On January 16, 1943, the tanker Schenectady docked at the dock after returning from sea trials. The weather was sunny that day, and people not far away looked at the scenery in the distance in this sunny weather.
Suddenly, the screeching sound of metal tearing broke the rare silence, and people followed the sound to see a scene that they would never forget.
The oil tanker Schenectady, which had just stopped in the harbor, began to break in the middle, and as the crack became bigger and bigger, the sound became more and more harsh, and the people on the shore covered their ears and looked at each other in disbelief.
This crack started from above the hull and extended down to port and starboard, where the crack went all the way to the keel, causing the keel to break as well.
Eventually, the crack widened, and the whole ship broke in two, and the bow and stern touched the bottom of the water downward, revealing the surface of the water where the dragon had broken its bones. As the entire ship broke, a loud and piercing sound was heard, which was heard 2 kilometers away.
In fact, this is not the first time that this has happened to the Schenectady tanker, and this has happened more than 10 times before, but the fracture is not as serious as the Schenectady tanker, and the fracture is not as complete as this time, and it is completely broken into two parts.
However, the reason for this has not been found before, and why did the newly built and newly completed ship break into two pieces if it remained on the surface of the water and did not move? The United States has decided to investigate it thoroughly.
The reason for the rupture of the tanker was somewhat unexpected
If it is an old tanker, it is understandable that such a situation occurs. But the Schenectady was not an old ship, it was a new ship, a freshly finished tanker, and it was so close to the side of the ship that you could even smell the freshly painted paint.
During the investigation, the Schenectady was discovered, the first tanker built at the Swan Island Shipyard in Oregon.
The entire tanker was originally planned to be built in eight months, however, during the Second World War, these tankers were built to transport supplies, and the tasks for these tankers had already begun to be arranged at the moment they were set.
So the construction of these tankers can only be advanced, not postponed. It was against this background that the construction of the Schenectady tanker was carried out at a very fast pace. The keel was laid on July 1, 1942, and the hull was launched on October 24.
On December 31, less than two months after the launch, all the facilities on the ship had been installed in place, which means that the entire ship was completed six months after construction, about two months ahead of schedule.
At that time, the United States was still building very fast, because the war required hundreds of new ships to be built every year, and they were not small ships, but large ships or giant oil tankers.
After knowing this information, the investigators had their own guess in their hearts, the first time the oil tanker was built, and it was completed two months ahead of schedule, was it that the welder was sloppy in welding, so the welding did not meet the requirements, and the new oil tanker was broken in two?
In the end, after the inspection of professionals, it was found that the welding was fine. Ultimately, the problem is locked in to stress, climate, and design. Finally, it was determined that the cause of the fracture was brittle fracture, and the cause was "hydrogen", that is, "hydrogen embrittlement".
What is "hydrogen embrittlement" and why is it so scary?
Hydrogen embrittlement is very common in metal applications and occurs during metal smelting, processing, electroplating and heat treatment.
As for why hydrogen embrittlement occurs, there is currently a great controversy in the scientific community, and it is generally believed that hydrogen embrittlement is mainly caused by the following reasons;
1. Some metals have a relatively large affinity with hydrogen, in a hydrogen-rich environment, hydrogen atoms will penetrate into the interior of the metal, and supersaturated hydrogen will form oxides with atoms, forming atomic clusters.
As a result, the lattice structure of the metal changes, and these clusters of atoms occupy the cracks inside the metal, forming tiny cracks, which can break when extreme weather, such as cold weather, degrades the properties of the metal.
2. When the metal is refined, the internal temperature is very high, and hydrogen will penetrate into the metal and react with carbon to form methane, and the methane bubbles will accumulate and grow in the metal, and also form invisible bubbles in the metal, which will lead to a decline in metal properties and easy to fracture in extreme weather.
3. The atoms in the general metal show a regular arrangement, which is called the crystal lattice, and the hydrogen atom is relatively small because it has only one proton, and when the hydrogen atom enters the metal, it will enter the gap of the crystal lattice.
When the metal is stressed, due to the presence of hydrogen atoms, it will lead to uneven distribution of stress inside the metal, resulting in defects and microscopic cracks inside the material, resulting in the degradation of the performance of the metal material and the crack will extend, and in extreme weather, these cracks will further expand and fracture will occur.
4. The speed of the metal in the process of solidification is too fast, due to the previous contact with hydrogen, the hydrogen can not be released in time, and finally diffuses inside the metal, and continues to condense in the metal lattice, forming white spots, that is, tiny cracks.
Judging from the current research on hydrogen embrittlement, hydrogen embrittlement can only be prevented, not eliminated, and once hydrogen embrittlement is generated, it will always exist inside the metal.
How to prevent hydrogen embrittlement
In the universe, if you want to say that there are the most elements, it must be hydrogen, and in a galaxy, the largest proportion of weight must be the most hydrogen. The sun, for example, accounts for about 99.8% of the mass of the entire solar system, while hydrogen accounts for 71%, helium 27%, and other elements only 2%.
According to conservative estimates, hydrogen accounts for about 75% of the entire universe, and as for the elements behind hydrogen, they are all formed after nuclear fusion.
Although hydrogen is very widespread in the universe, it accounts for a relatively small proportion on the earth, only about 0.14%, because hydrogen is relatively light, easy to escape, and generally exists in the form of compounds.
Although there is little hydrogen on the earth, it is not absent, for example, in addition to carbon in coal, hydrogen is the second most important element, so when refining metals, it is inevitable to encounter hydrogen.
Since it is unavoidable, how to prevent it in order to minimize the impact of hydrogen on metals, so as to avoid hydrogen embrittlement?
At present, the way to avoid hydrogen embrittlement is mainly to improve the construction process, and try to use inert gas in the process of processing and forging to reduce the contact of hydrogen.
In addition, heat treatment and surface treatment are used to change the structure and state of metal grains. In addition, modern materials science and engineering methods are used to change the hydrogen resistance of metal materials, and alloys and other methods are used to reduce the lattice space inside the metal and not give hydrogen a chance.
In addition, during daily use, coatings or coatings are used to block hydrogen from entering the metal to increase the service life of the metal.
Through these methods, the dreaded hydrogen embrittlement can be effectively avoided, and the recurrence of the newly completed ship will break in two.