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Modern Steel Making Technologies

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CPM
- Crucible Particle Metallurgy(CPM™) is Crucible's proprietary technology, invented circa 1970. During the first stage of the process, molten metal is poured though a small nozzle with high pressure inert gas, transforming liquid stream into a spray of small, spherical droplets. Droplets fall through the cooling(or atomization) tower and solidify. Solidified particles are screened and collected into sealed containers and then consolidated using hot isostatic pressing(HIP) at temperatures close to those used for forging. Short list of CPM process benefits includes refined grain size, improved toughness, wear resistance, grindability, consistent heat treatment response, etc.


ESR
- Electroslag Remelting. Invented circa 1930. It took approx. 30 years for ESR to become widely acknowledged process for producing high quality steel. In ESR the consumable electrode is dipped into a pool of slag in a water-cooled mold. An electric current (typically AC) passes through the slag, between the electrode and the ingot being formed and superheats the slag so that drops of metal are melted from the electrode. Molten metal travels through the slag to the bottom of the water-cooled mold where it solidifies. The slag pool is carried upwards as the ingot forms. The new ingot of refined material builds up slowly from the bottom of the mold. ESR offers high quality, consistent output.


MM
- Micro-Melt(MM™) is Carpenter Technology's proprietary technology. During the first stage of the process, metal is melted, using air induction process and poured into refining ESH tundish(Electroslag heated tundish), where the metal is heated(using plasma torch) and purified, reducing the number of inclusions. Purified molten metal is then poured though a small nozzle with high pressure inert gas, transforming liquid stream into a spray of small, spherical droplets. Droplets fall through the cooling(or atomization) tower and solidify. Solidified particles are screened and collected into sealed containers under a gas shield, and then consolidated using hot isostatic pressing(HIP) at temperatures close to those used for forging. Carpenter's 2nd generation MM process produces powder particles with 150µm diameter, which is smaller than Bohler-Uddeholms's 3rd Generation PM process, producing 250µm powder. Presumably, 150µm powder would have either smaller, or at least similar size carbides as Bohler-Uddeholm's PM powder i.e. 2-4µm or smaller size carbides. Short list of MM process benefits includes refined grain size, improved toughness, wear resistance, grindability, consistent heat treatment response, etc.


MC
- Micro Carbide. Same as PM. The term is used by Henckels for some of their high end knives steel descriptions.


PM
- Powder Metallurgy. PM has been around since early 1900. During 1970s the PM process was refined to be used for tool steel manufacturing. PM process is being constantly refined, e.g. Bohler-Uddeholm is on 3rd generation of PM already. Some of the main objectives being reducing the particle and grain size, alloy purity, etc. PM process starts with melting metal using air induction process. Next, molten metal poured into refining ESH tundish(Electroslag heated tundish), where the metal is heated(using graphite electrodes) and purified, reducing the number of inclusions. Purified molten metal is then poured though a small nozzle with high pressure inert gas, transforming liquid stream into a spray of small, spherical droplets. Droplets fall through the cooling(or atomization) tower and solidify. Solidified particles are screened and collected into sealed containers and then consolidated using hot isostatic pressing(HIP) at temperatures close to those used for forging. Bohler-Uddeholm's 3rd generation PM process results in powder size of 250µm with carbide sizes of 2-4µm. Both, powder and grain size will vary from manufacturer to manufacturer. Short list of PM process benefits includes refined grain size, improved toughness, wear resistance, grindability, consistent heat treatment response, etc.


SF
- Spray Form(Osprey) process, developed circa 1970. SF is a new manufacturing technique that offers high alloyed tool steel with uniform carbide size and uniform carbide distribution. SF has fewer steps than PM and properties better than ingot steel, offering a better budget solution compared to PM. Similar to PM process, molten metal is injected into atomizing tower using high pressure gas. However, two oscillating nozzles are used to inject molten metal and the semi solid droplets are collected on the rotating metal disc(preform) moving upwards inside the atomizing tower. SF process produces uniformly distributed carbides of 10µm size. larger than modern PM process, but smaller than typical ingot steels.


VAR
- Vacuum Arc Remelting. Secondary melting process to improve alloy qualities including refined microstructure and further purification. Essentially, VAR is the process of remelting the steel in a vacuum controlled environment. The process can be highly controlled to achieve best desired results. Because of the high cost it is not used for most of the commercially available alloys.


VIM
- Vacuum Induction Melting. Process of melting metal under vacuum using electromagnetic induction. Originally developed for exotic metals and alloys, is becoming more widely used for high performance alloys for various industries. Metal is melted in a vacuum or in the inert gas environment, to prevent oxidization. Chemical reaction, dissociation and flotation remove dissolved and chemically bonded impurities. Result is very clean and homogeneous alloy.


Last updated - 02/27/15