GB2029297A - Production of foundry moulds or cores - Google Patents
Production of foundry moulds or cores Download PDFInfo
- Publication number
- GB2029297A GB2029297A GB7928884A GB7928884A GB2029297A GB 2029297 A GB2029297 A GB 2029297A GB 7928884 A GB7928884 A GB 7928884A GB 7928884 A GB7928884 A GB 7928884A GB 2029297 A GB2029297 A GB 2029297A
- Authority
- GB
- United Kingdom
- Prior art keywords
- process according
- composition
- silicon
- acid
- resin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
- B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
- B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Mold Materials And Core Materials (AREA)
Abstract
A process for the production of foundry moulds or cores is described in which a sand composition containing an acid-hardenable synthetic resin or resin precursor is hardened by a hydrogen halide produced in situ by reaction between a silicon halide and water and/or an aliphatic alcohol. The silicon halide may be injected into the shaped composition as a gas or as an aerosol and the water and/or aliphatic alcohol may be mixed with the sand composition before shaping or injected after shaping. The composition may also contain an alkali metal silicate which is also hardened by the hydrogen halide.
Description
SPECIFICATION
Production of foundry moulds or cores
This invention relates to the production of foundry moulds or cores.
According to the invention there is provided a process for the production of a foundry mould or core which comprises shaping a composition comprising particulate refractory material and an acid-hardenable synthetic resin or a precursor therefor, and hardening the composition with a hydrogen halide formed in situ by means of chemical reaction between a silicon halide and water and/or an aliphatic alcohol.
The particulate refractory material may be selected from any such material known for use in the production of foundry moulds and cores.
Examples of suitable materials include silica, olivine, chromite and zircon sands.
The acid-hardenable synthetic resin may be for example a furfuryl alcohol-formaldehyde resin, a urea-formaldehyde-furfuryl alcohol resin ora phenol-formaldehyde-furfuryi alcohol resin.
Alternatively an acid-hardenable synthetic resin precursor such as furfuryl alcohol which homopolymerises in the presence of an acid may be used.
There will usually be sufficient water present in commercially available acid-hardenable synthetic resins for reaction with the silicon halide. However if the mixture of particulate refractory material and acid-hardenable synthetic resin is completely anhydrous it is necessary to add water or alternatively an aliphatic alcohol such as methanol to the mixture before shaping, or to introduce water or an aliphatic alcohol into the shaped composition, for example in the case of water by injecting steam.
The preferred method of supplying the silicon halide to the shaped composition is to inject the silicon halide as a gas or aerosol.
Suitable silicon halides include silicon tetrachloride and silicon tetrafluoride. Silocon hydrogen halides such as Sic13 may also be used.
When the silicon halide is injected as an aerosol the carrier gas for the silicon halide may be for example air, oxygen, nitrogen or carbon dioxide.
The carrier gas may be passed through the liquid silicon halide at ambient temperature but in order to increase the initial hardening rate of the core or mould and decrease "gassing" time, the silicon halide may be warmed, for example to 35--400C, so as to incease the volatilisation of the silicon halide.
The silicon halide reacts with the water and/or the alcohol to produce a hydrogen halide such as hydrochloric acid, and the hydrochloric acid rapidly cures the acid-hardenable resin.
If desired an alkali metal silicate such as sodium silicate may be included in the composition. The hydrogen halide will also harden the alkali metal silicate thereby increasing the bond strength of the cured composition.
When an alkali metal silicate is present, and the silicon halide is injected using carbon dioxide as the carrier gas, addition chemical reaction takes place between the alkali metal silicate and the carbon dioxide giving further improvement in bond strength.
The acid hardenable synthetic resin or resin precursor will normally by used at a rate of up to 10% by weight based on the weight of the particulate refractory material, preferably 1.03..5% by weight.
The process of the invention has economic advantages compared with known processes in which resin bonded moulds or cores are hardened by introducing a hardening agent at ambient temperature, and the process is less hazardous.
