TPT May 2012

T echnology N ews

Continuous casting machines offer flexibility

Indutherm Erwärmungsanlagen GmbH – Germany

INDUTHERM continuous casting machines are designed to help save production costs and improve production flexibility. Tubes, strips or wires can be produced within min- utes, in every required size and in any alloy. The company states that its continuous casting systems are the only ones on the market with an optional vacuum function. With these machines, melting can take place under vacuum or inert gas atmosphere. This is suitable for all alloys containing copper such as brass, bronze, silver or red gold, as these materials tend to oxidise easily. Degasification under vacuum results in an improved semi-finished product, because of the absence of oxidisation. IF the properties of an engineering material are to be fully utilised, the processor must target a suitable surface quality. Determining the grain size of an abrasive is only one of several performance specifications. If a particular surface has to be observed the recommended procedure is to manufacture a sample. Verbal (qualitative) definitions and numeric (quantitative) data such as the Ra value for surface roughness alone cannot adequately describe a surface condition of stainless steel. With respect to surface treatment, the suitable choice of engineering materials is also important, in particular when smooth, high-gloss surfaces are the target. In a number of countries and market segments titanium alloy stainless steels are used in lieu of low-carbon varieties when greater resistance is required against inter- crystalline corrosion at the welds. Titanium alloy steels are unsuitable for decorative surface treatment, as the titanium content causes smearing when ground. Descriptions of surface qualities often make use of terms like grinding and polishing. In order to ensure that the targeted surface quality is actually obtained, the principal and the agent must reach a

Fax: +49 7203 9218 70 Email: ph@indutherm.de Website: www.indutherm.de

Indutherm VCC 1000 vacuum continuous casting machine

Continuous casting products

Mechanical surface treatment of stainless steel

clear and unambiguous agreement as to what the final result looks like and how it is reached. Grinding and polishing are forms of mechanical treatment that remove material. This process is effected with hard particles that are bonded firmly to each other or to a substrate. The surface effect depends on many factors, in particular the grain size and the type of abrasive. The term ‘grinding’ is used when undesirable surface layers, eg welding beads and tarnish, are removed. The term ‘polishing’ describes a decorative treatment that removes only little material. Unlike grinding and polishing, buffing is not designed to remove material from a stainless steel surface to any significant degree. It is a levelling process that makes the surface smoother and glossier. Pastes, liquids and even solid polishing agents can be used. Just like grinding and polishing, brushing too is a surface treatment process that removes material. The terms ‘brushing’ and ‘polishing’ are often confused. Brushing uses milder abrasives, and its purpose essentially consists in giving the surface a structure, and not in removing metal. On stainless steel, the look and surface quality of mechanically treated surfaces ultimately depend on many factors. These

include: the type of abrasive used (substrate, grain size, form and hardness); the number of treatment steps; the machines used and their drives; the types of substrate (eg belt, disc, wheel) and their flexibility; and the relative speed and contact pressure. The suitable choice of grinding method, equipment and agents depends on the material’s initial state, the accessibility of the surface for treatment, and the desired result. As an expert for mechanical surface treatment, Suhner can provide users with in-depth know-how. The company provides on-site consultancy free of charge as part of its demo services. The demo vehicles assigned to its specialists have all the usual machines, tools and abrasives on board, so the Suhner specialists can work on actual workpieces to present end-to-end solutions. Suhner Abrasive Expert AG – Switzerland Fax: +41 56 4642831

Email: info.sae@suhner.com Website: www.suhner.com Suhner Italia Srl – Italy Fax: +39 035 225 965 Email: info.it@suhner.com Website: www.suhner.com

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M ay 2012