Plastic Mould Steels

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Characteristics of plastic mould steels

In the plastics processing industry, the following criteria are of interest: long tool life, the possibility of supplying plastic parts of consistently high quality and the corresponding properties of the plastic mould steel resulting from the plastic used and the parts being manufactured.

Due to extensive experience, innovative Research and Development and intensive cooperation with companies in the plastic processing industry, BÖHLER is in a position to deliver the right steel to meet the exact chemical and mechanical properties required.

BÖHLER plastic mould steels are noted for their excellent thermal conductivity, corrosion resistance and high wear resistance and offer optimum dimensional stability, hardness, toughness and compressive strength.  And, if necessary, a combination of these properties.  In combination with good weldability (for repairs), low maintenance and consistent quality this translates as a maximum in cost effectiveness.







Grades  Description  Download 
Suitable for large and medium size moulds (over 400 mm thick) due to addition of Ni; no hardness decrease over the cross-section to the core; special melting technology ensures good machinability and excellent photo-etching properties, and very good polishability; mould inserts, mould carrier frames for plastic moulds; components for general mechanical engineering and tool manufacturing.  Delivered in high-hard condition.
Vacuum remelted grade with extremely fine microstructure and high cleanliness; excellent polishability, very good machinability and excellent photo-etching properties; mould inserts such as automotive headlight moulds, moulds for optical lenses, and moulds requiring extremely high mirror-finish.  Delivered in high-hard condition.
Special alloying ensures the absence of δ-ferrite; exhibits excellent corrosion resistance and polishability;  moulds and mould inserts for chemically aggressive plastics, e.g. PVC, and plastics containing aggressive fillers; components for general mechanical engineering and tool manufacturing which require corrosion resistant and low to medium temperature resistant properties.  Available in PESR (ISOPLAST) quality.
Electroslag remelted (ESR); exhibits excellent polishability with mirror finish, excellent corrosion resistance and wear resistance;  moulds and mould inserts which require excellent polishability and resistant against chemically aggressive plastics e.g. PVC, and and plastics containing aggressive fillers.
Special alloying for excellent machinability and corrosion resistance; mould holders, mould frames and bolsters, frame superstructures that need extensive machining for plastics processing and die casting industries, and ancillary plastics processing tools.
Special alloying for excellent machinability and corrosion resistance; mould holders, mould frames and bolsters, frame superstructures that need extensive machining for plastics processing and die casting industries, and ancillary plastics processing tools.
Pressurised electroslag remelted (PESR), exhibits extremely high polishability with mirror finish, excellent corrosion resistance and wear resistance, with high toughness, improved conductivity; moulds and mould inserts for chemically aggressive plastics, e.g. PVC, and plastics containing abrasive fillers, production of transparent parts such as optical lenses which require extremely high mirror finish.
Pressurised electroslag remelted (PESR), exhibits good polishability with mirror finish, excellent corrosion resistance and very high wear resistance, high hardness; moulds and mould inserts for chemically aggressive plastics, e.g. PVC, and plastics containing abrasive fillers, knives and tools for the food processing industry, and tools for medical and pharmaceutical industries.
PM stainless steel with extremely high wear resistance and corrosion resistance;  moulds and mould inserts for chemically aggressive plastics, e.g. PVC, and plastics containing abrasive fillers (particularly for large series), inserts for manufacturing of CD’s, moulds for the processing of duroplastics;  IC moulds and inserts, trim and form tools for semi-conductor industry;  knives for food processing and paper industries, rotary knives for meat processing industry;  injection nozzles, backflow and linings of cylinders for injection moulding machines.
Exhibits high compressive strength and high wear resistance; suitable for high-precision plastic injection moulds, e.g. for the production of cameral parts, electronic parts and household components, compression moulds of all types, moulds for elastomers, moulds for sealing rings (O-ring seals), components for hot-runner systems, tool holders, moulds for the production of tyre segments (rubber materials), high precision components for mechanical engineering.


Material Selection for Plastic Mould Manufacturing




Polishing of plastic mould steels

An important factor in obtaining good polishing finish is the steel quality.  Polishability depends also on the chemical composition, the microstructure, the inclusion level and the homogeneity of the steel.  Inhomogeneities in a tool steel may cause substantial problems during polishing. The homogeneity and cleanness of the steel can be substantially influenced by the production process.



During the polishing process it is important to ensure careful cleaning of the workpiece after each process step.  For very sensitive parts it is recommended to use ultrasonic cleaning.  Moreover, the polishing wheels should be covered after use to prevent accumulation of dirt or dust.  Eligible polishing agents are chromium oxide, polishing rouge, alumina, magnesium oxide and diamond powder.
The following polishing procedure is recommended:
–  starting out with a hard polishing tool and coarse paste,
–  changing over to a softer polishing tool, using the same, coarse paste,
–  continuing with a medium-hard polishing tool and medium-coarse paste,
–  then with a soft polishing tool and medium-coarse paste, and
–  concluding with a soft polishing tool and fine paste.



Surface quality criteria of BÖHLER Steels

The melting technology, constituting the first production step, plays a decisive role in the polishability of steels.





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Plastic mould steel applications