Coolant for aluminum. Effect of coolant on aluminum processing

To this end, Quaker Chemical Corp. conducted a series of end machining tests on aluminum workpieces to evaluate the effects of different cutting fluids on cutting power and cutting tool wear. When machining with a new cutting tool, the coolant had no effect on the machining forces generated at the same cutting speed. However, the more the tool processed the workpiece, the greater the difference in power required to effectively machine using different coolants.

These results show the following

The influence of metal fluid on cutting power is minimal when using new cutting tools. Thus, the difference between the effect of two different coolants on cutting power may not be noticeable until the cutting edges of the tool begin to wear.

The increase in power when milling aluminum is a direct result of cutting edge wear. The rate of this wear is directly affected by both the cutting speed and the metal cutting fluid used.
The relationships between these variables are linear (cutting speed, cutting edge wear and cutting power all increase together). Armed with this knowledge, manufacturers can potentially predict the condition of the cutting edge at any point in the milling process, as well as the required power at other, untested cutting speeds.

Getting into the laboratory

Testing focused primarily on two types of cutting fluids: microemulsion and macroemulsion, each of which was diluted at a concentration of 5% in water. The main difference between the two is the size of the suspended oil droplets. Macroemulsion contains particles with a diameter of more than 0.4 microns, which give the opaque white appearance of the coolant. Microemulsion has a smaller particle diameter and has a translucent appearance.

The experiment was carried out on a Bridgeport GX-710 three-axis CNC machine. The workpiece was a block of aluminum alloy 319-T6 measuring 203.2 by 228.6 mm by 38.1 mm, cast, containing copper (Cu), magnesium (Mg), zinc (Zn) and silicon (Si). Machining was carried out with an 18 mm diameter end mill with eight inserts with a 15-degree rake angle and 1.2 mm radii. It machined with an axial depth of 2 mm and a radial depth of 50.8 mm. Each coolant composition was applied to the cutting zone for 28 milling passes at two different cutting speeds, 6,096 rpm (1,460 m/min) and 8,128 rpm (1,946 m/min), to remove 1,321.6 material cm3. Feed rates at both speeds were 0.5 mm per revolution (0.0625 mm per insert per revolution).

Speed, wear and power

Power measurements for this study during processing were obtained using an instrumented monitoring and adaptive control system. The test results are shown in the charts in this article. As expected, more high speeds cutting resulted in higher processing speed. However, as described above, the differences in cutting power between the two fluids were minimal when machining with the new cutters.

At the beginning of the process, the workpiece material properties and cutting edge geometry are the dominant factors affecting cutting power. Differences between the performance characteristics of the metal environment arose only after the geometry of the cutting edge changed during wear. The choice of metalworking fluid directly affected the rate at which this wear occurred, and therefore the cutting power required at any given point in the milling operation.

Assuming a certain baseline performance level for the two fluids being compared, tests should be performed until the cutting inserts begin to wear to determine which coolant allows higher cutting speeds to be maintained for a longer period of time.

The plots made it possible to say that the rate of increase in power can be used to predict the condition of the insert at any given point in the milling operation. Likewise, power measurements taken at several cutting speeds can be used to obtain the required power at other, untested cutting speeds.

Proof

While the x-axis in Figure 1 consists of raw material removal volume data, Figure 2 uses the natural logarithm of this variable. Plotting the volume of material removed in this way results in a slope which is exact speed, with which the power increases with subsequent processing. This measurable measure is necessary to predict tool wear and cutting ability when various speeds cutting However, these data only indicate that cutting power and material removal volume increase together. Confirming insert wear is especially important because driving force increasing power requires additional testing (in particular, to correlate the slopes of the lines in Figure 2 directly with the wear of the insert that occurs during processing).

These tests added two additional cutting fluids: another macroemulsion and another microemulsion. Each of the four fluids was applied at a cutting speed of 1.946 m/min. until 660 cm3 of material was removed. This provided sufficient time for abrasive wear and, in some cases, metal-to-metal adhesion to occur. Flange wear measurements were then taken for the four fluids with respect to a parameter relating cutting power to metal groove volume (specifically, the slope of power compared to the natural volume of metal removed). As shown in Figure 3, this confirmed the linear relationship between insert wear and increased cutting power during machining.

Other findings

While the test results cannot necessarily be extrapolated beyond aluminum milling, the study shows that microemulsion performs better if the goal is to machine at the fastest possible speed. This is because a denser microemulsion with smaller diameter oil droplets tends to remove heat more efficiently than a macroemulsion and its relatively larger droplets. However, operations involving more at slow speeds cutting, can contribute to the macroemulsion and its comparatively greater lubricity.

Whatever the detail, best way Finding the right coolant means trying different formulations in action. Understanding the relationships between cutting speed, tool wear and cutting power, and how metalworking coolants can influence these factors, is critical to making the right choice.

The following requirements apply to the metalworking process of aluminum alloys:

1) high processing precision and low roughness;

2) high productivity and elimination of finishing work;

3) low sensitivity to scatter mechanical properties and geometric dimensions (variety of tool material grades);

4) relatively low cost of the tool.

