Sustainability in Manufacturing: The Recyclability of Tool Steel

Introduction

Sustainability has become a key focus in manufacturing as companies aim to reduce their environmental impact. One area where sustainability can be improved is through increasing recycling rates of manufacturing materials. Tool steel is a popular material used to make tools for metalworking, such as cutting tools, dies, and molds. While tool steel is highly durable, there are opportunities to recycle tool steel scrap and reduce raw material needs. This article will examine the composition, properties, and applications of tool steel, look at how tool steel is currently recycled, and discuss ways to improve the recyclability and sustainability of tool steel in manufacturing.

What is Tool Steel?

Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited for making tools. The primary characteristics of tool steels are high hardness, wear resistance, and ability to hold shape at high temperatures. Tool steels achieve these properties through careful control of their composition and microstructure.

The main elements added to produce tool steel include:

• Carbon – Provides hardness and strength. Tool steels typically contain 0.5-1.5% carbon.
• Tungsten – Improves hardness and temperature resistance. Often added in the form of tungsten carbide particles.
• Molybdenum – Enhances strength and machinability.
• Chromium – Increases hardenability, wear resistance, and corrosion resistance.
• Vanadium – Refines grain size for improved toughness and fatigue resistance.
• Cobalt – Strengthens the steel matrix and improves hot hardness.

There are several major types and grades of tool steel, which differ in their alloying elements. Some common classes include:

• Cold work tool steels – Air or oil hardened, used for punching, blanking, and cutoff dies.
• Shock resisting tool steels – Withstand shock and impact forces well. Used for hammers, chisels, pile drivers.
• High speed tool steels – Excellent hot hardness and wear resistance. Used for cutting tools, drills, saws.
• Hot work tool steels – Retain strength and hardness at high temperatures. Used for hot forming dies and hot shearing blades.
• Mold steels – Optimized for molding plastics or die casting metals. Good polishability and heat transfer.

Proper heat treatment is critical to develop the desired properties in tool steels. Treatments involve precisely controlled cycles of heating, soaking, and cooling/quenching.

Applications of Tool Steel

The unique properties of tool steels make them indispensable for manufacturing applications that involve high pressures, temperatures, stresses, and complex shaping. The major uses of tool steels include:

Cutting Tools

Cutting tools for machining, drilling, turning, milling, tapping, sawing, and more rely on tool steel for hardness and hot hardness. High speed tool steels can maintain their hardness and shape at temperatures exceeding 500°C. Common grades used are M2, M4, M42, T15, S7.

Dies and Punches

For blanking, punching, bending, drawing, and forming sheet metal, tool steels allow dies and punches to cut through metal without excessive wear. Shock resisting grades like S7 and D2 work well.

Molds

Injection molds for plastics and die casting molds for metals utilize tool steels that can withstand the high pressures, temperatures, and repetitive thermal cycling involved in molding. P20, H13, 420SS are common mold steel grades.

Extrusion and Drawing Dies

Extruding or drawing metals into continuous sections requires tool steels with exceptional resistance to wear and deformation at high temps and pressures. H13 is commonly used.

Rolling Mill Rolls

The work rolls in rolling mills that reduce the thickness of metal stock are subjected to high loads. Rolls made from tool steel have the necessary strength and hardness. Common grades are D2, A2, and 52100.

Metal Forming Tools

Stamping, bending, pressing, and forging tools utilized in metal forming see high mechanical and thermal stresses. Hot work tool steels like H13 and H11 are ideal.

As can be seen, tool steels are indispensable across many manufacturing processes for their hardness, wear resistance, strength, and heat resistance. Their ability to withstand extreme conditions repeatedly makes them well suited for tooling applications.

Recycling Tool Steel Scrap

Tool steel components have an inherently long service lifetime. However, when they do reach the end of usefulness, recycling the tool steel scrap has significant economic and environmental benefits.

Sources of Scrap

There are a few main sources of tool steel scrap in manufacturing:

• Worn-out tools and dies – Cutting tools, punch and dies, molds, etc. that have worn beyond repair or restoration. Proper maintenance can extend their lifespan.
• Machining waste – During machining and grinding of tool steel components, up to 40% of the original material can be removed as waste. Efforts to improve machining efficiency can reduce this.
• Overruns and rejects – Excess raw material, production rejects, and trial samples are inevitable sources of tool steel scrap.
• Refurbishment waste – Component refurbishment, such as mold repair by welding, generates scrap as material is removed.

Recycling Process

To recycle scrap and waste tool steel, the following key steps are involved:

• Collection and sorting – Scrap tool steel is collected and sorted by grade (based on alloy type). This may require removal of coatings or heat treatments.
• Crushing or shredding – The sorted steel scrap is crushed or shredded into smaller fragments to facilitate melting.
• Melting and alloying – The crushed steel is melted down in electric arc furnaces. Precise amounts of alloys like tungsten, chromium, and vanadium are added to achieve the composition needed.
• Refining – The molten steel undergoes slag removal, degasification, and other secondary refining processes. This improves purity and quality.
• Solidification and casting – The liquid steel is cast into molds or continuously cast into billets, blooms, or slabs. This produces recycled tool steel stock.
• Heat treatment – To achieve the desired properties, the recycled tool steel undergoes heat treatments like quenching, tempering, and annealing.

