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Secion 4. Science of materials
Secion 4. Science of materials Секция 4. Материаловедение
Kanayev Amangeldy T.,
L. N. Gumilyov Eurasian National University, Doc.Tech.Sci., Professor Bogomolov Alexey V.
S. Toraigyrov Pavlodar State University, Cand.Tech.Sci.
E-mail: bogomolov 71@ mail.ru Zhidkova Alena I., Tugumov Kuat K., Tashenov Serik Z.
S. Toraigyrov Pavlodar State University, students, the Faculty of Metallurgy E-mail: [email protected], kuat.93@ mail.ru, tashenov-serik07@ mail.ru
Strengthening of the transfer of angular profiles in the stream brake machine
Abstract: The given laboratory experiment is brought on searching for optimum mode thermal processing of building renting for Kazakhstan producers. In the given work the opportunity of improvement of quality of reinforcing bar from uninterrupt-edly-casted bars by deformation and thermal hardening is researched. Complex researching and development of technology of deformation and thermal hardening of reinforcing bar from uninterruptedly-casted bars.
Keywords: steel, profiles of rolling, continuously cast bars, thermal hardening
Shaped profiles of rolling (angular, channels, double-T and others) are characterized by irregular distribution of metals in section, which demands regulated selection of heat from different parts of their section in combined deformational and thermic working with rolling heat. During thermic correcting and deformational and thermic working of corner profiles it is necessary to consider that metal volume per unit top, therefore it is necessary to supply increased heat selection from the cornet top for equal cooling. In this connection the water quantity given to the top must be more over 15-20% than on the leg [1, 586-589].
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Секция 4. Материаловедение
For the providing with equal structural and phase transformation in section of the profile the water outlay correlation per unit cornet surface from above and below for the legs must be 1:1, for the top 1: (1,2-1,4). The researching shows that in the process of interrupted heat strengthening hogging happens to the side of more intensive cooling. In the result of this the maintenance in the process thermal hardening of given water outlay correlation from above and below for the top and it will provide equal cooling and prevent hogging [2, 126].
According to these conditions the universal installation of intensive and regulated cooling was used for the thermal correcting and hardening of equal corner profiles, which allowed, from the first side, to prevent large thermic and phase voltage calling hogging and from the second side, to intensity cooling process, which is important for thermal hardening low-carbon steel (Art. 3, art. 5) with high sense of critical heat strengthening speed.
The installation of rapid and regulated cooling includes two important blocks: the block of selected cooling of different elements of corner profile water stream and the block of deep cooling in vertical water stream.
Owing to good steam conditions and uninterrupted blows of steams on the metal surface film boiling stage by stream cooling is practically absent, that is conform to the cooling increasing.
Moreover at the result of rich inflow to the cooling surface and short — term contact with its water has no time to overheat and its cooling ability does not change. Stream cooling dignity, which is realized in the installation of rapid cooling, is an opportunity of intensive cooling changing in wide limits due to the changing of quantity and speed of water stream from the nozzle, and also cooling zone width by means of nozzle turning in collectors during tuning on definite profile size.
High cooling effectiveness in the second knot — in the rapid water stream on big stages of vertical water stream — may be explained by intensive diversions and team condensation, and also uninterrupted renewal incoming to the reaction water volume on the whole surface of cooling corner part, which is not possible to reach on the other ways of cooling.
For the installation of the technological factors on the mechanical means of corner profiles from the art. 3 kp and art. 3 sp. the deformational and thermic working was realized by different conditions. Temperature of rolling rinks was changed, and also duration of a pause between the end rolling rinks and the beginning of intensive cooling. Duration of intensive cooling and pressure of water in the chamber of intensive cooling constantly supported. Keeping Si in the steel was estimated on its mechanical properties. Technological conditions of processing and measured on standard methods mechanical properties of the strengthened structures from steel art. 3 kp and art. 3sp. are presented in the table 1-2.
