Tool Bit Research Articles

Determination of the thickness of a titanium carbide coating applied to a hard-alloy tool bit

1. A nondestructive method has been developed for determining the thickness of a TiC coating produced by deposition from a gaseous phase on a hard-alloy bit. The method enables coating thicknesses of up to 40 μ to be measured in 1min, while a similar determination by the metallographic method takes 5–6 h. 2. Measurements of thicknesses in the range from 1 to 10 μ are accurate to within 0.2 μ.

An Improved Method for Calculating Swab and Surge Pressures and Circulating Pressures in a Drilling Well

Abstract Shortcomings were found in the published techniques for calculating down-hole pressures in a drilling well. An improved method was developed that predicts down-hole pressures in good agreement with those measured in two weighted muds. The new method allows drilling fluid properties to vary with depth and has demonstrated the importance of properly modeling the drilling fluid properties in properly modeling the drilling fluid properties in calculating down-hole pressure changes. Introduction Controlling down-hole pressure during drilling is an essential part of well control. Circulating pressures connected with pump operation are usually pressures connected with pump operation are usually calculated using nomographs, slide rules, or simple computer programs. Bottom-hole pressure changes due to drillstring movement (swab/surge pressures) have been described by Clark, Burkhardt, and Moore. These pressure changes are generally calculated using approximate methods developed by Burkhardt (Bingham model) or Schuh (power-law model). The drilling fluid properties are generally assumed to be constant from the top to the bottom of the hole. In applying the conventional methods of calculating down-hole pressures to actual well situations, various shortcomings in the techniques were noted. To overcome these and to obtain as accurate a simulation as possible, a comprehensive theoretical technique using fundamental equations was developed and programmed for computer solution. Downhole pressures were measured in two wells to verify the accuracy of the new program and to provide insight into its shortcomings. CALCULATION OF PRESSURES To develop a comprehensive and general approach to calculating down-hole pressures it was decided to consider both the Bingham and the power-law models for the fluids. The works of Burkhardt, Melrose et al. and Dodge and Metzner were used to develop equations for the Bingham model. The equations for the power-law model were developed from the work of Schuh and Dodge and Metzner. In the Appendix we develop and discuss the equations as well as shortcomings found in the work of Burkhardt and Schuh. Equations are provided for the calculation of circulating and provided for the calculation of circulating and swab/surge pressures for both the Bingham and power-law models. This provides a means of power-law models. This provides a means of calculating the downhole pressures under two assumptions. In many cases the results obtained from the two models are in good agreement. The equations in the Appendix were programmed for computer solution. Complex well geometries can be investigated, as the program can handle as many as 10 sections of different geometry, where each section has a uniform description. If required, the maximum number of sections can be increased by minor modifications to the program. The effects of tool joints, drillpipe rubbers, and bit nozzles are included in the calculations. Mud properties are entered as the Bingham-plastic parameters, plastic viscosity and yield point. In parameters, plastic viscosity and yield point. In the power-law portion of the program, the Bingham parameters are converted to power-law constants. parameters are converted to power-law constants. Mud properties are allowed to vary with depth by specifying different fluid properties for each section. This is normally accomplished by allowing the mud properties corresponding to the temperature and pressure at the midpoint of the section to be representative of the whole section. If only surface properties are known, they can be used throughout properties are known, they can be used throughout the well, although pressure predictions will generally not be so accurate. In addition, mud properties can be different inside the pipe and in properties can be different inside the pipe and in the annulus. The program can be used to calculate circulating pressure losses and swab/surge pressures in the pressure losses and swab/surge pressures in the wellbore. If mud flow rates are entered, circulating pressures losses are calculated. If pipe speeds pressures losses are calculated. If pipe speeds are entered, swab/surge pressures are calculated. SPEJ P. 451

Effectiveness of the use of high impact energies for breaking hard ledge rocks

1. The higher the impact energy, the lower is the value of the stresses which must be induced in a rock mass being broken. 2. The use of high impact energies creates more favorable stresses for the percussion tool. 3. In the case of high-energy impact, with increasing hardness of the rock the rate of rock breaking will either decrease very slightly (in contrast with fracture by a cutting tool or roller bit) or even increase.

Effects of cutting fluids on machining of hyper eutectic Al-Si alloy

Effects of cutting fluids on tool wear, surface roughness and cutting force in machining of hyper eutectic Al-Si alloy with a carbide tool bit of K10 were studicd. Sevcral kinds of commercial cutting fluids such as compound oil, E. P. oil, soluble oil and light oil were used. The cutting fluids were supplied from the top surface of the rake at rates of 3.5-6.5l/min with use of an oil pump. The results obtained are as follows: The effect of the fluid on decrease of flank wear depended on the cutting speed, but was clearly noted even at such high speed cutting as that of 300m/min. For cutting faster than 200m/min, the soluble oil was most effective, while for lower speed cutting the light oil as well as the E . P. oil of low viscosity was desirable. The effect of the cutting fluid on surface roughness became less pronounced as the rake angle and the cutting speed were increased. However, it was found that the neat cutting oil and light oil were preferable to produce good surface finish. The smaller cutting fcrce was required when a tool with a smaller rake angle and the soluble and the light oil were used.