With these steps, recycled tool steel scrap can be converted back into stock suitable for reuse in manufacturing high-performance tools and dies.

Benefits of Recycling Tool Steel

There are significant benefits associated with recycling tool steel scrap:

• Reduces energy use – Recycling requires 90% less energy than producing virgin steel from iron ore. This provides major energy savings.
• Lowers emissions – Tool steel recycling emits 85% less greenhouse gases compared to virgin production. This decreases environmental impact.
• Conserves resources – Recycling reduces the amount of raw materials, like iron ore, coal, and alloying elements needed. This improves resource efficiency.
• Saves costs – Refining scrap into tool steel is more economical than virgin steel production, lowering materials costs.
• Consistent properties – The properties of recycled tool steel are often more uniform compared to newly produced steel.
• Supports circular economy – Recycling aligns with circular economy principles by extracting additional value from materials.

Given these significant benefits, prioritizing recycling practices for tool steel scrap and waste makes excellent economic and sustainability sense for manufacturers.

Improving Tool Steel Recyclability

While tool steel recycling is quite feasible, there are opportunities to improve recycling rates, process efficiency, and quality. Some ways to enhance tool steel recyclability include:

Design for Recyclability

Components can be designed to facilitate disassembly and recycling. Using mechanical fasteners instead of welds, minimizing intermaterial contact, and avoiding coatings that hinder separation all enable easier recyclability.

Improved Scrap Collection

Better scrap segregation, storage, and handling procedures allow for more scrap to be captured and recycled. Maintaining purity of alloys improves final recycled material quality.

Process Optimization

Advances in sorting, shredding, and steel melting technologies can boost efficiency and lower costs. For example, better spectrographic scrap analysis and inline melt composition measurement systems.

Recycling Process Developments

New processes aim to recycle tool steel with less remelting and refining for quality and cost benefits. An example is cold-bonding of tool steel powders into new stock.

Closed-Loop Recycling

Dedicated efforts to reuse tool steel scrap onsite, such as recasting sprues and risers into new ingots, reduces processing steps. This closed-loop approach lowers contamination.

Education and Training

Educating personnel on the importance of recycling, and proper scrap management procedures, ensures recycling captures the maximum amount of tool steel waste.

With rising emphasis on sustainability in manufacturing, increasing the recyclability of tool steels will continue growing in priority. A concerted effort across the design, use, maintenance, and recycling of tool steel can reap significant environmental and economic gains.

Challenges Hindering Tool Steel Recycling

While the benefits are substantial, there remain challenges that hinder achieving higher recycling rates for tool steel in industry:

Thermal Degradation

Repeated heating cycles during tool steel recycling can degrade properties and performance. This sets limits on the number of times tool steel can be recycled.

Contamination

Mixing of alloy types and introduction of impurities during recycling makes maintaining purity difficult. This reduces quality consistency in recycled tool steel.

Inventory Management

Lack of effective scrap inventory management and tracking systems prevents maximum capture and recycling of available tool steel waste and scrap.

Collection Logistics

Transporting and collecting widely dispersed scrap tool steel products from various sites to centralized recycling facilities poses logistical challenges.

Identification Difficulties

Insufficient marking and record-keeping of tool steel types and grades complicates identification during sorting and recycling.

Process Costs

The costs of collection, transport, sorting, and recycling can still exceed purchasing primary tool steel for some smaller organizations and limit recycling.

Limited End Uses

Uncertainty about consistency in final properties of recycled tool steel limits feasible applications, hampering closed-loop recycling back into high-duty tooling.

Lack of Standards

Few clear standards or codes exist related to incorporating recycled tool steel into production. This can inhibit wider adoption.

Addressing these limitations by process improvements, tighter management, technological advances, and collaboration across the supply chain is key to maximize recycling opportunities for tool steel.

The Future of Tool Steel Recycling

Tool steel recycling has promising potential for growth in support of more sustainable manufacturing. Some likely advances include:

Increased Automated Sorting

Expanded use of XRF scanning, laser spectroscopy, and AI-powered image analysis will improve automated tool steel scrap sorting and purity.

Process Monitoring

In-line monitoring tools will provide real-time alloy measurements during melting, flagging any deviation from specifications to ensure consistent recycled material.

Advanced Metal Analysis

New metallographic and microanalysis tools will detect microstructural defects in recycled tool steel early to avoid quality issues.

Stronger Tool Steel Grades

Next-generation tool steels with added elements will boast improved durability. This will increase service lifetimes and reduce scrap rates.

Novel Reconditioning Methods

Innovative techniques to recondition and restore worn tool steel components will be developed as alternatives to recycling.