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Secion 4. Science of materials
Table 1. - Mechanical properties of steel art. 3kp after rolling and intensive cooling during 2 seconds under pressure 0,6 MPa
°c At ^ В ^Т ,%
H / мм2 H / мм2
900 < 1 390 280 24
1000 < 1 370 250 25
1070 < 1 365 235 25
940 5 370 260 25
1000 5 355 245 26
1070 5 350 230 25
940 10 365 240 25
1000 10 350 235 26
1070 10 345 225 26
Commentary — st. 3kp (%: — 0,19; Mn — 0,56; Cr — 0,23; Si — 0,04; P < 0,04; S< 0,04).
Table 2. - Mechanical properties of steel art. 3sp after rolling and intensive cooling during 2 seconds under pressure 0,6 MPa
tK n °C Ат ^т ^5,%
H / мм2 H / мм2
900 < 1 580 400 14
975 < 1 525 380 19
1070 < 1 485 370 21
900 5 560 385 15
975 5 515 375 20
1070 5 485 345 21
900 10 515 375 16
975 10 480 340 19
1070 10 460 325 20
Commentary — st. 3kp (%: — 0,19; Mn — 0,56; Cr — 0,23; Si — 0,04; P < 0,04; S< 0,04).
The given tables show, that important technology factors thermal hardening of low carbonic steels in which strengthening processes during and upon termination of hot deformation proceed with the big speed, is t, r, and r, directly influencing temperature and final mechanical properties of a strengthened product.
The temperature of the rolling end has special value, which for the investigated angular structures makes 880-900 °C. Cooling from such temperatures can pass pro-
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Секция 4. Материаловедение
cesses static cell formation and recrystallization that changes structure in comparison with that, which was at the moment of the end of rolling.
Therefore among parameters on which the structure formed during hot rolling is estimated, for results of deformational and thermal hardening its thermal stability is important. As it was already marked, it is connected with the structure and properties of martensite, formed at deformational and thermic hardening, in many respects inherit subgrain structure and dislocation textures of initial heat formed austenite. In this connection the preservation of optimum structure, formed during and upon termination of hot deformation, has important and in some cases defining value [3, 58].
In determining ofa chemical composition ofa material for mass production ofthermally strengthened fittings from rolling heating plays a role of an effective alloying and a micro alloying. The widest distribution has received silicium because of relative availability and low cost in metallurgy which is entered into steel as a deoxidant and the alloying element.
Silicium besides ability to oxidize steel actively, due to the ease of transfer of its valence electrons from an external cover 5s23p2 to the atoms of oxygen having an external electronic cover 2s22p with achievement of steady electronic configurations 2s22p6 as a result of it. There is an available very useful property for alloys hardening: ability to raise firmness of martensite against tempering.
Silicium makes difficult and ambiguous impact on toughness, plasticity and impact strength of iron and steel. This influence changes depending on the content of the silicium, other alloying elements in steel and nature of its thermal processing.
The majority of researchers [4, 47] express unanimous opinion that silicium at its contents to 1,5-2%, as well as manganese, makes strengthening effect on iron and steel, practically without worsening thus plasticity. However, the estimate of influence of silicium on impact strength and resilience to fragile destruction of iron also became considerably more contradictory. A. P. Guljaev has showed that in pure (0,002% C) iron of vacuum smelting adding 1% of Si is essentially reduce Tcr and only during further increasing of its concentration in an alloy, It is observed the increasing of the temperature, though at 2% of Si iron appears even less inclined to fragility, than in its absence. This positive effect is connected with oxidize effect of silicium in steel.
M. P. Brown considers that silicium, especially in a complex with manganese and lame, provides significant reinforcement while saving high plasticity and viscosity if the content of carbon isn’t higher than 0,25%. while working with steel 0,35% С, in the tempered and high-released condition it was found out that unlike manganese, when we increase the content of silicium to 2,5% plasticity continuously improves. The presence of silicium in high-thermo strengthened steels is obligatory, in connection with its beneficial effect on sub-structure of martensite. There is data that silicium (under 2%) reduces a tetragonality of initial martensite lattice and reduces tendency to formation of hardening cracks as reduces a sample deformation during hardening.
