INVESTIGATION OF STRUCTURE AND PROPERTIES OF STAMP STEEL FOR MANUFACTURE OF PIPE TOOLS AFTER CONDUCTING STRENGTHENING THERMAL THERMAL AND THERMAL
Purpose. The aim of the research is to use modern types of chemical-heat treatment and application of nanostructured wear-resistant coatings to strengthen pipe tools for corrosion-resistant pipes - pipe press tool (needle-mandrels and matrix rings) and tool for cold roller rolling of special-thin pipes - support bars and rollers.
Methods. For the study were made:
- needles-mandrels of a pipe-profile press with a force of 16 MN in the amount of 3 (three) pieces of steel - 4H5МF1S with a diameter of 50 mm and a length of 1300 mm and subjected to hardening heat treatment (step hardening from 1050 - 1070°С and double tempering at 550 - 570° (1 tempering) and 530 - 550°С (2 temperings) in shop conditions;
- matrix rings of a pipe-profile press with a force of 16 MN in number of 10 (ten) pieces: from steel 5X3V3MFS (DI-23): 6 (six) pieces (1 piece with a diameter of 63,5 mm, 2 pieces with a diameter of 73.5 mm, 3 pieces with a diameter 71.5 mm); made of steel 4Х5МF1S 4 (four) pieces with a diameter of 71.5 mm and 73.5 mm and subjected to hardening heat treatment (step hardening from 1080 - 1100°С and double tempering at 550 - 570°С (1 tempering) and 530 - 550° C (2 l temperings) in the shop;
- rollers of the HPTR mill in the amount of 3 (three) pieces of steel 4Х5МF1S instead of steel 60S2HFA 65 mm wide under the diameter of the pipe 16 mm and subjected to hardening heat treatment (step hardening with 1070 - 1080°С and double tempering at 550 – 570 °С(1 tempering) and 530 – 550 °С (2 temperings) in shop conditions;
- 6 (six) support bars 210 mm long, 80 mm wide and 47.42 mm high and track widths 25 mm and 20 mm (under a pipe with a diameter of 15-22 mm and 23-30 mm, respectively) made of steel 4H5MF1S instead of steel 60S2HFA and subjected to hardening heat treatment (step hardening with 1080 - 1100°С and double tempering at 550 - 570°С (1 tempering) and 530 - 550°С (2 temperings) in shop conditions;
For the study, also from forgings with a diameter of 250 mm were cut witness samples with a size of 20 × 20 × 20 mm and subjected to a similar heat treatment to experimental samples of the tool. Goal. The aim of the research is to use modern types of chemical-heat treatment and application of nanostructured wear-resistant coatings to strengthen pipe tools for corrosion-resistant pipes - pipe press tool (needle-mandrels and matrix rings) and tool for cold roller rolling of special-thin pipes - support bars and rollers.
Electronic studies of metallographic sections (original sections were cut into thin samples of 5 mm), prepared and studied on a scanning electron microscope (REM), high resolution (up to 60 A) and exceptional depth of field which made it almost indispensable for metallographic research.
Measurement of the surface hardness of the samples after nitriding, carbonitriding, combined treatment was performed using a microhardness tester (microscope) - type PMT-3 at a load of 100 gs HB0,1
X-ray diffraction analysis of the experimental samples of the instrument was performed on an X-ray diffractometer DRON-2.0 in cobalt Co-Kα radiation using Fe selectively absorbing filter. The diffracted radiation was recorded by a scintillation detector.
Results. Graphs of change of microhardness from the surface to the center of samples after chemical-thermal and combined processing are constructed and investigated, the optimum mode of ionic nitriding, carbonitration, combined treatments is offered, carbonated layer and coating layer (microstructural and electronic), X-ray diffraction analysis of prototypes of the tool. The result is the development of optimal modes of thermal strengthening of the pipe tool, which provide its high performance. As a result, the steel acquires high hardness on the surface HV0,1 860-1150, which does not change when heated to 600- 650° C, high wear resistance, high endurance limits, corrosion resistance.
Originality. For the first time, the choice of a more efficient mode of heat strengthening of a pipe tool (with micro and X-ray structural studies) has been scientifically substantiated, which allows its use in real conditions of corrosion-resistant pipe production at pipe enterprises PJSC Centravis Production Ukraine, Oscar LLC and others.
Practical implications. Improving the technology of heat treatment of pipe tools (hardening with tempering and subsequent ionic nitriding, carbonitriding, combined treatment with single and multilayer coatings instead of the usual technology - tempering with tempering) will increase tool life by 30-40% and reduce processing costs. , as well as improve the quality of the inner surface of the pipes.
Loginov, Yu. N. & Ignatovich, Yu. V. (2014)/ Tool for pressing metals. Textbook. Ekaterinburg: Uralskii universitet
Belyaev, S. V., Dovzhenko, I. N., Sokolov, R. E., Rudnitsky E. A. & Peshchansky A. S. (2007). Abstract of lectures on pressing technology. Krasnoyarsk.
Chechulin, Yu. B.(2017). Cold rolling of pipes. Moskva: Metallurgiia
Lezinskaya, E. Ya. et al (2019). Collection of lectures on the technology of production of stainless steel pipes. Centravis.
Lakhtin, Yu. M. & Leontieva V. P. (2010). Materials science. Textbook for universities. Moskva: Mashinostroenie
Fetisova, G.P. (2008). Metallurgy and technology of metals. Moskva: Vysshaia shkola
Arzamasov, B. N., Bratukhin, A. G., Eliseev, Y. S. & Panayoti, T. A. (1999) Ionic chemical-thermal treatment of alloys in gaseous media. Moskva: Izd. MGUM. im.N. E. Bauman
Andreev, А. А, Sablev, L. P., Shulaev, V. M & Grigorev, S. N.(2005). Vacuum arc devices and coatings. Kharkiv: NSC KIPT
Lakhtin, Yu.M. (1993). The current state of the nitriding process. Moskva: Metallurgiia
Chatterjee-Fisher, R. & Ayzell, F. (1990). Nitriding and carbonitriding: Textbook. Ed. by Supova, A. V. Moskva: Metallurgiia.
Andreev, A. A., Sablev, L. P. & Shulaev V. M. On the role of atomic nitrogen in the chemical-thermal treatment of steels in a gas vacuum-arc discharge. Sb. report 5th Int. conf. "Equipment and technologies for heat treatment of metals and alloys", Kharkiv: NSC KIPT, 2005, Part 1, 246 - 250
Liopo, V.A. & Voyna V. V. (2003). X-ray diffractometry. Textbook. Grodno: Kupala State University of Grodno
Bolshakov, V. I. (2010). Equipment of thermal shops, technologies of heat treatment of metal products. Dnepropetrovsk: Dnepr-VAL
Alexandrov, V. A. & Bogdanov, K. V. (2005). Nitriding of the tool from high-chromium and high-speed steels. Techno Sphere, (5), 14-20