JOURNAL OK SCIENCE & TECHNOLOGY • No 94 - 2013 THE GRINDING PROCESS ENHANCEMENT IN MACHINING HARDENED C45 STEEL USING SEGMENTED GRINDING WHEELS NANG CAO HIEU QUA CUA QUA TRINH GIA CONG VAT LIEU THEP C45 NHIET LUYEN SU' DUNG DA M A I CO BE MAT LAM V!$C G I A N DOAN Nguyen Tien Dong", Nguyen Thi Phuong Giang", Pham Due Binh'', Banh Tien Lonf " Hanoi University of Science and Technology * Thai Nguyen University of Technology Received October 01, 2012; accepted March 20, 2013 ABSTRACT C45 steel has a wide range of industrial fields due it can be used in many mechanical pa The conventional grinding wheels (continuous working surface) were used in finishing process C45 steel machine parts However, these kinds of grinding wheels had some disadvantages du high cutting force and high working temperature that lead to vary damaged on workplace surfa The cutting efficiency of abrasive grains and the grindabilities of grinding wheels were reduced paper, the grinding process of machining hardened C45 steel using newly developed grinding iv and conventional grinding wheel was observed Discontinued rate i] is defined as a ratio betwee discontinued regions and the circumference of the grinding wheel's working sudace There wer newly developed grinding wheels with different rj (10.91%, 16 37%, 18.19%, 20.01% and 21.83% respectively) and one conventional grinding wheel, which has rj of 0% were used to grind hard C45 steel The results showed that material removal rates, V^i in a unit time of grinding wheel w 16.37% was 13.2% higher than that of conventional grinding wheel Keywords Hardened 45 steel, segmented, grinding wheel, brown AI2O3, material removal rate TOM T A T Thip^ C45 li mpt vat lieu rit biin nginh ca kha ning tham gia vio nhiiu than phin chi tiit miy cac loai miy moc thiit bi Gia cdng tmh lin cu6i cic bi mit chi tiit hi$n thw&ng si> dpng qui trinh mii v&i di mii trdn thdng thw&ng Tuy nhien qui trinh gia cdng di mii cd han chi li Itic cit, nhiit cat l&n ndn thw&ng giy cic khuyit tit tren bi m$t chi tiet gia cdng; hieu qua bdc tich vit lipu dd cQng cd nhwng h^n chi nhit dtnh lim giim ning d ciia di vi nang suit gia cdng Bii bio niy de c$p din vipc st> dung di mii giin do^n m&i duvc phS triin di mii thip C45 nhi$t luypn Ty 16 giin do^n q cua di mii duvc tinh bing ty sd giu-a ting cic phin giin do^n tren bi m^t cua di mii so v&i chu vi toin b0 bi m$t ctJa di NSm vidn di mii c6 g tri 7] khic (lin Iwgt li 10.91%, 16.37% 18 19%, 20 01%, 21.83%) vi m0t viin di mii thdn thw&ng cd ty le giin do?n ij = 0% dwpc st> dpng di mii thip C45 Kit qui cho thiy thi tich kim lo duvc h&t dl mpt dan vi th&i gian Vu mil thip C45 nhi$t luy$n si> dung di mii giin do^n c 1$ n=16 37% cao han din 13.2% so v&i di mii thdng thtf&ng v&i bi mit lim vi$c lien tpc INTRODUCTION Of all the machining processes in common use these days, grinding is undoubtedly the least understood and the most involved than the others machining used in practice This is due to the complexity of the grinding process with its complex tooling stt-ucture, high cutting speeds, and small depth of cut that vary from grain to grain Grinding process can get the surface roughness of Ra 1.25 - 0.63 |im and the accuracy of 002 0.003 mm [1] The conventional grinding wheels with circumference working surface were used to grind workpiece surface However, these kinds of grinding wheels had a high cutting forces and a high working temperature thus lead to vary damaged on workpiece surface and to reduce grindability of grinding wheels Recently, there have been many researches deal with enhancing the grindability of conventional grinding wheels Some reseaches working on the structure of grinding wheels, i.e., arranging the abrasive grains on JOURNAL OF SCIENCE & TECHNOLOGY • No 94 - 2013 wheel siuTace to develop a new kind of grinding wheel The others researches working with controling the parameters of grinding process Taghi Tawakoli et al reported that composite material with ceramic substrate was ground by grinding wheels with segmented working isurface shown lower cutting forces than conventional grinding wheels [2] Dong et al revealed that hexagonal structure grinding wheels shown times higher of grains efficiency in compared with conventional grinding wheels in machining magnesium alloys and sapphire substrate C45 steel has a wide range of industrial fields due it can be used in many mechanical parts In this paper, newly developed