塑性 塑性是指金属材料在载荷作用下，产生塑性变形（永久变形）而不破坏的能力。

Plastic plasticity refers to the ability of a metal material to undergo plastic deformation (permanent deformation) without failure under load.

硬度 硬度是衡量金属材料软硬程度的指针。目前生产中测定硬度方法常用的是压入硬度法，它是用一定几何形状的压头在一定载荷下压入被测试的金属材料表面，根据被压入程度来测定其硬度值。

Hardness is a pointer that measures the softness and hardness of a metal material. At present, the most commonly used hardness measurement method in production is the Indentation hardness method, which uses an indenter with a certain geometric shape to press into the surface of the metal material to be tested under a certain load, and determines its hardness value according to the degree of indentation.

常用的方法有布氏硬度（HB）、洛氏硬度（HRA、HRB、HRC）和维氏硬度（HV）等方法。

The commonly used methods include Brinell hardness (HB), Rockwell hardness (HRA, HRB, HRC), and Vickers hardness (HV).

疲劳 前面所讨论的强度、塑性、硬度都是金属在静载荷作用下的机械性能指针。实际上，许多机器零件都是在循环载荷下工作的，在这种条件下零件会产生疲劳。

The strength, plasticity, and hardness discussed earlier on fatigue are all indicators of the mechanical properties of metals under static load. In fact, many machine parts operate under cyclic loads, which can lead to fatigue.

冲击韧性 以很大速度作用于机件上的载荷称为冲击载荷，金属在冲击载荷作用下抵抗破坏的能力叫做冲击韧性。

Impact toughness refers to the load applied to the machine at a high speed, which is called impact load. The ability of metals to resist damage under impact load is called impact toughness.

强度 强度是指金属材料在静荷作用下抵抗破坏（过量塑性变形或断裂）的性能。由于载荷的作用方式有拉伸、压缩、弯曲、剪切等形式，所以强度也分为抗拉强度、抗压强度、抗弯强度、抗剪强度等。各种强度间常有一定的联系，使用中一般较多以抗拉强度作为基本的强度指针。

Strength refers to the resistance of metal materials to failure (excessive plastic deformation or fracture) under static load. Since the Mode of action of load includes tension, compression, bending, shear and other forms, the strength is also divided into tensile strength, compressive strength, Flexural strength, shear strength and so on. There is often a certain connection between various strengths, and in use, tensile strength is often used as the most basic strength indicator.

方管的用途有建筑，机械制造，钢铁建设等项目， 造船，太阳能发电支架，钢结构工程，电力工程，电厂，农业和化学机械，玻璃幕墙，汽车底盘，机场,锅炉建造，高速路栏杆，房屋建筑，压力容器，石油储罐，桥梁，电站设备，起重运输机械及其他较高载荷的焊接结构件等。

The square tube is used for building, machinery manufacturing, steel construction and other projects, shipbuilding, solar power generation support, steel Structural engineering, power engineering, power plant, agricultural and chemical machinery, glass curtain wall, automobile chassis, airport, boiler construction, highway railings, housing construction, pressure vessels, oil tanks, bridges, power station equipment, lifting and transportation machinery and other high load welding structural parts.