For sophisticated moulds

The all-new XPM plastic mould steel

When it comes to creating moulds for plastic, the demands placed on steel producers are constantly on the rise. The tool steel specialists at Schmiedewerke Gröditz GmbH have therefore developed a new steel concept: the high-strength, pre-hardened XPM plastic mould steel. This product is suitable for even the largest moulds and wall thicknesses.

Moulds for plastic parts are made from steel – and they are constantly getting bigger. The result of this is that the existing steel standards are no longer adequate for the new quality requirements. Tool steel 1.2738, for example, has asserted itself as the standard grade for manufacturing premium-quality plastic moulds, yet it is steadily approaching its physical limitations. These limitations include inhomogeneity within the material, poor graining behaviour and processing issues.

XPM is taking the market by storm

The solution to these problems is the new, pre-hardened XPM plastic mould steel, which is significantly harder and can achieve up to 42 HRC. XPM is an evolution of the basic standard grade 1.2738, featuring a modified chemical composition and adaptations to the heat treatment process that takes place at the steel plant. In comparison to conventional steel concepts, which involve the subsequent curing of the finished product, a pre-hardened XPM steel mould can be produced significantly more quickly and therefore more cost effectively. As a result of the significantly lower C equivalent, XPM is noticeably easier to weld than 1.2738, meaning there are only minimal curing effects. This reduces the risk of sub-seam cracks whilst also making it possible to use cold welding for smaller repairs. The thermal conductivity of XPM is higher than 1.2738. This quality accelerates injection moulding cycles. As such, XPM plastic mould steel is ideal for use in a whole host of applications, including in the automotive industry.

Improved resilience

XPM steel has a homogeneous, low-segregation structure as a result of its modified alloy concept and special heat-treatment technology. The microstructure is largely even throughout the entire ingot – even at extreme dimensions. By lowering the carbon content and using micro-alloying technology, it is possible to increase its resilience, which in turn can accommodate higher strengths. Furthermore, improved resilience also means a lower risk of cracks in the tool under critical operating conditions.

Two types of XPM

XPM steel is constantly undergoing improvements down to the last detail. This plastic mould steel is currently available in two different hardness ranges: from 34 to 38 HRC and from 38 to 42 HRC. The exceptional purity and homogeneity of the steel results in a uniform machinability that is better than ever. In terms of machinability, by adapting the processing parameters, it is even possible to achieve a hardness of up to 42 HRC. The low residual stress means there is generally no need for any interim easing of tension. The greater homogeneity and uniform hardness also result in exceptional graining qualities and polishability. In fact, XPM with 42 HRC can even be polished to a high-gloss finish. The special grade product XPM VICTORY ESR offers outstanding quality assurance. The abbreviation ‘ESR’ stands for electro-slag remelting, a process that ensures maximum purity and homogeneity. This product is particularly suitable for moulds requiring a mirror finish.

Diverse areas of application

XPM moulds can be used in a whole host of different applications. These include sophisticated plastic parts with grained surfaces for interior components within the luxury car manufacturing industry, or even large plastic parts for outdoor use, such as bumpers, mudguards and boot lids. Its outstanding polishability makes XPM VICTORY ESR perfect for moulds that require a high-gloss finish – such as car headlight components or the visible parts of consumer electronics. A further area of application for XPM plastic mould steel, which is becoming increasingly popular, is large plastic pressing moulds for processing reinforced plastics.

XPM: Two types of steel for plastic moulds

XPM is renowned for its largely uniform microstructure – even at extreme dimensions. The homogeneity of the steel results in improved machinability and resilience, which means there is a lower risk of cracks.

The special grade XPM VICTORY ESR offers first-rate quality assurance. This product is particularly suitable for moulds requiring a mirror finish.