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Development Of Mould Sealing Paste For Magnesium Alloy Castings
Abstract: Mould sealing agent/paste is used to seal the two sand mould haves while assembling moulds with core. Sealing paste is applied on peripheral edges of lower mould (drag) and upper mould (cope) is assembled with bottom mould. In between the parting lines of top and bottom mould there is chance,of minor gap due to imperfect mould/assembly/warpage. To avoid chances of molten alloy leakage from this gap, mould sealing paste is applied in sand casting method. Different types of sealing paste are used for non-ferrous alloys. Commonly used sealing material is bentonite-water mix. This is sticky in nature and provides fair sealing. When magnesium alloys are cast through sand casting method, performance of bentonite-water mix is not satisfactory. Sand moulds shall be thoroughly preheated to remove traces of moisture (since magnesium alloy is very reactive with moisture) thus moulds shall be warm during pouring of molten magnesium alloy. Due to warm mould, bentonite water mix starts drying and while assembling the mould there are chances of improper cope and drag closing resulting into gap between the two. Since Magnesium alloy reacts vigorously with moisture, it may start burning when it comes in contact with sealing material (bentonite/water) resulting into severe fire hazards. There are non reactive ceramic pastes with adhesive properties. Application of these pastes causes difficulty in separation of mould halves and may cause damage to the non ferrous castings (comparatively lower strength than ferrous castings) while knock out. To avoid the event of molten alloy leakage and fire hazard, alternate mould sealing paste was required. Vegetable oil (coconut oil with commercial purity) is mixed with bentonite powder (200 mesh size) to prepare the paste. This paste can be applied on upper portion of lower mould half at peripheral edges and top mould can be assembled on it. It provides perfect sealing and in extreme case of coming in contact with molten Magnesium alloy, doesn"t initiate the burining of alloy and subsequent fire.
Notices, Deadlines & Correspondence
Patent Information
Applicants
HINDUSTAN AERONAUTICS LTD.
Inventors
1. AMIT SHRIVASTAVA
2. R.RAGHAVENDRA
Specification
1) Title of the invention
Development of Mould Sealing Paste for Magnesium Alloy Castings
2) Field of invention
The present invention is mould sealing paste for sand casting foundry technology dsigned to avoid molten Magnesium alloy leakage from mould parting line and subsequent fire hazard.
3) Use of invention
The paste is used for sealing two mould halves iri sand casting process for all Magnesium alloys.
4) Prior art
To seal the mould (prepared with addition of inhibitors) earlier Bentonite/ Clay was mixed with water to prepare the paste and.same used to be applied at the upper peripheral edges of bottom mould half.
5) Draw backs of prior art
Bentonite (clay) and water mix paste becomes hard (dries faster) due to mould heat and doesn't provide perfect sealing. Secondly if it comes in contact with molten magnesium alloy, there are always chances for metal burning and severe fire hazard. However, ceramic paste available in market works as adhesive and causes difficulties in separating two moulds halves while knock out operation.
6) Comparison between prior art and present invention
Bentonite water mix doesn't provide perfect sealing and causes buring and fire hazard if it comes in contact with molten Magnesium alloys. However invented mould seal paste doesn't decompose when it comes in contact with molten Magnesium Alloy, thus avoids chances of fire hazard. Secondly it doesn't act as adhesive and seperation of mould halves during knock out is easier. More than 300 gear cases are poured in HAL Foundry & Forge Division with almost 300kg molten Magnesium alloy and not a single incidence of mould leakage and subsequent fire hazard is reported.
7) Aim of the invention
Aim of the invention is to develop a mould sealing paste which can provide perfect mould sealing and avoid incidences of subsequent fire hazards due to metal leakage or reaction of alloy with sealing agent itself. Secondly, smooth knock out operation by ease in seperation of mould halves.
