The Story of China and Stainless Steel Foil

Have you ever seen stainless steel thinner than 1/4 of A4 paper? This stainless steel product looks like tin foil and can be gently torn by hand and is called “hand-tear steel”. Its thickness is only 0.02 mm, and it is widely used in high-precision cutting-edge equipment manufacturing industries such as aerospace, medical equipment, precision instruments, new energy, and 5G communications. However, for a long time, only a few countries in the world can produce “hand-torn steel”, and China was once restricted by purchase.

China is a big producer of stainless steel, but also a big consumer. However, the “Pearl” on the “crown” of stainless steel, the soft stainless steel precision foil with a thickness of only 0.02 mm, was once restricted by purchase.

Taiyuan Iron and Steel Co., Ltd., located in Taiyuan, Shanxi Province, was formerly known as the Northwest Steel Plant, which was founded in 1934. After the founding of New China, it was renamed TISCO. It is the earliest enterprise in China to develop and produce stainless steel. It has long been focusing on the development of special steel mainly made of stainless steel.

In 2008, Taiyuan Iron and Steel invested 1 billion yuan to launch the only one set of stainless steel precision strip production line in China at that time in the precision strip company, and integrated the introduction of the world’s top equipment at that time. The thinnest design limit of the rolling mill is 0.02 mm. .

The subsequent installation, as well as the commissioning stage of the mechanical, electrical, production and other processes, are all guided by foreign experts who follow the door.

In 2012, the precision strip line was put into production as scheduled.

Each process and process knew that it was difficult, but I didn’t expect it to be so difficult. Great efforts have been made round after round, but the long-awaited results have not been achieved. In the end, only 0.3 mm thick plates with specifications between 0.1 and 0.5 mm can be rolled, which has never been achieved. design standards.

The goal is beautiful, but the reality is cruel.

Foreign experts sometimes believe that it is the cause of insufficient precision in equipment installation; sometimes they speculate that it is the result of insufficient precision of the selected materials.

In 2010, when Duan Haojie, just 24 years old, entered the factory, he plunged into the challenge of “tear steel by hand”. For 12 years, he has been “bundled” with this rolling line. Today, Duan Haojie has grown into the director of the precision strip steel research and development center, leading a group of young people to provoke the research and development of “hand-torn steel”.

When he saw Duan Haojie, he was rushing back to the office from the workshop. As he took off his helmet, he recalled that at that time, the company had made various adjustments and attempts for the various “insufficient” analysis of experts, but it still ended in failure.

In mid-2014, the foreign expert left after holding on for nearly four years. Before leaving, he left a meaningful sentence: “The raw materials are similar, the personnel are similar, and the management is similar. However, the difference is a lot worse.”

Duan Haojie heard the expert’s “assertion” with his own ears.

Seeing that the research and development has failed, and there are no foreign experts, no one dares to try it easily. The design limit of the rolling mill is the minimum specification of 0.02 mm, which has become a number on the specification and cannot be realized in reality.

With the launch of this rolling line, many young people who have just graduated came with dreams. For example, Hao Yali, who is in charge of technology management in the R&D center, entered the Precision Strip Steel Company a year earlier than Duan Haojie, and is also 36 years old this year. Most of the R&D team members of “Hand Tear Steel” are young people born after 1986.

In the R&D room, next to the rolling mill, they were eager to try and their passion was flying, but now, their mood has fallen to the bottom.

Ideal, is it shelved?

Two

Fast forward to 2016. In late February of this year, a new leader took office in the cold wind.

Needless to say, the new head of Precision Strip “was ordered in distress”. 7 years of listing and 7 years of losses are the status quo of the company.

Therefore, the target given by the group is to realize a profit of 1 yuan.

How to reboot? In the production workshop, the world-class high-end equipment is producing some “road goods” that are not competitive in the market step by step. In this regard, everyone’s heart is not the taste.

Has the potential of this first-class good equipment been fully tapped? Good equipment, must come in handy! The new leader quickly made a decision – to return to the research and development of “hand-torn steel”!

However, where is the key to the door to “Tear Steel”?

Liao Xi, who is the same age as Duan Haojie and Hao Yali, is the chief precision foil process engineer of Precision Strip Steel Company. In university, his major is not related to stainless steel technology, but he has been fighting for 10 years in the “hand-tear steel” project. He clearly remembered that morning, the factory leaders convened technical, rolling mill and other process-related personnel, held a special meeting with users, and held a kick-off meeting in the afternoon. The factory leaders made a request to everyone: continue to tackle key problems and produce China’s own “hand-torn steel”!