However, the processing of these materials causes significant difficulties associated with their high viscosity, which leads to the formation of built-up edge, overheating and a decrease in the durability of the cutting tool, and a decrease in the quality of the processed part.

The use of modern machine tools, tools with wear-resistant coatings and the supply of cutting fluids (cooling fluids) to the cutting zone does not always ensure the required quality and productivity parameters. Nevertheless, today metal-cutting machines meet the requirements of precision. The offered range of tools and the results of numerous studies allow us to select cutting inserts, the use of which maximizes productivity and quality of processing.

At the same time, despite the development large quantity coolant brands and tests in this area do not exist unified methodology, ensuring the selection of the most effective coolant. Selecting an effective coolant grade, according to available data, can reduce cutting forces by 20%. Therefore, it is advisable to develop a methodology that ensures the selection of such a brand.

In general, coolants have lubricating, cooling, washing, dispersing, cutting, plasticizing and other effects on the cutting process. One of the main functional effects of coolant is the lubrication effect, since a decrease in friction in the cutting zone leads to a decrease in the intensity of tool wear, a decrease in cutting forces, an average cutting temperature, and the roughness of the workpiece. Therefore, it is necessary to study the lubricating effect of coolant in order to select a specific grade for processing these alloys.

Study of the lubricating effect of coolant

The lubricating effect is assessed based on the test results on both the metal cutting machines during processing and on friction machines. The use of friction machines allows not only to reduce the consumption of materials, the coolant itself and the time spent, but also to eliminate the influence of other actions. Therefore, the lubricating effect of coolant in this work was assessed based on the results of tests on a friction machine. In Fig. Figure 1 shows a friction machine used for coolant research.

Since turning is the most common type of machining, for the research we used a friction machine loading scheme that made it possible to simulate this type processing, - “block - roller” scheme (Fig. 2).

The block is made of machining tool material - hard alloy T15K6. One of the most common representatives of aluminum alloys, D16 alloy, was chosen as the material for the manufacture of rollers.

The research was carried out at a pressure force on the block P=400 N and a roller rotation speed n=500 rpm. The loading force is selected in accordance with the cutting forces that arise during metal processing of these alloys. The roller rotation frequency is obtained by calculation from its diameter and cutting speed recommendations.

The roller was installed on the shaft and brought into contact with the block. The chamber was closed with a lid and filled with the coolant being tested. Then the roller rotated with a frequency n, and through the loading mechanism the load was smoothly applied to the block until its value was reached R.

According to the instrument readings, the maximum and minimum value friction moment. The average value of the moment was obtained as the arithmetic mean of the results of five experiments. Based on the available data, the actual friction coefficient was calculated f according to the formula:

For testing, 10% aqueous solutions of several brands of coolant were used: Addinol WH430, Blasocut 4000, Sinertek ML, Ukrinol-1M, Rosoil-500, Akvol-6, Ekol-B2. In addition, the tests were carried out without the use of coolant.

The research results are given in table. 1.

The results of the conducted studies make it possible to evaluate the lubricating effect of the tested coolants when processing the presented groups of materials. The data obtained provide the possibility of selecting the most technologically effective coolant for processing the given materials based on their lubricating effect.

The effectiveness of using each brand of coolant must be determined in comparison with processing without the use of coolant. The value of efficiency K cm for lubricating action when processing various materials is determined by the formula:

The lower the K cm value, the more effective this brand is in processing the tested material. In table Figure 2 shows the effectiveness of the tested brands of coolant in terms of lubricating effect.

It is known that when processing with low speeds, when the coolant best gets into the cutting zone, the lubricating effect of the coolant is greatest influence. Thus, the use of cutting fluids with a high lubricating effect is advisable for roughing.

According to the table 2 shows that when processing aluminum alloy D16, the most effective lubricating fluids are the Rosoil-500 (K cm = 0.089), Aquol-6 (K cm = 0.089) and Ekol-B2 (K cm = 0.096) brands.

Conclusions

1. The work carried out experimental studies of the lubricating effect of the tested coolants. The presented results make it possible to select the most effective brand of coolant for roughing of aluminum alloys.

2. The results of the work will be especially useful in the production of aircraft parts, since aircraft parts are subject to increased requirements for the quality and accuracy of processing.

3. The use of effective coolant ensures the maximum possible reduction in friction and average cutting temperature, which leads to extended tool life, reduced cutting forces, reduced surface roughness, and increased processing accuracy.

The aluminum drawing process involves processing the metal by pressure, during which a workpiece with a diameter of 7-19 mm is pulled through a hole of a smaller diameter. Production involves the use of cutting fluids (coolants) of a certain type.

For wire rod with a cross-section of 7.2 mm to 1.8 mm, the processing process takes place on multiple equipment without slipping. In this case, aluminum is used, which has greater density.

