RESEARCH ON THE INFLUENCE OF SOME PARAMETERS ON TURNING PROCESS OF CAST IRON

RESEARCH ON THE INFLUENCE OF SOME PARAMETERS ON TURNING PROCESS OF CAST IRON

Nguyen Ba Phuong

M.S., Institute of Materials Science, Vietnam Academy of Science and Technology,

Vietnam, Hanoi

Ngo Huy Khoa

PhD., Institute of Materials Science, Vietnam Academy of Science and Technology,

Vietnam, Hanoi

Do Thi Duyen

M.S., Institute of Materials Science, Vietnam Academy of Science and Technology,

Vietnam, Hanoi

Pham Duc Thang

Assoc. Prof., Ph.D, Institute of Materials Science, Vietnam Academy of Science and Technology,

Vietnam, Hanoi

Nguyen Trung Kien

M.S., Institute of Materials Science, Vietnam Academy of Science and Technology,

Vietnam, Hanoi

Do Nguyen Huy Tuan

M.S., Institute of Materials Science, Vietnam Academy of Science and Technology,

Vietnam, Hanoi

Nguyen Thi Hong Nhung

M.S., Sao Do University, Ministry of Industry and Trade,

Vietnam, HaiDuong

Duong Thi Ha

M.S., Sao Do University, Ministry of Industry and Trade,

Vietnam, HaiDuong

ABSTRACT

Cast iron is an alloy of iron and carbon (carbon content greater than 2.14%) and some other elements such as: Si, Mn, P, S, Cr, Ni, Mo, Mg, Cu... It is widely used to make machine case, base unit, pulley, crankshaft, flywheel and basic construction. Besides, the cast iron is also used to recover copper through cementation process. To facilitate this process, the cast iron needs to be turned to produce flat cast iron particles less than 1 cm in size. Turning process is performed on the work material at different cutting speeds, from 10 to 28 m/min for depth of cut in range of 5 - 20 mm, rate from 0.1 - 0.4 mm, protrusion distance of the shaft 1500, 2000 and 3000 mm/rev respectively. The cast iron granulation efficiency of this method is from 91 to 92%.

Keyword: Cast iron, turning process, cutting speed, depth of cut, feed rate, protrusion distance of the shaft.

Acknowledgment: This study was supported by the Vietnam Academy of Science and Technology with the project: "Completing the recycling technology of nix grain waste or copper slag into granular cast iron as raw materials for the cementation process of copper powder in hydrometallurgical copper sulphate solution from ore or waste containing copper – Code: UDSXTN.02/21-22.

1. Introduction

Turning is a method of cutting metal, performed by the movement of the workpiece and the turning tool. In which, the main operation is the circular motion of the workpiece forming the cutting motion, along with the translational movement of the tool [1,2]. This is a basic machining method in manufacturing, so now there are many studies being carried out to find and improve the turning process so that suit each material and reduce production costs [3-5]. Currently, one of the popular turning methods is the CNC turning. It has helped to automate the material removal process and improve product quality [6-8].

In the case of feed shaft turning, the cross feed Sng = 0, otherwise the longitudinal feed will be non-zero. For face turning or cutting off, the longitudinal feed Sd = 0 and the cross feed Sng will be non-zero.

The turning method has some characteristics as follows [9]:

- The turning method is based on the circular motion of the workpiece and the reciprocating motion of the cutting edge.

– The magnitude of the cutting speed is based on the strength of the workpiece as well as the abrasion resistance and heat resistance of the cutting piece.

- Feed is the length of the cutter in one revolution of the workpiece, roughing turning uses large feeds, finishing turning uses small feeds. The depth of cut is determined through the movement of the tool.

– Turning tools usually have a structure that includes a tool hilt and replaceable cutting pieces. Usually, with different types of turning, a suitable tool will be needed.

Currently, CNC turning helps greatly to increases the accuracy and glossiness of product and also helps to increase productivity in production. The operating principle of this method is that the movement of the lathe includes the rotation of the workpiece and the tool feed.

- Rotation of workpiece: generating cutting speed

- Tool feed: produces productivity and surface gloss.

Types of tool feeds:

- Longitudinal feed: reciprocating motion parallel to the center line of the lathe

- Cross feed: reciprocating motion in a direction perpendicular to the center line of the lathe

- Tilt feed: movement in which the direction of displacement forms an angle with the center line of the machine

- Curve running feed: machining profiled surfaces

General principle: The material to be processed will be mounted on the chuck that has a circular motion, the tool is mounted on the carriage to perform the cutting process as required.

2. Experimental procedure

Firstly, mount the cast iron bar to the chuck. The chuck will rotate during the whole working process. This mounting is very important because improperly placed can both cause danger and lead to the wrong size of the part after machining.

 Secondly, choose the right tool. The tool that selected for turning process cast iron is made of high-speed steel so that the turning process runs seamlessly from start to finish.

Next, proceed to adjust the lathe. Both the tool and the workpiece must be set up properly. If any of the setup steps are omitted, the results will not meet the needs or an error will occur.  

Finally, conducting experiments with a 15x10x5 cm cast iron bar and surveying the parameters: cutting speed from 10 to 28 m/min with cutting depth in the range of 5 – 20 mm, rate from 0.1 - 0.4 mm, protrusion distance of the shaft 1500, 2000 and 3000 mm respectively.

3. Results and discussion

3.1. Effect of cutting speed on cast iron granulation efficiency

Table 1.

 Effect of cutting speed on cast iron granulation efficiency

From Table 1, it shows that when the cutting speed increases from 10 to 28 m/min, the cast iron granulation efficiency increases from 43.18 to 91.12%. The reason is that the higher the cutting speed, the more particles are produced in the same time period. However, when the cutting speed is in the range of 26 - 28 m/min, the efficiency hardly changes much.

3.2. Effect of protrusion distance of the shaft on cast iron granulation efficiency

Table 2.

Protrusion distance of the shaft - 1500 mm/rev

Table 3.

Protrusion distance of the shaft - 2000 mm/rev

Table 4.

Protrusion distance of the shaft - 3000 mm/rev

From Tables 2, 3, 4, it is shown that depending on the case of different cutting depths, we will have the right feed rate to achieve the highest cast iron granulation efficiency. For the 15x10x5 cm cast iron bar, we choose a cut depth of 5 mm with a suitable feed rate of 1.1 - 1.5 mm/rev.

3.3. Effect of feed on cast iron granulation efficiency

Table 5.

 Effect of feed on cast iron granulation efficiency

When the feed increased from 0.10 to 0.14 mm, the cast iron granulation efficiency increased from 80.08 to 92.06 % as shown in Table 5. The reason is that when the feed is increased, the quantity of cast iron is separated from the workpiece more. However, we also see that when the feed is from 0.14 to 0.30 mm, the cast iron granulation efficiency is almost unchanged and the feed is between 0.30 and 0.40 mm, the cast iron granulation efficiency is gradually reduced due to the low cutting force. When the feed is larger, it will hinder the movement of the tool.

4. Conclusions

To make flat cast iron particles with a size of less than 1 cm suitable for the production scale as well as economic efficiency, CNC turning method is a feasible method. The main optimal parameters are as follows:

- The tool is made of high-speed steel

- Cutting speed: 26 m/min

- Depth of cut: 5 mm

- Feed rate: 1.5 mm/rev

- Feed: 0.14 - 0.30 mm.

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