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EAF: Recycled steel scrap is melted and purified in a furnace, with the alloying elements mixed in until the composition is just right. Chemicals are added to keep oxidation at bay and remove impurities, and it’s then poured into a ladle (an oversized bucket with a spout). It’s then put into giant ingot molds and carefully cooled.Â

What is hardened steel used for

This group has three main sub-types (covered below), each with average hardness, as well as high wear resistance and hardenability, used for making larger parts or ones that need to be hardened with minimal distortion.

“Until now, it has been impossible to continuously recycle products made of carbon fibres. Given that most recycling involves shredding, cutting or grinding, fibres are worn out, decreasing a future product’s viability,” said Dr Hadigheh.

Hardsteel composition

“To combat this issue and to support a true circular economy, we developed an efficient and cost-effective method for recycling carbon fibre, which is present in tablets through to BMWs.”

Hardened steel vs stainless steel

This group falls under the water-hardening category, and the metals are highly wear-resistant, but not shock-resistant. They also can’t really deal with very high temperatures. They’re used for paper-cutting blades, broaches, burnishing tools, and plug gauges.

Tool steels are hard, tough, and wear-resistant metals that won’t soften at high temperatures. They’ll typically have 0.7–1.5 wt% carbon in them, but some can have anywhere from 0.2–2.1 wt%. Although a higher carbon level will make the steel stronger and more hardenable, it will also make it brittle and less easy to weld. When cold-worked, tool steels are around 60/62 HRC on the Rockwell C hardness scale, but could range between around 58/64 HRC (some have been known to reach 66). Tool steel can withstand heat treatment, with the specific temperature being dependent on its exact composition. Here’s what it looks like before it’s made into tools:

As the celebrity of the bunch, you wouldn’t want to use these costly steels if, for instance, a W-type would do the trick. Manufacturers tend to reserve these for applications that other steels can’t handle. They don’t have a lot of alloying metals (they like to work alone) and don’t need much treatment. There are two groups of special-purpose tool steels, described below.

These are strong steels with good abrasion resistance used for thread-cutting chasers, arbors, bushings, and die blanking.

As promised in the intro, here’s a look at the different types of tool steel grades which, as you’ll see, differ in both composition and characteristics.

Hardened steel grades

CRFP composites are present in products such as wind turbines, aeroplane parts, vehicles such as cars and ships, and everyday technology such as laptops and mobile phones.

These are air-cooled steels with low distortion (especially A6), as well as tough and easily machined. Common applications include arbors, blanking, and die bending.

In recent years there has been an increased focus on the circular economy and a heightened demand for products made of recyclable materials, however many materials can only be recycled so many times before they begin to wear out.

The research was supported by the Australian Government through the Australian Research Council’s Discovery Early Career Researcher Award (DECRA) fellowship scheme (project number DE200100406), which was received by Dr Hadigheh.

“The 2016 Australian National Waste Report concludes that the use of composite materials is creating future challenges to recycling. Plainly put, if we do not develop efficient and cost-effective methods to recycle carbon fibre composites, we risk damaging the environment significantly,” said Dr Hadigheh.

HSS can hold their own in super high temperatures without losing any hardness and are named after their speedy cutting and feed rates. You’ll find many cutting tools, saw blades, and tool and drill bits made from HSS. They’re also abrasion-resistant, thanks to the included tungsten and vanadium.

Hardened steel material list

In 2010, the global production of fibre reinforced polymers (FRP) was approximately 6 million tonnes with a projected growth of 300 percent in the next decade. With this projection, the consumption of FRPs will exceed 18 million tonnes by 2025, with an end-product value of AUD $80 billion.

“We embarked on the project with the aim of producing high grade, low cost structural materials made from recycled carbon fibre composites, for use in industries from aerospace and automotive through to sporting goods and renewable energy and construction.”

“To do this we used a two phased, optimised process. The first step is called “pyrolysis”, which breaks down a material using heat, but significantly chars the materials which prevents it from developing a good bond with a resin matrix. The second process, oxidation, uses high temperatures to remove this char.

