Functional and Operational Requirements to Be Fulfilled by Conical Picks Regarding Their Wear Rate and Investment Costs

User’s choices of conical picks currently involve specifying their material and geometric parameters (functional requirements), incorporating the place and conditions of their work (operational requirements). The selection is usually made based on solely one criterion, which is the price. Thus, at the stage of both purchase and operation, the quality of picks, as well as their matching for a specific machine, are not assessed. The problem of defining whether the producer has fulfilled the user’s requirements arises only when the user questions the picks’ quality. Analysis of this problem has resulted in developing assumptions, concepts and research procedures based on the cutting process requirements. The procedure allows conducting tests to determine the geometric parameters of a pick, the type of material of the pick body and WC-Co insert, as well as the pick wear rate (intensity). The C2 index describes the wear rate (intensity)—the smaller its value, the slower the pick’s wear. Laboratory tests were carried out at the AGH University of Science and Technology in Kraków, Poland. Following the developed method and procedure, the quality of picks was precisely and unambiguously assessed. The C2 index, apart from testing the quality of picks, was also used to forecast their wear. Based on the C2 index, a method is proposed to estimate the wear rate of conical picks provided by different manufacturers and determine the acceptable unit price and operating costs. Thus, it is possible and reasonable to precisely define the investment requirements and appropriately select the pick. Relevant tests were carried out for eight different types of conical picks used in roadheaders, longwall shearers and shaft-boring roadheaders.

Evaluation of the Quality of Conical Picks and the Possibility of Predicting the Costs of Their Use

Currently, the user’s choice of a conical pick involves specifying its geometric and material parameters, taking into account the place and conditions of its work. The selection is then made, usually on the basis of solely one criterion, which is the price. Thus, at the stage of both purchase and operation, the quality of picks and their suitability for a specific machine and the processed mineral are not assessed. Therefore, a method was developed to enable conducting tests that determine the geometric parameters of a pick, the types of materials of the pick body and WC insert as well as the pick wear rate (intensity) in a laboratory workstation. The wear rate (intensity) is described by the C2 index – the smaller is its value, the slower is the pick’s wear. The C2 index has been used to forecast the wear of picks and to determine their unit price and operating costs. This allows for precise determination of investment requirements and a proper selection of the pick.

Effect of contact characteristics on the self-rotation performance of conical picks based on impact dynamics modelling

Conical picks have a harsh working environment and 70% of their failures are caused by wear. It has been found that conical picks can rotate while interacting with the working material. This self-rotation ability is an important factor affecting pick wear, but the self-rotation mechanism remains unclear. Researching the mechanism involves the impact and friction dynamics of the interaction between a pick and its holder. Thus, a dynamic finite-element numerical model for the pick–holder interaction is established. How the handle–holder gap width, pick body and handle lengths and pick handle diameter affect the settling time and the percentage of time with no contact is studied to compare the numerical results with the equivalent effects on the rotation angle in experiments. Doing so indicates that the main factor in the self-rotation ability of a conical pick is not the magnitude of the contact load but its duration. The present research provides a new method for revealing the mechanism for the self-rotation of conical picks.

Influence of the Hard-Faced Layer Welded on Tangential-Rotary Pick Operational Part on to Its Wear Rate

Problems related with abrasive wear of tangential-rotary picks during cutting process and its limitations, have been discussed in the present study. Essential for the parameters of cutting process geometrical, kinematic and material parameters of tangential-rotary picks and types of their wear, have been discussed. Testing procedure in aspect of the wear of tangential-rotary picks and their durability estimation, has been described. Manners of the abrasion of pick body and pick edge of the tangential-rotary picks, have been determined. Particular attention was paid to procedure of hard facing of the pick operational part and its influence onto mining process. Results of examination of tangential-rotary picks with hard facing layer on operational part near insert made of abrasion sintered carbide are also cited.

Distribution of WC Particle in Cast Steel and its Effect on Abrasion Resistance

Aiming at the problem of short service life of abrasion resistance materials, the addition of ceramic particle like WC is used to improve abrasion properties of the cutting pick body. One kind of wear-resistant alloy has been prepared through mixing WC and other metal powder together and consolidating at high temperature in order to solve the segregation phenomenon of WC phase caused by its high density. After casting, the segregation phenomenon has almost faded away. Abrasion test results show that the abrasion property of the casting samples, which are added with wear-resistant ingredient and treated by different heat treatment processes, is better than that of the conventional cutting picks. Distribution of WC phase in cast steel was examined by SEM with EDS and FESEM. The result shows that WC exists in both steel matrix and cast inclusions evenly. Due to the excellent wet ability between WC and molten steel, the WC particle is covered by steel matrix firmly enough to avoid the flaking off during the abrasion process. At the same time, the WC particle itself has good wearing properties. It is the most important reason for the reinforcement of abrasion resistance of cast steel.

Mechanical Analysis of Warm Extrusion Precision Forming on 42CrMo Steel Cutting Pick

Cutting pick is a kind of widely-used consumptive mining tool. The traditional producing technics of cutting pick body is foundry, or machining after roughly forging, or machining directly from metal bar. By former technics, the property of products is poor, and by latter, the material availability is low and the cost is high. The patent technology for cutting pick body warm extrusion introduced in this paper can overcome all the disadvantages mentioned above. In this paper, by analyzing the characteristic of cutting pick body warm extrusion, adopting the principle of power balance to solve the approximate solution of strain forces, the approximate calculating formulas of extruding power are deduced. The main factors affecting on extrusion force are determined theoretically. This research can be used as basis to design tooling and choose proper equipment for this new technology.

Researches of Warm Extrusion Forming Technology and Property on 42CrMo Steel Cutting Pick

Cutting pick is a kind of widely-used consumptive mining tool, however its body is easy to break in the mining producing process, the problem that pick body easy to break could be solved by using the warm extrusion forming techniques under the premise of without raising the material level. This paper mainly focuses on the structural characteristics and material technological properties of 42CrMo high-strength steel cutting pick body, and adopts the power balance principle got the approximation of the deforming force, and derived the approximate calculation formula of warm extrusion force for cutting pick body; and analyzed the temperature field, equivalent stress, strain field and metal’s flowing rate field of warm extrusion forming by adopting numerical simulation method, and verified the result with the experiment. The result shows that the material organization grains of cutting pick produced by the new technique could be refined; the pressing direction of cutting picks’ shape outline forms forging streamlines, the quality is good. In a word, this new technique could completely meet the requirement of cutting pick.