Rail is the abbreviation of railway track. It is made of manganese steel with high hardness and toughness. The manganese steel is hard, wear-resistant and has a certain impact toughness, which meets the conditions for manufacturing rail.
In addition, manganese rail has a high density. When the oxide rust film is formed on the surface, it will form a protective effect on the interior and will not affect the use. Iron and steel are distinguished by their carbon content. The iron-carbon alloy with a carbon content of less than 2% is steel, and the iron-carbon alloy with a carbon content of more than 2% is called pig iron.
From a metallurgical point of view, there is no such thing as stainless iron. Stainless steel is also a kind of steel. Steel has toughness, elasticity and rigidity. As far as rust is concerned, rust is not corrosion resistant. The main element that determines the corrosion resistance of stainless steel is chromium.
Steel containing more than 10.5% chromium will not rust. At this time, the oxidation of chromium and corrosive medium will form an oxide film on its surface, which can prevent basic further corrosion.
The cost of making iron is far lower than that of stainless steel. In the design and manufacture of some products with short service life and iron quality that can meet the requirements of material use, iron will be used.
Rail is a common saying. In fact, it is a rail. In order to improve the compressive and wear resistance, manganese is usually added. Stainless steel is resistant to oxidation and corrosion, and chromium and molybdenum elements are usually added. The strength, wear resistance, flexibility, plasticity, corrosion resistance, etc. shall be comprehensively considered in the use of steel rail, but the high-strength wear resistance is shouxuan, and stainless steel cannot meet the requirements and will not be used. The reason why it can not meet the requirements is that it is not durable enough, and it is easy to be damaged under thermal expansion and contraction. Stainless steel can be easily damaged under daily wind, rain and sun exposure. Although the high-speed rail looks rusty, there is only a layer of rust on the surface, and the interior is still intact.
In addition, manganese rail has a high density. When the oxide rust film is formed on the surface, it will form a protective effect on the interior and will not affect the use.
First of all, technically speaking, most people think that stainless steel is not rusty, but in fact, stainless steel is also rusty like other alloys, but the color of the oxide film (rust) on the surface of stainless steel after rust is the appearance color of stainless steel, and this layer of oxide film is relatively dense, which can protect the internal structure from further oxidation and rust. However, the oxide film can still be corroded under certain conditions, especially in humid acidic environment.
Therefore, stainless steel cannot be used in many cases. There are many kinds of stainless steel, and the hardness of stainless steel (especially austenitic stainless steel) is relatively low. For example, it is difficult to make a sharp edge when it is used to make a knife, and it is easy to become blunt even if it is used; Experienced people know that the bright stainless steel plate is easy to be scratched because of its soft texture.
So technically speaking, stainless steel is not rustless, but the color after rust is similar to that before rust; Its performance is not suitable for all places, so stainless steel can not be used to replace other materials.
In terms of resources, nickel and chromium used in stainless steel are relatively scarce minerals, especially nickel is relatively scarce. Useful and easy to use things always need to be used in key places, and can’t be wasted at will. In terms of cost, we will consider the cost of purchasing materials, making parts and installing machines. The price of stainless steel is not only a little higher than that of ordinary steel, aluminum, magnesium aluminum alloy, plastic and other materials, but several times higher. As long as cheap materials can meet the requirements, who will use expensive materials?
In addition, even if other materials are rusty and not corrosion resistant, there are many surface treatment technologies that can protect materials from corrosion. For example, painting, powder spraying, electroplating, electrophoresis, surface oxidation, surface chemical treatment (nitriding, cyanidation, etc.) can improve the surface corrosion of materials. So it is not necessarily that rusty materials cannot be used in corrosive places.
To sum up, stainless steel can not be used to replace all other materials. Zhiyou can select a suitable material for the part after fully considering the factors such as part function, material performance, working environment, part cost, processing performance and possibility. It cannot be said that all stainless steel materials should be used instead. In mechanical major and material major, there are special material courses to introduce how to select materials and material properties.
The railway track is the established operation track of the train, and is an indispensable mode of railway technology at present. Everyone should have noticed that basically all the railway tracks are rusty, even the newly built railway tracks are like this. Rusty iron products will become very fragile even if their service life becomes shorter.
Post time: Mar-01-2023