Can they afford this national mission?

Compared with the large factory of TISCO with thousands of employees, Precision Strip Steel Company is a small factory with only more than 200 employees in total. Therefore, as soon as this request was put forward, there was a “uproar” very soon.

However, the new leadership is still “overbearing” to make a decision. The confidence to support this “overbearing” is still the set of world-class equipment.

Soon, the whole factory started with equipment and opened the road to decipher the “hand-torn steel” password. The first is to comprehensively clean up the “strip steel channel” to remove the dirt in the lye circulation box; another 1.2 million yuan was spent to replace the rolling oil; the rolling mill oil scraping roller was also replaced from once every two months to half. moon.

Since then, “Double Precision Management”, which combines equipment function precision and process technology precision, has been fully implemented in Precision Strip Steel Company.

The words of foreign experts are still in my ears. The team abandons the idea of ​​”similarity” in all processes, and focuses on equipment, materials, craftsmanship, personnel, etc., one link at a time.

A piece of “hand-torn steel” original steel strip with a thickness of 0.8 mm, a width of 600 mm and a length of over a kilometer. To become a finished product with a thickness of 0.02 mm and a width of 600 mm, it is necessary to overcome the four technical problems of rolling, annealing, high-grade surface control and performance control. After cold rolling, bright annealing, stretch leveling, stress relief, slitting Slitting line cuts 5 large production lines.

“One round involves more than 100 employees and more than 20 processes, and the round of battle is one month.” Liao Xi said.

The goals are hard and the production lines are long. If something goes wrong, you have to start all over again.

First, change the raw materials, and after trying everything, switch from the basic materials of ordinary electronic products to the production of special varieties of materials.

Another case of perforation. After many observations and studies, it was caused by impurities in the material, which was eventually traced back to the upstream and eliminated from the smelting process.

into rolling. From 0.8mm to 0.02mm, the difference is 0.78mm. This thickness is almost negligible in life. However, for “Tear Steel”, it is a long and difficult “road”. A piece of “hand-tear steel” is from thick to thin, just like “rolling dough”, it needs to be “rolled” down by 0.1 mm and 0.1 mm. The “rolling pin” is a precision machine composed of 20 rollers, and there are thousands of arrangements and combinations.

Duan Haojie said that 80% of the difficulties in the research and development of “hand-tear steel” are concentrated on the ratio of rolls in the rolling mill. Every time the material is “rolled” thin, it is necessary to explore the best way from tens of thousands of permutations and combinations.

Careful and precise. However, it broke again.

This is a problem that often occurs in the rolling process. Because the material is too thin, the coiling tool cannot be used in the belt threading process, and the steel belt will be torn off by the personnel with a little force during the manual process. Initially, the steel belts were broken every two days. Often, after finally rolling for more than 100 meters, it is instantly broken into steel powder.

Like the powder, there are also hearts that are carried one by one in front of the rolling mill.

A pile of white crystals was scattered in the roller system, and it took eight or nine hours to clean it at a time.

Boiled until I lost my temper.

This is a 260-meter-long “road”. As you move forward carefully, you will encounter a “drawing belt” again.

“It’s like a piece of cloth, if it doesn’t unfold, it always pulls in the middle.” They likened it like this.

“When the temperature is high, the material becomes soft, and it will be pumped as soon as it passes the roller.” Now, Liao Xi can’t help but frown.

It was September 2017, but no one could feel the coolness and comfort of autumn, and the atmosphere of despair permeated the workshop.

You know, each roll of stainless steel raw material reaches 3,000 meters and is worth 100,000 yuan. It hurts!

“I can’t do it anymore!” Liao Xi said, “I can’t afford to waste it!”

After learning about the situation, the factory launched a “fault-tolerant” mechanism in a timely manner, giving each R&D personnel a certain number of mistakes and product meters, and at the same time encouraging employees to complete 1 ton of qualified “hand-torn steel”, and the assessment is based on 75% of ordinary products. -100 times of production.

Morale, once again raised.

The factory leaders even squatted on the front line and watched the scene.

The precision strip workshop is not large, 120 meters from south to north and 160 meters from east to west. At one time, the “top leader” in the factory ran back and forth in this small space, often taking 20,000 steps a day.

