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Processes

PROCESSES

Materials are produced at our mills in Sweden and Austria.

The process routes are designed for the production of tool steel, the four main processes being:

Conventional
Electro Slag Remelting (ESR)
Powder Metallurgy

Throughout our entire history we have been among the first to develop and use new processes and technologies. 

Sophisticated techniques are used to control the entire production process.  This ensures that all materials are produced in accordance with specifications, which guarantees that our customers will always receive the same high quality material.



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CONVENTIONAL

The production facilities of Uddeholm are tailor-made for the production of tool steel bars and comprise units for melting, ladle treatment, forging, rolling, heat treatment and machining. The whole process is strictly controlled to ensure world-class quality.

The conventional production route consist of four general steps:

Electric Arc Furnace
Ladle Furnace
Up-hill Casting
Hot Working and Heat Treatment

Sophisticated techniques are used to control the entire production process. This ensures that all steels are produced in accordance with specifications, which guarantees that our customers will always receive the same high quality material.


 Electric Arc Furnace

The process route for conventional ingot production of tool steel consists of scrap-based steelmaking via a primary melting furnace and refining treatment in secondary units.

In the first stage recycled steel, ferroalloys and slag formers are loaded into an EAF-furnace and melted by electric energy transferred by arcs between three graphite electrodes and the steel scrap.

Ladle Furnace

After melting, a secondary metallurgical treatment is applied.  An important aspect of secondary metallurgy is the application of vacuum. Here, dissolved elements such as H, N and O are removed by purging inert gas into the melt and exposing it to a low partial pressure. The strong mixing between high-basicity slag and the steel bath results in favourable conditions for the removal of sulphur and slag inclusions. 

Up-hill Casting

Casting into ingot moulds requires a close control of the melt temperature to avoid segregation and inclusion clustering. Shrouded uphill casting is used to achieve the best result.

Hot working and heat treatment

Hot working and heat treatment aim to produce a bar material with high homogeneity through plastic deformation. This is achieved through forging or hot rolling. After hot working the bar material is subjected to a heat treatment operation, either soft annealing or hardening and tempering.



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ESR

In Electro Slag Remelting (ESR), the ingot is built up in a water-cooled mould by melting a consumable electrode immersed in a superheated process slag. An electrical current flowing through the liquid slag, which provides the electrical resistance, generates the heat.

As the slag temperature rises above the liquidus temperature of the steel, the tip of the electrode melts. The reaction between slag and steel droplets results in a significant reduction in sulphur and non-metallic inclusions.

The directional solidification of the ingot from bottom to top results in an ingot with a high homogeneity and freedom from macro-segregations. This gives uniform mechanical properties in the longitudinal and transverse directions after hot working.

By utilising homogenisation annealing of ingots/billets, a high ingot break down and special heat treatment methods for structure refinement, the strategy is fulfilled in optimising steel properties for an extended tool life.

A further development in ESR technology by remelting under protected atmosphere has strengthened the already unique ability of the process to produce material in large cross sections with superior properties.

 



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POWDER METALLURGY

High Alloy Steels will gain improved properties by increasing the solidification rate. This gives a fine microstructure and small, well-distributed carbides in the matrix.

During Powder Metallurgy (PM), the melt stream is atomised by nitrogen gas into small droplets with an average size of 50-100 µm. The powder is filled into capsules directly in order to avoid contamination. With hot isostatic pressing (HIP), the powder is consolidated to 100% density.

By using a special refining sequence, the cleanliness of the molten steel is improved prior to atomisation. This results in improved mechanical properties and an extremely low non-metallic inclusion level ("SuperClean").

The HIP'ed PM capsules are hot forged and rolled to smaller bar sizes followed by heat treatment and machining.

PM steels are used in very demanding applications within the segments of cold work, plastic and cutting tools.



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PROCESS DEVELOPMENT

Continuous development of the production processes ensures that the routines are safe in terms of the working environment and reliable in terms of product quality.

To improve products and production processes, we use new techniques to control critical processing steps, thereby improving the quality and yield of material.  Close co-operation with universities and institutes provides short lead times for transferring new technical solutions into production surroundings.

We use excellent engineering tools for simulation of manufacturing processes to produce high performance products. Upgrading of existing products or the introduction of newly developed steels requires the revision or fine-tuning of a number of processing steps in steel making, hot working and heat treatment. The possession of advanced simulation programmes and a unique database consisting of various process parameter values facilitate the process development work.



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