Heat Treatment and Metallurgy Lab

Carbonitriding is a heat treatment process by which carbon and nitrogen (via ammonia gas) permeate the surface layer of steel components. The process involves temperatures of around 850°C followed by quenching in oil or gas solutions. Successful completion of this process will grant the steel components a variety of beneficial properties, most notably increased wear resistance Carbonitriding: the diffusion of carbon and nitrogen atoms into the surface of a metal to increase hardness; nitrogen is usually added to the endothermic atmosphere Heat Treatment: The temperature used for carbonitriding should be around 850°C (1550°F). This is lower than the temperature used for carburizing, and the time for which the part will be heat treated for is shorter as well. These lower temperatures used for carbonitriding compared to carburation also means there is less distortion of the part, especially during quenching. However, this is a higher temperature than what is used for standard nitriding...

  Case hardening Process Case hardening is a material processing method that is used to increase the hardness of the outer surface of a metal. Case hardening results in a very thin layer of metal that is notably harder than the larger volume of metal underneath of the hardened layer. - It is mainly used on low-carbon steels. The part is heated to 871–954 °C (1600–1750 °F) - Attempt to harden an entire metal object. One reason is efficiency. Less energy and less time are required to heat the outermost surface of a metal as opposed to its entire cross section. - A hard outside shell and a more ductile interior. What Types of Metals Can Be Case Hardened? Metals that can be case hardened are generally limited to ferrous materials, although there are special cases such as the Nitriding of some titanium or aluminum alloys. The ferrous metals commonly case hardened are. Gears Fasteners Camshafts Rods Pins   --BENEFITS OF CASE HARDENING Creating a more durable product Increases wea...

HEAT TREATMENT  SOAKING OR HOLDING HEATING CONTROLLED COOLING HEATING CYCLE

The Annealing process:- Annealing is a heat treatment process that changes the physical and sometimes also the chemical properties of a material to increase ductility and reduce the hardness to make it more workable Annealing steel consists of heating a metal above a critical temperature and then cooling at a rate that will produce a refined microstructure. Annealing is most often used to soften a metal after cold working, to improve machinability, or to enhance properties like electrical conductivity. Annealing works in  three stages  – the recovery stage, recrystallization stage and the grain growth stage. These work as follows: 1. Recovery Stage This stage is where the furnace or other heating device is used to raise the temperature of the material to such a point that the internal stresses are relieved. 2. Recrystallization Stage Heating the material above its recrystallization temperature but below its melting point causes new grains to form without any residual stresses....

The Normalizing Process Heat Treatment:- Normalizing heat treatment is a heat treating process used to provide uniformity in grain size and microstructure in some steel grades. Process:- Normalizing is the process of heating a material to a temperature above a critical limit and then cooling in open air. Normalizing maybe used as part of a 3 step heat treatment process for high strength steels. This is the first step followed by austenitizing/quenching and tempering. Recovery stage Recrystallization stage Grain growth stage Recovery Stage During the recovery stage, a furnace or other type of heating device is used to raise the material to a temperature where its internal stresses are relieved. Recrystallization Stage During the recrystallization stage, the material is heated above its recrystallization temperature, but below its melting temperature. This causes new grains without preexisting stresses to form. Grain Growth Stage During the grain growth, the new grains fully develop. Thi...

Heat Treatment Processes:- Heat treatment of  steels is the heating and cooling of metals to change their physical and mechanical properties, without letting it change its shape. improving formability, machining, etc. Heat Treatment Process Steps:- In simple terms, heat treatment is the process of heating the metal, holding it at that temperature, and then cooling it back. During the process, the metal part will undergo changes in its mechanical properties. This is because the high temperature alters the microstructure of the metal. And microstructure plays an important role in the mechanical properties of a material. Holding:- During the holding, or soaking stage, the metal is kept at the achieved temperature. The duration of that depends on the requirements. For example, case hardening only requires structural changes to the surface of the metal in order to increase surface hardness. At the same time, other methods need uniform properties. In this case, the holding period is long...

INCLUSION RATING TESTING:- Non-metallic inclusions process :- Non-metallic inclusions are chemical compounds and non metals that are present in steel and other alloys. They are the product of chemical reactions, physical effects, and contamination that occurs during the melting and pouring process. Sources of inclusions formation Non-metallic inclusions that arise because of different reaction during metal production are called natural or indigenous. They include oxide , sulfide , alumina silicate and Globular oxide .Singl Globular oxide Apart from natural inclusions there are also parts of Slag, refectories , material of a casting mould (the material the metal contacts during production) in the metal. Such non-metallic inclusions are called foreign, accidental or exogenous. Most inclusions in the reduction smelting of metal formed because of admixture dissolubility decreasing during cooling and consolidation. Non-metallic...