Centrifugal casting hollow plunger process and hollow plunger

Abstract

The invention relates to a centrifugal casting hollow plunger process and a hollow plunger, comprising: S1, loading a plunger mold onto a centrifuge and starting the centrifuge; S2, pouring an outer layer of molten iron with a temperature of T1 into the plunger mold, and withdrawing a pouring port after pouring, wherein the outer layer of molten iron is cold hard cast iron molten iron and is used for casting the outer layer of the hollow plunger; S3, after the outer layer of molten iron is cooled to T2, pouring an inner layer of molten iron with a temperature of T3, so that the inner layer of molten iron and the outer layer of molten iron are completely combined, wherein the inner layer of molten iron is gray cast iron molten iron or ductile iron molten iron and is used for casting the inner layer of the hollow plunger; S4, when the inner layer of molten iron is cooled to T4, closing the centrifuge, erecting the plunger mold and placing it in a bottom mold; S5, pouring a bottom layer of molten iron with a temperature of T5, wherein the bottom layer of molten iron is gray cast iron molten iron or ductile iron molten iron. The present invention adopts a centrifugal compounding process to greatly increase the alloy content of the surface material of the hollow plunger, thereby improving the surface hardness, wear resistance, corrosion resistance and other properties.

Description

Technical Field

[0001] The invention relates to the field of plungers, and in particular to a centrifugal casting hollow plunger process and a hollow plunger. Background Art

[0002] At present, the plungers of hydraulic plunger cylinders used in hydraulic equipment are generally cast by conventional high-phosphorus chilled cast iron. Cast iron plungers have the following disadvantages:

[0003] 1. The surface hardness is low (HRC≤50), it is not wear-resistant, easy to corrode, and has poor mechanical properties. It is easy to scratch its surface during use. If the surface hardness is forcibly increased, its mechanical properties will be greatly reduced, and serious problems such as cracking and breakage will easily occur.

[0004] 2. The conventionally cast plunger has loose structure and low tensile strength, especially the hollow plunger is prone to oil leakage, pressure drop and other problems.

[0005] 3. The surface of the conventionally cast plunger is prone to casting defects such as pores, sand holes, inclusions, etc., which affect the surface quality. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a centrifugal casting hollow plunger process, which adopts a centrifugal composite process to greatly increase the alloy content of the hollow plunger surface material, thereby improving the surface hardness, wear resistance, corrosion resistance and other properties.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a centrifugal casting hollow plunger process, comprising:

[0008] S1, loading the plunger mold onto a centrifuge and turning on the centrifuge;

[0009] S2, pouring the outer layer of molten iron at the temperature of T1 into the plunger mold, and removing the gate after pouring. The outer layer of molten iron is chilled cast iron, which is used to cast the outer layer of the hollow plunger;

[0010] S3, after the outer layer of molten iron is cooled to T2, an inner layer of molten iron at a temperature of T3 is poured in, so that the inner layer of molten iron is completely combined with the outer layer of molten iron. The inner layer of molten iron is molten gray cast iron or ductile iron, which is used to cast the inner layer of the hollow plunger;

[0011] S4, when the inner layer of molten iron is cooled to T4, the centrifuge is turned off, the plunger mold is erected and placed in the bottom mold;

[0012] S5, pouring bottom molten iron with a temperature of T5, the bottom molten iron is gray cast iron or ductile iron, and is used to cast the hollow plunger bottom at the inner bottom of the inner layer of the hollow plunger.

[0013] Further, T1 is 1450°C;

[0014] and / or T2 is 1200°C;

[0015] and / or T3 in the range of 1450-1500°C;

[0016] and / or T4 is 1200°C;

[0017] and / or T5 is in the range of 1450-1480°C.

[0018] To further increase the compressive strength of the outer wall of the hollow plunger bottom at the interface, the process also includes:

[0019] S6, using a pressing die to press the bottom molten iron, wherein the lower surface of the pressing die is a downwardly convex arc surface, so that the upper surface of the bottom of the hollow plunger forms a downwardly concave arc surface;

[0020] S7, demoulding after cooling.

