European Union EN ISO 4957 standard consists of several grades of tool steels
for plastic injection moulds. In addition to these, some steel manufacturers have ...
CAE DS – Mould Design
Injection moulding mould cavity materials Tampere University of Technology – Tuula Höök Plastic mould cavity plates, cavity inserts, fixed cores and moving cores are usually made of some special mould steel grade or in some cases partly of high strength copper alloy. Prototype mould cavities and cores are commonly made of aluminium alloy. Small series plastic mould cavity can be manufactured to the frame material, typically 1.1730 steel. The most common special mould material groups are: −
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Quenched and tempered steels: Commonly used in very large moulds, moulds for average production volumes, as a high strength frame material and for materials, which are not particularly abrasive. These steels are intended for use as supplied, without hardening. If it is necessary to raise the surface hardness and strength these materials can be carburised, nitrided, flame hardened of induction hardened. It is also possible to use some electrical or chemical plating method. The selectable treatments depend on grade. Through hardening steels: Commonly used in moulds for large production volumes and for abrasive materials. Also if it is necessary to use high injection pressure or high closing forces. These steels are typically rough machined, hardened and finishing machined after the heat treatment process. Finishing machining is possible either with high speed machining or electro discharge machining methods. Stainless mould steels: Commonly used for corrosive materials in order to avoid costly plating and re-plating operations. There are some special steel grades, which are both abrasion and corrosion resistant. These qualities are difficult to achieve in the same steel grade. Hot working tool steels: Used in demanding applications if there is a need for high strength, hardness and toughness. High strength copper alloys: Commonly used in applications where good thermal conductivity is important. Aluminium alloys: Commonly used in prototype moulds or in moulds for small production volumes.
The important material characteristics in injection moulding applications are: − − − − − −
good thermal conductivity sufficient hardness, toughness and strength machinability possibility to make the required surface finishing and surface treatment operations: for example polishing and nitrating if plastic resin requires: resistance to abrasive conditions if plastic resin requires: resistance to corrosive conditions
Table 1 compares some of the characteristics of tool steels, structural steel, stainless steel and beryllium copper. Beryllium copper is one of the high thermal conductivity copper alloys used in injection moulding moulds.
Injection molding mould materials - 1
CAE DS – Mould Design European Union EN ISO 4957 standard consists of several grades of tool steels for plastic injection moulds. In addition to these, some steel manufacturers have patented steel grades like Uddeholm Corrax. There are also some DIN standard grades, which are not a part of EN ISO 4957. Tables 2 – 5 list some of the most common tool steel grades for plastic injection moulds.
References Böhler-Uddeholm, http://www.bohler-uddeholm.com Cogne Acciai Speciali S.p.a., http://www.cogne.com Dörrenberg Edelstahl, http://www.doerrenberg.de Industeel, http://www.industeel.info Kind&Co Edelstahlwerk, http://www.kind-co.de Matweb, the online materials information resource, http://www.matweb.com Metal Ravne, http://www.metalravne.com Schmidt + Clemens Gruppe, http://www.schmidt-clemens.com Schmolz + Bickenbach Group, http://www.schmolz-bickenbach.com ThyssenKrupp Services, http://www.tkm-international.com/engl/prod/werkzeugstahl.html
Injection molding mould materials - 2
CAE DS – Mould Design
Table 1. Comparison of some of the most important characteristics of tool steels, structural steel, stainless steel and beryllium copper. Steel
Analysis
Thermal conductivity, W/m °C
Coefficient of thermal expansion 1 / °C
Yield strength Rp0,2 MPa
Elongation, %
Hardness
AISI 1045/1050 (1.1730) low alloy steel
C: 0,47 – 0,55 – Mn: 0,60 – 0,90
49,8 in room temperature
12,4 x 10-6 in 250 °C
425 in room temperature
20 in room temperature
183 – 255 HB
BÖHLER N360 ISOEXTRA stainless steel
C: 0,30 - Si: 0,60 - Mn: 0,40 - Cr: 15,00 - Mo: 1,00 - N: 0,40
14 in room temperature
11,6 x 10-6 in 400 °C
Uddeholm Impax Supreme, tool steel for injection moulding moulds
C: 0,37 – Si: 0,30 – Mn: 1,40 – Cr: 2,00 – Ni: 1,00 – Mo: 0,20 – S:
