STEEL Talk presents to you interesting stories of Science, Technology, Energy, Environment, Life — and of course STEEL!

Medical dramas depict events and stories that happen at a hospital. In a scene inside the operating room, a doctor asks for a scalpel, a surgical instrument. Then, it is handed over instantly. The shining silver-looking surgical tools here seem threatening, but they’re actually the opposite once you get to know them. In fact, these steel-made tools play a crucial role in saving our lives.

“Cleanliness” and “hygiene” would be the two keywords that people are most interested in these days, due to the COVID-19 pandemic. The government, local authorities, corporates, and individuals are all doing their best to sanitize public places, such as hospitals, theaters, and public transportation facilities. The most needed and useful thing here is medical stainless steel known as “Surgical Steel.” POSCO Newsroom presents to you the secrets of the life-saving surgical steel.

l No More Germs! Stainless Steel Innovates the Medical Field

Before we learn more about surgical steel, let’s first go back to when stainless steel was invented.

It was only after the invention of stainless steel in 1913 that patients could get medical treatments in sanitary environments. In the past, many people lost their lives due to infections while undergoing medical treatment in an unsanitary environment.

The World Health Organization (WHO) has also cited that one of the most serious challenges that the modern healthcare industry faces is patient infections during treatment. Hundreds of millions of patients worldwide are exposed to diseases caused by infection every year, so maintaining a clean and healthy environment is paramount.

In fact, a publication by WHO in 2010 revealed that per 100 patients, seven in developed countries, and ten in developing countries suffer from healthcare acquired infections (HAIs). In high-income countries, about 30% of intensive care unit patients suffer from HAIs while the figure is two to three times higher in the case of low-income countries.

So what’s so special about surgical steel, or medical stainless steel? The answer is that it’s an excellent material in terms of hygiene! Surgical steel is resistant to corrosion, which means that there is no need to worry about any corrosion or degradation. Another advantage would be that it can be safely sterilized without any other side effects. Stainless steel is used in hospitals all around the world, in surgical knives, injection needles, and screws to hold broken bones, since it is safe to the human body — even inside!

What if we don’t use surgical steel? Rusty steel will penetrate your body, which can eventually cause tetanus, a terrible disease, or infection of various germs. Then how come stainless steel can be rust-free? Let’s look into the answer!

l Stainless Steel: The Secret Lies on the Passive Film!

Stainless steel is alloy steel made by adding chromium, carbon, nickel, manganese, etc. to iron (Fe). So, it is a highly corrosion-resistant material and versatile because it has excellent malleability to deform and it can withstand high external impact.

Stainless steel does not rust easily thanks to its special protective film called, ‘passive film,’ on the surface. This special protective film is chromium oxide (Cr2O3), which is formed spontaneously through the oxidation of chromium (Cr). Approximately 2nm (2mm divided by 1 million) in thickness, the film is so thin that it is invisible to bare eyes but it’s extremely solid and protects the base iron from oxidation. Even when a part of the film is destroyed due to a scratch, it quickly regenerates as the chromium meets oxygen again.

l Sterilizing Power, the Amazing Property of Stainless Steel!

In 2017, the International Stainless Steel Forum (ISSF) published a study result on its website demonstrating the amazing sterilizing power of stainless steel.

The study was jointly conducted by Manchester Metropolitan University in the UK and AgroParisTech, one of the most prestigious universities in the field of life and environmental science in France. The study explains how hygienic and crucial stainless steel is to use in environments where we are exposed to germs, like hospitals. Here is a brief explanation.

First, the researchers prepared two stainless steel samples. One was aged stainless steel (A), which was contaminated and cleaned repeatedly on purpose, and the other was newly-made stainless steel (B). Both sample (A) and (B) were exposed to ‘Staphylococcus aureus,’ a deadly bacteria responsible for food poisoning and infections, and ‘Pseudomonas aeruginosa,’ a bacteria difficult to treat. Both samples were then cleaned with the same disinfectant.

What was the difference between sample (A) and (B)? Surprisingly, the two samples showed almost no difference. Both samples were revealed to be 99.9 percent effective against Staphylococcus aureus and 97.6 percent effective against Pseudomonas aeruginosa. The experiment confirms that stainless steel can be used hygienically and safely over a long period of time.

