerate the solidification rate of the large casting. There are few precipitated and reactive porosity defects. The comparative effect of the hub body obtained in this embodiment and the hub body obtained by conventional sand casting is shown in Figure 3, a is the hub body obtained by conventional sand casting, b is the hub body obtained in this embodiment, It can be seen that the inner shrinkage cavity (looseness) and slag inclusions of the hub body casting obtained in this embodiment are significantly less than those obtained by conventional sand casting. According to the comparison between theoretical analysis and computer numerical simulation, it is found that the swirl pouring method promotes the heat transfer efficiency of castings/molds and can reduce the solidification time by about 1/10.

Example 2

Fig. 4 is an axial sectional view of the casting core of Example 2.

This embodiment is basically the same as Embodiment 1, the difference is that the casting core 5 of the large propeller hub body mold in this embodiment is provided with a cooling water channel 6, as shown in Figure 4, the cooling water channel 6 is fixed on the bottom of the sand box through a rigid base . In order to enhance the cooling water 7 effect, the water inlet 8 of the cooling channel 6 is arranged at the bottom of the mold, and the water outlet 9 is arranged at the top of the mold. The cooling channel 6 is made of red copper. When the casting mold is used to cast a large propeller hub body casting, the heat of the sand core can be taken away in time by the cooling water 7 in the cooling water channel 6 to realize the effect of cooling from the inside. The mutual cooperation of internal and external heat exchange accelerates the solidification rate of large hub body castings and reduces the precipitation and reactive pore defects.

Using computer numerical simulation analysis, on the premise of not damaging the strength of the casting core, when the diameter of the cooling channel 6 is 120 mm and the water flow rate is controlled at 1.6 m/s, the solidification time can be reduced by about 3/10. It can be seen that setting the cooling water channel 6 in the casting core can effectively solve the problem that the casting core 5 inside the large marine adjustable pitch propeller hub body is very large. When the hub body solidifies, a large amount of heat is accumulated inside the casting core and cannot be discharged, resulting in As the temperature rises, the heat transfer effect becomes poor.

Example 3

This embodiment is basically the same as Embodiment 1, except that the included angle between the axis of the sprue of the large hub body casting mold and the tangent line of the runner in this embodiment is 30°.

In this embodiment, the included angle between the axis of the inner runner and the tangent of the runner is 30°, which can effectively reduce the degree of turbulence during filling of the casting and accelerate the solidification rate of the large casting. There are few precipitated and reactive porosity defects.

Example 4

This embodiment is basically the same as Embodiment 2, the difference is that the casting core of the large propeller hub body in this embodiment is provided with an air-cooling passage, the air inlet of the air-cooling passage is arranged at the bottom of the mold, and the air outlet is arranged at The top of the mold.

The casting mold of the large hub body in this embodiment can cast a large hub body with few precipitated and reactive pore defects.

The present invention is not limited to the pouring process and casting mold of the large hub body described in the above embodiments, wherein the change of the size of the large hub body, the change of the angle between the flow direction of the melt and the bottom surface of the cavity when the melt enters the cavity and cooling System changes are within the protection scope of the present invention.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. A pouring process for a large paddle hub body, characterized in that it comprises the following steps: the melt enters the cavity from the bottom of the casting mold, and the flow direction of the melt entering the cavity and the angle between the bottom surface of the cavity are 20- 80°. 2. The pouring process for the large hub body according to claim 1, wherein the angle between the flow direction of the melt and the bottom surface of the cavity when it enters the cavity is 30-60°. 3. According to claim 1 or 2, the pouring process of the large hub body is characterized in that, when the melt enters the cavity in multiple strands, the angle between the flow direction of each strand and the bottom surface of the cavity is the same, and each The angle between the flow direction of the strand melt and the radial direction of the melt inflow on the bottom surface of the cavity is the same. 4. The pouring process for large hub body according to claim 1 or 2, characterized in that a cooling system is arranged in the sand core of the casting mold. 5. A casting mold for a large hub body, characterized in that it includes a cavity, an inner runner and a runner, the runner is an annular passage arranged under the cavity, and the radius of the ring is the same as that of the hub body The ingate is installed at the bottom of the cavity, one end is connected with the runner, and the other end is connected with the inside of the cavity; the angle between the axis of the ingate and the tangent of the runner is 20-80°. 6 . The large hub body casting mold according to claim 5 , wherein the included angle between the axis of the inner runner and the tangent line of the runner is 30-60°. 7. The large hub body casting mold according to claim 5 or 6, characterized in that, when there are multiple inrunners, the included angles between each inrunner and runner are the same, and each inner runner The included angle between the axis of the runner and the radial direction of the runner at the bottom of the cavity is the same. 8. The large hub body casting mold according to claim 5 or 6, characterized in that, the cross-sections in the longitudinal direction of the runner and the inner runner are both rectangular. 9 . The large hub body casting mold according to claim 5 , wherein a cooling water channel is arranged in the sand core of the casting mold. 10 . The large hub body casting mold according to claim 9 , wherein the water inlet of the cooling channel is arranged at the bottom of the mold, and the water outlet is arranged at the top of the mold. 11 .