8) Summary of the present invention
The present invention is development of Mould Sealing Paste for Magnesium alloy castings to be used in sand casting process. Bentonite powder (200 mesh size or finer) is mixed with vegetable oil (coconut oil with commercial purity) and semi solid paste is prepared. This mix is brought in contact with molten alloy and tested for initiation of buring in molten alloy. It is observed that mix doesn't initiate fire of molten alloy. Paste developed at Foundry & Forge Division of HAL provides perfect sealing for sand moulds, easy seperation of moulds after solidification of alloy during knock out of moulds and doesn't initiate fire in molten alloy when it comes in direct contact of molten metal.
9) Brief description of drawings
Not Applicable
10) Statement of invention
Development of Mould Sealing Paste for Magnesium Alloy Castings for sand casting method.
11) Detailed description of invention
The present invention is best suited for all Magnesium alloys (Mg-Zn-Zr-RE; Mg-Zn-RE; Mg-Ag-NdRE; Mg- Al-Zn-Mn) when poduced through sand casting process. Mould Sealing paste is prepared with Bentonite (clay: Powder of 200 mesh or finer size) mixed with vegetable oil preferably coconut oil. Semi solid paste has to be preared to serve the purpose of mould sealing. Composition may vary depending on the ambient temperature to achieve sufficient flow through 8 to 10 mm orifice. Mix may be filled in plastic container having 8 to 10 mm orifice and applied on mould by applying pressure on plastic container just like tomato souce. Quantity to be mixed in following ratio
Bentnite powder: 200 gm
Vegetable oils (preferably coconut oil): 80 to 120 ml
12) Drawings & worked examples.
Not Applicable
TITLE: Development of Mould Sealing Paste for Magnesium Alloy Castings
"We claim"
1. Mould Sealing Paste for Magensium Alloy Castings developed at Foundry & Forge Division, Hindustan Aeronautics Limited in new sealing agent, the details of which are not available in open literature.
2. The process has been developed by Foundry and Forge Division of HAL, Bangalore and the parameters are optimised for all Magensium alloys castigs produced through sand castings process.
3. The use of vegetable oil to prepare sealing paste is new concept for Magnesium alloy castings produced through sand casting method to achieve leakage free ,thus resulting safe pouring without subsequent fire hazard.
4. The composition of mix (paste) is optimized.
5. The sealing paste is effective for all Magnesium Alloys.
Documents
Application Documents
| # | Name | Date |
|---|---|---|
| 1 | 6109-CHE-2015-FER.pdf | 2021-10-17 |
| 1 | 6109-CHE-2015-Other Patent Document-131115.pdf | 2015-11-24 |
| 2 | 6109-CHE-2015-Form 5-131115.pdf | 2015-11-24 |
| 2 | Correspondence by Applicant_Form18_21-08-2019.pdf | 2019-08-21 |
| 3 | 6109-CHE-2015-Form 3-131115.pdf | 2015-11-24 |
| 3 | Form18_Normal Request_21-08-2019.pdf | 2019-08-21 |
| 4 | 6109-CHE-2015-Form 1-131115.pdf | 2015-11-24 |
| 4 | 6109-CHE-2015-Form 2(Title Page)-131115.pdf | 2015-11-24 |
| 5 | 6109-CHE-2015-Form 1-131115.pdf | 2015-11-24 |
| 5 | 6109-CHE-2015-Form 2(Title Page)-131115.pdf | 2015-11-24 |
| 6 | 6109-CHE-2015-Form 3-131115.pdf | 2015-11-24 |
| 6 | Form18_Normal Request_21-08-2019.pdf | 2019-08-21 |
| 7 | 6109-CHE-2015-Form 5-131115.pdf | 2015-11-24 |
| 7 | Correspondence by Applicant_Form18_21-08-2019.pdf | 2019-08-21 |
| 8 | 6109-CHE-2015-FER.pdf | 2021-10-17 |
| 8 | 6109-CHE-2015-Other Patent Document-131115.pdf | 2015-11-24 |
Search Strategy
| 1 | 275SSME_12-04-2021.pdf |