[0021] Furthermore, the arc surface of the lower surface of the pressing mold includes a central plane and an arc-shaped chamfered surface surrounding the periphery of the central plane.

[0022] Furthermore, the pressing die includes a pressing portion and a connecting rod connected to the center position of the upper surface of the pressing portion, and the connecting rod is perpendicular to the pressing portion.

[0023] Furthermore, a plurality of holes are provided at intervals on the upper end of the connecting rod, and the plurality of holes are arranged in a vertical direction.

[0024] Further, the mass percentage of each component of the chilled cast iron molten iron is:

[0025] C: 2.90%-3.6%; Si: 0.25%-0.8%; Mn: 0.5-1%; P: 0-0.4%; S: 0-0.1%; Cr: 0.5-1.5%; Mo: 0.2-0.4%; Ni: 0.5-1.5%; the balance is Fe.

[0026] The present invention also provides a centrifugally cast hollow plunger, comprising a hollow plunger outer layer, a hollow plunger inner layer and a hollow plunger bottom arranged in sequence from the outside to the inside, the hollow plunger outer layer and the hollow plunger inner layer are both centrifugally cast, the hollow plunger bottom is located at the inner bottom of the hollow plunger inner layer, the hollow plunger outer layer is cold-hardened cast iron, and the hollow plunger inner layer and the hollow plunger bottom are made of gray cast iron or ductile iron.

[0027] Furthermore, the upper surface of the bottom of the hollow plunger is a downwardly concave arc surface.

[0028] After adopting the above technical solution, the present invention has the following beneficial effects:

[0029] 1. The present invention adopts a centrifugal composite production process, and the outer layer of the hollow plunger is made of chilled cast iron, which greatly increases the alloy content of the surface material of the hollow plunger, thereby achieving a significant enhancement of the main working performances such as surface hardness (HRC50-60), wear resistance, and corrosion resistance;

[0030] 2. After high-speed rotation in the centrifuge, the surface structure of the working layer is uniform and fatal, without defects such as pores, sand holes, looseness, etc.; the density of the working layer can be increased by more than 2% compared with gravity casting under the same conditions, and the service life can be increased by 25% to 100%;

[0031] 3. The inner layer and bottom of the hollow plunger are made of gray cast iron or ductile iron, which improves the tensile and compressive mechanical properties of the hollow plunger and eliminates quality problems such as cracking and breaking;

[0032] 4. The hardness of the entire hardness layer changes very little, and the hardness drop from the outside to the inside does not exceed 5HS. The hardness layer has a uniform structure, which ensures the stability of the plunger quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the centrifugally cast hollow plunger of the present invention;

[0034] Figure 2 It is a structural schematic diagram of the pressing mold of the present invention;

[0035] Figure 3 It is a structural schematic diagram of the pressing die of the present invention pressing down the bottom of the centrifugal plunger. DETAILED DESCRIPTION

[0036] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0037] Embodiment 1

[0038] like Figure 1 , 2 , 3, a centrifugal casting hollow plunger process, comprising:

[0039] S1, loading the plunger mold onto a centrifuge and turning on the centrifuge;

[0040] S2, pouring the outer layer of molten iron at a temperature of T1 into the plunger mold, and removing the gate after pouring. The outer layer of molten iron is chilled cast iron, which is used to cast the outer layer 1 of the hollow plunger;

[0041] S3, after the outer layer of molten iron is cooled to T2, an inner layer of molten iron at a temperature of T3 is poured in to completely combine the inner layer of molten iron with the outer layer of molten iron. The inner layer of molten iron is molten gray cast iron or ductile iron, which is used to cast the inner layer 2 of the hollow plunger;

