Experimental Evaluation of Effect of Die Angle on Hardness and

International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

Experimental Evaluation of Effect of Die Angle on Hardness and Surface Finish of Cold Forward Extrusion of Aluminum G. A. Chaudhari1,S.R. Andhale2, N.G. Patil3 1

Mechanical Engineering Department, D. N. Patel college of Engineering, Shahada. 2 Head, Mechanical Engineering Department, M.I.T. Aurangabad. 3 Mechanical engineering Department, M.I.T. Aurangabad. On examination of the extrusion load as a function of die land length, it is evident that the extrusion force required increased as the die land increased [2]. Geometrical characteristics of the extrusion die influence both the extrusion process and the mechanical properties of the extruded material. Experimental investigations have made to achieve the effect of die reduction ratio, die angle & loading rate on the quality of cold extruded parts, extrusion pressures & flow patterns for both lead and aluminum [3]. Previous research has shown that extrusion die geometry, frictional conditions at the die billet interface and thermal gradients within the billet greatly influence metal flow in cold extrusion [4]. It has been reported the investigation on the effects of die geometry & other extrusion parameter on the structure, flow pattern, extrusion pressure & mechanical properties of shaped extrusion [5]. It has been investigated that the optimum process parameter corresponds to minimum extrusion load using the Finite Element Method (FEM) and Artificial Neural Network (ANN) cooperatively for direct extrusion of aluminum rod.[6] The ability of crystalline material, particularly metals, to change plastic deformation rather than fracture is an invaluable property. Extruded and deformed products have undergone plastic deformation & this deformation increases their mechanical properties can only be relieved by an appropriate heat treatment process [7].

Abstract - An experimental investigation was made on the effect of die angle on the quality of extruded product i.e surface finish and hardness of cold extruded aluminum. The semi die angle (α) considered for the experiment were 30 0, 450 and 600. The first experiment was to extrude the aluminum alloy AA6351 without lubricant. The second experiment was to extrude aluminum AA1100 with two different lubricants. The load required to extrude aluminum was found to be less at 450 die angle. The surface roughness is measured on the circumference of extruded product as well as in the longitudinal direction of the extrusion, for the first and second experiment respectively. No variations were found in surface finish by varying the die angle. Higher hardness values were found with 300 and 600 die angle. Also higher hardness values were observed with petroleum jelly.

Keywords- forward extrusion, conical die, AA6351, Hardness I. INTRODUCTION Extrusion, one of the most important metalworking processes. Commercial extrusion of lead pipes started early in the 19th century. In cold extrusion, the high pressure force the material through a cavity enclosed between a punch and die. Cold extrusion can be used with any material that possesses adequate cold workability e.g. tin, zinc, copper and its alloys, aluminum and its alloys. If product can’t be fully shaped in a single operation, the extrusion process may be performed in several stages [1]. The punches and dies used in cold extrusion are subjected to severe working conditions and are made of wear resistant tool steel e.g. high chromium steels. Extrusion produces compressive and shear forces in the stock. No tensile force is produced, which make high deformation possible without tearing the metal.

II. PRESENT INVESTIGATION An experimental investigation was undertaken to determine experimentally the effect of die angles on the surface finish and hardness of cold extrusion of aluminum AA 6351 and AA1100. Experiments were conducted on the universal testing machine using three different die with 30 0, 450 and 600 die angles. 334

International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012) The lubricants used during the experiment programme were grease and petroleum jelly. The surface roughness and hardness were measured on the extruded product with and without lubricant III. EXPERIMENTAL RESEARCH A. Billet preparation The billets of initial diameter & height 17.7 & 24 mm respectively had a chemical composition as presented in table1. The billets were cut from a bar of 19 mm & taken a light turning cut to remove impurities & surface imperfections. Later on the billets were subjected to annealing treatment to eliminate any residual stresses present prior to extrusion. This consists of heating the billets to 3450 in a muffle furnace soaking at this temperature for 15 min. followed by gradually cooling in air to room temperature.

Fig-1 Extrusion die punch assembly on UTM.

The dies are designed in accordance with guidelines proposed by P.Vijay [8]. The container and die are made integral. So three dies were made with 300, 450 and 600 semi die angle. The material used for the die and punch were tool steel D2 and D3 respectively with hardness of 65 HRC. The die and punch was heat treated to increase hardness. The die set was finished.

