What's the Conventional Technical Parameters of Chemical Strengthened Soda Lime Glass？

2026-08-10

Soda-lime glass is the most common type of float glass. Chemical tempering (ion exchange) strengthens it by exchanging smaller sodium ions in the glass surface with larger potassium ions from a molten salt bath, creating a surface compressive stress layer. Ordinary soda-lime glass has relatively slow ion diffusion and noticeable stress relaxation, so the depth of layer (DOL) is usually shallow and cannot easily reach the levels achieved with aluminosilicate glasses. Chemical tempering of ordinary soda-lime glass is less effective than that of aluminosilicate glass (the latter commonly achieves CS of 650–1000+ MPa and DOL of 30–100+ μm).

Core Stress Parameters (Most Important)

Parameter	Typical Value	Remark
Surface Compressive Stress (CS)	400–750 MPa (commonly 400–650 MPa; up to ~800 MPa in some cases)	Chemically strengthened glass is typically required to exceed 450 MPa. Float soda-lime glass commonly achieves around 600 MPa. Excessively high CS can make post-cutting difficult or create excessive central tension.
Depth of Layer (DOL or DOC)	5–30 μm (commonly 5–20 μm; longer processes can reach 20–50 μm or more, but CS decreases)	Ordinary soda-lime glass struggles to achieve deep layers and is more susceptible to surface scratches. ASTM C1422 classifies products based on CS and case depth.

Example reference values:

Shorter process: CS ≈ 600–750 MPa, DOL ≈ 5–10 μm
Medium process: CS ≈ 450–600 MPa, DOL ≈ 12–25 μm
Longer/higher-temperature process: CS drops to ≈ 450–550 MPa, DOL can reach 20–40+ μm

Central tension (CT) is usually low (a few MPa to several tens of MPa, depending on thickness and the CS × DOL balance). Thin sheets generally remain cuttable after treatment.

Other Mechanical Properties

Flexural strength (e.g., four-point bending): Annealed soda-lime glass is typically 40–100 MPa; after chemical tempering it can reach 200–600 MPa (often 3–5 times higher or more, depending on surface condition and test method). Some studies report values around 400+ MPa.
Vickers hardness: Increases by about 8–20%, commonly reaching 650–750 kgf/mm² (HV) (original ≈ 500–600 HV).
Impact and scratch resistance: Significantly improved, but protection against deep scratches is limited due to the relatively shallow DOL.
Strength gain: Roughly 3–8 times that of annealed glass (depending on test method and surface defects).

Process and Other Related Indicators

Typical process conditions: Molten KNO₃ (or with a small amount of NaNO₃), temperature ≈ 400–470 °C, time 4–24 hours (or longer). Higher temperature and longer time increase DOL but reduce CS due to stress relaxation.
Optical properties: Transmittance decreases slightly (≈ 1–2%); optical quality remains largely unchanged with no significant distortion like that seen in thermally tempered glass.
Basic physical properties (e.g., thermal expansion coefficient): Essentially unchanged (≈ 8.5–9.5 × 10⁻⁶/°C).
Applicable thickness: Especially suitable for thin glass (0.1 mm to a few mm); thicker plates can also be treated but with lower efficiency.

Application scenarios of chemically tempered soda-lime glass

Chemically strengthened soda-lime glass is mainly used where thin, strong, and optically clear glass is needed, especially when thermal tempering is not suitable (e.g., very thin sheets or complex shapes).

Common applications include:

Cover glass for smartphones, tablets, laptops, and other electronic displays (entry-level or cost-sensitive devices)
Protective covers for instruments, meters, and control panels
Watch crystals and camera lens covers
Architectural glass (thin partitions, decorative panels, or safety glazing in specific cases)
Automotive and transportation interiors (instrument clusters, displays)
Sight glasses / viewing windows for equipment and containers
Pharmaceutical or laboratory containers and vials (where moderate strengthening is required)
Touchscreens and interactive kiosks

detail_application(1).png

It is preferred for thinner glass (usually under 3–4 mm) that needs higher strength without optical distortion. For higher performance (deeper compressive layer and better drop resistance), aluminosilicate glasses are usually chosen instead.