High-strength bolts are fasteners made from high-strength steel and possess high tensile and yield strengths. They are primarily used in applications that withstand heavy loads or require extremely high connection strength and safety, such as in building steel structures, bridges, machinery, and the automotive industry. Their design aims to achieve a tight fit and reliable force transmission between connected components through the high strength of their materials and precise preload control.
The essential difference between high-strength bolts and ordinary bolts:
The core differences between the two are reflected in three aspects: material properties, force-bearing principles, and application scenarios. They are as follows:
Different Material Strengths
Ordinary bolts are typically made of low-carbon steel (such as Q235) or medium-carbon steel. They have low tensile strength (generally ≤400MPa) and even lower yield strength (≤235MPa). They primarily transmit loads through shear or tensile forces within the bolt shank.
High-strength bolts are made of high-strength alloy steel (such as 40Cr, 20MnTiB, etc.). After heat treatment (quenching and tempering), they can achieve tensile strengths exceeding 800MPa (common grades include 8.8 with a tensile strength of ≥800MPa and 10.9 with a tensile strength of ≥1000MPa). Their yield strength is also much higher than that of ordinary bolts (8.8 with a yield strength of ≥640MPa and 10.9 with a yield strength of ≥900MPa), allowing them to withstand greater preloads and working loads. Different load-bearing principles
Ordinary bolts: "Preload" is generally not emphasized during connection. Instead, the primary focus is on the fit between the bolt shank and the hole (a clearance fit or transition fit). Force is transmitted through shear on the shank or compression on the connected parts. Essentially, "load is applied to the shank."
High-strength bolts: During connection, a specified preload must be applied using a tool such as a torque wrench. This creates significant friction between the connected parts, with most of the load transmitted through friction (a friction-type connection). Even in compression-type connections, preload can reduce the actual load on the bolt shank. Essentially, "friction is primary, with shank load as a secondary factor."
Different application scenarios
Ordinary bolts: Suitable for applications with low loads and low connection strength requirements (such as furniture, light equipment, and temporary fixtures). Strict torque control is not required during installation, and they can be repeatedly disassembled.
High-strength bolts: Used in applications with high loads, frequent vibration, and extremely high safety requirements (such as steel structure beam-column connections, bridge joints, and wind turbine equipment). Preload must be controlled according to specifications (using torque or rotation angle methods) during installation, and in most cases, reuse is prohibited to prevent preload fading and material fatigue. Different Manufacturing Processes
Ordinary bolts: The processing process is simple, and they are generally used directly after cold heading, without heat treatment (or only simple annealing).
High-strength bolts: They undergo rigorous heat treatment (quenching and tempering) to improve the material's strength and toughness, and achieve higher thread precision (to prevent loss of preload due to thread defects during installation).
In short, ordinary bolts are "passive load-bearing" fasteners, while high-strength bolts are key connectors that "actively control" force. The former relies on its own strength to "bear" the load, while the latter relies on the friction generated by the preload to "lock" the load. This is the most fundamental difference between the two.
In short, ordinary bolts are "passively loaded" fasteners, while high-strength bolts are key connectors that "actively control force" - the former relies on their own strength to "bear" the load, while the latter relies on the friction formed by the pre-tightening force to "lock" the load. This is the most essential difference between the two.
Email: cast@ebcastings.com
High-strength bolts are fasteners made from high-strength steel and possess high tensile and yield strengths. They are primarily used in applications that withstand heavy loads or require extremely high connection strength and safety, such as in building steel structures, bridges, machinery, and the automotive industry. Their design aims to achieve a tight fit and reliable force transmission between connected components through the high strength of their materials and precise preload control.
The essential difference between high-strength bolts and ordinary bolts:
The core differences between the two are reflected in three aspects: material properties, force-bearing principles, and application scenarios. They are as follows:
Different Material Strengths
Ordinary bolts are typically made of low-carbon steel (such as Q235) or medium-carbon steel. They have low tensile strength (generally ≤400MPa) and even lower yield strength (≤235MPa). They primarily transmit loads through shear or tensile forces within the bolt shank.
High-strength bolts are made of high-strength alloy steel (such as 40Cr, 20MnTiB, etc.). After heat treatment (quenching and tempering), they can achieve tensile strengths exceeding 800MPa (common grades include 8.8 with a tensile strength of ≥800MPa and 10.9 with a tensile strength of ≥1000MPa). Their yield strength is also much higher than that of ordinary bolts (8.8 with a yield strength of ≥640MPa and 10.9 with a yield strength of ≥900MPa), allowing them to withstand greater preloads and working loads. Different load-bearing principles
Ordinary bolts: "Preload" is generally not emphasized during connection. Instead, the primary focus is on the fit between the bolt shank and the hole (a clearance fit or transition fit). Force is transmitted through shear on the shank or compression on the connected parts. Essentially, "load is applied to the shank."
High-strength bolts: During connection, a specified preload must be applied using a tool such as a torque wrench. This creates significant friction between the connected parts, with most of the load transmitted through friction (a friction-type connection). Even in compression-type connections, preload can reduce the actual load on the bolt shank. Essentially, "friction is primary, with shank load as a secondary factor."
Different application scenarios
Ordinary bolts: Suitable for applications with low loads and low connection strength requirements (such as furniture, light equipment, and temporary fixtures). Strict torque control is not required during installation, and they can be repeatedly disassembled.
High-strength bolts: Used in applications with high loads, frequent vibration, and extremely high safety requirements (such as steel structure beam-column connections, bridge joints, and wind turbine equipment). Preload must be controlled according to specifications (using torque or rotation angle methods) during installation, and in most cases, reuse is prohibited to prevent preload fading and material fatigue. Different Manufacturing Processes
Ordinary bolts: The processing process is simple, and they are generally used directly after cold heading, without heat treatment (or only simple annealing).
High-strength bolts: They undergo rigorous heat treatment (quenching and tempering) to improve the material's strength and toughness, and achieve higher thread precision (to prevent loss of preload due to thread defects during installation).
In short, ordinary bolts are "passive load-bearing" fasteners, while high-strength bolts are key connectors that "actively control" force. The former relies on its own strength to "bear" the load, while the latter relies on the friction generated by the preload to "lock" the load. This is the most fundamental difference between the two.
In short, ordinary bolts are "passively loaded" fasteners, while high-strength bolts are key connectors that "actively control force" - the former relies on their own strength to "bear" the load, while the latter relies on the friction formed by the pre-tightening force to "lock" the load. This is the most essential difference between the two.
Email: cast@ebcastings.com
