industry

INTRODUCTION

Cold pilgering is one of the two major method used in seamless tube production. Other major method is cold drawing but cold pilgering has several advantages that are:-

  • High production rate {upto6m/min for stainless steels)
  • Decrease in eccentricity(30-50%improvement)
  • Large area reduction{upto70-90%for different metals)
  • Narrow dimensional tolerance {variations of less than10µm can be achieved)
  • High surface quality {Ra values=50.4µm can be achieved) and
  • Improving the grain structure of the material

This method is suitable for the most metals however different metals exhibit different maximum area reductions. This type of high precision tubes are demanded in a wide range of industries e.g, oil and gas, nuclear, medical, aerospace, heat exchanger,etc.

There are two common techniques of cold pilgering which are HPTR {High Precision Tube Roller) and VMR {Vertical Mass Ring). The main difference between these methods is that HPTR has constant cross-sections of groove and mandrel whereas VMR has much more complicated groove and mandrel design where the cross-sections vary along the rolling direction. This complex design enables higher output rates and makes VMR the most common technique. However, HPTR is preferred for some specific applications such as for tubes with extreme diameter to wall thickness {D/t) ratios, larger than100/1, for nuclear fuel cladding.

Lubrication

Lubrication is a key factor in the cold pilgering operation in terms of productivity as in most metal forming operations. This is due to several reasons.

First of all, it preserves the surfaces quality of the tool and tube which is a highly important criterion for cold finishing processes. A bad lubricant increases the friction and accelerates material transfer from the tube surface to the tool surface.Built up material on the tool surface causes scratches on the tube, making it necessary to grind the surface of the tool more often, and reduces tool Iife.

Secondly, it functions as a coolant to reduce the heat generated by friction between the work piece and the tool. Temperature control is important as a too high temperature may burn the lubricant.

Thirdly, it prevents the preform from getting stuck on the mandrel.

The ID Lubricant

  • Provides extreme pressure lubrication & cooling to the mandrel
  • Prevent scratching of the mandrel
  • Maintain high quality surface finish on the inside of the tube

The OD Lubricant

  • Lubricates the roller to reduce wear
  • Lubricate the machine parts

Product Selection criteria

Will depend upon the following machine conditions

These verity of the operation condition

  • Load
  • Feed rate
  • Stroke rate
  • Type of material
  • Input tube Dia and thickness etc
  • Other consideration such as cleaning or machine lubrication

The following criteria are considered when selecting lubricant by customer

  • Lubricity performance
  • The environmental issues
  • The corrosion protection
  • The influence of lubricant and flow on friction and surface topology

Considering the above criteria HPPL has developed Neat oils with suitable viscosity which forms optimum film thickness to reduce the friction. This film thickness depends on the viscosity of the oil selected.

For further details about the recommendation/selection of products to suit to your machine & operation conditions you may please contact our Sales & Services department.