Application of Boron Nitride in High Temperature Release Agent

First, the lubricity of boron nitride

 

Boron nitride was introduced more than 100 years ago. Its earliest application polymorph is hexagonal boron nitride as a high-temperature lubricant, abbreviated as: h-BN, or a-BN, or g-BN (ie graphite-type boron nitride). Hexagonal boron nitride is absolutely smooth, the friction coefficient between the powders is very low, and the atomic structure contains boron and nitrogen in each layer. There is no BN bond between the layers, so the plane slides between each other, thereby obtaining softness and lubrication. The effect is very suitable as a high temperature release agent application.

 

From the application or the downstream product system of the application, there are basically the following:

 

Various optical glass release agents

 

Metal forming release agent and metal wire drawing lubricant

 

Metallurgical separation rings for continuous casting of steel, etc.

 

Figure 1 BN atomic structure diagram

 

Second, the advantages of boron nitride release agent

 

Excellent lubricity: special fine powder blending, strong and effective adhesion to the mold surface, forming an excellent lubrication effect.

 

It can extend the life of the mold: effectively reduce the loss of the mold, and reduce the time required to clean the mold. The glass processing process can minimize the surface defects of the glass product and make the glass easier to demould.

 

Good operability: special spray formulations that can be applied evenly to the mold surface using a manual method (Figure 2).

 

High temperature resistance: Excellent thermal shock resistance. Even if it is heated at a temperature of 1500 °C, it will not break even if it is repeated several times. It can be used safely even when heated to 2200 °C.

 

Fast drying speed: special quick-drying formula, fast drying speed, improve production efficiency and reduce cost.

 

Low friction coefficient: friction coefficient u is only 0.16, does not increase at high temperature, is higher than molybdenum disulfide, graphite is resistant to high temperature, oxidizing atmosphere can be used to 800 ° C, vacuum can be used to 2000 ° C.

 

Good corrosion resistance: with general metals (iron, copper, aluminum, lead, etc.), rare earth metals, precious metals, semiconductor materials (silicon, silicon, potassium arsenide), glass, molten salt (crystal, fluoride, slag) ), inorganic acids and alkalis do not react.

 

Machinability: Its Mohs hardness is 2, so it can be processed into high precision parts and components by general machining methods.

 

Third, the application of boron nitride release agent in the demoulding of glass mold

 

With the rapid development of China's wine, food, beverage and other industries, the demand for various types of packaging glass bottles has increased. The determinant bottle-making machine has become a mainstream model for glass bottle production and is widely used, and the determinant bottle-making machine is running faster and faster, and the requirements for the glass mold lubrication release agent are getting higher and higher. The traditional glass mold lubrication demoulding method uses manual or mechanical spraying of animal and vegetable oils, which generally has poor effects.

 

The use of boron nitride lubricating material significantly improves the lubrication release effect. At present, the application of boron nitride release agents is mainly divided into the following three categories:

 

One type is water-based medium, adding high-temperature binder and other additives to make a water-based lubricant, which is applied to the surface of the mold at one time and dried for film formation.

 

The other type is oil as a medium, adding an auxiliary agent to make an oily lubricant, and continuously brushing or spraying in the operation of the determinant bottle making machine.

 

A commonly used boron nitride release agent is a high viscosity mineral oil coated with boron nitride, and is mixed with water under the action of an emulsifier to form an emulsified oil type glass mold lubricating release agent. Boron nitride: grease: water = 1:4:10, when the amount of emulsifier is 7wt%, the obtained emulsified oil release agent has good stability, good release property, and has the characteristics of thin oil film and uniform distribution. The use of boron nitride to lubricate the release agent improves the yield of the bottle, reduces the consumption of the lubricant release agent, and purifies the production environment.

 

Boron nitride release agent can also be applied to flat glass processing, which can greatly improve the working environment and improve product efficiency. Especially for curved glass processing, the effect is more significant:

 

Difficult deep bend

 

Shaped

 

Hot melt

 

Clear light and so on.

 

Fourth, the application of boron nitride release agent in metal casting smelting and welding

 

Hexagonal boron nitride has excellent chemical stability and can resist neutron radiation from nuclear reactors. It can not be affected by acid or alkali. In an inert atmosphere (nitrogen or argon), the decomposition temperature is as high as 2500 ° C, which is exhibited under extreme conditions. Excellent chemical stability.

 

Hexagonal boron nitride can be made into a boron nitride separation ring (Fig. 3) for horizontal continuous casting of steel. Hexagonal boron nitride is very stable to carbon and carbon monoxide at 1800 ° C, and is not corroded by molten glass, silicon, boron, non-oxide slag, molten salt (borax, cryolite) in steel.

 

Hexagonal boron nitride can be made into a composite shell for the casting of titanium. The chemical stability of titanium metal is poor. When the high temperature of forging is severely deformed, the metal flow produces a fresh surface which is prone to sticking, which causes the forging and the mold to be scrapped at the same time. The boron nitride release agent composite shell is applied to the surface of the mold to avoid direct contact between the titanium metal and the mold.

 

Hexagonal boron nitride can also be used for welding and furnace brazing processes, which can protect the surface of the workpiece from damage caused by splashing of the welding slag, and can also play a protective role in the metal welding process.