Today, we learned about stainless steel that saves our lives. The scary-looking medical tools in the hospital might look differently to you now that you know about what surgical steel is. Stainless steel in the hospitals might look threatening, but remember! They’re actually our life-savers!

It’s because stainless steel keeps it clean. Stainless steel keeps it safe. How? POSCO Newsroom reports.

l Surgical Steel Keeps It Sterile

Surgical steel is a variety of stainless steel used in biomedical applications. It’s commonly used in scalpel, screws that stabilize broken bones, and in needles, etc. Needless to say, hygiene comes as the utmost priority. It’s highly resistant to corrosion and heat, making it suitable as biomedical material — it can also be sterilized at high temperatures.

Some commonly accepted types of surgical steel include austenitic 316 stainless steel (STS) and martensitic 440 and 420 STS. 316 STS is highly durable and corrosion-resistant alloy steel with high amounts of chromium, nickel, and molybdenum. It’s a popular material for screws and joints that hold bones together. The 420 and 440 STSs are both chromium-alloy high-carbon steel — highly durable and corrosion-resistant just like 316 STS. The 420 and 440 STSs are excellent choices for general-purpose knife steel, including surgical scalpel.

| Hygiene Starts with Squeaky Kitchenwares

The first place to spot stainless steel is perhaps the kitchen. Before STS, most kitchen utensils came in cast iron or brass. Cast irons were heavy, and brasswares were prone to rust. Aluminum took over shortly after — but aluminum was susceptible to dents.

Enter stainless steel. It practically became a go-to material for kitchenware as well as tableware, because STS is lightweight — it’s easy to wash and rust-free. STS overcame all the shortcomings of previous metal kitchenware.

Highly resistant to corrosion, and toxic-free even when boiled, stainless steel is not only cost-efficient, but it also resists the buildup of harmful bacteria — which is why STS is increasingly becoming the popular choice for the kitchen industry. From baby feeding tools, cutleries, dishwashers to water purifiers, it’s easy to spot STS in virtually all cooking materials.

In the past, stainless steel was intended mostly as internal use. However, the demand for STS as external material is increasing along with the recent hype of metallic design. STS rice cooker, for example, is made of STS inside and out. Virtually everything that comes in contact with the rice grain is STS — from the cover to inner pot. STD rice cooker not only enhances hygiene and durability, but it also creates a sense of luxury.

| Surgical Steel Accessories, Goodbye to Metallic Allergy

Extremely hygienic, stainless steel is an ideal biomedical metal as it comes in direct contact with the human body. The human body is 70% water and is rich in chloride ions, which can cause corrosion. That’s why biometals must be rust-free. Iron, gold, silver, and platinum used to be favored choices for biometals, but as of late STS is also gaining popularity.

The use of surgical steel reaches beyond the medical industry — it also makes for excellent accessories. Not only is it hygienic, but it also retains its original color even after long-term use. Compared to other metals, It is lightweight and is easy to work with. When set against gold or silver, surgical steel is more cost-efficient. It is highly corrosion-resistant, ideal for those susceptible to metallic allergies.

| Silver White Titanium, A Dream Material

Because of its eco-friendly nature, titanium is often called ‘green metal for the 21st century.’ Titanium comes in various colors and its excellent moldability is on par with that of 304 stainless steel. Not only is it corrosion-resistant, but it also requires virtually no maintenance, which makes it truly a dream material. It is 40% lighter than steel (carbon steel) but twice as strong. However, the cost of titanium is 40 to 80 times higher than carbon steel — and 10 to 20 times higher than STS.

Due to its outstanding biocompatibility, titanium is the premier biometal. Titanium creates no toxic wear or corrosion residue with minimal risks of inflammatory and toxic reactions. As for titanium implant, because of titanium’s ability to withstand the harsh bodily environment, a titanium implant is insoluble, and chemically impermeable preventing reactions between the metal and the surrounding environment even when the implant becomes loose. Titanium can also help prevent the risk of osteoporosis and bone destruction, which is why it is widely used in ergonomics and general medicine, such as artificial bones, heart valves, and implants.

| Both Steels — Still, Different All the Way

Steel products can be categorized into two main categories: carbon steel and stainless steel. Both are steel. Still, they are entirely different. By adding additional elements to Fe, the Fe becomes STS — immune to rust, i.e. stain-less, which is how it earned its nickname, ‘the flower of steel.’