Recycling Process Improvements

Emerging processes like additive manufacturing powder recycling and liquid metal extraction could provide cleaner, more efficient tool steel recycling.

Increased Adoption

With rising focus on sustainability and the circular economy, use of recycled tool steel will expand across more applications and utilize more scrap.

Promoting research, collaborating across the supply chain, and investing in advanced capabilities will be pivotal to realize the full potential of tool steel recycling.

Case Studies in Tool Steel Recycling

To illustrate tool steel recycling further, here are some real-world examples and case studies:

Kennametal’s Tool Steel Recycling Program

Kennametal, a major tooling manufacturer, operates an internal program to collect, clean, and recycle worn tungsten carbide tooling scrap into new tool steel. This closes the material loop and significantly lowers their tooling material costs.

Optimizing Cutting Tool Recycling

An aerospace parts maker analyzed their manufacturing operations to identify procedures that maximized material utilization and tool life. They achieved a 70% reduction in cutting tool scrap generation, allowing more of their carbide and tool steel waste to be recycled.

Automated Scrap Metal Sorting Facility

A metals recycling company installed an automated scrap sorting system using X-ray fluorescence, optical sensors, and AI-based object recognition. The technology boosted identification accuracy and quadrupled their annual scrap tool steel recovery rates.

Closed-Loop Recycling of Stamping Die Waste

A auto part stamping plant implemented processes to capture all their die scrap, segregate by alloy, and remelt it onsite into new tool steel feedstock billets. This reduced their die steel purchases by 80% and cut facility emissions.

Recycled Tool Steel for Plastic Injection Molds

A plastic parts manufacturer qualified recycled H13 tool steel from scraps and defective molds to build new injection molds, rather than purchasing new tool steel. This lowered their mold costs by 15% with no loss in performance.

These examples highlight the proven value – both economic and environmental – in maximizing tool steel recycling in manufacturing operations.

Key Takeaways on Tool Steel Recyclability

To summarize the key points on enhancing sustainability through improving the recyclability of tool steel:

• Tool steel’s properties like hardness, strength, and heat resistance make it vital for durable manufacturing tools and dies across industries.
• Recycling tool steel scrap provides major benefits including reduced emissions, energy savings, resource conservation, and costs savings versus primary production.
• However, various challenges like contamination, inconsistent properties, and inventory issues, hinder achieving higher tool steel recycling rates currently.
• Opportunities exist to improve recyclability through strategies like design for recyclability, closed loop practices, education, advanced sorting processes, and cross-supply chain collaboration.
• Emerging technologies and continued focus on sustainable manufacturing will drive further improvements in tool steel recycling rates and process efficiency in the future.
• With concerted effort, the recyclability of tool steels can be enhanced to support competitive and environmentally-responsible manufacturing.

Conclusion

Tool steel is a critical material that enables durable and high-performance metal manufacturing across many industries. However, tool steel production has a significant environmental footprint. Recycling of tool steel scrap into new stock provides major sustainability benefits and cost savings versus primary production.

While current recycling rates are reasonable, challenges remain to improve recyclability. Addressing factors like contamination, inconsistent properties, and process economics through technological and supply chain initiatives will be key to maximize tool steel recycling. With the rising emphasis on circular manufacturing principles, tool steel recyclability will continue growing in importance in the future. An increased focus across the design, production, and recycling of tool steel components can lead to reduced environmental impact and secure access to affordable materials for essential manufacturing applications.

Frequently Asked Questions on Tool Steel Recyclability

What are the main alloying elements used in tool steels?

The primary alloying elements in tool steel include tungsten, molybdenum, chromium, vanadium, and cobalt. These enhance properties like hardness, toughness, heat resistance, and machinability.

What are some examples of manufacturing tools made with tool steel?

Typical uses of tool steel include cutting tools, metal stamping dies, plastic injection molds, extrusion dies, rolling mill rolls, punch and blanking dies, and metal forming tools.

How is tool steel scrap recycled?

Key steps in tool steel recycling are collection, sorting by alloy type, shredding, melting and re-alloying, refining, recasting, and heat treatment to finish properties. This converts scrap back into usable tool steel.

What are challenges currently limiting tool steel recyclability?

Challenges include contamination during recycling, inconsistent final properties, high collection and processing costs, difficulty identifying alloys, limited applications for recycled products, and lack of recycling standards.

How can the recyclability and sustainability of tool steels be improved?

Strategies include design for recyclability, process optimization, employee education on recycling, stronger information management and tracking, advances in sorting and analysis, closed-loop practices, cross-industry collaboration, and emerging recycling technologies.

Why is tool steel recycling important for manufacturers?

Tool steel recycling provides substantial cost savings, energy and emissions reductions, resource conservation, supply security, and support for circular economy goals compared to primary production. This makes it an important sustainability strategy.

What does the future look like for tool steel recycling in manufacturing?

The future outlook is positive, with expected growth in automated intelligent sorting, real-time alloy analysis during remelting, high-performance tool steel development, novel reconditioning techniques, and increased adoption of recycled tool steel across more applications.