CN109848364B - Boron nitride coating for pressure casting and preparation method thereof - Google Patents
Boron nitride coating for pressure casting and preparation method thereof Download PDFInfo
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- CN109848364B CN109848364B CN201811510196.3A CN201811510196A CN109848364B CN 109848364 B CN109848364 B CN 109848364B CN 201811510196 A CN201811510196 A CN 201811510196A CN 109848364 B CN109848364 B CN 109848364B
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Abstract
The invention discloses a boron nitride coating for pressure casting and a preparation method thereof, wherein the boron nitride coating is prepared from the following raw materials in parts by weight: 20-50% of hexagonal boron nitride, 10-30% of alumina sol, 2-10% of reinforcing material, 0.5-2% of sodium tripolyphosphate, 1-5% of attapulgite, 0.2-0.6% of isooctanol and the balance of softened water. The preparation method comprises the following steps: mixing and stirring sodium tripolyphosphate, alumina sol, attapulgite and softened water to form a uniform solution, putting hexagonal boron nitride powder and a reinforcing material into a ball mill, ball-milling for a certain time, taking out, gradually adding into the uniform solution, strongly stirring for a certain time, and adding isooctanol until no bubbles are generated. The coating disclosed by the invention adopts a water-based system, has no volatilization of harmful substances in the using process, and is clean and environment-friendly. In addition, the silicon carbide and the silicon nitride whisker are used as reinforcing materials, so that the hardness of the coating is improved, the technical requirements in the pressure casting field are better met, the forming rate of the casting is improved, and the production cost is reduced.
Description
Technical Field
The invention relates to the technical field of metal and alloy casting, in particular to a boron nitride coating for pressure casting.
Background
Due to the wetting action between the metal melt (aluminum, copper, magnesium, zinc and the like) and the die, after casting is finished, solidified residual metal liquid can be firmly bonded with the casting die, and the surface layer of the die often falls off and is damaged when residual metal materials are cleaned, so that the service life of the die is shortened, the labor intensity of workers is improved, and the production time is prolonged. On the other hand, the fallen small particles of the die enter the metal melt, so that the product quality of the casting is reduced.
Punch lubricants, and the like. The existing release agent for metal hot forming generally adopts water-based graphite or oil-based graphite, dust or oil gas in the production process is evaporated and seriously polluted, the working condition is poor, the forge piece is also polluted, subsequent alkali washing or acid washing or shot blasting cleaning is needed, the environment is further polluted, and the problem needs to be solved systematically. in the process of die casting, in order to prolong the service life of the die cavity and punch and to ensure smooth demolding of die casting, and to ensure smooth surface and complete and clean contour of die casting, some auxiliary materials, such as demolding agent,
As an inert inorganic high-temperature-resistant lubricating material, the boron nitride coating has excellent high-temperature lubricity, chemical inertia and acid and alkali resistance. The alloy does not adhere or infiltrate into molten metal liquid, can completely protect the surface of refractory materials or ceramic utensils which are directly contacted with molten aluminum, magnesium, copper, zinc alloy and slag, greatly prolongs the service life of the utensils, and is applied to the field of casting in recent years.
For example, patent CN107201066A discloses an anti-sticking aluminum coating. The coating can prolong the service life of equipment, is convenient for cleaning after casting, simultaneously prevents fine particles of refractory materials from entering an aluminum melt, and improves the cleanliness of products. According to the invention, the CN103708843A patent takes boron nitride powder with large particle size and boron oxide as main bodies, and at a low temperature stage, the boron oxide is melted to form a high-viscosity melt, so that the adhesive force of the boron nitride coating is enhanced. The boron nitride generated by the reaction has higher activity, can promote the sintering of the boron nitride coating, has small sintering shrinkage of the coating, and avoids the separation from the matrix. We also previously filed a related patent for aqueous boron nitride coatings (application No.: 201810761677.5). However, in the pressure casting, it is found that neither commercially available nor laboratory self-made boron nitride coatings can fully satisfy the technical requirements in the pressure casting field, and the defects include short service life, low forming rate and the like.
Disclosure of Invention
The invention provides a boron nitride coating for pressure casting, aiming at the current situation of the boron nitride coating and the problems in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
the boron nitride coating for pressure casting is prepared from the following raw materials in parts by weight: 20-50% of hexagonal boron nitride, 10-30% of alumina sol, 2-10% of reinforcing material, 0.5-2% of sodium tripolyphosphate, 1-5% of attapulgite, 0.2-0.6% of isooctanol and the balance of softened water.
The hexagonal boron nitride coating for pressure casting has the particle size of 30.0-100.0 mu m and the purity of more than 95%.
The boron nitride coating for pressure casting is characterized in that the reinforcing material is a silicon carbide whisker, a silicon nitride whisker or a composite of the silicon carbide whisker and the silicon nitride whisker.
