# How to let water destroy a block of steel? [closed]

I would like to find out what methods can be used to let water either crush or an equivalent word to turn a steel block into smithereens[obviously not by corrosion] but if it's not possible carve a large hole through it or just cut through it.

I do know that water can crush cars and break through glass. Smashing against water at high speeds can also be like smashing against concrete, so it should work the other way round.

Just gonna set the steel block to be 2meter by 2meter by 2meter big, density is 8,050kg/m^3 , tensile strength of 53700psi and a hardness of 131 Vickers.

• So just destroy the block of steel but if it's not possible then carving or cutting a hole? – Planarian Aug 20 '16 at 8:35
• Ah yeah, gonna edit a bit – Skye Aug 20 '16 at 8:35
• This appears to be a purely physics question with no apparent connection to the world in which this event occurs. – Frostfyre Aug 20 '16 at 12:14
• Why do you specifically rule out corrosion? A steel block under heap of gold and silver coins in boiling seawater would corrode quite rapidly, acting as a sacrificial anode to the gold/silver coins' cathode. – SudoSedWinifred Aug 20 '16 at 19:35

You are looking for waterjet steel cutting, apparently.

This video shows how it works: https://www.youtube.com/watch?v=_FIsrYzyvlg

Basically, thin and fast stream of water can cut thorough steel. It is efficient enough to be an industrial standard. Adding abbrasives help, but isn't strictly necessary. Also, sand on river banks, ocean bottoms etc is common.

• To cut into steel like that you need to mix an abrasive (eg Al2O3) with the water. It would take a long time to make a hole, water jets don't make good drills. – James K Aug 20 '16 at 16:06
• @JamesK Sure it helps, a lot, but it isn't strictly nessesary. – Mołot Aug 21 '16 at 10:16
• Why someone put yellow tab under my answer? Blocks of steel are cut to splinter by water on daily basis. This is widely known industry practice, what more would anyone need for "empirical evidence"? – Mołot Sep 3 '16 at 13:34

Hydraulic shock using explosives will crush steel. The cube of steel needs to be immersed in water, held firmly in position, and an explosive charge is detonated. The resulting shock wave will crush the cube into whatever shape the outer structure holding it underwater is.

Methods of Explosive Forming

Explosive Forming Operations can be divided into two groups, depending on the position of the explosive charge relative to the workpiece.

· Standoff Method

In this method, the explosive charge is located at some predetermined distance from the workpiece and the energy is transmitted through an intervening medium like air, oil, or water. Peak pressure at the workpiece may range from a few thousand psi (pounds/inch2) to several hundred thousand psi depending on the parameters of the operation.

Contact Method

In this method, the explosive charge is held in direct contact with the workpiece while the detonation is initiated. The detonation produces interface pressures on the surface of the metal up to several million psi (35000 MPa).

This will not smash the steel cube to smithereens, but it will crush it out of the shape of a cube.

## REFERENCES

Amit Mukund Joshi Explosive Forming an Overview found here

D E Strohecker, R J Carlson, S W Porembka, Jr., and F W Boulger, Explosive Forming of Metals (DMIC Report 203, May 8, 1964) [Defence Metals Information Center, Battele Memorial Institute, Columbus, Ohio 43201] [found here]2

D J Mynors, B. Zhang, "Applications and capabilities of explosive forming", Journal of Materials processing Technology, 125-126 (2002) pp 1-25 found here

• Thanks for pointing this out. I will get back to it. A bit too busy now. Scout's honor. – a4android Sep 2 '16 at 23:54

Here's a fun way to do it.

First strip the atmosphere off of planet earth. The continents can stay if you have good aim. Now put your steel block in a retrograde orbit around the sun. It will have a nice peaceful time up there toodling around at 30 km/s right up until it hits the pacific ocean which is coming at it in the other direction at 30 km/s.

The only danger is you might hit the ocean floor before the thing goes poof. Aim deep. 3,688 meters lasts little over 5% of a second at these speeds. But if you do, no one will care since we'll all have already suffocated.

If you insist on more time you can aim to hit the ocean at an angle. If you manage to thread it just right you get as much as 7.2 seconds before you start having to move geography around.

If the thing some how survives that I say we drop it in the nearest black hole.

• A worldbuilding answer for an un-worldbuilding question. – Necessity Aug 21 '16 at 0:10

Mild steel has a yield stress of 250 Megapascals. For a 4 metre area, a force of 1billion N would be required to deform the steel.

Using the drag equation $F = 0.5 C ρ A V^2$, if the steel block hit water at a velocity of less 350m/s it would only be elastically deformed. 350m/s is by coincidence about the speed of sound in air. You would have to get hit the block with water at Mach 1 before you see anything.

To actually destroy the block would require much higher forces. You quote a tensile strength of about 370 Mpa, but that is for the metal in extension, and we are applying a compressive force. I estimate that one would need to increase speeds by an order of magnitude (3500m/s) to actually destroy the block. At these speeds the compression of the water in front of the block would cause heating, and ablation. In essence you have an underwater meteor.