H-13 vs. S-5 2

[mechims]

Can anyone give me some pros and cons for switching from h-13 to S-5? This particular application will be for nozzle tips for injection molding.

Thanks

 

[EdStainless]

Why are you wanting to change from H13? What is the failure mode?
S-5 can be used in a harder condition, but it is less resistant to temperature and has little corrosion resistance.
What is your environment and temperature?

There are some other options.
I'll let one of the tool steel guys go into detail.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[mechims]

The reason for the change will be purely cost. A vendor received a load of S-5 and will cut us a good price for the transition, with comparison to the H-13. Temperature range would be from 200-550F.

 

[NickE]

The S5 while being able to resist shock better for the same HRc, will not support the same wear resistance. There are much fewer carbides in the S5. (ok, well thats the way it looks from chemistry.) The S5 also looks harder to heat treat. (more distortion and decarb. Also while I dont know if your temps are high enough for this to be a concern, the H13 is a HotWork tool steel that has a High resistance to softening, while S5 has a Low resistance to softening at temp.

Nick
I love materials science!

 

[Maui]

S5 has an attainable hardness of about 60 HRC, compared to a maximumm hardness of about 53 HRC for H13. If you heat treat a sample of each material to the same hardness level S5 will have better wear resistance, but lower toughness than H13. Keep in mind that H13 is a hot work tool steel, and exposures to temperatures below 900 F during service will not have any substantial effect on the hardness of the part. This is not true for S5. Depending upon the hardness that you are aiming for, the temperature extreme of 550 F could result in some amount of softening during use. What hardness will you aim for?


Maui

 

[mechims]

46-48 Rockwell C for both. Most likely both will be heat treated in some way, shape, or form.

 

[metman]

H-13 I think is easier to weld but I will have to verify this.

I will have to check my Tool Steel text to compare hardnes at 550 temperng temperature keeping in mind what Nick says about more carbides in H-13. Does not seem like high enough temperature to affect hardness apreciably. It would seem a very likely substitution even though you don't need impact resistance and even if it does wear a little faster maybe the cost difference would justify making/replacing nozzle tips slightly more frequently. This is also assuming your injection material is not more corrosive to the S-5.

Are you injecting a variety of platstics or essentially one compound? In other words; is the H-13 really needed for it's corrosion resistance in your application?

 

[mechims]

As of right now the H-13 (heat treated) tips are used in a wide variety of plastics, temperatures, and machines. H-13 has been used for years at this company and it (the company) is resistant to change. S-5 wear resistance is a concern, but if it is off set by the cost/manufacture of the tip, I think the company might be willing to try it on a temporary basis. With the understanding that nozzle tips are a consumable product that needs to be replaced periodically no mater what material it is made of.

 

[metman]

mechims
OK this is as I suspected.

H-13 has an initial hardness of about HRC 55 and tempers to about HRC 53 between 450 to 800F and then increases slightly to about HRC 54 at 850F then drops off in hardness at higher temperatures. Hence giving good hot work properties.

S-5 initial hardness is about HRC 62 and tempers to about 56 at 550F.

I just re-read that you use these nozzles at HRC 46-48. Therefore you would be tempereing the S-5 somewhere above 800F to achieve this working hardness and therefore should not experience softening at 550F.

Usual working hardness for S5 is HRC 50-60 with a wear resistance factor of 2.
Usual working hardness for H13 is HRC 40-53 with a wear resistance factor of 3.

After re-reading maui's comments I had to double check about toughness (even though I doubt this is an issue in your application). I assumed S5 would be tougher than H13 since S5 is shock resisting by definition. In the general properties section they show H13 rated at 9 for toughness vs S5 rated at 8. This I am guessing is because the usual working hardness for H13 is much lower than for S5. The impact curve for S5 is unnotched Charpy whereas for H13 it is notched Charpy so can't compare without further digging but hopefully this academic for now.

In summary I don't see how you can go too far wrong by testing on a temporary basis but keep good records on which nozzles are exposed to which molding materials. If 550F is your max, then temperature should not be a factor.

You could be using additives in your moulding materials that are extremely abrasive so wherever you know that to be true, you might do best to stick with the known, more wear resistant H13 except by testing on an even more limited basis because once you experience negative feedback and given initial resistance to the idea, a good compromize could easily get deep-sixed.

 

[TVP]

Keep in mind that S5 may have a different response to heat treating, so distortion could be an issue with very precise dimensions. Also, S5 has a slightly higher coefficient of thermal expansion than H13, which could possibly affect any dimensions that are very closely toleranced.

 

[mechims]

The smallest tolerance would be +- 0.005 on all of the diameters.

 

[metman]

You should be able to easily allow for this even if you are not doing a post heat treat grind.

What is the largest diameter nozzle?

TVP,
Do you have the (I think you meant volumetric expansion for transformation to Martensite) expansion factors for these two alloys handy?

 

[mechims]

Nothing larger than 1".

 

[TVP]

metman,

No, I did not mean the volumetric expansion for transformation to martensite. Since the application involves cycling from ambient temperature to some elevated temperature, the coefficient of thermal expansion will have an effect on the dimensional change. I did, however, misread the temperature (200-550 F, not C). The difference at this temperature is not so large: 6.6 microinches/inch F for S5 vs. 6.4 for H13.

 

[metman]

TVP,
Thanks for clarifying. I misinterpreted your first post by combining the first and second sentences which are separated by the word "Also." And yes since the temperature is relatively low it just did not register consciously.