What is st37 steel and what is its use?
St37 is a metal that is widely used in the construction industry. Lightweight, corrosion resistant and good thermal conductivity, aluminum is chosen as one of the building materials of car body and building skeleton. High consumption of aluminum in industry is not separate from casting technology.
Cooling test is performed using furnace test and cooling with water and oil lubricating 400 c SAE.
Experiment 1:
2 samples of stainless steel are heated to 400 to 8000 ° C, 33 minutes later the result is red and then blue and then cooled with brown water ash.
Experiment 2:
2 stainless steel samples were heated at 600 to 8000 ° C for 5 min and the resulting blue-red color was then cooled with water from gray to brown.
Experiment 3:
2 samples of stainless steel are heated at a temperature of 7000 to 8000 ° C, obtained in 2 minutes from a reddish-blue color, and after cooling with water from gray to brown.
Experiment 4:
2 samples of stainless steel are heated to a temperature of 40 to 8000 ° C. 33 minutes later to blue, then cooled with lubricating oil of black matter.
Experiment 5:
Two samples of stainless steel were heated at 6000 to 8000 ° C in 5 minutes and the resulting blue color was subsequently cooled with lubricating oil and the color of the substance was black.
Experiment 6:
2 samples of stainless steel are heated to a temperature of 7000 to 8000 degrees Celsius, obtained in reddish-blue in minutes, and then obtained with a lubricating oil that cools to a black color.
Introduction
The rapid development of industry at present, especially the machinery industry, also leads to the development of technology for the production of raw materials such as steel. Due to these conditions, the mechanical properties are sufficient and so that the lifespan can be increased. To overcome this, engine components are usually treated with heat treatment.
St37 steel equivalent to ALSL 1045 with chemical composition of 0.8% Mn, 0.5% C, 0.3% Si is one of the steels produced to make various construction components. Mechanical properties of st 37 steel are subjected to heat treatment under carburizing. One of the surface hardening processes is solid carburization, which aims to increase the amount of carbon.
Coated steel surface to obtain more hardness than the inner surface.
The solid carbohydrate process can improve the mechanical properties of machining components, such as:
- Increase the surface area
- Increase abrasion resistance against contact surfaces
Alloy steel is a steel that is formed in accordance with the intended purpose for mechanical improvement.
The properties or nature of the steel are consistent with the basic element of the steel.
Alloy steel is divided into 2 types:
- Low alloy steel (special alloy element <
- High alloy steel (special alloy element >0.8%)
St37 steel specifications (AiSi 1045)
It is a mild steel equivalent to AlSl 1045, with a chemical composition of 0.8% Mn, 0.5% C, 0.3% Si plus other elements with a hardness of 170 HB and a tensile strength of 650-800 (N / mm2) In general, St 37 steel can be used directly without heat treatment, unless special use is required.
Hardening process
The hardening process is done on the metal, to make the metal harder. Hardening is one of the heat treatment processes in which steel is heated to a certain temperature above the critical temperature (Ae3) and then kept for a long time, then immersed in water and oil or brine solution, depending on the type of steel. For Hypoeutectoid steel (hypoyotectoid: Includes peritectoid ferrite with eutectoid perlite, which includes eutectoid ferrite and cementite) at 300c – 500c above the Ae3 line on this steel. Its micron structure is ferrite + perlite to austenite structure, while Hypoeutektoid steel is perlite structure when heated to 300-500 above the Ae1 line. Figure 2.1 shows the cooling diagram for Hypoeutektoid steel, and the cooling diagram shows the effect of cooling rate and microstructure created by changing the cooling rate. Basically, an isothermal cooling diagram may change its location depending on the carbon composition. The larger the carbon composition, the closer the temperature curve will be to the y-axis, allowing more material to be completely transformed into the expected structure, such as the marten site structure, where the IT diagram for Hypoeutektoid carbon steel is too narrow in time to rapidly cool. It itself forms a martensite structure (in iron-carbon alloys and steels, martensite is formed by cooling austenite to have exactly the same chemical composition as primary austenite).
The hardening process of the steel surface layer is done by saturating the steel surface with carbon or other materials. At that time, the steel absorbs the saturated element and changes the carbon content that forms on the surface of the steel. Deeper penetration depends on the ability of this element to form a solid solution with steel. The elements that must be present in the industry to harden the surface coating are carbon, nitrogen, silicon and aluminum, which can form a solid solution. Increasing the temperature in the coating hardens and, conversely, affects the structure of the steel. At high temperatures the metal structure inside is damaged. In coating treatment, the surface hardening surface at high temperatures differs greatly in the carbon distribution in the diffusion layer. As the temperature increases, not only the diffusion rate of the steel elements increases, but also the velocity of this element is transferred from the environment to the steel surface, which increases more rapidly, in other words, the number of atoms adsorbed on the body surface Scatter the steel so that very high atomic concentrations lead to chemical alloys (carbides, nitrides, etc.) that cause the surface layer to become brittle.
Carburizing (Carbonation –carbon charcoal)
The process of enriching the workpiece layer with carbon is through thermochemical operations. It is generally re-applied to steels containing 0.2% carbon or less. Refining steel by decarbonization can improve the mechanical properties of steel because it causes wear resistance because the workpiece surface is high.
Carburizing process (Carbonation –carbon charcoal)
In this solid decarburization process, the carbon content in the surface layer of the body should be between 0.8 – 0.9%, in other cases more than 1 carbon content is higher than 1 is undesirable, because with a relatively high carbon level, the surface layer due to cementite formation (Fe3C is a compound between ferrous metal and carbon (6.67% carbon and 93.3% iron.) Is vulnerable. The placement of the object requires care to ensure that the mixture used is sufficient to supply the carbon used, where the surface is separated by a charging mixture and there are no tangential components on the side of the box. The distance between the components of the carburizing material is not less than 20 mm to 25 mm is not the same as the box wall. When the carburization medium is compacted, the box is closed and all open parts are sealed with clay or clay. This is to prevent air from penetrating into the box or it burns due to heating of the carburetor environment and the material is oxidized, then the box is fed into the heating kitchen and heated to a temperature of 8600 to 9200. The temperature is kept at the carburetor temperature for several hours to obtain the desired coating.