Let's start with trivia.
The reason why the screen can withstand hundreds of thousands of folds without deformation or breakage is because the hand-torn steel is used as a mask version in the substrate, which increases the foldability and reduces the weight of the fuselage.
The mask is a special kind of hand-torn steel.
Once upon a time, just like a chip being stuck in the neck, hand-torn steel has also been monopolized by Western countries for a long time.
Western companies are not only asking for sky-high prices, but people are still reluctant to sell high-end products to us, and all the products that can be seen in China are low-end goods.
Today, this has changed dramatically.
The mainland can not only make hand-torn steel, but also thinner, tougher and more uniform than foreign products, and the processing level is more advanced!
What is so powerful about this steel, and how does China break the monopoly of foreign countries?
Tear steel, a stainless steel foil, must be controlled to a thickness of less than 0.025 mm, which is only about a quarter of A4 paper.
Because it is thin enough, it can be easily torn by hand, so it has the name of "hand tearing".
Tear the hand-torn steel with bare hands
In addition to being ultra-thin, tear steel has many impressive properties.
From the perspective of mechanical properties, the grain size (grain size in the metal) of hand-torn steel reaches 9 grades, which belongs to the ultra-fine level.
The smaller the grain, the stronger and harder it is, and the more ductility and toughness.
For the manufacture of flexible screens, hand-torn steel is as soft as silk and can be folded continuously for 200,000 times.
From the perspective of optical properties, the surface of hand-torn steel is very smooth, even comparable to the mirror surface used in daily use, and it is just right to produce soft, bent, and pasted flat mirrors, which can replace glass flat mirrors.
The hand-torn steel itself is stainless steel, which also has the properties of weak corrosion resistance, high temperature resistance, oxidation resistance, and also has a good shielding effect on electromagnetic waves.
Hand-torn steel with a variety of excellent characteristics is widely used in high-end manufacturing industries including aerospace, automobile manufacturing, electronic equipment, etc., and hand-torn steel can also be seen everywhere in the fields of daily necessities and building decoration.
For example, the solar panels of spacecraft are folded when they are on the ground and do not open until they are in space.
The selection of materials under space conditions, corrosion resistance, oxidation resistance, cold and heat resistance are the basic requirements, light weight, foldable is a bit difficult, plus the need to shield electromagnetic waves - so all things considered, tear steel is the most ideal substrate material.
Solar panel unfolding in space (schematic)
Because of its high temperature resistance and high strength, in the aerospace field, hand-torn steel can be used as an important component material for the manufacture of jet engine combustion chamber blades, avoiding the adverse effects of high heat environment on engine working conditions.
In the military field, there are many electronic devices that need to shield electromagnetic waves, and hand-torn steel is undoubtedly the best choice.
In the civilian field, there are many uses for hand-torn steel.
For example, for high-grade batteries, the wrapping layer of energy storage requires a certain degree of corrosion resistance, but also compatible with strength and toughness, as well as lightness, and hand-torn steel naturally becomes the preferred material.
The reason why the screen can withstand hundreds of thousands of folds without deformation or breakage is that hand-torn steel is used as a mask version in the substrate, which increases the foldability and reduces the weight of the fuselage.
Foldable screen phone
As a core material, hand-torn steel is also widely used in high-tech products in computers, medical equipment, home improvement hardware, construction, bridges, machinery manufacturing and other fields.
Tearing steel is ubiquitous and has become an indispensable material.
Although hand-torn steel is good, it is not something that can be made by trying to build.
For nearly 30 years, the West has monopolized the manufacturing technology of tearing steel, and China wants it, but can only buy it.
Before 2012, the mainland could only roll out 0.1-0.5 mm thick steel plates, and there was a great demand for low-cost, high-quality hand-torn steel of 0.05 mm, accounting for eighty percent of the global market.
The import price of an ordinary A4 paper-sized piece of hand-torn steel is about 400 yuan, and the mainland spends a large amount of foreign exchange reserves to buy hand-torn steel every year.
Moreover, at that time, the advanced manufacturing technology of 0.02 mm hand-torn steel was firmly grasped by several countries such as Japan and Germany, and in order to curb the development of the mainland in this field, these countries also banned the sale of high-end products to the mainland.
So, what is the difficulty of making a steel foil as thin as a cicada's wings from thick steel plates?
The hand-torn steel is too thin, and the manufacturing standard must be controlled within 0.02 mm from the perspective of thickness and accuracy alone, and the error cannot exceed one thousandth of a millimeter.
Therefore, if ordinary steel is to be thinned, the forging process like gold leaf will not work, because the thickness cannot be guaranteed, and the steel can only be rolled into hand-torn steel by using a precisely controlled strip rolling mill.
This is the key to the hand-torn steel process.
If you can't eat hot tofu in a hurry, the same is true for rolling steel, which needs to be carried out by a special 20-roll reversible cold rolling mill, where the thicker steel plate is thinned little by little, and finally rolled to a thickness of 0.02 mm.
The mainland rolled steel foil is basically the same idea, but when the thickness of the steel plate is rolled to about 0.05 mm, the requirements for the machine are higher.