The preparation method of the boron nitride coating for pressure casting comprises the following steps:
(1) mixing and stirring sodium tripolyphosphate, alumina sol, attapulgite and softened water according to the weight ratio to obtain a uniform solution;
(2) putting hexagonal boron nitride powder and a reinforcing material into a ball mill according to the weight ratio, and taking out after ball milling for a certain time;
(3) gradually adding the hexagonal boron nitride powder and the reinforcing material taken out in the step (2) into the uniform solution prepared in the step (1), uniformly stirring, adding isooctanol, and continuously stirring until no bubbles are generated;
the above operations were all carried out at room temperature.
The ball-material ratio in the step (2) is 10:1, and the ball milling time is 30-120 min.
The whisker is a single crystal short fiber with a diameter of 0.1-2 μm and an aspect ratio L/D of 10 or more. The strength of the material is related to the number and the number of defects in the material. The smaller the single crystal, the fewer the defects and the higher the strength. The strength of a general material is only one percent or even one thousandth of the theoretical strength, namely, various defects exist in the material. It is believed that the strength of the whisker due to the low number of defects may be close to the theoretical strength of the material. The whisker materials commonly used in comparison include silicon carbide whisker, aluminum oxide whisker, silicon nitride whisker and the like. In addition, the silicon carbide whisker, the alumina whisker, the silicon nitride whisker and the like have good lubricity and have the advantages of stable chemical property, high thermal conductivity, small thermal expansion coefficient, good wear resistance and the like at high temperature.
Therefore, in the boron nitride coating for pressure casting, the reinforcing material can greatly improve the hardness of the coating, and the proper addition amount can reduce the loss of the release agent caused by pressure under the condition of not improving the friction coefficient, reduce the spraying times of the release agent and reduce the production cost.
In addition, the use of the hexagonal boron nitride with large particle size in the coating can overcome the phenomena of cracking, falling off and the like caused by mismatching of thermal expansion coefficients of raw materials in the coating at high temperature. From the bridging viewpoint, the boron nitride particles with different particle sizes are mixed to enable the coating to form relatively compact accumulation, which is beneficial to forming a surface with better lubricating property, meanwhile, the reinforcing material can effectively enter large particle gaps, the contact points among the particles are increased rapidly, the coating is formed more compact accumulation, and the hardness of the coating surface is improved.
The invention has the beneficial effects that: compared with the prior boron nitride coating technology, the invention adopts the crystal whisker as the reinforcing material, ensures no pollution in the using process, is clean and environment-friendly, has good high-temperature lubricating property, greatly increases the surface hardness of the coating, and is particularly suitable for the field of pressure casting. In addition, the coating can also keep longer service life in a high-pressure casting state, reduces the spraying times of the coating, saves labor force, improves production efficiency and reduces production cost.
Detailed Description
The present invention will be further described with reference to the following examples. It is to be understood that the following examples are illustrative only and are not intended to limit the scope of the invention, which is to be given numerous insubstantial modifications and adaptations by those skilled in the art based on the teachings set forth above.
Example 1
The boron nitride coating for pressure casting in the embodiment is prepared from the following raw materials in parts by weight: 20% of hexagonal boron nitride, 10% of alumina sol, 2% of silicon carbide whisker, 0.5% of sodium tripolyphosphate, 5% of attapulgite, 0.2% of isooctanol and the balance of softened water.
The preparation method of the boron nitride coating for pressure casting in the embodiment is as follows:
(1) mixing and stirring sodium tripolyphosphate, alumina sol, attapulgite and softened water according to the weight ratio to obtain a uniform solution;
(2) putting hexagonal boron nitride powder and a reinforcing material into a ball mill with a ball-to-material ratio of 10:1, and taking out after ball milling for 30 min;
(3) gradually adding the hexagonal boron nitride powder and the reinforcing material taken out from the step (2) into the solution prepared in the step (1), uniformly stirring, adding isooctanol, and continuing stirring until no bubbles are generated.
Example 2
The boron nitride coating for pressure casting in the embodiment is prepared from the following raw materials in parts by weight: 40% of hexagonal boron nitride, 20% of alumina sol, 5% of boron nitride whisker, 1% of sodium tripolyphosphate, 3% of attapulgite, 0.5% of isooctanol and the balance of softened water.
The preparation method of the boron nitride coating for pressure casting in the embodiment is as follows:
(1) mixing and stirring sodium tripolyphosphate, alumina sol, attapulgite and softened water according to the weight ratio to obtain a uniform solution;
(2) putting a certain amount of hexagonal boron nitride powder and a reinforcing material into a ball mill, wherein the ball-to-material ratio is 10:1, and taking out after ball milling for 60 min;
(3) gradually adding the hexagonal boron nitride powder and the reinforcing material taken out from the step (2) into the solution prepared in the step (1), uniformly stirring, adding isooctanol, and continuing stirring until no bubbles are generated.
Example 3
The boron nitride coating for pressure casting in the embodiment is prepared from the following raw materials in parts by weight: 50% of hexagonal boron nitride, 30% of alumina sol, 10% of silicon carbide and silicon nitride composite, 2% of sodium tripolyphosphate, 1% of attapulgite, 0.6% of isooctanol and the balance of softened water.
