CN110090927B - Method for solving stress cracks of aviation stainless steel investment casting - Google Patents
Method for solving stress cracks of aviation stainless steel investment casting Download PDFInfo
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- CN110090927B CN110090927B CN201910503916.1A CN201910503916A CN110090927B CN 110090927 B CN110090927 B CN 110090927B CN 201910503916 A CN201910503916 A CN 201910503916A CN 110090927 B CN110090927 B CN 110090927B
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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
- B22C9/04—Use of lost patterns
- B22C9/046—Use of patterns which are eliminated by the liquid metal in the mould
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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
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Abstract
The invention provides a method for solving stress cracks of an aviation stainless steel investment casting, which comprises the following steps: the method comprises the following steps: opening a new inner gate: forming a new inner gate by arranging a transition arc at two sides of the original inner gate; step two: opening a pouring gate stress groove: cutting a section of arc groove near the stress concentration part on the new inner gate; step three: and (3) tree formation: when the trees are assembled, the new inner sprue is bonded in the center of the casting beam structure, one side with the transition arc is connected with the beam structure, and the other side is bonded with the riser. Step four: preparing a shell: when the shell is manufactured, the shell is manufactured by adopting silica sol coating, and the number of the manufactured shell layers is 7-8; step five: pouring: and pouring by adopting an intermediate frequency furnace. The contact sectional area of the new inner sprue and the casting beam structure is unchanged, and feeding of the casting beam structure can be guaranteed. And a scheme of a bottom pouring type gating system is adopted, and a casting without the defects of shrinkage cavity and shrinkage porosity is ensured to be obtained through reasonable casting parameters.
Description
Technical Field
The invention relates to the technical field of aviation, in particular to a method for solving stress cracks of an aviation stainless steel investment casting.
Background
At present, the factory produces a cylindrical thin-wall type aviation stainless steel casting made of 17-4PH materials, the wall thickness is 2.78-4.25mm, and the unit weight of the part is 2.8 kg. There are stringent aviation casting standard non-destructive testing and dimensional tolerance requirements.
17-4PH is a commonly used martensite precipitation hardening type stainless steel composed of copper, niobium/columbium in aviation investment casting, has low carbon content and chemical composition similar to domestic brand 0Cr17Ni4Cu4 Nb. The material has poor casting performance and large contractibility, and is more required to be sequentially solidified during casting and not easy to be fed.
The tubular casting has a beam structure with a length of 120.5mm, a width of 12.5mm and a height of 9.8 mm. In order to prevent the shrinkage cavity and shrinkage porosity defect of the structure, a square inner sprue is required to be placed in the center of the cross beam. However, the shape of the inner gate is not consistent with that of the beam structure, the cooling speed of the inner gate is slow, and the free line shrinkage speed is lower than that of the beam structure, so that the stress at the joint of the inner gate and the beam structure is too concentrated and exceeds the strength limit of the material at high temperature, and finally cracks are generated at the joint of the inner gate and the beam structure, as shown in 5 in fig. 1, the requirement of fluorescent inspection acceptance cannot be met, the proportion of crack defects reaches 65% -75%, a large number of parts are repaired and scrapped, and the casting cost and the dispatching requirement are seriously influenced.
Disclosure of Invention
The invention aims to provide a method for solving the stress crack of an aviation stainless steel investment casting,
the technical scheme of the invention is as follows:
a method for solving stress cracks of an aviation stainless steel investment casting is characterized by comprising the following steps:
the method comprises the following steps: opening a new inner gate: under the premise of keeping the contact sectional area of the original inner gate and the beam structure unchanged, two sides of the original inner gate are provided with a transition arc to form a new inner gate;
step two: opening a pouring gate stress groove: cutting a section of arc groove near the stress concentration part on the new inner gate, wherein a new stress concentration point is formed at the top of the arc groove, and the original over-concentrated stress is dispersed;
step three: and (3) tree formation: when assembling trees, the new inner sprue is bonded in the center of the casting beam structure, one side with a transition arc is connected with the beam structure, and the other side is bonded with a riser; the joint of the inner sprue and the beam structure is smoother without visible wax seams by brushing the joint of the inner sprue and the beam structure with bonding wax.
Step four: preparing a shell: when the shell is manufactured, the shell is manufactured by adopting silica sol coating, and the number of the manufactured shell layers is 7-8;
step five: pouring: and (3) pouring by adopting an intermediate frequency furnace, stably injecting the alloy liquid from a side pouring gate by using a teapot bag, performing point supplement from a riser to a pouring gate cup when the casting cavity is full of the alloy liquid, and adding a little riser covering agent on the riser after pouring.
And in the second step, the radian radius of the transition arc is controlled to be R40-50 mm. The depth of the gate stress groove is controlled to be 3-5 mm.
The scheme is further improved, and in the step five, the roasting and heat preservation temperatures of the formwork are controlled as follows: 900 ℃ and 1000 ℃, and the alloy tapping temperature is controlled at 1610 ℃ and 1640 ℃.