Schematic diagram of the engineering of the twenty-high reversible cold rolling mill
At this thickness, the 20 rollers on the machine must be re-equipped with each roll to ensure a precise fit with each other.
At this precision, there are tens of thousands of different variations of all the rolls in the whole process, and there is only one correct answer.
It is also necessary to take into account that the steel foil is already very thin at this time, and it still needs to be constantly annealed and heated, stretched and straightened, and it will tear and break if you don't pay attention to it.
Such a precisely controlled rolling process of alternating hot and cold has to be done at least a few times.
It's like weapon forging in some online games, each forging takes a huge risk, and if something goes wrong, all the work is lost.
Obviously, the steel that can withstand the test is by no means a "mortal tire", and the undesirable impurities such as aluminum, magnesium, oxygen, and sulfur must be removed as much as possible, otherwise the yield is extremely low.
This places high demands on the smelting of steel.
During the rolling process, the surface of the torn steel must also not leave any visible scratches, as well as marks, patterns, wrinkles or curls, which requires relatively dust-free production conditions.
Because it is so thin, any tiny particles mixed in the production process can lead to an increase in scrap rates.
Due to the above manufacturing difficulties, hand-torn steel has been unable to achieve domestic production.
The average price per ton of hand-torn steel imported by the mainland is close to 5 million yuan, which is twice the list price in the international market.
The mainland once considered introducing a Japanese production line, but was rejected by the Japanese side, and they also ridiculed: China will never be able to make hand-torn steel.
In the face of the technological blockade of Western countries, we have no choice but to rise to the challenge.
This time it's the national team!
At the beginning of 2016, Shanxi TISCO set up a 15-person "hand-torn steel" innovation and R&D team, which lasted more than 2 years, after 711 test failures - equivalent to an average of one test failure per day - finally overcame 175 equipment problems and 452 process problems, and selected a successful rolling method from more than 40,000 roll permutations and combinations.
The whole process consists of 5 to 6 rolling mills, each of which requires more than 20 processes, and there is no room for error in more than 100 processes.
The production workshop of Shanxi Taigang Stainless Steel Precision Strip Co., Ltd
At the beginning of 2018, the team successfully produced a hand-torn steel with a thickness of 0.02 mm and a width of 640 mm, which not only broke the original monopoly of the West in terms of thickness, but also surpassed the previous width of 400 mm, which directly prompted the sharp price reduction of similar foreign products.
After the successful production of 0.02mm hand-torn steel, TISCO's R&D team was not disbanded, but continued to recruit.
In August 2020, TISCO's hand-torn steel technology once again set a new world record, with the thinnest thickness reaching 0.015 mm.
TISCO became the only enterprise in the world that could mass-produce wide soft stainless steel foil products at that time.
In 2023, according to the director of the company's R&D center, the thickness of hand-torn steel can already reach 0.012 mm.
0.015 mm thick tear steel
At the same time of technological breakthroughs, TISCO is also actively realizing the localization of equipment.
In May 2023, TISCO's No. 3 rolling mill project successfully passed the acceptance and started trial production, which is a domestic rolling mill production line, with a domestic production rate of more than 90%, and the rolling mill archway, back support bearing, and thickness gauge are all independently developed by the mainland.
TISCO Fine Belt No. 3 Rolling Mill
Among them, the PLC control system, which is the "brain" of the rolling mill, adopts the products independently developed by Baowu Group Baoxin Software Company, which can realize high-speed rolling and high-precision rolling, breaking the foreign monopoly in one fell swoop.
In view of the problems of oil mist, waste water, noise and solid waste pollution generated in the rolling process, the new production line adopts advanced treatment technologies and measures at home and abroad, and the whole set of equipment has reached the international advanced level in terms of energy consumption and environmental protection.
In addition to TISCO, Fujian Qingtuo Technology Co., Ltd. also announced in November 2023 that it had successfully used localized equipment to roll hand-torn steel with a thickness of 0.015 mm and a width of more than 600 mm.
Qingtuo company's hand-torn steel thickness measurement Screenshot source: Fu'an News
With double insurance, the production of hand-torn steel in mainland China no longer has to worry about the problem of stuck neck.
The breakthrough of hand-torn steel technology has not only created a high value-added myth in the steel industry, but also driven the development of downstream fields.
The raw materials of hand-torn steel are only 20,000 yuan a ton, after processing, the price is only half of the import, and the finished product can also be sold for more than 2 million yuan a ton, and the added value of science and technology is very high.
The price of shredded steel has been brought down, and all walks of life are willing to try to use it to develop new products.
For example, in the medical equipment industry, more flexible catheters and surgical instruments have been developed by using hand-torn steel, and energy storage batteries have also greatly popularized hand-torn steel, and the battery capacity of the same volume battery can be increased by 17% using 0.015 mm hand-torn steel.
It is foreseeable that the wave of innovation brought about by hand-torn steel technology will continue to spread.
I would like to consider the localization of tearing steel as a kind of manifesto:
As long as you work hard, no matter how difficult the technology is, you can "tear it"!