The following examples will serve to illustrate the invention: EXAMPLE 1
A resin binder was prepared having the following composition by weight Phenol-formaldehyde resin aqueous syrup (phenol : formaldehyde 1.0 : 2.0-solids content 65% by weight)
Furfuryl alcohol 54%
Furfuryl alcohol-formaldehyde resin (formaldehyde : furfurvl alcohol 1.0 : 0.65) 1 6% The resin was mixed with silica sand at a rate of 2 parts by weight of resin to 100 parts by weight of sand, and the sand-resin mixture was used to prepare standard compression strength test cores.
The cores were gassed with a mixture of silicon tetrachloride vapour and carbon dioxide (produced by passing carbon dioxide through silicon tetrachloride liquid at ambient temperature) for 1 5 seconds at a flow rate of 5 litres/minute, foliowed by a carbon dioxide gas purge,for 40 seconds at a flow rate of 5 litres/minute.
The compression strength of the cores was then determined and the following results were obtained:
Time Compression Strength
Kg/cm2
As gassed 30
After 1 hour 49
EXAMPLE 2
A resin/sodium silicate binder was prepared having the following composition by weight:
Aqueous sodium silicate silution (SiOz : Na20 2.0: l.O--Solids content 49% by weight 50% Urea-formaldehyde resin aqueous syrup (urea formaldehyde 1.0 :2.2 solids content 70% by weight) 25%
Furfuryl alcohol 25%
The binder was mixed with silica sand at a rate of 3 parts by weight of binder to 100 parts by weight of silica sand, and the sand-binder mixture was tested using the procedure described in
Example 1.
The following results were obtained: Time Compression Strength
Kg/cm2
As gassed 22
After 1 hour
Claims (13)
1. A process for the production of a foundry mould or core which comprises shaping a composition comprising particulate refractory material and an acid-hardenable synthetic resin or a precursor therefore, and hardening the composition with a hydrogen halide formed in situ by means of chemical reaction between a silicon halide and water and/or an aliphatic alcohol.
2. A process according to claim 1 wherein the water and/orn the aliphatic alcohol are mixed with the particulate refractory material and the acid hardenable synthetic resin or precursor therefor prior to shaping the composition.
3. A process according to claim 1 wherein the water is injected into the shaped composition as steam.
4. A process according to any of claims 1 to 3 wherein the silicon halide is injected into the shaped composition as a gas.
5. A process according to any claims 1 to 3 wherein the silicon halide is injected into the shaped composition as an aeorsol.
6. A process according to claim 5 wherein the aerosol contains air, oxygen, nitrogen or carbon dioxide as a carrier gas for the silicon halide.
7. A process according to any of claims 1 to 6 wherein the acid-hardenable synthetic resin is a furfuryl alcohol-formaldehyde resin, a ureaformaldehyde-furfuryl alcohol resin or a phenolformaldehyde-furfuryl alcohol resin.
8. A process according to any of claims 1 to 6 wherein the precursor is furfuryl alcohol.
9. A process according to any of claims 1 to 8 wherein the silicon halide is silicon tetrachloride, silicon tetrafluoride or a silicon hydrogen halide.
10. A process according to any of the preceding claims wherein the composition contains up to 10% by weight of the acid-hardenable synthetic resin or precursor therefor based on the weight of the particulate refractory material.
11. A process according to claim 10 wherein the composition contains 1.0-3.5% by weight of the acid-hardenable synthetic resin or precursor therefor based on the weight of the particulate refractory material.
12. A process according to any of the preceding claims wherein the composition includes an alkali metal silicate.
13. A process substantially as hereinbefore described with reference to either of the foregoing specific examples.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7928884A GB2029297A (en) | 1978-09-04 | 1979-08-20 | Production of foundry moulds or cores |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7835495 | 1978-09-04 | ||
| GB7928884A GB2029297A (en) | 1978-09-04 | 1979-08-20 | Production of foundry moulds or cores |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2029297A true GB2029297A (en) | 1980-03-19 |
Family
ID=26268738
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7928884A Withdrawn GB2029297A (en) | 1978-09-04 | 1979-08-20 | Production of foundry moulds or cores |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2029297A (en) |
-
1979
- 1979-08-20 GB GB7928884A patent/GB2029297A/en not_active Withdrawn
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |