CN113909435A - Casting method of ductile iron small-sized hydraulic part - Google Patents
Casting method of ductile iron small-sized hydraulic part Download PDFInfo
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- CN113909435A CN113909435A CN202110416840.6A CN202110416840A CN113909435A CN 113909435 A CN113909435 A CN 113909435A CN 202110416840 A CN202110416840 A CN 202110416840A CN 113909435 A CN113909435 A CN 113909435A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/08—Features with respect to supply of molten metal, e.g. ingates, circular gates, skim gates
- B22C9/082—Sprues, pouring cups
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Abstract
The invention provides a casting method of a small-sized hydraulic part of ductile iron. According to the casting method of the small-sized hydraulic part of the ductile iron, molten iron enters from the bottom, so that an oxide film generated in a casting system is prevented from being rolled into bubbles to enter a cavity, the defect of holes is remained in a casting, the actual flowing area of the molten iron in the casting system is gradually enlarged, the static pressure exerted on the molten iron is reduced, the inflow molten iron speed is reduced, the molten iron splashing phenomenon is eliminated, the problem of bubble rolling caused by reoxidation is avoided, the molten iron filling process is stable, the molten iron is pure, and the casting quality is high.
Description
Technical Field
The invention relates to a casting method, in particular to a casting method of a ductile iron small-sized hydraulic part.
Background
In the production process of castings, particularly small-sized ductile iron hydraulic parts, the problem of casting scrapping caused by internal holes after machining often occurs, so that the loss of casting and machining links is large, the production cost is increased, the final assembly progress is seriously influenced, and the delivery of the whole machine is delayed.
The traditional theory considers that the internal hole of the hydraulic part is the defect of shrinkage cavity and shrinkage porosity and is caused by shrinkage and insufficient molten iron feeding when molten iron is solidified. Therefore, the top surface is fed by a large riser, the thick part is provided with an external chill for enhancing cooling, the feeding efficiency is improved, and the pouring temperature is reduced to reduce the total shrinkage. However, these measures cannot completely eliminate the problem of voids, and are troublesome in operation and low in casting yield (molten iron utilization).
The new theory considers that the internal hole of the hydraulic part is a pore defect and is caused by that molten iron in a cavity is disordered and involved into an oxide film to generate bubbles and the bubbles are left in the molten iron (casting) due to a gating system. Therefore, the solution to the problem is to change the gating system to a top-pouring or side-pouring mode in the past to a bottom-pouring open mode so as to avoid the oxide film from being rolled into the bubble to enter the cavity, and to reduce the molten iron inflow speed so as to avoid the problem that the oxide film is rolled into the bubble again due to splashing caused by too high inflow speed.
Disclosure of Invention
【1】 Technical problem to be solved
The invention aims to provide a casting method of a small ductile iron hydraulic part, which has the advantages of simple process, low cost and good forming effect.
【2】 Technical scheme for solving problems
The invention provides a casting method of a ductile iron small-sized hydraulic part, wherein liquid metal enters a cavity from the bottom of the cavity of a sand mold.
Further, a pouring gate 41 with an open upper end is arranged on the sand mold, the pouring gate is communicated to the bottom of the cavity through a flow channel, and a dead head 31 is arranged at the top of the cavity.
Further, one or more liquid inlets 44 are formed in the bottom of the cavity, and the liquid inlets 44 are communicated with the pouring gate through the runner.
Further, the horizontal height of the pouring gate is higher than that of the highest point of the cavity, and the horizontal height difference between the pouring gate and the cavity is greater than or equal to 5 cm.
Further, the sand mold comprises an upper sand mold 11 and a lower sand mold 12, a cavity is formed between the lower end of the upper sand mold and the upper end of the lower sand mold, and a sand core 21 is arranged in the cavity and forms the cavity 100.
Further, the runner includes a first runner 42, a second runner 43 and a third runner 44 which are connected in sequence, the first runner is vertically arranged, the top of the first runner is communicated with the sprue gate, the second runner is horizontally arranged, and the third runner is communicated with the bottom of the cavity.
Further, the sectional area Σ of the first flow path 42, the sectional area Σ of the second flow path 43, and the sectional area Σ of the third flow path are increased in this order.
Further, Σ directly: Σ horizontal: Σ — 1: (1.5-2.0): (2.0-2.5).