TABLE1: CHEMICAL COMPOSITION (WT%) OF THE BILLET MATERIAL

_____________________________________________ Si

0.83 Mn

0.565

Mg

0.807

Fe

0.227

Zn

0.008

Ni

IV. EXPERIMENTAL TECHNIQUE A. Experimental description and extrusion procedure Extrusion tests were conducted on a 40 ton universal testing machine. Extrusion tests were conducted with a loading rate of 2.6 mm/min with reduction ratio 0.37 is kept constant for 300, 450 and 600 die. The extruded products were cut to about 3 mm to eliminate the effect of light back pressure. Loads were taken at every 1mm movement of punch

nil Pb

0.014

Cu

0.064

Ti

0.022

Cr

0.018

Al

97.438

B. Surface finish/quality of products The dimensional accuracy of the products was checked using vernier caliper so as to compare with dimensions of the dies. The surface roughness along the circumference for AA6351 and in longitudinal direction for AA1100 on experimental surface of extruded product was measured using the digital surface roughness tester C. Hardness Hardness properties of extruded aluminum alloy product were carried out on a Vickers hardness tester at a gap of 2 mm at four locations on the surface in extruded direction for AA 6351. The micro hardness was also measured from surface to core for aluminum AA11100 with micro hardness tester.

__________________________________________ B. Extrusion tool design An extrusion tool was designed and manufactured for the experimental programme. It consists of mainly three parts, the punch container and die.

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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012) V. RESULTS AND DISCUSSION

70

A. Extrusion load versus displacement curve For first experiment, figure 2, shows that extrusion load versus punch displacement curve for aluminum alloy AA6351 without lubricant

60

Load, KN

50

90

40 30 Die angle, α = 30°

20

Die angle, α = 45°

80

10


70

0

Load, KN

60

0

1

2

3

4

5

50

6

7

8

9

10 11 12 13 14 15 16 17 18 19

Displacem ent, m m

40 Die angle, α = 30°

30

Figure 4. Load versus displacement curve for AA1100 with petroleum jelly.


20


10 0 0

1

2

3

4

5

6

7

8

9

In addition to this the extrusion load required to extrude aluminium with petroleum jelly compared to grease is higher due to low viscosity of petroleum jelly which provides higher metal to metal contact.

10 11 12 13 14 15 16 17 18 19

Displacem ent, m m

Figure2. Load versus displacement curve for AA6351 .

TABLE 1: EXTRUSION LOAD VALUES FOR DIFFERENT DIE ANGLE & 45

LUBRICANT

.

40 35

Material

Load, KN

30

Lubricant

Die angle (α) 30

Extrusion load (KN) 70.81

___

45

59.40

60

75.51

30

39.85

45

28.55

60

37.68

30

48.21

45

30.01

60

59.82

25 20

Aluminum


15


10


AA 6351

5 0 0

1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19

Displacem ent, m m

Grease Aluminum AA1100

Figure3: Load versus displacement curve for AA1100 with grease

Petroleum

The average load corresponding to steady stage is considered as extrusion load. Therefore from figure 2, 3 and 4, the extrusion load was tabulated in table1. This is due to increased contact length between the die & billet leads to higher frictional power losses. It further increases with increase in die angle 600 is due to redundant deformation. The extrusion force at 450 die angle is minimum due to least redundancy energy at this particular die angle.

Jelly

B. Surface finish of extruded product It may be seen from table2 3, 4, it is observed that the surface roughness has increased during extrusion. But also from table 3, 4 it has seen that the surface roughness values are higher for grease as compared to petroleum jelly. The result indicates that there are no significant deviations in surface finish with variations in die angle.

336

International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012) This is due to same frictional condition conditions exit for the three cases. Also strain hardening does not have effect on surface roughness. Higher surface roughness values exist for grease compared to petroleum jelly. This is due to existence of grease in solid state at room temperature affects the surface condition of the work piece & coarse roughness condition is observed in cold extrusion. C. Hardness Figure 6 shows that average hardness of extruded product is 68 HV5, 66.5 HV5, and 63.5 HV5 for 30 0, 450 and 600 die angle respectively for AA6351. The results indicate that there is increase in hardness with decrease in die angle. This is due to more strain hardening because of higher load required in overcoming friction in 30 0 die angles. Whereas higher hardness values in 600 die angle is a result of redundant deformation.

