TPT November 2015

Article

Quaker Chemical Corporation

This was supported via subsequent examination of the tool used with AE 208, which showed clear signs of galling and crater wear. Following machining, the level of wear on the flank face surfaces of the drills was measured. Micrographs of the drills following machining for the three fluids are shown in Figure 3. As seen, and consistent with the cutting forces measured, Quakercool ® 750 TP machined with considerably less wear (0.26mm 2 total wear area) relative to that measured for MB 365 and AE 208, which respectively gave 0.43mm 2 and 0.41mm 2 flank wear area on the cutting edge. In addition, consistent with the sharp transition to lower cutting forces observed during machining, a large area of galling is seen near the nose area of the drill used with AE 208. While the differences obtained between the fluids in both cutting force and tool wear may at first seem small, they nevertheless reflect noticeable differences in the performance properties of the fluids, which can potentially yield significant differences in the overall efficiency of a pipe thread cutting operation. Quakercool ® 750 TP is a water-based thread cutting fluid, which to date yielded up to 30 per cent increase in cutting insert life in thread cutting operations at different OCTG producers in USA. Considered to be a high tech thread cutting fluid as a result of its compositional and physical properties, and bases for utility, Quakercool ® 750 TP delivers multiple benefits for current pipe threading applications. In general, water-based thread cutting fluids function by providing lubrication and cooling to the operation, as well as serving to facilitate chip removal during and after the cutting process. Pipe threading fluid – Quakercool ® 750 TP

Figure 2: Axial drilling force – AISI 4140 steel

Machining performance The increase in axial cutting forces, which happens as machining continues, offers a useful measure of the tool wear rate occurring on the cutting edge. Soon after the start of machining and a brief initial wear-in time, a period of steady state tool wear is reached. A gradual increase in tool wear occurs and correspondingly results in a gradual increase in cutting forces. Since the slope or intensity of this increase is highly dependent upon the heat and friction generated during cutting, the increased rate of the cutting forces within this region provides a useful measure of the lubrication and cooling properties provided by the fluid. Analysing the cutting forces for the three fluids tested (Figure 2), it is seen that a considerably lower rate of cutting force increase is obtained with use of Quakercool ® 750 TP, indicating conditions of higher lubrication and lower wear. Also of note is the sharp transition to lower cutting forces at hole number 124 seen for AE 208. Such a sharp drop in cutting forces is commonly seen immediately following the formation of catastrophic wear such a cracking, galling or chipping of the cutting edge.

There are three basic types of water- based fluids which are typically used for pipe threading operations: oil-in- water macroemulsions, oil-in-water microemulsions and solution synthetic fluids. Each type of fluid offers certain advantages as well as certain limitations with regard to the thread cutting performance they supply. Macroemulsions are opaque white or yellow-white liquids that consist of oil droplets of sufficient size (typically between 0.5 and 4mm diameter) suspended in a continuous phase of water. Microemulsions are defined as a thermodynamically stable system of water, oil and amphiphile existing in a single phase.

Figure 3: Micrographs of flank face of used tools

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N ovember 2015