Advantageous effects
1. New gate form. Under the premise of keeping the contact sectional area of the inner pouring gate and the cross beam structure unchanged, larger transition arcs are arranged on two sides of the inner pouring gate, so that the joint of the inner pouring gate and the cross beam structure is more smooth, heat junctions are reduced, and feeding and stress dispersion of castings are facilitated.
2. And opening a sprue stress groove. A section of arc groove is cut near the stress concentration part on the new inner sprue, a new stress concentration point is formed at the top of the arc grooves, and the original over-concentrated stress is dispersed, so that the damage and deformation of the original over-concentrated stress to a casting beam structure are reduced and avoided.
Drawings
FIG. 1 is a view showing the structure of a new in-gate of the present invention.
FIG. 2 is a schematic view of the new runner system of the present invention.
FIG. 3 is a graph of casting stress for the present invention.
Detailed Description
The present invention will be further described with reference to the following specific examples.
As shown in fig. 1-3, 1-new ingate, 2-transition arc, 3-stress groove, 5-original crack generation place, 6-side gate, 7-riser and 8-casting;
a method for solving stress cracks of an aviation stainless steel investment casting is characterized by comprising the following steps:
the method comprises the following steps: opening a new inner gate: on the premise of keeping the contact sectional area of the original inner gate and the beam structure unchanged, two sides of the original inner gate are provided with a transition arc 2 to form a new inner gate, so that the joint of the new inner gate and the beam structure is smoother, the heat section is reduced, and the feeding and stress dispersion of a casting are facilitated.
Step two: opening a pouring gate stress groove: a section of arc groove is cut near the stress concentration part on the new inner sprue, a new stress concentration point is formed at the top of the arc grooves, and the original over-concentrated stress is dispersed, so that the damage and deformation of the original over-concentrated stress to a casting beam structure are reduced and avoided.
Step three: and (3) tree formation: when assembling trees, the new inner sprue is bonded in the center of the casting beam structure, one side with a transition arc is connected with the beam structure, and the other side is bonded with a riser; the joint of the inner sprue and the beam structure is smoother without visible wax seams by brushing the joint of the inner sprue and the beam structure with bonding wax.
Step four: preparing a shell: when the shell is manufactured, the shell is manufactured by adopting silica sol coating, and the number of the manufactured shell layers is 7-8;
step five: pouring: and (3) pouring by adopting an intermediate frequency furnace, stably injecting the alloy liquid from a side pouring gate by using a teapot bag, performing point supplement from a riser to a pouring gate cup when the casting cavity is full of the alloy liquid, and adding a little riser covering agent on the riser after pouring.
In the step two, the radian radius of the transition circular arc 2 is controlled to be R40-50 mm. The depth of the gate stress groove is controlled to be 3-5 mm.
The scheme is further improved, and in the step five, the roasting and heat preservation temperatures of the formwork are controlled as follows: 900 ℃ and 1000 ℃, and the alloy tapping temperature is controlled at 1610 ℃ and 1640 ℃.
The working principle is as follows:
analysis of crack causes
After pouring, the alloy liquid in the casting cavity is cooled and solidified, and the inner pouring gate and the pouring gate are cooled and solidified slowly because of wrapping refractory cotton. In the cooling process of the casting after solidification, the cooling speed of each part is inconsistent with that of the inner sprue, the starting line of the beam structure shrinks, but the inner sprue connected with the beam structure is still in the initial solidification stage, the deformation of the beam structure of the casting is completely determined by the beam structure of the casting, the beam structure of the casting drives the inner sprue to shrink together, and the casting does not generate thermal stress at this time.
Along with the increase of the cooling time, the temperature difference between the two parts is gradually increased, and the solid phase of the casting beam structure forms a complete framework. The shrinkage of ingate is gradually larger than the casting beam structure, because the ingate is connected with a riser, the ingate is compressed at the moment, the casting beam structure is elongated, the pressure stress is generated in the ingate, the casting beam structure generates the tensile stress, and the stress value is maximum when the temperature difference between the two is maximum. When the stress value exceeds the strength limit of the casting material at this high temperature, cracks can develop.
Novel inner gate principle
The transition circular arc of novel ingate can reduce the hot node between ingate and the foundry goods, reduces and concentrates the deformation, dilutes the runner and contracts the obstacle, helps the feeding of foundry goods crossbeam structure simultaneously. And the runner stress groove can disperse the tensile stress of the over-concentrated inner runner in the later stage of casting solidification shrinkage, so that a new stress concentration point is formed at the top of the arc grooves, the stress directly acting on the beam structure is reduced, and the generation of cracks or deformation of the beam structure is avoided.
The contact sectional area of the new inner sprue and the casting beam structure is unchanged, and feeding of the casting beam structure can be guaranteed. The scheme of a bottom pouring type gating system is adopted, and a casting without the defects of shrinkage cavity and shrinkage porosity is ensured to be obtained through reasonable casting parameters.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (3)
1. A method for solving the stress crack of an aviation stainless steel investment casting,
the casting is a tubular thin-wall aviation stainless steel casting, the tubular casting has a beam structure, a square original inner sprue is arranged in the center of the beam,
the method is characterized by comprising the following steps:
step one, opening a new inner gate: on the premise of keeping the contact sectional area of the original inner gate and the beam structure (9) unchanged, two sides of the original inner gate are provided with a transition arc (2) to form a new inner gate (1);
step two, forming a gate stress groove (3): cutting a section of arc groove near the stress concentration part on the new inner gate, wherein a new stress concentration point is formed at the top of the arc groove, and the original over-concentrated stress is dispersed;
step three, tree grouping: when the trees are assembled, the new inner sprue is bonded in the center of a casting beam structure, one side with a transition arc is connected with the beam structure, and the other side is bonded with a riser (7); the joint of the inner sprue and the beam structure is smoother without visible wax seams by brushing the joint of the inner sprue and the beam structure with bonding wax;
step four, preparing a shell: when the shell is manufactured, the shell is manufactured by adopting silica sol coating, and the number of the manufactured shell layers is 7-8;
step five, pouring: and (3) pouring by adopting an intermediate frequency furnace, stably injecting the alloy liquid from a side pouring gate by using a teapot bag, performing point supplement from a riser to a pouring gate cup when the casting cavity is full of the alloy liquid, and adding a little riser covering agent on the riser after pouring.
2. The method for solving the stress crack of the aviation stainless steel investment casting according to the claim 1, which is characterized in that:
in the second step, a transition arc (2) is arranged at the inner sprue, and the radian radius is controlled to be R40-50 mm;
the sprue is provided with a sprue stress groove (3), and the depth of the stress groove is controlled to be 3-5 mm.
3. The method for solving the stress crack of the aviation stainless steel investment casting according to the claim 1, which is characterized in that:
in the fifth step, the roasting and heat preservation temperature of the mould shell is controlled as follows: 900 ℃ and 1000 ℃, and the alloy tapping temperature is controlled at 1610 ℃ and 1640 ℃.
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| CN111054901A (en) * | 2019-12-31 | 2020-04-24 | 西安西工大超晶科技发展有限责任公司 | Method for solving streamline defect at lower end of ZL210A alloy casting linear chilling block |
| CN112893773B (en) * | 2021-02-23 | 2024-01-26 | 天长市兴宇铸造有限公司 | Module wax component structure for upper and lower shell castings in hook buffer device and tree assembling process thereof |
| CN113547082A (en) * | 2021-07-20 | 2021-10-26 | 上海电气集团上海电机厂有限公司 | Casting method of flame-proof motor fan |
| CN113458514B (en) * | 2021-08-17 | 2022-04-12 | 青岛青特众力车桥有限公司 | Hydrogen embrittlement device and method for bearing seat of middle-rear axle speed reducer |
| CN113828735B (en) * | 2021-09-18 | 2023-06-16 | 江苏金诺炉辊有限公司 | Pouring system and investment casting process of high-temperature alloy elbow |
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| JPS58159967A (en) * | 1982-03-19 | 1983-09-22 | Akebono Brake Ind Co Ltd | Casting device |
| CN201711494U (en) * | 2010-06-30 | 2011-01-19 | 浙江红马铸造有限公司 | Ingate for precision casting |
| CN204413057U (en) * | 2014-12-31 | 2015-06-24 | 鹰普航空零部件（无锡）有限公司 | Model casting is clear cup cover plate easily |
| CN204867312U (en) * | 2015-08-18 | 2015-12-16 | 东风精密铸造安徽有限公司 | Reduce gate stick of foundry goods crackle |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104889320A (en) * | 2015-06-17 | 2015-09-09 | 广东鸿特精密技术股份有限公司 | Process method for forming grooves in gravity casting mold cavity surface |
| CN107866531A (en) * | 2017-12-28 | 2018-04-03 | 青岛宏新天机械有限公司 | A kind of breeches joint casting craft |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58159967A (en) * | 1982-03-19 | 1983-09-22 | Akebono Brake Ind Co Ltd | Casting device |
| CN201711494U (en) * | 2010-06-30 | 2011-01-19 | 浙江红马铸造有限公司 | Ingate for precision casting |
| CN204413057U (en) * | 2014-12-31 | 2015-06-24 | 鹰普航空零部件（无锡）有限公司 | Model casting is clear cup cover plate easily |
| CN204867312U (en) * | 2015-08-18 | 2015-12-16 | 东风精密铸造安徽有限公司 | Reduce gate stick of foundry goods crackle |
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Address after: No.18 Furong 5th Road, Xishan Economic Development Zone, Wuxi City, Jiangsu Province Applicant after: Yingpu Aviation Technology Co., Ltd Address before: No.18 Furong 5th Road, Xishan Economic Development Zone, Wuxi City, Jiangsu Province Applicant before: IMPRO AVIATION COMPONENTS (WUXI) Co.,Ltd. |
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