Stainless steel is an alloy steel that enhances the properties of steel by adding extra elements to iron (Fe). The core element is chromium (Cr) — and it contains carbon, nickel, manganese, molybdenum, etc. depending on its target function. The innate surface aesthetics of STS can do away with the need for additional surface treatment. STS is highly corrosion-resistant, hygienic and widely applicable. Besides, it can also mold into various shapes and can withstand high external impact.

Stainless steel can be rust-free because of the ‘passive film’ formed on the surface. This special protective film is chromium oxide (Cr2O3). TheCr2O3 is formed spontaneously through the oxidization of the chromium. Approximately 2nm in thickness, the film is so thin that it is invisible to bare eyes, but it’s extremely solid. The passive film protects the base iron from oxidization, therefore, stopping it from going rusty. Even when the film gets a scratch, it quickly regenerates as the chromium encounters oxygen again.
* 2nm is an equivalent of 2mm divided by 1 million

Due to its high resistance to fire and heat, stainless steel is being widely applied to kitchen appliances, elevators, building interior and exterior materials, as well as other electronic appliances. It’s widely utilized across major industries such as chemical and heavy industry, etc. According to the Korea Iron and Steel Association, the demand for STS stood at 1 million tons in 2018 — in Korea alone. With 27%, the auto industry had the highest demand for the material, followed by home appliances (15%), construction materials (13%) and steel pipes (11%). Annually, POSCO produces 2 million tons of STS — 60% of which the company exports.

The annual titanium production is at 2,400 tons. POSCO imports Ingot, an intermediary material from POSUK in Kazakhstan, a joint venture between POSCO and UKTMP. The company produces and sells the metallic titanium of over 99% purity by rolling it at its steelworks. POSCO’s titanium steel sheets come in various sizes: over 0.4mm in thickness, 1219mm in width. POSCO also supplies hot-rolled and cold-rolled steels, and thick plates — as coils or as sheets depending on customer specification.

As for titanium, South Korea used to be 100% reliant on imports, until POSCO launched titanium business. Thanks to POSCO’s expansion into titanium, Korea became self-sufficient when it comes to the titanium used in shipping and nuclear industries. About 90% of POSCO titanium is used in heat exchangers for power generation in shipbuilding.

| Stainless Steel: How to Keep It Longer and Cleaner

Since the invention of stainless steel, many changes have occurred in our daily lives. Hygiene, in hospitals and kitchens, has improved above all. POSCO Newsroom came up a few commonly asked questions about STS.

Q. I heard that stainless steel products should be ‘conditioned’ before first use. What does it mean, and why?
A. Manufacturing oils are applied, so the stainless steel products retain their shiny surface quality. Before using an STS product, it’s important to remove any traces of manufacturing oils.

Here is how it’s done: put a small amount of vegetable oil on a soft kitchen towel and wipe your new STS cookware. Repeat this process until all the black traces of manufacturing oils are gone. Wash it in warm, soapy water with vinegar for ten minutes. Rinse thoroughly, and it’s ready for its use.

Q. How do I remove spots on my stainless steel cookware?
A. Occasionally, white, cloudy spots can form on kitchen utensils. These spots essentially come from mineral deposits left on the surface after boiling water — they can come from both salt and/or calcium deposits.

The spot is alkaline, so it can be removed with acid. If acidic detergent isn’t available, the spots can be removed by bringing water to boil with vinegar or citric acid inside.

If the inside of a stainless steel pot ever burns, the stain can be wiped by bringing it to boil with baking soda, wiping it with a sponge afterward.

It’s always a good idea to preheat the stainless steel utensils before cooking. If you add ingredients before it is preheated, it can cause smoke and food ingredients will stick to the pan. It may take a bit of getting used to, but once you get the hang of it, you will realize the STS is one of the safest and the most hygienic cookwares.

Q. Stainless steel isn’t magnetic, but why do they sometimes stick to magnets?
A. There are indeed STS products with magnets like STS cutleries. The parts that actually stick to magnets are often ordinary steel coating, not STS.