Hardened steel mechanical properties

Hot or cold drawing: This process is used to make smaller or uniquely shaped tools with high tolerances. As these steels aren’t very ductile, several passes at temperatures of up to 1000°C are needed, but you’ll only be able to go over it once (and lightly) with cold drawing to prevent breakage.

Researchers from the University of Sydney’s School of Civil Engineering have developed an optimised method for recycling CFRP composites while maintaining 90 percent of their original strength.

They are typically disposed of in landfills or by incineration, which pose significant threats to both the environment and public health.

The vast majority of existing recycling methods also cause a major reduction in the mechanical and physical properties of the recovered material, weakening its core functionality.

This is a high-carbon tool steel that has lower hardenability than other types due to its low alloy content and needs water quenching. These steels harden well but could become brittle, and the quenching tends to make it prone to cracking or warping. It’s one of the more affordable options but hasn’t got the highest heat resistance. It’s mainly used for basic stuff like reamers and embossing and cutting tools.

The United States, Japan and China lead the world in carbon fibre manufacturing. The researchers hope to increase the capacity of the Australian industry and work with manufacturers of wind turbines and commercial aircraft, as well as producers of sporting goods, and the construction, automotive and ship-building industries.

Annealing: To make the steel easier to work with and less brittle, its molecular structure can be changed with annealing, which is heating it at a steady and high temperature for a certain amount of time before cooling it right down again.Â

Hardened steel properties

In addition to carbon, tool steels will have other elements to improve their strength and change their properties according to what exactly the tool is needed for. For instance, nickel or cobalt can be added to give the metal extra strength and high-temperature resistance, while adding carbide former made from different combinations of iron-based alloys, like tungsten, vanadium, chromium, and/or molybdenum, can make it more wear-resistant.

Hardened Steel Price

“Pyrolysis and oxidation alone are not enough to preserve carbon fibres and these processes have existed for some time already. To ensure a high quality recovery and economic efficiency, thermal decomposition of CFRPs need to be guided by analysing the energy required to initiate a chemical reaction in the composit, and separate carbon fibres from the surrounding resin matrix.

Used to make lots of tools other than cutters, H-grade boasts the ability to work well in high heats for long stretches at a time. It’s low carbon with a good amount of alloying metals in it. There are three types in this category:

Although the main method for making tool steel is via electric arc furnaces (EAF), this is not the only way. Below we’ll cover the processes used to make it.Â

Materials that are used to make tools should understandably be particularly hardy, and tool steel fits the bill. “Tool steel” as a term refers to carbon and alloy steels that are strong enough to be made into tools that can work on wood, plastic, and other metals in various processes, like stamping and forming, to name just a couple. Hand tools, drills, cutters, and bits are more often than not made from tool steel, as are larger items like machine dies and plastic extruding machinery. There are several different types of tool steels that are categorized into grades (and there are a few sub-grades, too), so to figure out what each grade is good for, keep reading. We’ll also cover what exactly is in tool steel and how it’s made.

“What makes our method so successful is that we have added specific parameters – such as temperature, heating rate, atmosphere or time spent being oxidised and heated – that preserve the functionality of carbon fibre.”

With a shorter hardening range and lower hardening temperature, these types are slightly less hard than tungsten types (listed below) but are more durable.

“Globally and in Australia there has been a march towards better recycling processes, however there is often the belief that a material can be recycled an infinite amount of times – this simply isn’t the case. Most recycling processes diminish mechanical or physical properties of materials,” said the study’s lead researcher Dr Ali Hadigheh.

Designed for use in high-stress but low-temperature conditions, this type has high impact toughness, fair hot hardness (but can’t be classed as a hot-hard tool steel), and low abrasion resistance. It’s often made into chisels, collets, and shearing blades.

This is the case with carbon fibre reinforced polymer (CFRP) composites, non-biodegradable materials which, until now, have lacked a viable recycling method.

“This presents a huge challenge and threat to our environment, as it has led to the production of virgin carbon fibre which contributes significantly to greenhouse gas emissions.

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