The Impact of the Lubricant Dose on the Reduction of Wear of QRO90 Steel Dies Used in the Forging Process of the Valve Forging Made of High-Nickel Steel

TThe paper presents the results of research on the influence of the settings of lubrication and cooling system parameters (solenoid valve opening time and lubricant feed pressure in terms of its quantity) in order to select the optimal lubricating conditions and thus reduce the wear of the dies used in the first forging operation of the valve forging made of high-nickel steel. Based on the observation of lubrication in the industrial process, it was found that a significant part of the lubricant fails to reach the die cavity, reaching the outside of it, which causes die wear due to seizure resulting from adhesion of the forging material to the tool surface, as well as high lubricant consumption and dirt in the press chamber. The authors proposed their own mobile lubricating and cooling system, which allows for a wide range of adjustments and provided with automatic cleaning procedures of the entire system, unlike the fixed lubrication system used so far in the industrial process. First, tests were carried out in laboratory conditions to determine the highest wettability and the lubricant remaining inside the tool cavity. These tests determined the lubrication system parameter settings which ensured that the greatest amount of lubricant remains in the cold die cavity without the forging process. Then, to verify the obtained results, tests were carried out in the industrial process of hot die forging of valve forgings, for short production runs of up to 500 forgings. The results were compared with the measurement of changes in the geometry of tools and forgings based on 3D scanning and surface topography analysis with the use of SEM. For best results (the variant of the setting of the dose and the time of exposure to lubricant), the forging process was carried out with the use of a new tool, up to the maximum service life.

Hydrogen effect on the high-nickel surface steel properties during machining and wear with lubricants

Purpose: The aim of the proposed research is to investigate the hydrogen effect on the high-nickel steel surface properties changing during machining and wear with participation of lubricant-cooling environments. Design/methodology/approach: The approach of the fracture mechanics and physicalchemical methods surface properties investigation was used to formulate the conclusions. Applying of lubricant-cooling (liquid, solid, gaseous) technological environments (LCTE) has change the morphology of chips and roughness of contact 23Ni1Mo3Ti steel surfaces depending on the experimentally fixed hydrogen concentrations (4.62…12.0 ppm). It correlates with both the roughness of the treated surface and the nature of the cutting products fragmentation: the maximum concentration of hydrogen - in the chips coincides with the minimum size of its defragmentation and reduction of the surface roughness. For nitrogen and oxygen, a similar relationship is traced poorly. Findings: On the basis of the fracture mechanics approaches it is confirmed, that in the conditions of the application of hydrogen containing (as chemical composition) (up to 12 ppm) and hydrogen accumulated (in nano container) (up to 600 ppm) LCTE, hydrogen enters the near crack initiation contact zone before fracture and taking part in changing structural material fracture mechanisms, improves its mashinning processes. Research limitations/implications: The results obtained on laboratory specimens should be tested during machining of real details made from high-nickel steel. Practical implications: The created technological approaches can be used in practice evaluation of mechanical properties and residual of modern gas turbine parts. Originality/value: It was shown, that hydrogen containing (in chemical composition) and hydrogen accumulated (in nano container) LCTE permits the hydrogen to enter in the near crack initiation contact zone before fracture and taking part in changing structural material fracture mechanisms.