CC BY
4
SRSTI 55.03.35
https://doi.org/10.48081/ABUL1117
*A. A. Sagitov1, K. T. Sherov2, B. T. Mardonov3, J. R. Ravshanov4,
G. M. Tussupbekova5
1,2,5S. Seifullin Kazakh Agrotechnical Research University,
Republic of Kazakhstan, Astana;
3,4Navoi State University of Mining and Technology,
Republic of Uzbekistan Navoi.
*e-mail: almat1990@mail.ru
STUDY OF RELATIONSHIP BETWEEN THE PROCESSED MATERIAL
HARDNESS AND THE PRETREATMENT SPEED
This research is funded by the Science Committee of the Ministry of Science
and Higher Education of the Republic of Kazakhstan (Grant No. AP14972884). This
research has shown that a serious limiting factor inhibiting the use of harder metals
and alloys as dressing materials is the loss of form stability of the cutting edge when,
due to high contact loads, it is plastically deformed with deterioration of cutting
properties caused by changes in the geometry of the cutting edge. To address this
issue, a study of the relationship between the hardness of the machined material
and the pre-treatment rate was carried out. Pretreatment was carried out on two
heat-treated hardened 20X steel materials with a hardness of HRC 21...23 and HRC
19...20.
As a result it is established that by varying the hardness of the machined material
during tool lapping it is possible to increase the hardening effect and significantly
reduce the material consumption.
Also plots of influence of pre-treatment duration on tool life of T5K10 when
turning steel 20X (HRC 16...17) and influence of hardness of working material on
optimum rate of pre-treatment of R6M5 tool and time of pre-treatment are presented.
Keywords: Hardness, pre-treatment, hardening, optimum rate, wear resistance,
pre-treatment time.
Introduction
The existence of optimum regimes of tool pre-treatment is theoretically and
experimentally proved [1–5], but their fast and reliable determination is still an open
question. Taking into account that the main role in formation of the wear resistant
contact secondary structures is played by the deformation hardening processes, it is
necessary to solve the optimization of the pre-treatment mode from the deformationthermal
point of view. Deformation hardening processes during tool pre-treatment are
realized on the background of technological factors, therefore when solving problems
of optimization of pre-treatment it is necessary to take into account all technological
features of exploitation of concrete type of the tool [6].
Numerous experimental studies have established that for the majority of metalcutting
tools, optimum conditions for pre-treatment lie in the area of reduced cutting
conditions, which can be achieved by reducing either the cutting speed or feed rate. In
order to clarify the efficiency of pre-treatment when varying different parameters of
cutting conditions, a special series of experiments was presented, when an optimum
condition was achieved by autonomous undercutting of cutting speed and feed.
The effect of improved durability when running at a reduced speed was almost twice
as effective as running at the optimum cutting speed compared to running at the optimum
feed rate, and this process of varying the cutting speed is much easier to implement [6].
Materials and methods
The optimum mode of tool pretreatment provides the best deformation and thermal
hardening conditions, which can be further improved if the pretreatment is carried out on
a harder material. To clarify this circumstance by special experiments a study was carried
out to find out the effect of hardness of the machined material on the wear resistance
of the secondary contact structure [5, 7]. The results of this series of experiments are
presented in figure 1, where the effect of hardness ratio of machined material to tool
material on the degree of increase of tool material durability after machining in relation
to a conventional tool is presented [7].
Figure 1 – Effect of hardness ratios of machined (NP) and tooled (NT) materials on
the magnitude of the increase in pre-treatment durability
The dependence has monotonically increasing character, showing that with the
increase of hardness of the processed material the hardening effect of working surfaces
of the tool increases, thus the degree of increase of durability can reach values at a level
of 4.5...4.6 times. The character of the specified dependence once again confirms that
deformation processes play an important role in the mechanism of formation of wearresistant
secondary contact structure [6–8].
A serious limiting factor restraining the use of harder metals and alloys as running
materials is the loss of dimensional stability of the cutting wedge, when, due to high
contact loads, its plastic deformation occurs with deterioration of cutting properties
caused by changes in the geometry of the cutting edge. According to the existing
conceptions [9–11] the loss of form stability takes place, when the hardness ratio of
tool material to tool material is greater than 1.4...1.6. Then the boundary of loss of form
stability on figure 1 can be represented by the vertical line, drawn through the abscissa
axis at the level of . A doubling of the resistance takes place starting with a hardness
ratio of 0.5. Therefore the range of hardnesses of processed materials providing double
increase of firmness is 0,5...0,65 [6-8].
An important parameter of the pre-treatment process is its duration, which determines
the degree of completion of the secondary structure.
Results and discussion
Experimental studies on the pre-treatment of lathe cutters were carried out in the
laboratory of the «Technological machinery and equipment» department of the S.
Seifullin Kazakh Agrarian-Technical Research University. Machining of workpiece
from steel 20X during pre-treatment of cutters was made on screw-cutting lathe 1K62.
