Fatigue: The discussed intensity, plasticity, and hardness are all mechanical property indicators of metal under static load. In reality, many machine parts operate under cyclic loads, where fatigue in the parts occurs under such conditions.

Plasticity: The plasticity of Q345b square tubes refers to the ability of the metal material to undergo plastic deformation under load without breaking.

Impact toughness: It is the ability of a metal to resist damage under impact loading.

Hardness: The hardness of rectangular tubes refers to the hardness of the metal material. Currently, the commonly used method for hardness measurement in production is the indentation hardness test. This method involves pressing a head with a certain geometric shape into the surface of the metal material under a certain load, and determining the hardness based on the magnitude of the pressure.

Strength: The strength of rectangular tubes refers to the metal material's ability to resist failure under static load conditions (excessive plastic deformation or fracture). Since the action of load can take the form of tension, compression, bending, and shearing, strength is further categorized into tensile strength, compressive strength, bending strength, and shearing strength.