How to Distinguish Between Ordinary Bolts and High-Strength Bolts

2025-09-05 08:13:55

One intuitive way to identify ordinary bolts and high-strength bolts is by observing their appearance and specifications. High-strength bolts are often paired with extra-wide or tall washers and nuts, have a smoother surface finish, and, to prevent strength reduction caused by corrosion, are usually treated with galvanizing, nickel plating, or passivation to ensure good corrosion resistance.

In addition, you can check the markings on the bolts. High-strength bolts typically have clear markings indicating their strength grades, such as 10.9 or 12.9, while ordinary bolts may only be marked as 4.6 or 4.8.

To fundamentally confirm the strength grade of a bolt, performance testing can be conducted. Ordinary bolts have limited tensile and shear strength, and generally cannot pass the strict tests required for high-strength applications. High-strength bolts, on the other hand, must meet more technical requirements, with tensile strength and yield strength far exceeding those of ordinary bolts.

A commonly used test is the tensile test. Ordinary bolts are more likely to break during a tensile test, which shows their lower hardness and elongation properties. In contrast, high-strength bolts can withstand much longer under the same test conditions without failing.