What is Tempered Glass? Chemical Toughening or Physical Strengthening?

What is Tempered Glass?

Tempered glass is glass that has been subjected to a special treatment process to form a compressive stress layer on the surface of the glass. Tempered glass is actually a kind of pre-stressed glass. In order to improve the strength of the glass, chemical or physical methods are usually adopted to form a compressive stress layer on the surface of the glass. When the glass is subjected to external forces, the surface stress is firstly cancelled out, which improves the bearing capacity of the glass, enhances the performance of the glass itself such as the mechanical strength and thermal impact strength, and has a special fragmentation state.

Advantages of Tempered Glass?

Compared with common glasses, tempered glass has greatly improved in its bending strength, impact strength and thermal stability.

• Bending Strength

The bending strength of tempered glass is 4~5 times greater than that of the common glass. For instance, a tempered glass panel with size of 6 mm*600 mm*400 mm can support the mass of 3 people (about 200 kg) without damage. Tempered glass with a thickness of 5~6 mm has a bending strength of 1.67*10² MPa;
The stress distribution of tempered glass is parabolic in the direction of its thickness. The surface layer is compressive stress, and the inner layer is tensile stress. When it is subjected to bending load, as a result of force synthesis, the maximum stress value is not on the surface of the glass, but moves to the inner layer of the glass, so that it can withstand greater bending load. The deflection of tempered glass is 3~4 times larger than that of ordinary glass. For example, for a piece of tempered glass, about 6 mm*1200 mm*350 mm, its maximum bending can reach 100 mm.

• Impact Strength

The impact strength of tempered glass is 3~10 times higher than that of well annealed ordinary clear glass. For example, the impact strength of 6 mm thick tempered glass is 8.13 kgm, while that of ordinary plate glass is 2.35 kgm.

• Thermal Stability

Tensile strength of tempered glass is also increased. The modulus of elasticity decreased. In addition, the density is also lower than the annealed glass. From the thermal stability coefficient K formula can be seen, tempered glass can withstand sudden temperature changes in the range of 250 ~ 320℃, while the same thickness of common glass can only be withstood by the 70 ~ 100℃. For instance, tempered glass with 6 mm*510 mm*310 mm spread in the snow, poured with lead water of 1 kg, 327.5℃, and the tempered glass will not break.

• Safety

Tempered glass damaged first in the inner layer. The crack propagation speed caused by the role of tensile stress damage is very quick, while the outer layer of compressive stress must keep the broken inner layer is not easy to peel off the role. Therefore, when tempered glass breaks, only small fragments without sharp corners are produced.

• Other Properties

Tempered glass has a large distribution of stresses that are balanced against each other, so it can no longer be cut. During tempered glass processing, the glass surface cracks are reduced, and the surface condition is improved, which is the reason for the good strength and thermal stability of tempered glass.

Wide Application of Tempered Glass

Tempered glass has been widely used in automotive, construction, aviation, train and ship transport, household appliances, household furniture, sanitary ware, electronics, chemical engineering, and other industries. And, with the popularity of electronic devices, the demand of tempered glass in electronics products grow rapidly.
Cover glass panels made of tempered glass can be widely used in electronic and communications equipment, industrial control equipment, medical equipment, smart home, security monitoring systems, retail, service industry, banking, and financial services. Henping Industry, a professional tempered glass panel manufacturer, is specialized in providing high quality custom cover glass panels for different applications. If there are any questions, just contact us to get more information!

Custom Tempered Glass Panel Surface Treatment

Tempered glass panels, especially designed for industrial control equipment, medical devices, electronic displays or touch screens, may require surface treatments to meet specific performance requirements. Common surface treatments for tempered glass include anti-reflective (AR), anti-fingerprint (AF), anti-glare (AG) and more.

Anti-Reflective (AR)

When cover glass panel is used in high brightness environments or in direct sunlight, light reflection needs to be reduced to improve visibility, then tempered glass is usually treated with anti-reflective coating. AR tempered glass panel for display devices such as touchscreens and electronic displays can improve display effect and reduce eyestrain. AR tempered glass for precision instruments such as some medical devices can ensure a clear line of sight and accurate readings.