а)
b)
Figure 2 – shows the workpieces and cutters used during pre-treatment
1 – with hardness НRС 21...23; 2 – with hardness НRС 19...20;
a) workpieces of 20X steel hardened by heat treatment; b) undercutting tools from
Т5К10
Figure 2 – Workpieces and cutters used during pre-treatment
Figure 3 shows the pre-treatment process for picks.
а)
b)
c)d)
Figure 3 – Process of pre-treatment of cutters
а) cutter №1; b) cutter №2; c) cutter №3; d) cutter №4
Figure 4 shows the machined workpieces during pre-treatment.
а)
b)
Figure 4 – Machined workpieces during pre-treatment
1 – frequency of rotation nsp = 20 rpm; 2 – frequency of rotation nsp = 40 rpm;
3 – frequency of rotation nsp = 63 rpm; 4 – frequency of rotation nsp = 80 rpm
a) workpiece with a hardness of НRС 21...23; b) workpiece with a hardness of
НRС 19...20
In figure 5 results of researches on influence of duration of the period of preliminary
pre-treatment on durability of the cutter from Т5К10 at turning 20Х with НRС 16...17
on modes V=60 м/min; S=0,2 mm/rev; t=0,3 mm are resulted.
Pre-treatment was carried out on two heat-treated hardened 20X steel materials with
a hardness of HRC 21...23 and HRC 19...20. In the first case, the pre-treatment speed was
Vn = 3 m/min, and in the second case, Vn= 6 m/min. The pre-treatment time was varied
from zero to 6 minutes. The received results showed the following: at pre-treatment on
a workpiece with hardness 21...23, optimum duration of pre-treatment was 3 minutes,
and at cutting on a material with hardness 19...20 – 5 minutes, i.e. with increase of
hardness of processed material, duration of pre-treatment providing maximal durability
decreases. Depending on the pre-treatment time the character of wear accumulation
curve also changes. Thus, with the pre-treatment duration shorter than the optimum,
the catastrophic wear area is faintly visible on the blunting curve, which disappears as
the pre-treatment duration approaches the optimum one. Pre-treatment at the optimum
variant provides tool operation up to the accepted criterion of blunting in the mode of
steady-state wear. If the pre-treatment period is longer than the optimum, tool durability
decreases due to the high value of pre-treatment wear. Optimum mode of pre-treatment
corresponds to the value of pre-treatment wear in the range hp = 0,18 ... 0,22 mm.
Figure 5 – Effect of pre-treatment duration on durability of T5K10
cutter when turning steel 20X (HRC 16...17)
1 – hardness of pre-treatment steel HRC 19...20; 2 – hardness of pre-treatment
steel HRC 21...23
In earlier works on pre-treatment in order to substantiate the physical nature of
optimum regimes the studies on the independent influence of temperature and velocity
factors on the formation of wear resistant contact structures have been given [12–14].
In particular, it was noted that in the real process of cutting the temperature and velocity
factors are inseparable and are determined by machining modes. It was found that the
experimental character of the influence of cutting speed on the hardening and wear
resistance of the secondary contact structure of the tool is determined by temperature
factors, while the degree of hardening and the numerical value of wear resistance are
determined by the speed factor. In addition, it has been shown that the autonomous
velocity effect represents one of many, and not always dominant, factors responsible for
the degree of hardening. Indeed, the amount of hardening is determined by the degree
of plastic deformation, the numerical value of which depends on specific contact loads,
contact adhesion forces, process duration and sliding speed. Therefore, it can be assumed
that in many cutting modes, the contact layers of the tool reach the ultimate hardening
state, and the degree of completion of this process will mainly depend on time.
The effect of the hardness of the material to be machined on the optimum pretreatment
speed and pre-treatment time is shown in Figure 6, from which it can be seen
that the optimum pre-treatment speed and time decrease as the hardness increases.
Figure 6 – Influence of hardness of the machined material on the optimum pretreatment
speed of the R6M5 tool and the pre-treatment time
1 – pre-treatment time τpr; 2 – pre-treatment speed Vpr
The optimum pre-treatment speed in this case for a high-speed tool can be determined
according to the empirical formula
Vopt=1,87–0,047⋅HRCm
where Vopt is the optimum pre-treatment speed, m/s;
HRCm is the hardness of the pre-treatment material.
Based on the above it is possible to conclude that by varying the hardness of the
workpiece during tool-hardening it is possible to increase the hardening effect and
significantly reduce material consumption. So, we are using steel with hardness HRC
20, optimum cutting speed is 28 mm/min, and grinding time is 5 minutes, while length
of the travelled path (or material consumption) is 160 m. With steels in hardness HRC
23, an optimum cutting speed of 4 m/min and a pre-treatment time of 3 minutes, which
corresponds to a travel distance of 12 m. Hence, pre-treatment on a billet with HRC 23
saves more than 10 times the material, and shortens the process by more than 15 times
compared with the raw steel process.
Conclusions
1. The efficiency of the pre-treatment of cutting tools can be improved by using steels
with higher hardness as the pre-treatment material. Higher contact loads occurring during
the cutting process provide greater strain hardening and shorten the pre-treatment time.