The preparation method of the boron nitride coating for pressure casting in the embodiment is as follows:
(1) mixing and stirring sodium tripolyphosphate, alumina sol, attapulgite and softened water according to the weight ratio to obtain a uniform solution;
(2) putting a certain amount of hexagonal boron nitride powder and a reinforcing material into a ball mill with a ball-to-material ratio of 10:1, and taking out after ball milling for 120 min;
(3) gradually adding the hexagonal boron nitride powder and the reinforcing material taken out from the step (2) into the solution prepared in the step (1), uniformly stirring, adding isooctanol, and continuing stirring until no bubbles are generated.
For comparison, according to the above preparation method, without adding the reinforcing material under the premise that the contents of other components are not changed, comparative examples 1, 2 and 3 without adding the reinforcing material are obtained, which correspond to the preparation methods of example 1, 2 and 3, respectively.
The boron nitride coatings obtained in the 3 examples and the 3 comparative examples are sprayed on a die-casting die, after high-temperature treatment, the friction coefficient of the surface coating, the hardness of the coating and the molding rate of the casting are subjected to comparative tests, and the specific experimental comparison results are shown in the following table.
The results show that: under the same experimental conditions, the boron nitride coating obtained in the embodiment has better hardness and higher casting forming rate, and the friction coefficient of the boron nitride coating is not obviously increased.
The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (3)
1. The boron nitride coating for pressure casting is characterized by being prepared from the following raw materials in parts by weight: 20-50% of hexagonal boron nitride, 10-30% of alumina sol, 2-10% of reinforcing material, 0.5-2% of sodium tripolyphosphate, 1-5% of attapulgite, 0.2-0.6% of isooctanol and the balance of softened water;
the particle size of the hexagonal boron nitride is 30.0-100.0 μm, and the purity is more than 95%;
the reinforced material is silicon carbide whisker, silicon nitride whisker or the composition of the silicon carbide whisker and the silicon nitride whisker.
2. The method for preparing a boron nitride coating for die casting according to claim 1, characterized by comprising the steps of:
(1) mixing and stirring sodium tripolyphosphate, alumina sol, attapulgite and softened water according to the weight ratio to obtain a uniform solution;
(2) putting hexagonal boron nitride powder and a reinforcing material into a ball mill according to the weight ratio, and taking out after ball milling for a certain time;
(3) gradually adding the hexagonal boron nitride powder and the reinforcing material taken out in the step (2) into the uniform solution prepared in the step (1), uniformly stirring, adding isooctanol, and continuously stirring until no bubbles are generated;
the above operations were all carried out at room temperature.
3. The method for producing a boron nitride coating material for die casting according to claim 2, characterized in that: the ball-material ratio in the step (2) is 10:1, and the ball milling time is 30-120 min.
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| CN111019408A (en) * | 2019-12-17 | 2020-04-17 | 大连新翔工业材料有限公司 | Anti-sticking aluminum coating |
| CN111590017B (en) * | 2020-05-26 | 2021-07-27 | 陕西宝塔山油漆股份有限公司 | Self-lubricating non-stick aluminum-melting environment-friendly coating and film and preparation method thereof |
| CN111702124B (en) * | 2020-05-26 | 2022-08-09 | 襄阳聚力新材料科技有限公司 | High-strength high-toughness cast steel lost foam coating and preparation method thereof |
| CN112552720A (en) * | 2020-12-08 | 2021-03-26 | 江苏常铝铝业集团股份有限公司 | Refractory material coating for resisting aluminum alloy melt corrosion and preparation and coating methods thereof |
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| WO2006070021A1 (en) * | 2004-12-31 | 2006-07-06 | Viking Advanced Materials Gmbh | Coating system |
| CN102533423B (en) * | 2011-12-02 | 2013-10-30 | 华中科技大学 | Non-graphite type lubricant for hot die forging of metal and preparation method of non-graphite type lubricant |
| CN104646605B (en) * | 2015-03-05 | 2016-07-20 | 苏州宇希新材料科技有限公司 | A kind of Cast aluminium alloy gold coating |
| WO2017117324A1 (en) * | 2015-12-29 | 2017-07-06 | Momentive Performance Materials Inc. | Boron nitride coatings for metal processing and methods of using the same |
| CN105750481B (en) * | 2016-03-31 | 2017-12-26 | 宁夏共享化工有限公司 | A kind of water based paint for preventing large-scale steel-casting orange peel defect |
| CN106010763A (en) * | 2016-06-14 | 2016-10-12 | 山东南山铝业股份有限公司 | Hot-forging lubricating agent and preparation method and application thereof |
| CN107141863B (en) * | 2017-05-16 | 2019-03-29 | 江南大学 | A kind of high-intensity corrosion coating and the preparation method and application thereof |
| CN107243594A (en) * | 2017-06-14 | 2017-10-13 | 合肥市旺友门窗有限公司 | A kind of used in aluminium alloy casting insulating refractory coating and preparation method thereof |
| CN107201066B (en) * | 2017-07-28 | 2019-10-15 | 宋振亚 | A kind of anti-sticking aluminium paint |
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