Anti-fingerprint (AF)

Anti-fingerprint tempered glass is usually used in high-touch frequency touch screen devices to reduce fingerprint retention, keep the screen clean and improve the user experience. Devices that require frequent operation and cleanliness, such as certain medical devices and public information screens, is highly recommended with AF tempered glass. (You may also like: Custom Anti-fingerprint Tempered Glass for Smart Home Devices >>)

Anti-Glare (AG)

Anti-glare tempered glass is great choice for devices used outdoors or in bright light environments to reduce direct reflection of light and prevent visual discomfort or blurred vision. Tempered glass with AG treatment can greatly reduce interference from surrounding light sources and improve reading and viewing comfort, so it is widely used in display devices in offices, classrooms, or other indoor environments. (Read more: AG Glass Cover Panel Technical Guide >>)
The choice of whether and how to treat the surface of tempered glass depends on the specific application needs, the environment in which it is used, and the user experience required. If you don’t know how to choose it for your glass panel, just contact us to get more cases for references.

How Tempered Glass is Made?

To ensure optimum performance and safety of the final glass product, tempered glass processing generally involves the following steps:

• Raw Material Selection: Select suitable glass materials. Generally, float glass is usually used as the base material for tempered glass in the market.
• Cutting: Cutting large pieces of glass to the required size. This step is usually carried out before the glass is fully tempered, as once tempered, the glass cannot be cut or machined.
• Edge Finishing and Hole Drilling: If required, the glass is edge polished and holes are drilled. These processes should be completed before tempering to avoid glass breakage.
• Cleaning: Thoroughly clean the glass before tempering to prevent impurities from being burned into the glass at high temperatures, which may affect its strength and appearance.
• Heating: Heat the glass close to its softening point, usually between 600°C and 700°C. The glass should be heated evenly to ensure that the entire glass is heated to its softening point. The heating process needs to be uniform to ensure that the entire piece of glass is heated consistently.
• Rapid Cooling (quenching): After heating, the glass is rapidly cooled (quenched). This is achieved by blowing cold air over the glass surface. Rapid cooling creates compressive stress on the surface of the glass and tensile stress in the interior, thus increasing the overall strength of the glass.
• Quality Inspection: Tempered glass is subject to stringent quality checks, including strength tests, dimensional checks and visual inspections to ensure that it meets the appropriate standards.
• Packaging and Transportation: Qualified tempered glass will be properly packaged to ensure that it is not damaged during transportation.

What’s Difference between Chemical Tempered Glass and Physical Tempered Glass?

Chemical toughening and physical strengthening (thermal strengthening) are actually two different strengthening methods in tempered glass manufacturing, which respectively constitute a key step in the tempered glass processing, but have different positions and roles in the whole process.

Physical Strengthening

Raw Material Selection – Cutting – Edge Polishing and Hole Drilling – Cleaning – Heating and Rapid Cooling (Quenching): Physical Strengthening – Quality Inspection – Packaging and Delivery

Physical strengthening significantly increases the strength of glass, which is typically three to five times stronger than untreated glass. When broken, the glass shatters into small particles, reducing the risk of injury. There are some limitations on glass size and thickness. The heat strengthening process may result in a slight change in glass size. Physically strengthened tempered glass is widely used in architectural, automotive, furniture and other applications where large size and high security are required.

Chemical Toughening

Raw Material Selection – Cutting – Edge Polishing and Hole Drilling – Cleaning – Chemical treatment (Ion exchange): not involve high temperature heating, but adopt chemical treatment. – Quality Inspection – Packaging and Delivery

Chemical strengthening improves the impact resistance and bending strength of the glass without changing the size and shape of the glass, suitable for complex shaped glass. No size limitation, suitable for small size glass. Increased strength is evenly distributed. Larger fragments when broken, less safe at the edges than physically strengthened glass. Chemically strengthened toughened glass is suitable for glass products that require a high degree of durability and strength, but in smaller sizes, such as screens for certain electronic devices.
It is important to note that both physical and chemical strengthening need to be carried out after the glass has been cut and any shape processing has been completed, as once the glass has been strengthened it can no longer be cut or modified in shape. The strengthening process is a critical step in increasing the strength and safety of the glass, and the choice of strengthening method depends on the requirements of the final product and the application scenario.