2. Pre-treatment increases not only the wear resistance of tool working surfaces,
but also the operational reliability and heat resistance of contact structures.
Based on the above, it can be concluded that by varying the hardness of the machined
material during the tool pre-treatment period it is possible to increase the hardening
effect.
Funding. This research is funded by the Science Committee of the Ministry of
Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14972884).
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*А. А. Сагитов1, К. Т. Шеров2, Б. Т. Мардонов3,
Ж. Р. Равшанов4, Г. М. Тусупбекова5
1,2,5С. Сейфуллин атындағы Қазақ агротехникалық зерттеу университеті,
Қазақстан Республикасы, астана қ;
3,4Навои мемлекеттік тау-кен технологиялық университеті,
Өзбекстан Республикасы, Навои қ.
Материал 17.08.23 баспаға түсті.
ӨҢДЕЛГЕН МАТЕРИАЛДЫҢ ҚАТТЫЛЫҒЫ МЕН АЛДЫН АЛА
ӨҢДЕУ ЖЫЛДАМДЫҒЫ АРАСЫНДАҒЫ БАЙЛАНЫСТЫ ЗЕРТТЕУ
Зерттеуді Қазақстан Республикасы Ғылым және жоғары білім
министрлігінің Ғылым комитеті қаржыландырады (грант № AP14972884).
Зерттеулер көрсеткендей, қатты металдар мен қорытпаларды түзету
ретінде қолдануға кедергі келтіретін маңызды шектеу факторы кесу жиегінің
геометриясының өзгеруінен туындаған кесу қасиеттерінің нашарлауымен
жоғары жанасу жүктемелерінің әсерінен пластикалық деформацияланған
кезде кесу жиегінің пішінге төзімділігін жоғалту болып табылады. Бұл
мәселені шешу үшін өңделген материалдың қаттылығы мен алдын ала өңдеу
дәрежесі арасындағы байланыс зерттелді. Алдын ала өңдеу HRC 21...23
және HRC 19...20 қаттылығы бар 20Х қатайтылған болаттан жасалған екі
термиялық өңделген материалда жүргізілді.
Нәтижесінде, құралды сыру кезінде өңделетін материалдың қаттылығын
өзгерту арқылы беріктендіру әсерін арттыруға және материалды тұтынуды
едәуір азайтуға болатындығы анықталды.
Сондай-ақ, алдын-ала өңдеу ұзақтығының 20Х (HRC 16...17) болатты
өңдеу кезінде T5K10 құралының тұрақтылығына әсер ету графиктері және
өңделетін материалдың қаттылығының Р6М5 құралын алдын ала өңдеудің
оңтайлы жылдамдығына және алдын ала өңдеу уақытына әсері келтірілген.
Кілтті сөздер: қаттылық, алдын-ала өңдеу, шынықтыру, оңтайлы
жылдамдық, тозуға төзімділік, алдын-ала өңдеу уақыты.
*А. А. Сагитов1, К. Т. Шеров2, Б. Т. Мардонов3,
Ж. Р. Равшанов4, Г. М. Тусупбекова5
1,2,5Казахский агротехнический исследовательский университет имени
С. Сейфуллина, Республика Казахстан, г. астана;
3,4Навоийский государственный горно-технологический университет,
Республика Узбекистан, г. Навои.
Материал поступил в редакцию 17.08.23.
ИССЛЕДОВАНИЕ ВЗАИМОСВЯЗИ ТВЕРДОСТИ
ОБРАБАТЫВАЕМОГО МАТЕРИАЛА И СКОРОСТИ
ПРЕДВАРИТЕЛЬНОЙ ПРИРАБОТКИ
Исследование финансируется Комитетом по науке Министерства
науки и высшего образования Республики Казахстан (грант № AP14972884).
Проведенные исследования показали, что серьезным ограничивающим
фактором, препятствующим использованию более твердых металлов и
сплавов в качестве правки, является потеря формоустойчивости режущей
кромки, когда под действием высоких контактных нагрузок она пластически
деформируется с ухудшением режущих свойств, вызванных изменением
геометрии режущей кромки. Для решения этой проблемы было проведено
исследование связи между твердостью обработанного материала и степенью
предварительной обработки. Предварительная обработка проводилась на
двух термообработанных материалах из закаленной стали 20Х с твердостью
HRC 21...23 и HRC 19...20.
В результате установлено, что, изменяя твердость обрабатываемого
материала при притирке инструмента, можно повысить эффект упрочнения
и значительно снизить расход материала.
Также представлены графики влияния продолжительности
предварительной обработки на стойкость инструмента Т5К10 при токарной
обработке стали 20Х (HRC 16...17) и влияния твердости обрабатываемого
материала на оптимальную скорость предварительной обработки
инструмента Р6М5 и время предварительной обработки.
Ключевые слова: твердость, приработка, закалка, оптимальная скорость,
износостойкость, время приработки.