[0042] S4, when the inner layer of molten iron is cooled to T4, the centrifuge is turned off, the plunger mold is erected and placed in the bottom mold;

[0043] S5, pouring bottom molten iron with a temperature of T5, the bottom molten iron is gray cast iron or ductile iron, and is used to cast the hollow plunger bottom 3 on the inner bottom of the hollow plunger inner layer 2;

[0044] Specifically, the outer layer 1 of the hollow plunger is made of cold-hardened cast iron, which greatly increases the alloy content of the surface material of the hollow plunger, thereby achieving a significant enhancement of the main working performance such as surface hardness (HRC50-60), wear resistance, and corrosion resistance; the material of the inner layer 2 of the hollow plunger and the bottom 3 of the hollow plunger is made of gray cast iron or ductile iron, thereby improving the tensile and compressive mechanical properties of the hollow plunger, and eliminating quality problems such as cracking and breakage.

[0045] S6, use a pressing mold 10 to press the bottom molten iron, the lower surface of the pressing mold 10 is a downward convex arc surface, so that the upper surface of the hollow plunger bottom 3 forms a downward concave arc surface; the upper surface of the hollow plunger bottom 3 forms an arc, which can increase the compressive strength of the outer wall of the hollow plunger bottom 3 at the interface.

[0046] In this embodiment, the grey cast iron may be HT250 and the ductile iron may be QT400.

[0047] S7, demoulding after cooling.

[0048] This embodiment adopts a centrifugal composite production process. After high-speed rotation in a centrifuge, the surface structure of the working layer is uniform and has no defects such as pores, sand holes, and looseness. The density of the working layer can be increased by more than 2% compared with gravity casting under the same conditions, and the service life can be increased by 25% to 100%.

[0049] In this embodiment, generally, T1 is 1450° C., T2 is 1200° C., T3 is in the range of 1450-1500° C., T4 is 1200° C., and T5 is in the range of 1450-1480° C. During the production process, infrared temperature is measured and timed.

[0050] In this embodiment, before S1, it also includes: according to products of different specifications, respectively calculating the weight of molten iron required for the hollow plunger outer layer 1, the hollow plunger inner layer 2 and the hollow plunger bottom 3, and smelting the molten iron.

[0051] In this embodiment, if Figure 2As shown, the pressing die 10 includes a pressing part 101 and a connecting rod 102 connected to the center position of the upper surface of the pressing part 101, and the connecting rod 102 is perpendicular to the pressing part 101. The upper end of the connecting rod 102 is provided with a plurality of holes 103 at intervals, and the plurality of holes 103 are arranged in the vertical direction. The arc surface of the lower surface of the pressing part 101 includes a central plane and an arc chamfered surface surrounding the periphery of the central plane; the upper end of the connecting rod 102 extends upward beyond the plunger mold, and the pressing part 101 of the pressing die 10 can be adjusted horizontally through the relative position of the hole 103 and the plunger mold to prevent the pressing part 101 from being skewed.

[0052] In this embodiment, the mass percentage of each component of the chilled cast iron molten iron may be:

[0053] C: 2.90%-3.6%; Si: 0.25%-0.8%; Mn: 0.5-1%; P: 0-0.4%; S: 0-0.1%; Cr: 0.5-1.5%; Mo: 0.2-0.4%; Ni: 0.5-1.5%; the balance is Fe.

[0054] Embodiment 2

[0055] like Figure 1 , 2 As shown in Figure 3, a centrifugally cast hollow plunger comprises a hollow plunger outer layer 1, a hollow plunger inner layer 2 and a hollow plunger bottom 3 which are arranged in sequence from the outside to the inside, the hollow plunger outer layer 1 and the hollow plunger inner layer 2 are both centrifugally cast, the hollow plunger bottom 3 is located at the inner bottom of the hollow plunger inner layer 2, the hollow plunger outer layer 1 is cold-hardened cast iron, and the hollow plunger inner layer 2 and the hollow plunger bottom 3 are made of gray cast iron or ductile iron.

