Thursday, April 12, 2012

Tool Steel - Low Friction Coatings For Metalworking

Tool steel metalworking got you down? Not when you choose low friction coatings, the right lubrication system.

Why?

Because lubricating your tool steel can lower friction, reduce adhesive wear. But it can also help purge metal debris from the workpiece interface. Sometimes, too, it can help dissipate frictional heat. Ultimately, your goal is to produce surfaces free of defects.

Of course lubricant choice will vary with environment. Here, for the following examples: extrusion, cutting or forming, we offer these suggestions.

Extrusion of tool steels, particularly at higher temperatures, presents many challenges. Not only is there both adhesive and abrasive wear, but the concern of oxidation products, too. Iron oxide, for example, derived from available oxygen, can dramatically accelerate wear. Minimum, consider oxygen content of your material, stripping the oxides through grit blast, or even maintaining an atmosphere free of oxygen. Proper lubrication should ensure continuous lubrication, a coefficient of friction comparatively low, thermal insulation, and chemical compatibility with both the tool steel and billet. Consider compounds like boron nitride.

For cutting tool steel, fluids (oils) and dry film lubricants generally serve best. And their contributions are typically multi-dimensional: dissipating heat (especially with water miscible fluids), reducing adhesive wear, lowering friction coefficient, flushing away loose metal debris, and inhibiting corrosion.

In forming tool steel applications, such as flat stock (sheet metal), galling is the primary issue. Additional requirements for the lubricant include reducing both abrasive wear and chemical corrosive products. Light duty forming may require simply a low molecular weight mineral oil or soap to prevent wear. More extreme conditions may require solid film soaps, to prevent excessive wear. In some instances, dry film lubricants, such as polyethylene (PE), Teflon or polytetrafluoroethylene (PTFE), which are applied in the form of coatings or powders, may offer excellent means to prevent adhesive wear.


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