Special requirements are applied to the structural-mechanical characteristics of rod bolt products manufactured by cold die forging of pearlite steel class. A very common and productive method of obtaining finished metal products with high mechanical properties is their landing on cold heading (cold-heading) machines made of rolled metal, which must have a certain quality along the entire length: a sufficient ductility, homogeneous structure and parameters of technological properties, absence of any defects. Hardware plants receive the initial blank for the manufacture of various fasteners in the form of hot-rolled steel, which is not possible to use for the landing of high-strength hardware, due to the poor quality structure and surface layer. Therefore, the calibrated rolled stock is subjected to intermediate heat treatment before driving, which should guarantee the quality of the metal products at transitions of the cold heading. Further, the driven products of strength class 8.8 and up, made of alloy steel grades, must be subjected to hardening with subsequent tempering. However, such thermal operation often leads to decarburization of the surface, cracking and warping of finished products, thus increasing labor intensity, energy consumption and, consequently, the final production cost. The paper proposes an alternative method of the rolled stock structural preparation, which includes isothermal treatment of pearlite steel grades 35X and 38X, which excludes from the technological process the recrystallization annealing and quenching with the release of finished bolt products, and which minimizes any appeared scratches, warping and decarburization on the rolled stock and the rolled product. The structure of rolled stock induced in the drawing die, and the surface hardening by reduction, and thread rolling provide the parameters of mechanical properties of M8 bolts and pins, corresponding to the strength class 9.8.

One of the most important objectives of the modern car production development is to improve the quality of metal products and parts made from it, increase their efficiency, reliability, service life, bringing these indicators to the level of the world standards, ensuring the competitiveness of domestic products at the foreign market. The structural safety of motor vehicles is largely determined by the operational reliability of the constituent elements. Car fasteners made of high-carbon and alloy wire, including hardware items, are among the critical and widely used parts in mechanical engineering. The most common and progressive method of their manufacture is the cold upsetting from rolled bar material. The bar material surface condition has a significant impact on its quality. Hot rolled products from metallurgical plants are typically delivered to the processing facilities covered with scale and rust. To improve the surface quality of semifinished metallurgical products for rerolling at the stage of wire preparation for drawing, it is subjected to continuous mechanical or chemical cleaning. Traditionally, the technology of surface scale removing by etching is used in production. This method of scale removal provides a high level of cleaning, but there are problems with the disposal of spent acid solutions, reducing the steel ductility. Mechanical methods of scale removal have been widely introduced recently, although the use of mechanical scale removal devices also does not completely solve the problem. The paper considers the possibility of using advanced electron plasma treatment technologies for these purposes and the influence of traditional methods and this scale removing method from the rolled steel surface on the quality of metal preparation for upsetting.

In all industry sectors and in the automotive industry, in particular, structural materials that undergo various treatment methods are widely used. Various types of plastic deformation are widely used in the manufacture of products and structural elements made of low-carbon sheet steels. The authors studied the effect of the degree of technological deformation on the fatigue process parameters of flat low-carbon steels. It has been established that the preliminary deformation within the uniform limits causes an increase in fatigue resistance. The kinetic diagrams of the fatigue failure are used to estimate the change in durability from the rate of accumulation of fatigue damage at the cyclic deformation stage until the moment of origination and propagation of the fatigue crack. The ratio of the duration of fatigue failure stages of some sheet automotive steels depending on the degree of preliminary strain by stretching at a given amplitude stress of the cycle is revealed.