With finer drawing (0.59-0.47 mm), aluminum is processed on sliding machines. The speed of passage of the workpiece through the equipment is 18 m/sec. In this case, a wire drawing lubricant in the form of an emulsion is used.

The choice of lubricants also depends on the type of processing equipment. If during operation the equipment applies coolant by splashing, the volume of the pump should be taken into account. IN lately Low-viscosity materials are more often used for aluminum forming.

Since aluminum forming produces a high concentration of abrasion particles, drawing lubricants must have a low viscosity. This will extend the life of the coolant and increase the efficiency of the process.

Moreover, an increase in viscosity is observed with increasing fineness of processing. Coarser aluminum drawing processes require thicker oils, while finer operations use liquid lubricants.

Aluminum drawing, the coolant for which has a set of required characteristics, must be based on mineral oils or synthetic substances. This will maximize the protection of the surfaces of mechanisms and processed materials from wear and corrosion.

Drawing of aluminum wire with annealing places increased demands on lubricants regarding its temperature characteristics. During such a process, no deposits should remain on the surface of the material.

World famous manufacturer of cutting fluids high quality is the German brand Zeller Gmelin. The company has developed a range of products to help optimize the aluminum drawing process.

Sale of cutting fluids directly from the manufacturer

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Anyone, even a novice metalworking specialist, knows that when performing turning work on a machine, it is necessary to use cutting fluids (coolants). The use of such technical fluids (their composition may vary) allows you to solve several important problems simultaneously:

• cooling of the cutter, which is actively heating up during processing (accordingly, extending its service life);
• improving the surface finish of the workpiece;
• increasing the productivity of the metal cutting process.

Types of coolant used in turning

All types of coolant used for turning operations on a machine are divided into two large categories.

Water-based coolant
Oil based coolant

Such liquids remove heat from the processing area much worse, but provide excellent lubrication of the surfaces of the workpiece and tool.

Among the most common coolants that are used for this are the following.

• A solution of technical soda ash (1.5%) in boiled water. This fluid is used when performing rough turning on lathe.
• An aqueous solution containing 0.8% soda and 0.25% sodium nitrite, which increases the anti-corrosion properties of the coolant. It is also used for rough turning on a machine.
• A solution consisting of boiled water and trisodium phosphate (1.5%), almost identical in its cooling effect to liquids containing soda ash.
• An aqueous solution containing trisodium phosphate (0.8%) and sodium nitrite (0.25%). It has improved anti-corrosion properties and is also used when performing rough turning on lathes.
• A solution based on boiled water containing special potassium soap (0.5–1%), soda ash or trisodium phosphate (0.5–0.75%), sodium nitrite (0.25%).

• A water-based solution containing 4% potassium soap and 1.5% soda ash. Coolants containing soap are used when performing roughing and shaped turning on a lathe. If necessary, potassium soap can be replaced with any other soap that does not contain chloride compounds.
• A solution based on water, to which emulsol E-2 (2–3%) and technical soda ash (1.5%) are added. Coolant of this type is used in applications where the cleanliness of the machined surface is not required. high requirements. Using such an emulsion, workpieces can be processed on a machine at high speeds.
• An aqueous solution containing 5–8% emulsol E-2 (B) and 0.2% soda or trisodium phosphate. Using such a coolant, finish turning is performed on a lathe.
• An aqueous solution containing emulsol based on oxidized petrolatum (5%), soda (0.3%) and sodium nitrite (0.2%). This emulsion can be used when performing rough as well as finishing turning on a machine; it allows you to obtain surfaces of higher purity.
• Oil based fluid containing 70% industrial oil 20, 15% 2nd grade linseed oil, 15% kerosene. Coolant of this composition is used in cases where high-precision threads are cut and workpieces are processed with expensive shaped cutters.

• Sulfofresol is an oily cutting fluid activated by sulfur. This type of cutting fluid is used when turning with a small cut section. When performing rough work, characterized by active and significant heating of the tool and the workpiece, the use of such coolant can be harmful to the machine operator, since it emits volatile sulfur compounds.
• A solution consisting of 90% sulforesol and 10% kerosene. This liquid is used for thread cutting, as well as for deep drilling and finishing of workpieces.
• Pure kerosene is used when it is necessary to process workpieces made of aluminum and its alloys on a lathe, as well as when finishing using oscillating abrasive bars.

Features of the use of cutting fluids

In order for the use of coolant to be effective, several simple rules should be taken into account. The flow rate of such a liquid (regardless of whether it is an emulsion or an aqueous solution) should be at least 10–15 l/min.

It is very important to direct the flow of coolant to the place where the maximum amount of heat is generated. When turning, such a place is the area where the chips are separated from the workpiece.

From the very first moment of turning on the machine, the cutting tool begins to actively heat up, so coolant should be supplied immediately, and not after some time. Otherwise, when something very hot is cooled sharply, cracks may form in it.

More recently, an advanced cooling method has been used that involves applying a thin stream of coolant from the back surface of the cutter. This cooling method is particularly effective when a lathe requires a tool made of high-speed alloys to process a workpiece made of difficult-to-cut materials.