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At the same time, there are also other estimates of influence of silicium on properties of iron and steel. So, increase of the content of silicium up to 0,6% doesn’t influence on impact strength of technical (0,05% C) cast iron, but at further growth its concentration it sharply decreases L. I. Gladstein and D. A. Litvinenko have noted the increase Tcr in the normalized construction steel from 1,46% of Si. It is specified (K. Taffner, K. Meyer) that at the contents over 0,5% silicium makes negative impact on Tcr of hot-rolled construction steel, and at the contents over 0,37% silicium makes an adverse impact on work of distribution of cracks in normalized and improved steels with 0,15-0,20% of C.
Provided analysis of the researches results from various authors testifies that influence of silicium on a ratio of durability, plasticity and tendency of iron and steel to fragile destruction is ambiguous. It is in a difficult dependence on the content of carbon, other elements in steel, technology of its production and thermal processing. Therefore according to data it is not possible to choose the optimum maintenance of these elements.
Systematic researches were required [5, 20] in this field, especially when we know the specificity of the final product — high-strength fixture steel of periodic profile which has active-operating concentrators of tension (system of cross-section and longitudinal edges of rigidity) and testing difficult influence of external and internal forces during a work in preintense beton.
As a result of the carried-out laboratory researches of fixture steel of 35 GS at increase in the content ofsilicium up to 1,5% on weight strength goes up to 100-140 MPas, a fluidity limit goes up to 50-120 MPas, relative lengthening reduces to 2,4-2,9%.
From experimental data follows, that decrease in the end of rolling with 1070 C up to 900 C leads to growth of strong properties though at pauses 3 s and 6 s growth of strengthening properties weakens in a greater degree, than more pause (6 s). Mechanical properties of carbonaceous steel St.3 sp by deformational and thermic hardening can be raised up to a level of mechanical properties of low-alloyed steels 12G2S, 09G2S by the standard 27772-88 rolling for thew building steel constructions. It gives the opportunity to replace low-alloyed steel 12G2S, 09G2S by deformational and thermic hardening of carbonaceous steel with the economy of alloying elements. Besides such replacement allows to improve technology of hot rolling as a rolling of firmer and less plastic alloyed steel, it is replaced soft rolling with more plastic low-carbon steel. The experiments show, that, despite of heat of the end of rolling, the effect of high-temperature machining expressed in additional increase of durability at satisfactory of plasticity in comparison with properties, received at usual training from oven heating, comes to light absolutely definitely.
This article was prepared within the program of basic and applied researches of the Ministry of Education and Science of the Republic of Kazakhstan on a subject from 1796\GF «Development of technology of the integrated production of high-strength fixture hire from continuously cast preparations».
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References:
1. Kanaev A. T., Reshotkina E. N., Bogomolov A. V Defects and Thermal Hardening of Reinforcement Rolled from Continuous Cast Billet//Steel in Translation, 2010, Vol. 40, No. 6, pp. 586-589.
2. High-strength fixture steel. Kugushkin A. A., Uzlov I. G., etc. — Moscow: Metallurgy, 1986, 272 s.
3. Kanayev A. T., Nechaev U. S., Prohorchenko N. V To the question of mechanism of the thermic and mechanical hardening of low-carbonic and low-alloyed steel. Metals, News RAN, 1995, N2, p. 57-60.
4. Bogomolov A. V. , Kanayev A. T., Kaken A. S. Influence of silicium on operational properties of accessorized steel.//Materialy VIII Mifdzynarodowej nau-kowi-praktycznej konferencji «Naukowa przestrzen Europy — 2012» Vol. 37.: Przemysl. Nauka i studia — pp.47-49.
5. Kanaev A. T., Bakizhanova D. S., Bogomolov A. V.//Nauka I Studia, 2013 No. 30 (98), pp. 19 -23.
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