PHP© “very high deformity” wires
WHAT ARE PHP© COLD HEADING WIRES?
Phosphate-coated wires to which sodium soap is applied at “very high pressure” during the skin-pass process. This innovative process radically improves performance because of the low coefficients of friction obtained.
WHICH PROCESSES DOES THIS NEW SEBIR PRODUCT ACCEPT?
The processes admitted are all those that involve skin-pass: K, GK, KGK, GKGK. The only processes not accepted are KG and GKG.
WHICH QUALITIES DOES THIS NEW SEBIR PRODUCT ACCEPT?
This process can be applied to any of the wire qualities produced by SEBIR.
WHICH WIRE DIAMETERS DOES THIS NEW PRODUCT BY SEBIR ACCEPT?
Diameters range from 1.80 up to 40 mm.
INTRODUCTION TO THEORETICAL PRINCIPLES OF PHP©
The random roughness generated by the phosphate coating of a wire shows a relation between the “apparent surface area” (ASA) and the “real surface area” (RSA): RSA/ASA> 20. This relation is highly favourable if we are able to coat that real surface with the adequate lubricant.
The PHP process applies lubricant (sodium soap) at very high pressure, which makes the lubricant coating attain values over 80%. With conventional technologies these values range between 42 and 48% of the RSA.
This extra reserve of lubricant is used depending on the needs of each stage of the forming process. The application of sodium stearate over the layer of zinc phosphate crystals at “very high pressure” allows a closer contact between the (PO4)2Zn3 crystals and the sodium soap, which reacts with the phosphate to give a uniform and continuous layer of zinc stearate (excellent lubricant). This fully covers each and every crystal of the phosphate layer.
The resulting coefficient of friction is very low (μ=0.04) and in addition, due to the lubricant reserve, it remains very low throughout the forming of the part.
ADVANTAGES OF USING
This technology achieves a coefficient of friction at the beginning of the forming of μ=0.04. After finishing the most complex forming, this coefficient is still at very high values of μ=0.16 compared to wires using conventional technology that are at μ=0.40.
THIS RESULTS IN THE FOLLOWING ADVANTAGES:
- PHP wires make it possible to produce highly complex parts that couldn’t even be manufactured with PHOSPHATE-POLYMER process wires.
- PHP wires extend the life of forming tools as a result of lower temperatures and workloads on tools because of reduced coefficients of friction.
- PHP/LR (low roughness) wires allow adapting the roughness to the customer’s particular needs. Depending on the lubricant used, levels of roughness can attain Ra ≤ 0.22. This makes it possible to have parts with a skin-pass which is the equivalent to regrinding, and saves costly machining operations.
EVOLUTION OF THE COEFFICIENT OF FRICTION