segmented grinding wheels were used to grind hardened C45 steel NEWLY DEVELOPED GRINDING WHEELS WITH SEGMENTED GRINDING WHEEL SURFACES The Fig.l shown the newly developed brown AI2O3 grinding wheels had segmented regions on the working surface and conventional grinding wheel Discontinued rate Tj is defined as the ratio between the segmented regions on the wheel surface and the circumference working surface of the grinding wheel The segmented grinding wheels were characterized by its angle between segmented parts a, width w and depth / of segmented parts as shown in Fig.2 There were five segmented grinding wheels with different TJ (10.91%, 16.37%, 18.19%, 20.01% and 21.83% respectively) and one convential grinding wheel with T] of 0% were used to grind hardened C45 steel as shown in Fig.3 The parameters of all grinding wheels were shown in Table Fig.l Segmented grinding wheel (a) and conventional grinding wheel (b) Chieu rpng va chieu Table Parameters of all the grinding wheels Outside diameter: Inside diameter: Wheel thickness; Abrasive grain: Grain size: Bonding material: Width of segmented, w: Depth of segmented, t: 350 mm 127 mm 40 mm Brown AI2O #46 Ceramic 10 mm 15 mm sau phan xe ranh (1) W Fig.2 Segmented grinding wheels were characterized by its angle between segmented parts oc, width w and depth t of segmented parts JOURNAL OF SCIENCE & TECHNOLOGY * No 94 - 2013 EXPERIMENT PROCEDURE Grinding process was taken on plane grinding machine OKAMATO made in Japan The samples were hardened C45 steel with HRC of 42-43, which had dimensions of 100x35x40 mm as shown in Fig.4 The sample was fixed on the grinding table by magnetic clamp as shown in Fig.5 The real total cutting depth and the material removal rates were observed Segmented g r i n d i n e wheels Angle between The numbers segmented parts Discontinued o f segmented z a (degree) rate n (%) 12 30 1091 18" " " "20 1637 20 " 18.19 is" ""22" 20 01 "1636 24 21 83 " "]5 Conventional g n n d i n g wheels T\ = % Fig.3 Discontinued parameter rj for segmented and conventional grinding wheels For all the experiments, cutting spec was 35 m/s and table feeding speed V^m was m/min The cutting depths were changed t 0.015 mm, 0.025 mm and 0.05 mm respective! The experiment was finished after 10 times cutting The real total cutting depth A taken by Mitutoyo's electronic caliper mode Mituotyo500-17X-20 The real material removal rate, Fi/canbi calculated as: „ _ V^i ^'^'-mT- S^.£^.V^^mm\ 10 L '•"T"^ Where: V^i the total removed volume after 10 times ol cutting T time for cutting times (s) A the real total cutting depth (mm) L the distance in I cutting time, L = 2x300 = 600{mm) the tablel feeding V bm Vftm=12m/mins=200mm/s speed , Sw sample area = a x b (mm^) is the area of workpiece Fig4 Tim hardened C45 steel wilh IIRC of 4243 EXPERIMENT DISCUSSIONS RESULTS AND The relationship between removal material rate and the number of segmented for both conventional and segmented grinding wheels with different cutting depth ras shown in Fig, It can be seen that in Fig.6 (a) fw increased rapidly then stabilized when the number of segmented increased under the cutting depth condition of 0.015 mm Whenfte cutting depth change to 0.025 and 0.05 mm, Vji increased and obtained a highest value by the grinding wheel with segmented number of l!i e.g., discontinous rate r\ = 16.37% Fig The sample was fixed on ihc grinding able by magnetic clamp JOURNAL OF SCIENCE & TECHNOLOGY 4> No 94 - 2013 T= 0.025 mm j ' I" I9i 16 37 18,19 20 01 2} 83 1091 10 91 16 37 The grindingwheel's g wheel's discontinued rale, Tj (%) 1637 The grindingwheel's IB 19 20 01 18 19 20 01 2183 discontinued rale, rj (%} 21 83 discontinued rale, ij (%) Fig.6 The real material removal rate as function the grinding wheel's discontinued rate rj witf cutting depth t ofO 015 (a), 0.025 mm (b) and 0.05 mm (c) In the grinding process, abrasive grains were moving in random orbits, scratching and making random grooves to create a new surface .A smoother surface is obtained by a large number of cutting grains In conventional grinding wheels, the grinding chips were • formed and moved along and opposite direction with cutting speed on the wheel surface Cutting speed Droplets chips Abrasive grain Gnnding chip Grinding chips movement dirp.rpnj\ -^ Fig.7 The explaination of grinding wheel becomes dull phenomenon, reducing grindability The grains size were very small and tht space