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Sheet metal bending tools are subject to different kinds of abrasions and stresses. For this reason, the tools have to be resistant and durable, to reduce damages to the sheet metal as well as to the mechanical processing.
In order to achieve this, it is necessary to apply surface treatments on dies and punches, to increase:
- hardness
- strength
- durability.
In this article, we are going to talk about a really popular tool surface treatment: phosphating.
What is phosphating.
It is a surface treatment for all tools: punches and dies. It is a chemical process which creates phosphate crystals. The layer of phosphate crystals increases the tool surface protection.
Phosphate coated tools achieve a higher corrosion protection, preventing steel oxidation. This reduces the risk of rust formation.
The layer of phosphate crystals provides the tool surface with anti-galling, anti-wear and self-lubricating properties (which can be maintained/increased through periodical application of lubricating oils).
So phosphating makes punches and dies:
- more efficient
- better looking.
How does it happen?
During the treatment, a phosphate solution (e.g. manganese phosphate) is applied either by spraying the solution onto the tools or by immersing the tools into the solution. Phosphating is a conversion coating which converts the surface of the metal into a non-metal layer of phosphate crystals, with a thickness between 5 and 10 μm.
The phosphate crystals bonding with the substrate improve corrosion resistance of punches and dies, making the sheet metal bending processes far more performing.
Differences between phosphating and nitriding.
This article focused on nitriding, one of the heat treating processes carried out on tools. There are substantial differences between phosphating and nitriding:
- phosphating is a surface treatment (anti-oxidative) which does not change the structure of the tool. This is a treatment for punches and dies with a functional and aesthetic purpose, and can be applied to any tools, even at a later time.
- nitriding is a heat treating process in which nitrogen is introduced into the whole tool surface with the intention of hardening it. (Even harder than what is achievable with induction hardening, as it can also reach 65 HRC). Nitriding should be carried out as an alternative to induction hardening (or any other heat treatment). The best results are achieved on steel alloys. It is generally recommended for lower tools (dies) as the high surface hardness achieved provides high resistance to abrasions (sheet metal sliding along the die shoulders, and in those cases when sheet metal might damage the internal inclined surface of the die).
In addition, thanks to its hardness, it prevents sheet metal debris from adhering to the die surface. If these are not periodically swept away, they tend to "melt" on the surface and cannot be removed.
You might be interested in: Toughness of tools according to heat treatment.
Eurostamp, top quality tooling.
Since 1970 Eurostamp has been manufacturing high performing sheet metal bending tools, also thanks to the phosphating and nitriding heat treatments. These processes can be carried out upon the client's request or as a default process, depending on the sheet metal bending needs.
Contact Eurostamp.