[0056] like Figure 1 , 3 As shown, the upper surface of the hollow plunger bottom 3 is a downwardly concave arc surface, which includes a central plane and an arc-shaped chamfered surface surrounding the central plane.

[0057] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A centrifugal casting hollow plunger process, characterized in that: include: S1, loading the plunger mold onto a centrifuge and turning on the centrifuge; S2, pouring an outer layer of molten iron at a temperature of T1 into the plunger mold, and removing the gate after pouring. The outer layer of molten iron is chilled cast iron and is used to cast the outer layer of the hollow plunger (1); S3, after the outer layer of molten iron is cooled to T2, an inner layer of molten iron at a temperature of T3 is poured in, so that the inner layer of molten iron is completely combined with the outer layer of molten iron. The inner layer of molten iron is molten gray cast iron or ductile iron, and is used to cast the inner layer of the hollow plunger (2); S4, when the inner layer of molten iron is cooled to T4, the centrifuge is turned off, the plunger mold is erected and placed in the bottom mold, T4 is 1200℃; S5, pouring bottom molten iron at a temperature of T5, the bottom molten iron being gray cast iron or ductile iron, for casting a hollow plunger bottom (3) on the inner bottom of the hollow plunger inner layer (2); S6, using a pressing die (10) to press the bottom molten iron, wherein the lower surface of the pressing die (10) is a downwardly convex arc surface, so that the upper surface of the hollow plunger bottom (3) forms a downwardly concave arc surface, and the outer diameter of the lower surface of the pressing die (10) matches the inner diameter of the inner layer of the hollow plunger; S7, after cooling and demoulding, the hardness of the outer layer (1) of the hollow plunger and the inner layer (2) of the hollow plunger decreases from the outside to the inside by no more than 5HS.

2. The centrifugal casting hollow plunger process according to claim 1, characterized in that: T1 is 1450℃; and / or T2 is 1200°C; and / or T3 in the range of 1450-1500°C; and / or T5 is in the range of 1450-1480°C.

3. The centrifugal casting hollow plunger process according to claim 1, characterized in that: The arc surface of the lower surface of the pressing die (10) comprises a central plane and an arc-shaped chamfered surface surrounding the central plane.

4. The centrifugal casting hollow plunger process according to claim 1 or 3, characterized in that: The pressing die (10) comprises a pressing portion (101) and a connecting rod (102) connected to the center of the upper surface of the pressing portion (101), wherein the connecting rod (102) is perpendicular to the pressing portion (101).

5. The centrifugal casting hollow plunger process according to claim 4, characterized in that: A plurality of holes (103) are provided at intervals on the upper end of the connecting rod (102), and the plurality of holes (103) are arranged in a vertical direction.

6. The centrifugal casting hollow plunger process according to claim 1, characterized in that: The mass percentage of each component of the chilled cast iron molten iron is: C: 2.90%-3.6%; Si: 0.25%-0.8%; Mn: 0.5-1%; P：0-0.4%； S: 0-0.1%; Cr: 0.5-1.5%; Mo: 0.2-0.4%; Ni: 0.5-1.5%; the balance is Fe.

7. A hollow plunger prepared by the centrifugal casting hollow plunger process according to any one of claims 1 to 6, characterized in that: The hollow plunger comprises a hollow plunger outer layer (1), a hollow plunger inner layer (2) and a hollow plunger bottom (3) which are arranged in sequence from the outside to the inside. The hollow plunger outer layer (1) and the hollow plunger inner layer (2) are both centrifugally cast. The hollow plunger bottom (3) is located at the inner bottom of the hollow plunger inner layer (2). The hollow plunger outer layer (1) is chilled cast iron. The hollow plunger inner layer (2) and the hollow plunger bottom (3) are made of grey cast iron or ductile iron. The upper surface of the hollow plunger bottom (3) is a downwardly concave arc surface.

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