Furthermore, the rising height of the liquid metal in the cavity during casting is more than or equal to 10mm/s and less than or equal to 50 mm/s.
Further, the pouring time T satisfies:
μ: the material coefficient is 1-1.1 of cast iron, 0.8-0.9 of ductile iron and 0.6-0.8 of steel;
g, processing: the mass of the valve body casting is Kg;
b: the thinnest part of the casting has the wall thickness of unit mm.
【3】 Advantageous effects
According to the casting method of the small-sized hydraulic part of the ductile iron, molten iron enters from the bottom, and the defect that holes are left in a casting due to the fact that an oxide film generated in a casting system is rolled into a cavity to form bubbles to enter the cavity is avoided. The actual flowing area of the molten iron in the pouring system is gradually enlarged, the static pressure applied to the molten iron is reduced, the speed of the inflow molten iron is reduced, the splashing phenomenon of the molten iron is eliminated, and the problem of bubble inclusion caused by reoxidation is solved. The molten iron mold filling process is stable, the molten iron is pure, and the casting quality is high. The method for eliminating the small-sized hydraulic parts of the ductile iron has the advantages of simple process and convenient operation, improves the finished product rate of castings and reduces the production cost. The casting mould does not need to be provided with a large riser or an external chill, the production efficiency is improved, the parts are timely provided, and the delivery cycle of the whole machine is ensured.
Drawings
FIG. 1 is a schematic illustration of the casting of a ductile iron compact hydraulic press of the present invention;
Detailed Description
The following describes embodiments of the present invention in detail with reference to the accompanying drawings.
Referring to fig. 1, the present invention provides a method for casting a small hydraulic press of ductile iron, by which a small casting produced by the method can eliminate void defects of the casting.
The invention is characterized in that liquid metal enters the cavity from the bottom of the cavity of the sand mold. The liquid metal refers to a metal which is melted at a high temperature, generally called molten iron, for example, iron can be melted at a temperature of 1538 ℃, and the melting point of iron is 1538 ℃ and the boiling point of iron is 2750 ℃. The iron in the blast furnace contains carbon, namely iron alloy, the melting point of the alloy is lower than the melting point of the simple substance of the alloy, so that the iron in the blast furnace is melted between 1100 ℃ and 1200 ℃; for another example, steel is a generic term for iron alloys containing a small amount of carbon, the melting point of which is lower than that of the metals of which it is composed, 1535 ℃ for iron and about 1500 ℃ for ordinary steel.
A pouring gate 41 with an open upper end is arranged on the sand mold, the whole pouring gate is cylindrical or in a round table shape with a large upper end and a small lower end, the pouring gate (bottom) is communicated to the bottom of the cavity through a runner, and a riser 31 is arranged at the top of the cavity; one or more liquid inlets are arranged at the bottom of the cavity and are communicated with the pouring gate through a runner. Specifically, the sand mold comprises an upper mold 11 and a lower mold 12, wherein cavities are respectively arranged on the lower bottom surface of the upper mold 11 and the upper bottom surface of the lower mold 12, the two cavities are mutually covered to form a sealed cavity, a sand core 21 is arranged in the sealed cavity, so that a cavity 100 for casting forming is formed, a liquid inlet is arranged at the lower end of the cavity, a riser is arranged at the top of the cavity, and a contact surface between the upper mold and the lower mold forms a molding surface 112; the liquid inlet 44 is arranged at the bottom of the cavity, namely on the lower die, and is communicated to a pouring gate 41 arranged on the top surface of the upper die through a third flow channel 44, a second flow channel 43 and a first flow channel 42 which are connected in sequence; in order to reduce the static pressure, reduce the velocity of the inflowing molten iron, and eliminate the splashing phenomenon of the molten iron, thereby avoiding the problem of bubble entrainment caused by reoxidation, in the present embodiment, the pipe diameters of the runners are sequentially increased from the inlet end to the outlet end, that is, the sectional area Σ straight of the first runner 42 is smaller than the sectional area Σ horizontal of the second runner 43 is smaller than the sectional area Σ horizontal of the third runner, preferably, Σ straight: Σ horizontal: Σ — 1: (1.5-2.0): (2.0-2.5), it can make inside molten iron reach better mobility, and can avoid too big static pressure, has reduced the molten iron velocity of flow of exit end, has eliminated the molten iron phenomenon of splashing in the die cavity to avoid because the bubble that the molten iron reoxidation brought is drawn into the problem, whole pouring process molten iron fills the type stably, and the pure oxide film that does not have of molten iron, casting quality is high. The level height of the pouring gate is higher than that of the highest point of the cavity, the level height difference between the pouring gate and the cavity is more than or equal to 5cm, preferably 8cm, molten iron can fully enter each corner, particularly the top position of the cavity, and under the height difference, certain pressure can be generated, and the quality of castings is improved.
