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An Investigation of Adhesion Wear Behavior of Tool Steel on Blanking Die
Komgrit Lawanwong 1+, Natthasak Pornputsiri and Ghit Luangsopapun 2 1Department of Tool&Die engineering, Faculty of Industrial and Technology, Rajamangala University of
Technology Rattanakosin, Wang Klai Kang Wong Campus Prachubkirikhan 77110, THAILAND. 2Thailand Institute of Scientific and Technological Research, Pathum Thani 12120, THAILAND.
Abstract. This research work aims to exploration wear phenomenon on punch for blanking stainless steel. Three punch materials: JIS SKD11, SKH 51 and SKS 3 were studied. Those punches were hardened to fixed hardness 59 HRC. Stainless steel JIS SUS 430 having the same thickness of 2 mm were employed as workpiece material for the experiments. Clearance between punch and die of blanking tool was five percent of workpiece thickness. The strip was blanked into circular shapes of 25 mm. in diameter. Direct measurement of wear on blanking punch was carried out using optical microscope. Each punch was used for blanking 2,000 stroke/conditions. It was found that SKH 51 had shown lower wear than SK D 11 and SKS 3 respectively. The higher tungsten, molybdenum and vanadium content of SKH 51 increase the amount of carbide compound caused hard and durable of cutting edge. Beside, punch SKD 11 had shown highest adhesive because high chromium content has compatibility of elements. The compatibility of metal element caused of high adhesion, friction and wear rate. Punch material SKS 3 had shown high wear rate because of low chemical composition. Moreover punch SKS 3 had shown highest corrosion on cutting edge.
Keywords: Adhesion wear, Blanking die, Stainless steel, Tool steel, Blanking Punch
1. Introduction One of important process in the metal forming is the blanking process. Blanking and piercing operations
are widely used to cut sheet metal or plates by a shearing process between punch and die for mass production of precision engineering components. The quality of the parts, evaluated by the profile of the shaped surface depends on many factors such as tool design; punch material properties, stamping conditions and especially tool wear [1]. Tool wear in blanking process is very important in case of cutting high production. Hence the studies on tool wear have been able recently because the wear mechanism and contact conditions such as punch material conditions, surface roughness and generation of wear particles can not be explained. Many experimental researches have been done to investigate the wear phenomenon under the relatively simple tests [2–8] but the researches have been related to experimental observation of wear profiles on blanking tool could not explain wear phenomenon according to the increase of the number of pieces.
Furthemore, the high precision of the parts, smooth sheared edges and high tool life, many research have been conducted. Takaishi [9] measured the wear contour on die and punch in the shearing process of stainless steel sheets according to various clearances between die and punch. Choy and Balendra [10] analyzed the wear phenomenon with describing the wear punch profile as the changes of radius around punch edge. Aoki [11] observed wear profiles on punch during sheet metal shearing process. Tronel and Chenot [12] predicted tool wear in hot forging process by the finite element method. In this paper focuses wear behaviors of the punch using three kinds punches materials are investigated. In addition, the behaviors of adhesive wear on blanking punch investigate by SEM and EDS analysis.
+ Corresponding Author Tel.: + 66 32 618570 fax: +66 32 618500. E-mail address: [email protected]., [email protected], [email protected]
2011 International Conference on Advanced Materials Engineering IPCSIT vol.15 (2011) © (2011) IACSIT Press, Singapore
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2. Experimental Procedure The Stainless steel SUS 430 [JIS] is employed in the experiments. The chemical property of workpiece
material was shown in table 1. Sheet strip of workpiece material thickness is 2 mm and 30 mm in width. A mechanical property of workpiece material was shown in table 2. The workpiece strip is shown in Fig. 1. The chemical properties of punch materials were illustrated in table 3. The blanking tool was designed to blank circular part of 25 mm diameter. The punch cutting edge insert and die button were made from JIS SKD11, SKH 51 and SKS 3 steel fixed hardened to 60 HRC [Fig.2]. The cutting edge was designed as an insert to the punch shank as shown in Fig. 3 in order to be easily removed [Fig.3]. Tool clearance employed in this experiment was 5% of sheet thickness [0.1 mm]. The photograph of blanking tool and die set is shown in Fig. 4. Air feeder installed with die set was used in the experiment. Experiments were carried out using a 60 tons mechanical press [Fig.5]. Blanking operations were performed without lubricant.
Fig. 1: Workpiece strip Fig. 2: Blanking punch Fig. 3: Shank of punch
Fig. 4: Blanking die set with feeder Fig. 5: Mechanical press 60 tons
In general, the degree of wear is higher for blanking punch than die. Therefore only blanking punch
cutting edge is measured to quantity wear. The flank wear length and face wear length [Fig.6.] were measured under Optical microscope with program Axivo Version 5. Moreover, adhesive wear on blanking were observed by Scanning Electron Microscopy [SEM] and Energy Dispersive Spectrometry [EDS] analysis. Wear measurement have been made after 100, 200, 300, 500, 800, 1,000 and 2,000 strokes.
Table 1: Chemical compositions of workpiece material.(%)
Table 2: Mechanical properties of workpiece material.
