Category: Manufacturing Technology knowledge

Hardness indicates the ability of a material to resist the pressure of a hard object into its surface. It is one of the important performance indexes of metal materials. Generally, the higher the hardness, the better the wear resistance. Common hardness indicators include Brinell hardness, Rockwell hardness and Vickers hardness: 1. Brinell hardness (HB): press a hardened steel ball of a certain size (generally 10mm in diameter) into the material surface with a certain load (generally 3000kg) and keep it for a period of time. After unloading, the ratio between the load and its indentation area is the Brinell hardness…

Main forms of building metal corrosion:  (1) Uniform corrosion. The corrosion of the metal surface makes the section uniform and thin. Therefore, the annual average thickness loss value is often used as the index of corrosion performance (corrosion rate). Steel is generally uniformly corroded in the atmosphere.  (2) Pitting. The corrosion of metal is pitted and deep pits are formed. The generation of pitting corrosion is related to the nature of metal and its medium. Pitting is easy to occur in the medium containing chloride salt. The maximum hole depth is often used as the evaluation index for pitting corrosion.…

Plasticity refers to the ability of metal materials to produce permanent deformation (plastic deformation) without damage under the action of external force. When metal materials are stretched, the length and cross-sectional area will change. Therefore, the plasticity of metal can be measured by two indexes: the elongation of length (elongation) and the shrinkage of section (reduction of section). The greater the elongation and area shrinkage of metal material, the better the plasticity of the material, that is, the material can withstand large plastic deformation without damage. Generally, metal materials with elongation greater than 5% are called plastic materials (such as…

Many mechanical parts and engineering components work under alternating load. Under the action of alternating load, although the stress level is lower than the yield limit of the material, after a long time of repeated stress cycle, sudden brittle fracture will also occur. This phenomenon is called fatigue of metal materials. The characteristics of fatigue fracture of metal materials are:  (1) The load stress is alternating;  (2) The action time of load is long;  (3) The fracture occurs instantaneously;  (4) Both plastic and brittle materials are brittle in the fatigue fracture zone. Therefore, fatigue fracture is the most common and…

Metal materials refer to metal elements or materials with metal characteristics mainly composed of metal elements. Including pure metals, alloys, metal materials, intermetallic compounds and special metal materials. (Note: metal oxides (such as alumina) are not metal materials) 1. Meaning: The development of metal materials is closely related to the progress of human civilization. After the stone age, the bronze age and iron age are marked by the application of metal materials. In modern times, a wide variety of metal materials have become an important material basis for the development of human society. 2. Type: Metal materials are usually divided…

The characteristics of chemical reactions between metals and other substances are called the chemical properties of metals. In practical application, the corrosion resistance and oxidation resistance of metals (also known as oxidation resistance, which refers to the resistance or stability of metals to oxidation at high temperature) and the influence of compounds formed between different metals and between metals and non metals on mechanical properties are mainly considered. In the chemical properties of metals, especially the corrosion resistance is of great significance to the corrosion fatigue damage of metals.

1. Yield point（ σ s) When the stress of steel or sample exceeds the elastic limit during tension, even if the stress is no longer increased, the steel or sample continues to have obvious plastic deformation. This phenomenon is called yield, and the minimum stress value when yield phenomenon occurs is the yield point. If PS is the external force at the yield point s and fo is the cross-sectional area of the sample, then the yield point σ s =Ps/Fo(MPa) 2. Yield strength（ σ 0.2) The yield point of some metal materials is not obvious, so it is difficult…

According to the analysis of magnesium alloy, 6063 alloy has excellent processability and weldability, which is mainly related to the extrusion and polishing of magnesium alloy.6063 alloy is widely used in building profiles, irrigation pipes, pipes, rods and profiles for vehicles, platforms, furniture, elevators and fences.

Explanation of common aluminum alloy properties (I): 2024-LY12 aluminum alloy 2024 (LY12) is a typical hard aluminum alloy in aluminum copper magnesium system. Its composition is reasonable and its comprehensive properties are good. Many countries produce this alloy, which is the largest amount of duralumin. The alloy is characterized by high strength and certain heat resistance. It can be used as working parts below 150 ° C. When the temperature is higher than 125 ° C, the strength of 2024 alloy is higher than that of 7075 alloy. The formability is better in thermal state, annealing and new quenching state,…

For the car body, our direct feeling is "iron wrapped meat". Therefore, we take it for granted that the car shell is made of steel. In fact, with the continuous development of materials and manufacturing technology, more and more new materials have also joined the base camp of automobile manufacturing. Today, let's see what materials can be used for automobile body except steel? 1. Already popular - all aluminum alloy Audi's ASF (Audi space frame) is one of the pioneers of all aluminum alloy body. It has a history of 23 years, and a total of 9 Audi have been…