The sharpest knife in the world is ice! Why do you say that?

In the era of cold weapons, the sharpness of the knife determines whether it is really rare. There were many famous knives in ancient China, such as tangdao, Miao Dao and Embroidered Spring Dao. These knives all use different words to describe their sharpness. In particular, the popularity of some ancient costume-themed film and television dramas has made this ancient weapon well known to everyone. Every knife has been tempered and its blade is extremely sharp. It is also a bolt from the blue on the battlefield. Having a good knife has become the lifelong pursuit of countless heroes.

Compared with those ancient treasure knives, if you want to ask what is the sharpest knife now, some people will say it is a water knife. This is not a cold joke, nor is it stupid, because many people don't know what a water knife is. Let's see what is the sharpest water knife in the world and how sharp it is.

What is a water knife?

Water knife is also called water cutting, or high-pressure water jet cutting technology. The technology of cutting objects with water as a knife after water is pressurized was first used in aerospace industry. Because it has the advantages of not changing the physical and chemical properties of the cut object, high speed, high efficiency and low cost, it is widely used in cutting products in fiber, metal, ceramics, glass, composite materials and other industries.

Water has not only a soft side, but also a hard side, so there was a saying of terrazzo head in ancient China. People think that the sharpest substance in the world is water, and even the hardest thing will change under the repeated beating of water drops. Perhaps it was inspired by this that people began to use water to cut those hard objects.

This technology was first used in coal mining and mining to pressurize water to form high-pressure water flow, but the pressure of this water is relatively small, just like sanitation workers often see this water flow to clean up small advertisements on the road. Relatively speaking, the water pressure is not great.

Development of water knife

In the 1940s, Americans pressurized the water, and then the water flowed out of the designed tiny nozzle at high speed, which could be used for industrial processing. It also proved that the water jet was a real water jet because of its high cutting energy.

Later, the Soviets increased the pressure of water cutting to 200MPa, so that more objects could be cut.

By the end of 1960s, emery, quartz sand and other abrasives were added to the high-pressure water flow, which made the water jet more powerful and could cut almost any hard object.

After entering the new century, the development and application of water knives are more rapid, which has changed the whole cutting and processing industry and is developing towards intelligence. Now there are three-axis, four-axis, five-axis and even robot water cutting.

Using ultra-high pressure technology, water jet can pressurize ordinary tap water to a pressure of 300MPa ~ 500MPa, and then spray it out through a nozzle with an internal aperture of about 0.05 mm, forming a high-speed jet with a speed of about 800 ~ 1000 m/s, which has high energy and can be used for cutting soft materials. If a proper amount of abrasive is added to the jet, it can be used to cut almost all soft and hard materials.

The heat generated by water jet cutting will be immediately taken away by high-speed water jet, which will not produce harmful substances, and the material has no thermal effect, and can cut any curve.

What can be cut by water jet is mainly determined by water pressure. Pressurized water above 30MPa is a low-pressure water jet, which can be used for some simple cutting work. When it is increased to 100MPa, it becomes a high-pressure water jet, which can meet most cutting work. When the water pressure exceeds 200MPa, it is an ultra-high pressure water jet, which can even cut diamonds with a cutting width of only a few millimeters. At present, the highest cutting pressure can reach 600MPa. The general working pressure of domestic commercial water cutting equipment is as follows

Working principle of water knife

In order to achieve the cutting pressure, water needs to be pressurized by a booster pump to achieve the required pressure. The low-pressure oil from the oil pump pushes the plunger hydraulic cylinder to reciprocate and pressurize the water.

After the water jet became an industrial processing tool, it opened a new cutting history, which is also called the industrial trend of the next era. Do you want to know how sharp the water knife is? Let's see how the so-called hardest object in the world was defeated in front of the water knife.

How strong is the water pressure during water jet cutting? Some people cut rubber rollers with water jets. When the water jet approaches, the drum rotates rapidly, and the wheel rotates faster and faster under the continuous impact of the water jet, and the wheel begins to expand and expand, and finally bursts and bounces off. It turns out that the water is so fierce.