C Si Cr Fe
0.16 0.66 16.89 82.30
Yield Strength Tensile Strength Elongation Hardness
289 N/mm2 545 N/mm2 27 % 142 HV
∅ 25 mm
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Table 3: Chemical compositions of punch materials (%)
Material C Si Fe W Mn Ni Cr Mo V
SKD 11 0.95 0.32 82.30 0.70 0.49 0.25 10.33 0.72 0.3
SKH 51 0.80 0.40 76.79 11.25 0.25 0.35 4.38 5.10 1.88
SKS 3 0.95 0.72 91.35 0.7 1.10 0.25 6.72 - 0.20
Fig. 6: Measurement on punch cutting edge
3. Results and Discussions
3.1. Influence of Particle Adhesion to Tool Wears In the blanking experiments the level of face wear length is lower than flank wear length because punch
side slides back and forth against workpiece material during the blanking operation. Where as there is no sliding action between punch face and workpiece material.
The results of flank wear length and face wear length of blanking punch with number of workpiece are shown in Fig.7 and 8, respectively. From Fig. 7 and 8 the wear length on punch has been investigated up to 2,000 strokes. It was found that the flank wear length quickly increases at the beginning of experiments up to 500 strokes. After 1,000 strokes, wear length becomes to stable. In Fig. 11, face wear length quickly increases at the beginning of experiment up to 500 strokes. After 500 strokes, wear length becomes to stable.
Number of workpiece
Fig. 7: The relationship of flank wears with number of parts.
It was found that the flank and face wear length of punch material SKH 51 had shown lower wear rate than SKD 11 and SKS 3 respectively. The higher tungsten, molybdenum and vanadium content of SKH 51 increase the amount of carbide compound caused hard and durable of cutting edge. The flank and face wear length of punch material JIS; SKS 3 is larger than punch material JIS; SKD 11 and SKH 51, respectively. Since punch material SKS 3 has low molybdenum and chromium composition that show low wear resistance. On the other hand punch material JIS; SKD 11 and JIS; SKH 51 had shown nearly wear resistance trend. Moreover JIS; SKD 11 had shown adhesion of workpiece to blanking punch more than punch material JIS;
Flank wear position
Face wear positionB
lank
ing
dire
ctio
n
Flan
k w
ear
leng
th
Face wear length
Blanking direction
Flank wear
Flan
k w
ear l
engt
h (m
m)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 500 1000 1500 2000 2500
SKD 11
SKH 51
SKS 3
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SKH 51. Further more,it was found that punch material JIS; SKD 11 high chromium similar workpiece [SUS 430] has compatibility of element.
s
Number of workpiece
Fig. 8: The relationship of face wears with number of parts. Adhesion phenomenal of workpiece material with cutting had shown Fig.9-11. Adhesion of workpiece
on punch SKD 11 is large than punch SKH 51 and SKS 3. It was found that compatibility between workpiece material [high chromium content] and punch material [SKD 11 high chromium content] caused of adhesion on the surface. The compatibility of metal element caused of high adhesion, friction and wear rate. Adhesion of workpiece to blanking punch make sure the result of adhesion by EDS had shown in Fig.9.
Fig. 9: SEM image at 100X and EDS analysis of the adhesion on cutting edge of SKD 11.
Fig. 10: SEM image at 100X and EDS analysis of the adhesion on cutting edge of SKH 51.
SKH 51 100 Strokes
Blanking directionBlanking direction
SKD 11 100 Strokes
Blanking direction
Adhesion of workpiece
Blanking direction
0
0.1
0.2
0.3
0.4
0.5
0 500 1000 1500 2000 2500
SKD 11
SKH 51SKS 3
Face
wea
r len
gth
(mm
)
Blanking direction
Flank wear
Cr
Cr
28
Fig. 11: SEM image at 100X and EDS analysis of the adhesion on cutting edge of SKS 3
The results of SEM and EDS analysis from the experiments after 2000 strokes had shown in Fig.11-Fig.13. It was found that Fig.11-13 SEM image of surface cutting punch does not show adhesion of workpieces because junction of adhesion separated occurs at the interface. High pickup of workpiece on punch surface caused of high adhesion and high wear rate. EDS analysis had shown insignificant amount of adhesion on cutting edge. Furthermore, in the case of SKS 3 [Fig.11] had shown EDS analysis confirmed that there the high corrosion around surface.
Fig. 12: SEM image at 100X and EDS analysis of the adhesion on cutting edge of SKD 11.
Fig. 13: SEM image at 100X and EDS analysis of the adhesion on cutting edge of SKH 51.
Fig. 14: SEM image at 100X and EDS analysis of the adhesion on cutting edge of SKD 3
SKH 51 2000 Strokes
Blanking direction
Blanking direction
SKS 3 100 Strokes
Blanking directionBlanking direction
SKS 3 2000 Strokes
Blanking directionBlanking direction
Corrosion
SKD 11 2000 Strokes
Blanking directionBlanking direction
Cr
Cl
Cr
Cr
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4. Summary The aim of the study was explorations of adhesion wear on blanking die. Tool steel of higher tungsten,
molybdenum and vanadium content had shown high wear resistance and durable of cutting edge. Moreover, punch high chromium content had shown compatibility of metal elements cased of high adhesion, friction and wear rate. Punch material SKS 3 had shown high wear rate and high corrosion because low chemical composition content.
5. Acknowledgements The authors would like to give our attitude to Department of Tools and Material King Mongkut’s
University of Technology Thonburi (Thailand) for supporting the die equipment and Office of the Higher Education Commission for funding of the research.
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