Difference Between High-Strength Bolts and Ordinary Bolts

High-strength bolts and ordinary bolts are both common threaded fasteners for flange and pipeline connection,but they are greatly different in material,mechanical performance,tightening method and application scope.

1.Material&Strength Grade

Ordinary bolts are generally made of low-carbon steel,with low strength grades such as 4.8 and 5.8.Their hardness and tensile strength are relatively low.

High-strength bolts adopt high-quality alloy steel or medium carbon steel through quenching and tempering heat treatment.Common grades include 8.8,10.9 and 12.9,featuring high hardness,strong tensile resistance and yield strength.

2.Bearing Capacity&Safety

Ordinary bolts mainly rely on screw rod friction and simple locking to bear load,which are easy to deform,stretch or break under heavy pressure,vibration and impact.

High-strength bolts can bear large tension,shear and fatigue load.With uniform stress distribution,they are not easy to loosen or deform,ensuring long-term connection stability.

3.Tightening Requirements

Ordinary bolts only need simple manual tightening without strict torque standard.The installation is simple and low-cost.

High-strength bolts require controlled torque and diagonal symmetrical tightening in multiple steps.Strict construction standards are needed to avoid insufficient pre-tightening or excessive stress damage.

4.Service Working Conditions

Ordinary bolts are suitable for normal temperature,low pressure,light load and conventional mechanical connection with little vibration.

High-strength bolts are widely used in high-temperature,high-pressure,strong vibration,chemical corrosion and heavy-duty industrial occasions,especially for pipeline flanges,pressure vessels and structural engineering.

5.Durability&Cost

Ordinary bolts have poor oxidation and fatigue resistance,short service life and low purchase cost.

High-strength bolts have better wear resistance,high temperature resistance and anti-loosening performance.Although the price is higher,they reduce leakage,fracture and maintenance risks in harsh working conditions.

Core Summary

Ordinary bolts are cost-effective for light-load and conventional environments.High-strength bolts are the preferred choice for high pressure,high temperature,vibration and key flange connections to guarantee sealing and operational safety.