On the simple method to determine the machinability of the 2011 alloy

An experiment has been conducted on the simple method of determination of the machinability of the 2011 alloy. It has been found that if the effects of various cutting conditions on the surface roughness and the cutting force are known, the machinability can be simply evaluated by the number and the shape of chips. The chip char-acteristics sensitively depend on the method of tool bit setting and the stiffness of the machine tool.

Fatigue Performance Of Friction Stir Butt Welds In A6000 Series Aluminum Alloy

Friction stir welding is a novel solid state joining process for making low cost, energy efficient butt welds in aluminum alloy extrusions. The plate edges are clamped against a backing plate and the material is plastically deformed and stirred by a rotating tool moving along the joint line. The resulting weld bead is flush with the surface and exhibits little distortion. The material in the weld and heat affected zone (HAZ) has a fine-grained microstructure and a high tensile strength compared with welds produced by conventional arc welding methods. The present investigation was undertaken to determine the fatigue properties of friction stir welds in 5 mm thick plates in an AA6082 alloy. Extruded plates in the T4 condition were used in the test program. S-N tests in pulsating tension at R = 0.5 were performed on specimens with the weld transverse to the stress direction. Reference tests were made on the base material. Crack growth data were obtained for material in the weld metal, in the HAZ and base material. S-N tests were also made on conventional MIG butt welds from the same batch material to enable a comparison of the two welding methods. The results indicate that the fatigue strength of transverse friction stir welds is approximately 50 percent higher than the fatigue strength of MIG butt welds. The crack growth rates obtained for the weld material were lower than in the base material, probably due to a more fine grained microstructure in the weld region. INTRODUCTION The friction stir welding process has recently been developed as a cost effective alternative to conventional metal inert gas (MIG) and tungsten inert gas (TIG) Transactions on Engineering Sciences vol 8, © 1995 WIT Press, www.witpress.com, ISSN 1743-3533 226 Surface Treatment Effects II welding in aluminum alloys [1]. A major advantage of friction stir welding is that it is a solid state process involving a much lower heat input than that required in conventional arc welding methods. The weld itself and its adjacent narrow heat affected zone both have a very fine-grained microstructure with high mechanical strength. The high tensile strength of the weld material and the favorable geometry would also indicate that friction stir welds could have high levels of fatigue strength. A testing program was implemented to determine the fatigue properties of transverse butt welds of two alloys in the AA6000 series. The data presented in this paper are results from introductory tests on specimens fabricated from extruded plates in AA6082 material in the T4 temper condition. THE FRICTION STIR WELDING PROCESS In friction stir welding the plates to be joined are clamped on a backing plate to prevent movement A cylindrical shouldered tool with a specially profiled pin is rotated at a high speed, see Fig. la. The pin is slowly brought into contact with the joint line, and the material is heated by friction and plasticised in an annular volume around the pin. As the pin is lowered into the plates, soft material is extruded at the surface. Upon further lowering of the pin and movement along the joint line the shoulder face contacts the plate surface and the plasticised material is compressed against the face of the shoulder. The soft material is mashed by the leading face of the pin profile and transported to the trailing face of the pin where it consolidates and cools to form a solid-phase weld. The generation of a friction stir weld has many similarities with extrusion seam welds that form when material is joined in the weld chamber of an extrusion die [2]. The material flow, however, is somewhat different due to the more extensive mechanical mixing of the material from the two plates in the friction stir process. The properties of the weld are closely related to the tool technology. The tool bit shape and material determines the heating, plastic flow and forging pattern. Development of the friction stir welding process has up to now been concentrated mainly on butt and lap joints, however, introductory tests have shown that friction stir welding is suitable for a wide range of joint configurations [4], as shown in Fig. 2. EXPERIMENTAL PROGRAM The specimens were fabricated from AA6082 alloy plate material, in the T4 (as-extruded) condition. The plate thickness was 5 mm. The mechanical properties are listed in Table 1. Transactions on Engineering Sciences vol 8, © 1995 WIT Press, www.witpress.com, ISSN 1743-3533 Surface Treatment Effects II 227 Table 1. Mechanical properties of the AA6082 alloy in T4 temper.

ALX ALLOY

Abstract ALX is a composition of nonferrous materials with a cobalt base containing chromium, tungsten and carbon. This alloy is commonly supplied in the cast-to-shape form, having an as-cast hardness of Rockwell C60-62 and requiring no further heat treatment. ALX is also supplied as cast tool bit material and is useful where conventional high-speed steels or carbides do not function effectively. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as casting, forming, heat treating, and machining. Filing Code: Co-35. Producer or source: Allegheny Ludlum Corporation.

Effect of Grain Size and Subzero Treatment on Productivity of Four High-Speed Steels

Abstract In the investigation reported, the effect of grain size and subzero treatment on the productivity of four high-speed steels was studied by means of a series of turning tests on one alloy steel at a preselected uniform hardness. The material being cut, the shape of the tool bit, and the speed, feed, and depth of cut on the turning operation were held constant. Standard and subzero treatments were used at different hardening temperatures to develop different grain sizes and different hardening products. The results obtained show that the grain size, carbide solution, and type of martensite formed in the tool have a very marked effect on its cutting ability. It appears that subzero treatment is much more effective, when large grain sizes are developed.