Discover innovative techniques for tempering glass that boost its strength and safety, from traditional physical heat treatments to advanced chemical processes. Learn how these methods enhance durability and thermal resistance, shaping the design and functionality of glass in various applications. Dive into the world of tempered glass and see how it transforms everyday use!

 

 

Methods For Tempering Glass-Physically and Chemically

 

In an era where safety and durability are paramount, the glass industry is undergoing a significant transformation. Tempered glass, known for its safety, strength and resistance to thermal stress, is becoming an increasingly integral part of various applications, from architectural design to automotive manufacturing. Recent advancements in both traditional and innovative glass tempering techniques are significantly enhancing the material's capabilities, ensuring that it meets modern demands for safety and design elegance.

 

Know About Tempered Glass: 

 

Tempered glass is produced through a process that involves heating and cooling the glass to make it substantially stronger than ordinary glass. This technique allows the glass material to withstand high levels of stress and thermal shock. When broken, tempered glass shatters into small, blunt pieces, reducing the risk of injury—a crucial feature for safety in commercial and residential environments alike.

 

 

 

Physical and Chemical Methods for Tempering Glass: 

 

As one of the most common types of glass material in our lives, tempered glass is widely used in various fields like buildings, domestic appliances, electronics, auto industry, furniture,  etc. The functions of tempered glass products are different, the required glass materials are different, and the corresponding glass tempering processes are also different. The specific tempering processes for tempered glass fall into the following two categories: physical tempering and chemical tempering.

 

1. Physical Tempering

The principle of the physical tempering method is to heat the glass to a suitable temperature and then cool it quickly, causing the glass surface to shrink sharply and produce compressive stress. The middle layer of the glass cools more slowly and has no time to shrink, so it forms tensile stress, making the glass gain higher strength. Generally speaking, the higher the cooling intensity, the greater the strength of the tempered glass. There are many physical tempering methods, which can be divided into the following types according to the cooling medium-: Gas medium tempering method, Liquid medium tempering method,

Particle tempering method, Mist tempering method.

 

 

 

 

--1.1. Gas Medium Tempering Method

The gas medium tempering method is the air-cooled tempering method. Including horizontal air cushion tempering, horizontal roller tempering, vertical tempering and other methods. It is a production method that heats the glass to close to the softening temperature of the glass, which is in the range of 650 to 700°C, and then blows air on both sides of it to rapidly cool it to increase the mechanical strength and thermal stability of the glass. The quenching of heated glass is an important step in the production of tempered glass using physical tempering methods. The basic requirement for glass quenching is rapid and uniform cooling to obtain uniformly distributed stress. In order to obtain uniformly cooled glass, cooling must be required The device effectively evacuates hot air, facilitates the removal of accidental broken glass and should minimize its noise.

 

Air-cooled tempered glass has lower cost, larger output, higher mechanical strength, thermal shock resistance and higher heat resistance gradient. In addition to enhancing the mechanical strength, air-cooled tempered glass can form small fragments when broken. , can reduce the harm to the human body. However, air-cooled tempering technology has certain requirements on the thickness and shape of the glass. The minimum thickness of the glass tempered by domestic equipment is generally about 3 mm, and the cooling speed is slow and the energy consumption is high. For thin glass, there is also the problem of glass deformation during the tempering process, so it cannot be used in fields with high optical quality requirements. At present, air-cooled tempering technology is widely used, and the tempered glass produced is mostly used in cars, ships, and buildings.

 

Continuous Furnace to Heat and Cool Tempered Glass: 

 

 

 

--1.2. Liquid Medium Tempering Method

Liquid medium tempering method, that is to cool the heated glass with liquid material. That is, after the glass is heated to close to the softening point, it is placed in a quench tank filled with liquid for tempering. At this time, salt water can be used as the cooling medium, such as mixed salt water of potassium nitrate, potassium nitrite, sodium nitrate, sodium nitrite, etc. In addition, mineral oil can also be used as the cooling medium, and of course additives such as toluene or carbon tetrachloride can also be added to the mineral oil. Some special quenching oil and silicone oil can also be used.

 

During liquid tempering, since the edge of the glass plate enters the quenching tank first, bursting caused by uneven stress may occur. In order to solve this problem, air cooling or liquid spraying can be used to pre-cool, and then placed in organic liquid for rapid cooling. You can also put water and organic solution in the quenching tank. The organic solution floats on the water. When the heated glass is put into the tank, the organic solution acts as a pre-cooling, absorbs part of the heat, and then the heated glass enters the water to quickly cool down. Either immersion in the cooling liquid or liquid spray method can be used, but the immersion method is generally used. The difficulty of the liquid tempering method is to establish a reasonable liquid cooling process system. There are two issues that should be paid attention to during liquid cooling tempering: one is the excessive compressive stress layer produced, and the other is to avoid glass bursting.

 

Using the liquid medium tempering method, due to the large specific heat of water and the high heat of vaporization, the dosage is greatly reduced, resulting in lower energy consumption and lower costs. It also has fast cooling speed, high safety performance and small deformation. Since the glass is heated and then inserted into the liquid medium during cooling, glass plates with larger areas are prone to uneven heating, which affects quality and yield. The liquid cooling method is mainly suitable for tempering various thin glasses with a small area, such as glasses glass, LCD display glass, optical instrumentation glass, etc.

 

--1.3. Particle Tempering Method

 

The particle tempering method is a process in which the glass is heated to close to the softening temperature and then quenched in a fluidized bed by solid particles, generally alumina particles with a particle size of less than 200 moles, to strengthen the glass. In theory, using solids as cooling media can create thinner, lighter, and stronger tempered glass.