“The good methods are all ‘stared’ on the spot.” Liao Xi said.

After many times of staring, I finally found the key reason for the draw. Hu Shang, the chief electrical engineer of precision foil materials, took the initiative. He led the team to invent new technical methods and successfully solved this problem.

At the end of 2018, the first batch of wide-width soft “hand-tear steel” with a thickness of 0.02 mm and a width of 600 mm rolled off the production line perfectly from the mill master Wu Qiong. This young man is a veteran, his work center is as thin as a hair, and he cooperates perfectly with the scientific research team.

“Hand Tear Steel” made a successful appearance at TISCO. Similar products, the foreign width is up to 450 mm. Therefore, TISCO has become the only company in the world that can mass-produce wide-width ultra-thin stainless steel precision foils.

More than 700 days and nights, 711 failures, 172 equipment problems, 452 process problems… These series of numbers are deeply engraved in the golden key for cracking the “hand-torn steel” password.

Three

It took less than 3 years from the new leader taking office in 2016 to tackle key problems again, to the successful batch rolling of the first batch of “hand-torn steel”.

TISCO’s “Hand Tear Steel” is well-known at home and abroad and has received rave reviews.

The Precision Strip Man seems to be able to rest on the credit for a while. However, they quietly cleared their achievements, went back to the runway, and devoted themselves to the next round of high-end product research non-stop.

“The previous success only proves that Taigang has the ability to produce ‘hand-tear steel’, and more research and development is yet to come.” Whether it is a factory leader or a member of the research and development team, they all say this.

“Just starting out, just hitting the road.” Duan Haojie is more cautious, “We have some advantages in some specifications, but there is still a gap in overall quality. After all, foreign countries have nearly a hundred years of production experience.”

The thickness of 0.02mm is already the design limit of the rolling mill, but they have to continue to challenge and hit 0.015mm. Naturally, it is for the needs of customers.

However, dropping 0.005 mm is not as simple as continuing to “roll” down 0.005 mm. Under the huge rolling mill, 0.015mm is an almost imperceptible existence, so it keeps slipping during the process.

Continue to stare, continue to argue, continue to test.

On the morning of August 16, 2020, after various methods such as texturing the rolls were carried out by laser, the “hand-torn steel” with a width of 600 mm and a thickness of 0.015 mm was unveiled at 11:15.

It was Wu Qiong who completed this beautiful rolling.

In the industry, this thickness has become the “ceiling” of production technology in this field. This is the widest and thinnest “hand-tear steel” in the world.

So, what can be changed by reducing the thickness by 0.005 mm?

Liao Xi, who has faced the most customers directly, is the person who understands the product requirements best. He said: “If it is used as a battery coating film, the battery capacity can be increased by 17% with the same volume.”

The record-breaking 0.015mm once again witnessed the power of Chinese steel.

“I can’t be satisfied! I don’t dare to be satisfied!” This is the consensus of the R&D and rolling team of “Hand Tear Steel”. In the precision strip steel production line, no product can be said to be “mature and finalized”. The same is 0.02 mm, 0.015 mm, different customer needs, performance, surface, toughness, shape will be different. For customers, “hand-tear steel” is a raw material that needs to be reprocessed. All possible changes in the post-processing process of the customer are factors to be considered in the pre-production. Even the simple standard of no deformation after processing requires a lot of tempering from research and development to production.

“Each batch of products is personalized research and development and customization. Electronic products are upgraded quickly, and our craftsmanship will change accordingly.” Duan Haojie said, “So the pursuit of craftsmanship is never-ending.”

In the fall of 2022, another high-end product they are conquering has also taken shape. Expansion alloys for masks, which are also an upgraded version of “hand-tear steel”, are the main consumables for the production of OLED flexible screens, and are widely used in smartphones and wearable devices.

Compared with the previously produced “hand-tear steel”, this product has higher requirements in terms of performance, shape and surface, and is also the most difficult product to produce at present.

A mask the size of a mobile phone screen is made of expanded alloy, as thin as a cicada’s wings, and the sunlight penetrates softly. As everyone knows, each sheet is covered with 2 million to 4 million small holes, and the holes must maintain a symmetrical distance between them.

It is invisible to the naked eye, but it is a requirement that the craft must meet.

This product determines the core of the flexible screen

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