In order to achieve better pouring quality, the rising height of the liquid metal in the cavity during pouring is more than or equal to 10mm/s and less than or equal to 50 mm/s.
The pouring time T satisfies:
wherein mu is a material coefficient, cast iron is 1-1.1 (inclusive), ductile iron is 0.8-0.9 (inclusive), and steel is 0.6-0.8 (inclusive); g is the mass of the valve body casting, and the unit is Kg; b: the average wall thickness of the casting is in mm.
For example, if cast iron is used, the coefficient mu is 1, the workpiece mass G is 4Kg, and the average wall thickness b is 200mm,
during pouring, molten iron is injected from a pouring gate at the top of the upper die, and the molten iron enters the cavity along the runner, namely the molten iron sequentially passes through the first runner, the second runner and the third runner and then enters the cavity through a liquid inlet formed at the bottom of the cavity; in the molten iron injection process, as the actual flowing area of the molten iron in the system (runner) is gradually enlarged, the static pressure applied to the molten iron is reduced, the inflow molten iron speed is reduced, and the molten iron splashing phenomenon is eliminated, so that the problem of bubble inclusion caused by reoxidation is avoided, the molten iron filling process is stable, the molten iron is pure, and the casting quality is high; along with the continuous inflow of molten iron, the liquid level in the cavity gradually rises, and air above the cavity is extruded out of the cavity through a riser in the rising process; until the height of the molten iron is higher than that of the cavity, part of the molten iron enters a riser from bottom to top; the runner and the cavity are integrally formed into a communicating vessel, the liquid levels of the runner and the cavity are the same (in an unset state), after solidification, a product in the sand mold is connected with metal in the runner, after the product and the runner are taken out together, and redundant metal connected to the side wall of the product is removed through machining, including the metal in the runner and the redundant metal on a dead head.
According to the casting method of the small-sized hydraulic part of the ductile iron, molten iron enters from the bottom, and the defect that holes are left in a casting due to the fact that an oxide film is rolled into a cavity to form bubbles caused by a casting system is avoided. The actual flowing area of the molten iron in the pouring system is gradually enlarged, the static pressure applied to the molten iron is reduced, the speed of the inflow molten iron is reduced, the splashing phenomenon of the molten iron is eliminated, and the problem of bubble inclusion caused by reoxidation is solved. The molten iron mold filling process is stable, the molten iron is pure, and the casting quality is high. The method for eliminating the small-sized hydraulic parts of the ductile iron has the advantages of simple process and convenient operation, improves the finished product rate of castings and reduces the production cost. The casting mould does not need to be provided with a large riser or an external chill, the production efficiency is improved, the parts are timely provided, and the delivery cycle of the whole machine is ensured.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the technical principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The casting method of the ductile iron small-sized hydraulic part is characterized by comprising the following steps of: and liquid metal enters the cavity from the bottom of the cavity of the sand mold.
2. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the sand mold is provided with a pouring gate 41 with an open upper end, the pouring gate is communicated to the bottom of the cavity through a flow channel, and the top of the cavity is provided with a riser 31.
3. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: one or more liquid inlets are formed in the bottom of the cavity and communicated with the pouring gate through the runner.
4. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the horizontal height of the pouring gate is higher than that of the highest point of the cavity, and the horizontal height difference between the pouring gate and the cavity is more than or equal to 5 cm.
5. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the sand mold die comprises an upper sand mold 11 and a lower sand mold 12, a cavity is formed between the lower end of the upper sand mold and the upper end of the lower sand mold, a sand core 21 is arranged in the cavity, and the cavity 100 is formed.
6. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the runner comprises a first runner 42, a second runner 43 and a third runner 44 which are connected in sequence, the first runner is vertically arranged, the top of the first runner is communicated with the sprue gate, the second runner is horizontally arranged, and the third runner is communicated with the bottom of the cavity.
7. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the sectional area Σ of the first flow path 42, the sectional area Σ of the second flow path 43, and the sectional area Σ of the third flow path increase in this order.
8. The method of casting a ductile iron compact hydraulic press according to claim 7, wherein: sigma is as follows: Σ horizontal: Σ — 1: (1.5-2.0): (2.0-2.5).
9. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the rising height of the liquid metal in the cavity during casting is more than or equal to 10mm/s and less than or equal to 50 mm/s.
10. The method of casting a ductile iron compact hydraulic press according to claim 1, wherein: the pouring time T satisfies:
μ: the material coefficient is 1-1.1 of cast iron, 0.8-0.9 of ductile iron and 0.6-0.8 of steel;
g, processing: the mass of the valve body casting is Kg;
b: the thinnest part of the casting has the wall thickness of unit mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202110416840.6A CN113909435A (en) | 2021-04-19 | 2021-04-19 | Casting method of ductile iron small-sized hydraulic part |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110416840.6A CN113909435A (en) | 2021-04-19 | 2021-04-19 | Casting method of ductile iron small-sized hydraulic part |
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| CN101301681A (en) * | 2008-06-20 | 2008-11-12 | 上海市机械制造工艺研究所有限公司 | Casting method of tabular spheroidal iron piece and casting system thereof |
| CN203900397U (en) * | 2014-06-25 | 2014-10-29 | 中国西电电气股份有限公司 | Casting mold for conductive static contact base cast piece of high-voltage switch circuit breaker |
| CN105499495A (en) * | 2016-01-27 | 2016-04-20 | 娄底市现代精密铸造有限公司 | Dead-head-free sand mould casting technology and casting mould for ductile cast iron grinding disc |
| CN105798238A (en) * | 2016-06-02 | 2016-07-27 | 四川南车共享铸造有限公司 | Bottom gating system of cylinder cover |
| CN106583657A (en) * | 2016-12-13 | 2017-04-26 | 山西平阳重工机械有限责任公司 | Solidification and feeding method for complicated annular thin-wall shell steel casting |
| CN111496183A (en) * | 2020-04-28 | 2020-08-07 | 苏州中央可锻有限公司 | Pouring system and pouring process for ductile iron thin-wall part |
| CN111910118A (en) * | 2020-07-16 | 2020-11-10 | 陕西柴油机重工有限公司 | Method for forming nodular cast iron flywheel for high-power diesel engine |
| CN111940680A (en) * | 2020-07-14 | 2020-11-17 | 陕西柴油机重工有限公司 | Method for forming nodular cast iron flywheel of medium-high speed high-power diesel engine |
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2021
- 2021-04-19 CN CN202110416840.6A patent/CN113909435A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101301681A (en) * | 2008-06-20 | 2008-11-12 | 上海市机械制造工艺研究所有限公司 | Casting method of tabular spheroidal iron piece and casting system thereof |
| CN203900397U (en) * | 2014-06-25 | 2014-10-29 | 中国西电电气股份有限公司 | Casting mold for conductive static contact base cast piece of high-voltage switch circuit breaker |
| CN105499495A (en) * | 2016-01-27 | 2016-04-20 | 娄底市现代精密铸造有限公司 | Dead-head-free sand mould casting technology and casting mould for ductile cast iron grinding disc |
| CN105798238A (en) * | 2016-06-02 | 2016-07-27 | 四川南车共享铸造有限公司 | Bottom gating system of cylinder cover |
| CN106583657A (en) * | 2016-12-13 | 2017-04-26 | 山西平阳重工机械有限责任公司 | Solidification and feeding method for complicated annular thin-wall shell steel casting |
| CN111496183A (en) * | 2020-04-28 | 2020-08-07 | 苏州中央可锻有限公司 | Pouring system and pouring process for ductile iron thin-wall part |
| CN111940680A (en) * | 2020-07-14 | 2020-11-17 | 陕西柴油机重工有限公司 | Method for forming nodular cast iron flywheel of medium-high speed high-power diesel engine |
| CN111910118A (en) * | 2020-07-16 | 2020-11-10 | 陕西柴油机重工有限公司 | Method for forming nodular cast iron flywheel for high-power diesel engine |
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