 

The particle tempering method can temper ultra-thin glass with high strength and good quality. It is currently an advanced technology for manufacturing high-performance tempered glass. Compared with the traditional wind tempering process, the new particle tempering process has a large cooling energy of the cooling medium, is suitable for tempering ultra-thin glass, and saves about 40% of energy. However, the cooling medium cost of the particle tempering process is relatively high. The particle tempering method is suitable for tempering high-strength, high-precision thin glass and ultra-thin glass.

 

 

 

 

--1.4. Mist Tempering Method:

 

The mist tempering method uses atomized water as the cooling medium and uses spray exhaust equipment to make the glass cool more evenly during the tempering process, consume less energy, and have better performance after tempering. The spray exhaust equipment is composed of a number of grid-shaped barrel structures connected in parallel and arranged on the bottom plate. Each barrel structure is composed of a bottom plate, a partition, a nozzle and a number of exhaust holes. Similar to the gas method, but the cooling medium used is not air but atomized water. It is characterized by using atomized water as the cooling medium to temper the glass.

 

The specific heat of water is larger, and the heat of vaporization of water is also the highest among all liquids. During the tempering process of glass, water mist is continuously sprayed onto the heated glass surface. The particulate atomized water quickly absorbs heat and becomes 100°C water, and then vaporizes. Utilizing the characteristics of water's large specific heat and high heat of vaporization, a large amount of heat on the glass surface is instantly taken away and absorbed to quench and temper the glass, causing permanent compressive stress on the glass surface, thus improving the tensile strength of the glass to make out the tempered glass.

 

Atomized water can be sprayed onto the heated glass surface by compressed air blowing, steam blowing or hydraulic spraying. Because the atomized water will quickly absorb heat and vaporize and expand when it comes into contact with the red-hot glass, if it is allowed to Free diffusion, which will affect the uniform cooling of the glass and easily cause the glass to burst. To this end, a unique spray exhaust device needs to be designed so that the vaporized and expanded water vapor can be extracted timely without spreading along the glass surface. The cooling medium of the mist tempering method is easy to obtain, has low cost and does not pollute the environment. It can also temper thin glass that cannot be tempered by ordinary gas, liquid and particle tempering methods. However, cooling uniformity is difficult to control. The mist tempering method is difficult to control due to its cooling system and is currently rarely used. Acrylic lenses can be made using the mist tempering method.

 

 

 

2. Chemical Tempering Method

 

Chemical tempering refers to a tempering method that changes the surface components of glass through chemical methods and increases the surface lamination stress to increase the mechanical strength and thermal stability of the glass. Since it strengthens glass through ion exchange, it is also called the ion exchange strengthening method.

 

According to the type of exchanged ions and the temperature of ion exchange, it can be divided into ion exchange method below the transition point temperature and ion exchange method above the transition point temperature.

 

The principle of the chemical enhancement method is to change the surface composition of the glass based on the mechanism of ion diffusion. The glass is immersed in high-temperature molten salt at a certain temperature. The alkali metal ions in the glass and the alkali metal ions in the molten salt are diffused. Mutual exchange occurs, resulting in a "crowding" phenomenon, which causes compressive stress on the surface of the glass, thus increasing the strength of the glass.

 

 

 

 

The strength of chemically strengthened glass is close to that of physically strengthened glass. It has good thermal stability, low processing temperature, and the product is not easily deformed. Its products are not limited by thickness and geometric shape. The equipment is simple to use and the product is easy to realize. However, compared with physically tempering glass, chemically tempering glass has a long production cycle, low efficiency and high production cost. The fragments are similar to ordinary glass, poor safety, and its chemical properties are not good, and physical properties such as mechanical strength and impact strength are easy to fade and relax.the intensity decays quickly with time. Chemically tempered glass is widely used in flat glass of different thicknesses, thin-walled glass and special-shaped glass products for bottles and jars, and can also be used for fire-resistant glass. The lifespan of chemically tempered glass products is shorter, generally less than 3 years, while the lifespan of physically tempered glass products exceeds 30 years.

 

Glass tempering can use different processes according to the actual situation, or the above-mentioned glass strengthening technologies can be organically combined to give full play to their respective strengths and fully improve the strength of the glass.

 

 

 

About Huide Glass-Fabricating Factory for Tempered Glass: 

 

Huide Glass has been in that processing business of tempered glass sheets products for around 13 Years since 2011. We have strong production and development capabilities, and currently has 7 automatic cutting machines, 8 edge grinding lines, there are 8 CNC precision grinding processing centers; there are 3 tempering furnaces(one for North-Glass, one for Yihai, and one for continuous tempering furnace SOUTHTECH). we can fabricate tempered glass sheet products 3,000,000 square meter per year. 

 

 

 

 

Our tempered glass products includes tempered glass shelf for refrigerator, tempered glass door for refrigerators, tempered glass lid for household washing machines, tempered glass sheet for smart tea table top or bedside table top, tempered glass cover panel for water cleaner and water heater, tempered glass cover for advertising billboard, tempered glass top and front door panel for tea bar machine, tempered glass door sheet for ovens, tempered glass sheet for gas stoves, tempered glass cover panel for display cabinet, display box, or tempered glass cover sheet for showcase counter,etc, and also we can do customized manufacturing according to your unique real applications. if you want to know more, don't hesitate to contact us.