Tooling steel you used

[Wiseco]

Hi,

I would like to know which type of tool steel you used for making an injection tool set.

At our company, we oftenly used Impax Supreme which is a prehardened P20. It's kinda hard to turned but offer a good hardness and polishability.

I would like to try a stainless steel to make our mold to avoid corrosion in cooling channels. I've talked with a guy from Bohler Uddeholm, and he talk about the new M303 Extra which is a pre-hardened stainless steel. Does somebody use it to make cavity mold?

[JerryFlyGuy]

I'm no injection mold guy, but my experiance w/ Stainless is that it warps alot more than standard steels, it's not as bad as alum, but would this be an issue?

Jerry

[Wiseco]

hum...maybe but we are not making big mold.The biggest mold would be like 36" by 24" by 10". Maybe it wouldn't cause problems cause our mold are modulable (each cavity have it's own block)... dunno, this is why I'm here asking this.

Someone know what is the termal expension of a pre-hardened steel vs pre-hardened stainless? Like how much thousands/feet...

[keebler303]

stainless expands about 40-50% more than carbon steel but the warping is caused by residual stresses in the material. as it is machined, some of the stresses are relieved and warping becomes a problem.

Matt

[Wiseco]

Oh! I didn't think it was that much. By the way the guy from Bohler Uddeholm didn't metion of any warp... I'll verifyed with him.

Thanx!

[spider]

we do molds same size as you

-we use 4140 for prototype molds
-p-20 for normal molds
-when molding inserts are inserted into core shoes, we make the core shoes 4140 and inserts p-20.

I worked at a shop where they used stainless from time to time, but that was mostly because the customer requested it, or because they ware lens molds. They used p-20 supreme on the big size molds for facias and bumpers.

We mostly do molds for airbag covers, backcovers (behind steering wheel).....
The only time we harden anything is when we are woried abou it bending. Eg; slides with long noses, narrow high standing cores (for somekind of bushings)....

On the last one we had to hareden anything was on a mold for the ford shift knob. It had slides coring out from tob and the bottom of the knob...we hardend the slides and molding inserts to 54-56 RC and that was it.

[Mr.Miyagi]

I have been a moldmaker for about 25 years. and in my expirience we have alway's used 420ss for cavity / core blocks and ramax for molplates. if your core / cavity has shut-offs then you need to use dissimilar steels or galling will occur. you can also vary the rockwell of the cavity to core

[miljnor]

And 420ss generaly won't rust if hardend above 40RC.

[Shawn Lucas]

I have used SS many times for corrosion resistance on PVC molds. For an inexpensive anti-corrosion treatment for waterlines, I have them electroless nickel plated. It seems to help a lot.

Shawn

[Wiseco]

Originally Posted by Shawn Lucas ... For an inexpensive anti-corrosion treatment for waterlines, I have them electroless nickel plated. It seems to help a lot.

This treatment is it for SS or for tool steel?

[roboman]

Nickel plating is for the water lines in non SS steels.

If you have any metal rubbing or sliding across the 303 it is extremely likely to fuse and make a mess of things. For just two cavities closing in a blow mold it should be fine, ejector pins or slides are a major problem on pre hard 303. The 420-440 are used a lot in injection molds because they are magnetic (you can put them on the surface grinder or edm magnet) and because they act and machine more like tool steels then the gummy 300- SS. One thing to look out for is the fact that P20 has 15-20% better heat transfer then most other tool steels and most of the Stainless steels are 15-20% worse. So you can loose cycle time in a big way, if you design the mold to use the same cooling as you would have with P20

[Wiseco]

Oh! I didn't know about nickel plating cooling channel! How is it done in a round drilled channel?

If it can be done on our mold, I'll stick to P20 for sure! Thanx for the info!