How is cpm steel made

Stamping or Forming Tools. Industrial Knives and Slitters. Plastic Injection and Extrusion Feedscrews. Salt bath heat treatment will ensure maximum attainable toughness for a given hardening treatment. The higher austenitizing temperatures can be used to obtain higher hardness, at a slight decrease in impact resistance.

The lower austenitizing temperatures provide the best impact toughness. Austenitizing Temperature. Sintering is often used with materials that have an extremely high melt point, such as molybdenum. CPM-S30V contains a 1. This allows the atoms in the various materials to fuse together into one solid piece of stainless steel.

The vanadium carbides in S30V give the steel an extremely refined grain. The higher the alloy content and the higher the carbon content, the more detrimental are the effects of the segregation on the resultant mechanical properties of the finished steel product. The CPM process also begins with a homogeneous molten bath similar to conventional melting. Instead of being teemed into ingot molds, the molten metal is poured through a small nozzle where high pressure gas bursts the liquid stream into a spray of tiny spherical droplets.

These rapidly solidify and collect as powder particles in the bottom of the atomization tower. The powder is relatively spherical in shape and uniform in composition as each particle is essentially a micro-ingot which has solidified so rapidly that segregation has been suppressed.

The carbides which precipitate during solidification are extremely fine due to the rapid cooling and the small size of the powder particles. The fine carbide size of CPM steel endures throughout mill processing and remains fine in the finished bar.

One good example is vanadium where the vanadium carbides form at higher and higher temperatures in the liquid steel with further increases in vanadium. The high temperature and rapid diffusion in liquid steel means that the carbides can grow to very large sizes.

Their stability in the liquid also leads to the same problems described above where the carbides cannot be eliminated through thermal processing or forging. It had previously been discovered that with higher carbon contents that vanadium could be increased to high levels for better wear resistance see this article on development of high vanadium steels.

One method known to help with this problem of large carbides is to cool the steel more quickly as it solidifies. One simple way to do this is to use a smaller ingot size. It makes intuitive sense that very large multi-ton ingots cool very slowly with their large size, while a very small ingot cools more rapidly. A smaller dendrite size indicates that less segregation has occurred and the final carbide size is likely to be smaller [4]:. Powder metallurgy is a method by which very tiny ingots are formed.

Typically nitrogen is used in the production of tool steel. Each particle of the powder is like its own tiny ingot. Therefore the cooling rates are much faster than conventional casting.

You can see an animation of the process and then a video of it actually happening:. The HIP process is similar to forge welding for damascus. You can see a Bohler-Uddeholm video summarizing the entire process below where hopefully all of the background information described above makes it easier to understand what they are describing:. When all that process is complete you end up with a steel that has a much finer and more uniform carbide structure than in a conventionally cast steel, such as can be seen in a comparison with CM and CPM below:.

While powder metallurgy technology existed for some time prior, powder metallurgy with tool steel was first commercialized by Crucible Steel [6]. They first filed for a patent for the process and announced the future commercialization of powder metallurgy tool steel in [7][8]. Early tests were done at a pilot facility [6].

They then announced the successful production on a commercial-scale in December [9]. So while powder metallurgy already existed, Crucible was the company that spent the resources and dedicated the money to creating a full commercial-scale implementation of the process for tool steels. The overall process needed to be developed and designed with tool steel in mind. Early PM steels produced by Crucible were high speed tool steels starting with pre-existing steels such as T1 and M2 [7] followed by patents with specialized steels designed for powder metallurgy such as Rex 76 [10][11].

Crucible metallurgists recognized early on that the powder metallurgy process would allow them to develop steels with higher vanadium contents.