World Top 5 Tempered Glass Manufacturer

• Corning Inc

Corning is known for its innovative glass technology and highly durable products. Gorilla Glass is its famous product and is widely used in the displays of smartphones, tablets, and other consumer electronics.

• Asahi Glass Co., Ltd.

AGC is one of the world’s largest glass manufacturers, offering a wide range of types of industrial and architectural glass. AGC Glass also produces tempered glass specifically for electronic displays.

• Lens Technology

A Chinese company specializing in the production of touchscreens and cover glass, supplying many well-known mobile phone brands. Lens Technology is recognized for its high-quality tempered glass.

• SCHOTT

SCHOTT, a Germany manufacturer, produces a wide range of specialty glass and glass ceramics. SCHOTT supplies high-quality tempered glass for electronic displays and touchscreens.

• Nippon Electric Glass Co., Ltd. (NEG)

NEG is specialized in glass for LCDs and touch screens, is known for its advanced glass technology and high-quality products.

How to Choose a Reliable Tempered Glass Panel Manufacturer for Your Business?

In the process of tempered glass manufacturing, there are several technical difficulties and challenges. If a tempered glass panel manufacturer can deal these perfectly, then it can be a reliable vendor.

• Size and Shape Accuracy: how to ensure the accuracy of glass panel sizes and shapes is very important, especially for large or custom-made irregular shapes since it requires high-precision cutting and machining techniques.
• Edge Polishing and Hole Drilling: Good edgeworks and hole drilling requires special techniques for workers. Silked and experienced factory can hand it easily since it requires to control the stress concentration points to avoid weakening the overall strength of the glass.
• Internal Stresses Control: The internal stresses generated during the tempering process are critical to the strength and safety of the glass. Only precise control of these stresses ensures that the glass has sufficient strength and safety in the event of breakage.
• Quality of Glass Surface: The surface of toughened glass should be free from scratches, smudges or other defects. Maintaining a high-quality surface finish can be a challenge for tempered glass panel manufacturers, especially when additional surface treatments (e.g., anti-reflective, anti-fingerprint treatments) are applied.
• Environmental and Safety Standards Compliance: Compliance with environmental and safety standards during the tempered glass manufacturing process is also a challenge, especially when dealing with chemicals and high temperature materials.

If a tempered glass manufacturer can well deal with all above listed and other related challenges, it will be a reliable supplier with strong capacity and high technical standards.

What are the Determining Factors of Tempered Glass Panel Price?

The price of tempered glass used for display panels is determined by a number of factors, mainly including:

• Cost of raw materials: the quality and type of raw materials used for the glass directly affects the cost. Branded raw materials tend to cost more, but quality is guaranteed.
  Manufacturing process: The complexity of the manufacturing process for tempered glass also affects cost. For example, chemical strengthening processes are often more expensive than traditional physical strengthening.
• Product size and thickness: larger or thicker glass panels require more raw materials and energy to produce and therefore cost more.
• Surface treatments: Special surface treatments such as anti-reflective (AR), anti-fingerprint (AF) and anti-glare (AG) add additional costs.
• Technical Requirements and Quality Standards: Glass that meets high technical standards and stringent quality controls usually costs more. This includes precise dimensional control, defect-free surface quality, etc.
• Customization Requirements: Special designs, shapes or sizes can add to manufacturing costs.
• Brand and Reputation: Suppliers from well-known brands or with a good reputation in the market usually charge higher prices.

Other influencing factors include market supply and demand conditions, transport and logistics costs, tariffs and tax policies, etc.