between grains even smaller Grinding chips move and joint together to form largt droplets of hot metal, and hit hot abrasive grair to adhere them Under this condition, grinding chips fill up the spaces between abrasive grains It was difficult for grinding chips to take out ol cutting area thus grinding wheel become dull Grindability of grinding wheel reduced anc could not remove the workpiece material as shown in Fig.7 More over, in grinding process using conventional wheels, the coolant also was difficult to reach the cutting area lead to high cutting temperature and could not take oui grinding chips It is the main reason causes less cutting abilities of abrasive grains Conventional grinding wheel shown i lower value of material removal rate as in Fig.6 JOURNAL OF SCIENCE & TECHNOLOGY • No 94 - 2013 When using segmented grinding wheels, grinding chips can move and take out of cutting area due to the big space of segmented regions The coolant also can easly reach to cutting area, reduce cutting temperature and less dull of grinding wheel phenomenon as shown in Fig.8 Cutting abilities of grains was increased number of abraisve grains reduce when numbe of segmented increases, i.e., discontinous rat y\ increases, thus it is not enough abraslvi grains to remove workpiece volume in oa cutting time The real cutting depth A become smaller Therefore, the material removal ra[i Vki, shown the real value of removed workpiect volume, was decrease when discontinous rati r| increases CONCLUSIONS - Segmented grinding wheels shown tht advantage in material removal rate ii machining hardened C45 steel Fig.8 The coolant also can easly reach lo cutting area, reduce cutting temperature and less dull of grinding wheel phenomenon Segmented grinding wheel with r\ 16.37% shown a highest K^j value at any cutting depth If the discontinous rate r| increases, l^^i becomes smaller At least a critical number of abrasive grains were required to remove a unit of workpiece volume The - The segmented grinding wheel which i; 16.37% shown a highest V^i value at anj cutting depth It is about 13.2% highei compared with convenUonal grinding wheels due to grinding conditions were enhanced, i.e, sharpening abrasive grains and lower cutting temperature - It can be concluded that at least i number of abrasive grains is required to remow a unit of workipece volume in one cutting time REFERENCES Banh TiSn Long, Trin Sy Tiiy, Tran Thg Luc "Nguyen ly gia cong vat lieu" - Nha xuat ban Khoi hoc va ky thuat, Ha Noi 2001, Taghi Tawakoli, Bahman Azarhoushang "Intermittent grinding of ceramic matrix composite! (CMCs) utilizing adeveloped segmented wheel" International Joumai of Machine Tools k Manufacture 51 (2011)112-119 Tiendong Nguyen, Koji Matsumaru, Masakazu Takatsu* and Kozo Ishizaki "Abrasive grair efficiency and surface roughness for machining ceramics by newly developed cup-type diamond grinding-wheels" Adv in Tech of Mat.and Mat Proc J (ATM, ISSN 1440-0731), Vol 10 [2] 7? 84 (2008) Tien Dong NGUYEN, Koji MATSUMARU, Masakazu TAKATSU* and Kozo ISHIZAK "Abrasive Grain Efficiency and Surface Roughness in Machining Magnesium Alloys byNewl) Developed Cup-type Diamond-Grinding-Wheels" Materials Science Forum Vols 620-622 (2009 769-772 Micheie H Miller (I) and Xiaorui Fan (2) "Wheel wear during intermittent grinding" Departmen of Mechanical Engineering-Engineering Mechanics, Michigan Technological University (1)' Houghlcn, MI American Showa, Inc Sunbury, OH (2) Nguyen'Tien Dong, Nguyen Thj Phuang Giang - Trucmg DHBK Ha Npi "Kha nang giam lircci gia cong vat lieu ceramics sir dung da mai co hk mat lam viec gian doan" - Tap chi Khoahgcv C6ngnghe-S6 81, 86-90 Author's address: Nfiiiyen Thi Phuong Giang - Email: giang.nguyenthiphuong@hust.edu.vn Hanoi University of Science and Technology No.] Dai Co Viet Str,, Ha Noi, Viet Nam ... (2) Nguyen''Tien Dong, Nguyen Thj Phuang Giang - Trucmg DHBK Ha Npi "Kha nang giam lircci gia cong vat lieu ceramics sir dung da mai co hk mat lam viec gian doan" - Tap chi Khoahgcv C6ngnghe-S6... substrate C45 steel has a wide range of industrial fields due it can be used in many mechanical parts In this paper, newly developed segmented grinding wheels were used to grind hardened C45 steel... gian doan" - Tap chi Khoahgcv C6ngnghe-S6 81, 86-90 Author''s address: Nfiiiyen Thi Phuong Giang - Email: giang.nguyenthiphuong@hust.edu.vn Hanoi University of Science and Technology No.] Dai Co