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About the mould steel choosing

We all know that mould lifetime is one of the most important aspects of mould quality judgment, and it is usually depended on reasonable mould design, machining precision and suitable steel choosing etc. Mould structure design is the spirit of mould-making, so enough parts analysis and rich experience of designers are the mould-making guarantee. Machining precision is mostly lied on machines’ precision and workers’ attitude. Here we would like to give a detail explanation that the mould steel choosing according to our experience.

According to the different customers’ requirements, mould lifetime is usually split into the following three types:

Low production mould: under one hundred thousand shots;

It is advised that common pre-hardened steel can meet such objectives. (pre-hardened steel means that we can manufacture directly after purchase without any heat treatment later. The hardness is around 26-28HRC.) Such as local 718, local 2316H, P20, 1.2311 and 1.2711 etc. If the parts have high requirements in the appearance, It is better to choose local 718, which have high polishing character; If the plastic material is corrosive, for example: PVC, PP+30% GF and so on, it is better to choose local unti-corrosion steel 2316H. No any special requirements, common P20 is ok.

Medium production mould: around three hundred thousand to five hundred thousand shots;

The hardness should be much higher than low production mould, usually around 35-40 HRC, there are two methods to get this hardness: one is using pre-hardened steel directly, such as ASSAB 718HH, 1.2738, 1.2711 etc, before mould delivery, main inserts should be dealt with surface nitriding, 0.1-0.3mm deep and about 65HRC, which can greatly improve the mould life time. But surface nitriding must be depended on mould structure, if the mould contain many sharp angles, it cannot be nitriding. The other method is using hot work steel, such as H13, 1.2316, 1.2083, and 1.2344 etc. vacuum hardened to 45 HRC after roughing machining. The process craft of back method is much more complicated, machining cost is also much higher than the pre-hardened steel. According to our experience, the following pre-hardened steel can achieve very high hardness without heat treatment, they are Japan DaiDo NAK80, Tap-work and ASSAB S136H.

About the high production mould: more than 1 million shots;

Main inserts should be choose hot work steel , such as 1.2344, S136, 8407 and 1.2767 etc. after vacuum hardened the hardness can reach 50HRC at least, and P20 and 1.2311 for mould base. This craft require very high machining precision and worker skills, so the cost is also very high. 

(The above explain is just for reference, it is not suitable for any moulds. For exactly requirements, please contact us. )