Fig.5 Photograph of extruded product TABLE 2: SURFACE ROUGHNESS VALUE OF EXTRUDED PRODUCTS AA 6351.

Diameter, mm 17.7 17.7

3 4 5

14 14 14

Identification

Ra value observed (µm) 0.82 0.85

Billet material Billet material (annealed) Extruded (300) Extruded (450) Extruded (600)

70

65

Hardness, HV5

Sr. No. 1 2

0.78 0.79 0.79

60 Die angle, α = 30° Die angle, α = 45°

55

TABLE 3: SURFACE ROUGHNESS VALUES OF EXTRUDED AA 1100 WITH


GREASE

Identification

No

2

µm

1

Aluminum rod

1.429

2

Al 30 G

0.139

3

Al 45 G

0.149

5

50

Surface finish (Ra) in

Al 60 G

4

6

8

Distance, mm

Figure 6: Variation of hardness on extruded surface in extruded direction for AA6351.

85 80

0.150

Microhadness, HV

Sr.

TABLE 4. SURFACE ROUGHNESS VALUES OF EXTRUDED AA 1100 WITH PETROLEUM JELLY.

75

Die angle, α = 30° Die angle, α = 45° Die angle, α = 60°

70 65 60

Sr. No

Identification

Surface finish (Ra) in µm

55

1

Al 30 PJ

0.109

50

3

Al 45 PJ

0.097

5

Al 60 PJ

0.115

0.2 0.4 0.6 0.8 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 Distance from surface to core, mm

Figure 7: Variation of micro hardness form surface to core with grease for AA1100

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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012) 

It seems that from above figure7, 8 micro hardness from surface to core decreases for AA1100 with grease as well as petroleum jelly. Higher hardness values were found for 300 and 600 die angle. Because redundant and frictional deformations are concentrated near the extruded surface. Higher level of strain hardening results in the surface and near surface layers. It also seems from above data that the micro hardness values of extruded aluminium alloy with petroleum jelly are higher as compared to grease. This increase in hardness of aluminium alloy is attributed to low viscosity of the petroleum jelly. Low viscosity lubricant produces higher strain during extrusion gives higher hardness values.

The higher values of micro hardness are observed with petroleum jelly for AA100 due to low viscosity. VII. FUTURE SCOPE

There is further scope to get more precise results by considering more die angle with different lubricants. This work can be extended by using different reduction ratios as well as varying loading rate, to some ferrous extrudable material. VIII. ACKNOWLEDGEMENT

100 95

We are thankful to the Nasik Engineering Cluster for the manufacture of die set. We also appreciate to Department of civil Engineering and workshop, D. N. Patel college of Engineering, Shahada for their assistance and support.

Microhardness, HV

90 85 80 75 70


65


60


REFERENCES

55 50 0.2 0.4 0.6 0.8

1 1.5

2

2.5

3 3.5

4

4.5 5

5.5

6 6.5

[1]

Kalpakjian, ‘Manufacturing Engineering and Technology ‘AddisonWesley Publishing company, 3rd edition, 1995.

[2]

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[5]

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[6]

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[7]

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[8]

S.Kumar, P. Vijay, Die design and experiments for shaped extrusion under cold and hot condition, Journal of Material Processing Technology,190 (2007) 375-381.

7

Distance from surface to core, mm

Figure 8: Variation of micro hardness form surface to core with petroleum jelly for AA1100

VI. CONCLUSION During this experiment, the effect of die angle has been studied to determine its effect on surface finish and hardness of extruded product.  It was found that the load required deforming the billet during extrusion for 300 die and 600 die angles is higher as compared to 450 die angle for AA6351 & AA1100.  It shows no considerable variation on surface roughness with variations in die angle.  Products extruded with grease shows higher values of surface roughness.  The average hardness values found to be increased with decreased die angle and further increases with increase die angle. Hardness is found to be reduced at 450 die angle for AA6351 and AA1100.  The Micro hardness values from surface to core decreases for AA100 extruded with grease and petroleum jelly. 338