Also, it isn’t accurate to say that stainless steels aren’t magnetic. STS is divided into austenitic, ferritic, and martensitic based on their crystal structure. Austenitic stainless steels, which are most commonly used, aren’t magnetic — but martensitic and ferritic stainless steels can be slightly magnetic, albeit weak.

Although stainless steel is spotted everywhere, until now, it wasn’t always clear why it was called ‘flower of steel.’ Stainless steel is an indispensable material when it comes to hygiene, health, and safety. POSCO will continue to research to innovate the material to make our lives even safer and cleaner.

It is also the most common material found in medical supplies that contribute to people’s health and safety on a daily basis.  

Surgical Steel

“Surgical steel” is a term used to describe stainless steels for medical applications, and are generally made up of 316, 440 and 420 stainless steels. Surgical stainless steels are corrosion resistant, have a shiny, aesthetically pleasing exterior and are extremely hygienic. Plus, they have a long life cycle and require minimal maintenance.

Surgical steel is also used for screws and joints that hold bones together. (Source: National Geographic)

Due to these properties, surgical steel is the material found in medical equipment such as syringes, scalpels and gauges. Moreover, screws used to hold broken bones together and other parts for application inside the body are made of surgical stainless steel.

For the same reasons, surgical steel is also used to make jewelry.

Know anyone who is allergic to certain types of jewelry? Often times people think they are allergic to gold or silver, but chances are, they are allergic to other alloying elements, the most common one being nickel. In the United States, up to 17 percent of women and 3 percent of men are allergic to nickel, and the number is rising. Surgical steel with zero nickel content is a safe and cost-friendly alternative, and demand for the hypoallergenic material is growing.

Surgical steel is commonly applied to piercing jewelry. (Source: Elixa)

Surgical steel was a part of the 45.8 million metric tons of stainless steel produced globally in 2016, almost double the 24.5 million metric tons produced in 2005. The growing demand and application of stainless steel are playing a positive role in the economy, but it has also been the cause of environmental pollution.

POSCO’s Surgical Steel

One of POSCO’s surgical stainless steels is the PossRB1. It is comparable to the 420J2 stainless steel that is often applied to kitchen blades, however, it has a much higher level of hardness, and thus can be applied to surgical scalpels and razor blades.

Surgical scalpels come in direct contact with the body and need to be especially clean and non-corrosive. (Source: NY Times)

Another example is POSCO’s 304i stainless steel used to make syringe needles. It is an upgraded version of 304 stainless steel with a 9 percent nickel content, traditionally applied to syringe needles. The production process of syringe needles is demanding and require multiple steps to process into the desired thinness and diameter. To add, the materials need to be especially clean, or else the needle can fracture or not reach the desired thinness. POSCO’s 304i stainless steel is manufactured using POSCO’s strip casting technology and can be processed into the thinnest diameter requirements for 32 gauge needles (dental needles).

Syringe needles require a demanding production process. (Source: Tangent Industries)

POSCO’s poStrip Technology for Stainless Steel Production

In order to reduce the harmful environmental effects of steelmaking on the environment, POSCO partnered with the Research Institute of Industrial Science & Technology (RIST) in 1989, to come up with an innovative technology for stainless steel production called poStrip, or POSCO’s strip casting technology.   

The poStrip technology is an innovative way to make steel production more sustainable. (Source: POSCO E&C)

For more than 13 years, POSCO and RIST experimented with a twin-roll strip casting system where thin strips of steel can be produced in a single, continuous process. Hot molten steel passes through two cylindrical rollers that rotate and cool the hot steel sheets immediately, thus eliminating the need for hot rolling. In conventional casting processes, molten iron is poured into molding frames to produce steel slabs that are then rolled into sheets.

The new technology vastly reduced the cost of production, delivery time as well as the amount of harmful emissions created in the steelmaking process. In the end, POSCO’s poStrip technology was perfected and applied to various types and grades of POSCO’s stainless steels.

Not only is the innovative technology cost-effective and sustainable, it produces better quality steels.

In 2015, POSCO received the Steelie Award for Innovation of the year from the World Steel Association. POSCO was recognized for its high-quality stainless steel products that were produced with the innovative strip-casting production technology. POSCO will continue to research and improve the production and overall quality of stainless steels so that its partners can manufacture world-premium supplies, machines and architecture.