VOL. 18 September ISSUE YEAR 2017
in Vol. 18 - September Issue - Year 2017
Measurement of Ervin Life and Analysis of Wear Failure of Aluminium Cut Wire Shot for Blast Cleaning
Tab 1: Physical properties of aluminium cut wire shot
Fig 1: The relationship between the residual mass and the number of impact cycles
Fig 2: The morphology of different impact cycles of aluminium cut wire shot at the passivation rounded stage
Fig 3: The morphology of different impact cycles of aluminium cut wire shot at the stable wear stage
Fig 4: The morphology of different impact cycles of aluminium cut wire shot at the severe wear stage
Abstract: The Ervin test machine was used in this study to mimic the actual blast cleaning process, and the Ervin life of 1.0 mm aluminium cut wire shot would be conducted. The aluminium cut wire shot wear failure process was analyzed with wear morphology, relationship curve of different impact times and residual mass. The result shows that the Ervin life of 1.0 mm aluminium cut wire shot is 13566 times; the wear failure process can be divided into three stages: passivation rounded stage, stable wear stage, severe wear stage; and the surface area of the aluminum cut wire shot continued to produce work hardening in the wear failure process. Keywords: aluminium cut wire shot; Ervin life; wear failure; wear morphology
Aluminium cut wire shot is widely used for surface cleaning of aluminum, magnesium, zinc, copper workpiece and alloy casting, forming, and rolling workpieces. The Ervin life and the wear failure process are the two main aspects of the evaluation of metal abrasives. The paper simulates the wear failure process of shot blasting cleaning of metal abrasive aluminium cut wire shot, by measuring the relationship between residual amount of wear and impact cycle quantity, and observation of the surface morphology of the aluminium cut wire shot wear process. So it analyzes the wear failure process of metal abrasive aluminium cut wire shot and uses the area method to determine the Ervin cycle life.
2. Samples and Experimental Procedure
2.1 Experimental material Samples
For the aluminium cut wire shot sample used in this experiment, manufactured by Shandong Kaitai group, the physical properties are shown in Table 1.
2.2 Experimental method
15g samples were placed in Ervin test machine  to simulate the wear failure of 1.0 mm aluminum wire cut shot in the actual cleaning process, where the velocity of the shot was 61 m/s, and the target material hardness was 64 HRC. Removing the samples after a certain number of impact cycles, the diameter of 0.3 mm sieve removed the debris and after weighing and recording the residual mass, the HP SJ8250 scanner was used to record morphological changes of the aluminium cut wire shot. Then it was reloaded, and the above steps repeated until the residual mass was less than 5% of the initial weight and the experiment was stopped. After drawing the residual mass and the impact cycles relation curve, analysis of the wear failure process of aluminium cut wire shot was performed and calculation of the area under the curve done to measure Ervin life .
3. Results and Analysis
The relationship between the residual mass and the number of impact cycles is shown in Fig 1.
Wear failure process of aluminium cut wire shot can be divided into three stages : passivation rounded stage, stable wear stage, and severe wear stage, as shown in Fig 1. Impact cycles of 0 to 500 times is the passivation rounded stage, the columnar aluminium cut wire shot gradually becomes spherical (Fig 2), and the mass loss decreases quickly. The impact cycles of the stable wear stage is 500 to 10000 times, and the mass loss decreases slowly. Plastic deformation of aluminium cut wire shot occurred in the process of impact cycles because of low hardness and good plasticity. Aluminium cut wire shot becomes a polyhedral-shaped ball (Fig 3). At the same time, the internal energy  and the dislocation density increase, resulting in work hardening , and the hardness is improved. The average hardness of the shot core is 66HV and the average hardness of the surface area reaches 93HV. After 10000 times, the mass loss speeds up the decline and aluminium cut wire shot becomes smaller  (Fig 4). This is the severe wear stage. At this stage, after repeated work hardening, the surface area of aluminium cut wire shot reaches maximum fracture limit, and the microcracks of the aluminum cut wire shot gradually grow until they break.
According to SAE J445-2005 Metallic Shot and Grit Mechanical Testing, the area method is used to calculate the Ervin life of aluminum cut wire shot:
The Ervin life of aluminium cut wire shot = curve area / total mass = 203490 / 15 = 13566 times.
Experiments show that the 1.0 mm aluminium cut wire shot wear failure process is divided into three stages: the passivation rounded stage, stable wear stage and severe wear stage; the surface area of the aluminum cut wire shot continues to produce work hardening in the wear failure process, and the hardness is improved; at the severe wear stage, after repeated work hardening, aluminium cut wire shot is broken and becomes smaller; more importantly, the Ervin life of 1.0 mm aluminum cut wire shot is 13566 times, showing outstanding durability.
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Hongcong Sun, Ruwei Liu, Wenlong Zhu
College of Materials Science and
Engineering, Shandong University
Jinan 250061, P.R.China,
Shouquan Zhang, Jianwang, Gazhang
Shandong Kaitai Metal Abrasive Co, Ltd
Zouping 256217, P.R.China
Corresponding author: Ruwei Liu