Alatni čelik: Ocjene, Properties and Applications

Tool steel is at the heart of modern manufacturing, where precision and durability are desired and demanded.

It is a specialized type of steel designed to withstand the rigors of manufacturing and industrial processes.

Known for its exceptional hardness, otpornost na habanje, and strength, tool steel is crucial in various industries, from automotive and aerospace to electronics and consumer goods.

This article delves into tool steel’s types, nekretnine, i aplikacije, offering insights into its significance and the factors to consider when selecting the right grade for your needs.

1. What is Tool Steel?

Tool steel is a specialized category of carbon and alloy steels, designed specifically for the manufacture of tools. Here’s what makes it unique:

• Ugljik is the backbone of tool steel, contributing to its hardness and strength. Obično, tool steels contain between 0.7% do 1.5% carbon.
• Legirani elementi like chromium, tungsten, molibdenum, and vanadium are added to enhance specific properties:

• • Hrom povećava otvrdljivost, otpornost na habanje, i otpornost na koroziju. Na primjer, steels like D2 can contain up to 12% hrom.
  • Tungsten and Molybdenum enhance toughness and heat resistance, crucial for high-speed and hot work applications. M2 steel, a common high-speed steel, has around 6% tungsten.
  • Vanadijum forms hard carbides, improving wear resistance. AISI A11, na primjer, contains 1.5% vanadium.

The history of tool steel traces back to the late 19th century when the need for more durable tools led to the development of high-speed steels.

S vremenom, the evolution of tool steel has seen the introduction of various grades, each tailored for specific applications:

• W1, W2 (Water-hardening steels): Jednostavan, low-cost options for basic tools, often containing 0.90-1.40% carbon.
• A2, D2, O1 (Cold work steels): Designed for applications where the tool doesn’t get hot, with A2 offering high wear resistance due to its 5% chromium content.
• H13, H19 (Hot work steels): These can withstand temperatures up to 1200°F, with H13 containing 5% chromium and 1.5% molibdenum.

2. Types of Tool Steel

Tool steel is a versatile category of steel, each type crafted to meet specific industrial needs through a unique combination of alloying elements and heat treatments.

Here’s a detailed exploration of the different types:

Poređenje tabele: Tool Steel Types

Vrsta	Ključne karakteristike	Aplikacije
W-Type (Water-Hardening)	Isplativ, high-hardness	Hand tools, woodworking tools
Hladni rad (O, A, D)	High wear resistance, dimenziona stabilnost	Stamping dies, trimming tools, slitting knives
S-Type (Shock-Resisting)	Visoka žilavost, Otpornost na udarce	Dleta, jackhammer bits, udarci
H-Type (Hot Work)	Thermal fatigue resistance, visoka čvrstoća	Die-casting molds, hot forging tools
HSS (M, T)	Heat resistance, high cutting speeds	Bušilice, krajnji mlinovi, precision cutting tools
Special Purpose	Tailored for specific tasks	Plastic molds, niche industrial tools

3. Properties of Tool Steel

Tool steel’s properties are what make it indispensable in the world of manufacturing and tool-making. Here’s an in-depth look at the key properties:

Hardness and Toughness:

• • Tvrdoća: Tool steel’s hardness is its ability to resist indentation, scratching, or deformation. This property is critical for tools that need to maintain a sharp cutting edge or resist wear. Na primjer:

• • • D2 steel can achieve a Rockwell C hardness of 57-62, making it ideal for applications requiring high wear resistance.

• • Žilavost: While hardness is essential, toughness ensures that the steel can absorb energy without fracturing. A balance between hardness and toughness is crucial:

• • • A2 steel offers a good balance, with a hardness of 55-59 HRC after tempering, but with higher toughness compared to D2, making it suitable for tools that experience impact loads.

Otpornost na habanje:

• • This property is vital for tools that undergo abrasive wear, like cutting tools, umire, and punches.
    The presence of hard carbides, formed by elements like chromium, vanadium, and tungsten, significantly enhances wear resistance:

• • • High-speed steels like M2, sa 6% tungsten and 5% molibdenum, can retain their edge even after prolonged use due to the formation of hard carbides during heat treatment.

Heat Resistance:

• • For tools operating in high-temperature environments, heat resistance is key to prevent softening or distortion:

• • • Hot work tool steels like H13 maintain 90% of their hardness at 1100°F, making them suitable for die casting, kovanje, and extrusion where the tool encounters high temperatures.

Obratnost:

• • Some tool steels are designed to be machined with relative ease, reducing tool wear during shaping processes:

• • • O1 steel is known for its good machinability, making it easier to shape into complex forms before hardening.

Stabilnost dimenzija:

• • Precision tools require materials that maintain their shape under stress or temperature changes:

• • • A2 steel has excellent dimensional stability, ensuring that tools like gauges and measuring instruments maintain their accuracy over time.

Additional Properties:

• Otpornost na koroziju: Some tool steels, particularly those with higher chromium content like stainless tool steels, offer resistance to rust and corrosion,
  which is crucial for tools used in humid or corrosive environments.
• Toplotna provodljivost: This property affects how heat is transferred through the tool, influencing cooling rates and thermal expansion:

• • H13 steel has relatively high thermal conductivity, which helps in dissipating heat during hot work applications.

• Fatigue Resistance: Tools that undergo cyclic loading benefit from steels with high fatigue resistance:

• • S7 steel excels in this regard, making it suitable for tools subjected to repeated impacts.

• Modul elastičnosti: This measures the steel’s stiffness, indicating how much it will deform under load:

• • High-speed steels generally have a higher elastic modulus, allowing them to maintain their shape under cutting forces.

Balancing Properties:

• Trade-offs: Achieving an optimal balance between these properties is often a challenge. Na primjer:

• • Increasing hardness usually decreases toughness, making the steel more brittle.
  • Enhancing wear resistance might compromise machinability.

• Toplotni tretman: The properties of tool steel can be significantly altered through heat treatment:

• • Gašenje increases hardness but can make the steel brittle if not followed by tempering.
  • Kaljenje reduces brittleness by allowing some of the martensite to transform into tougher microstructures but at the cost of some hardness.

• Legirani elementi: The addition of specific elements like chromium, tungsten, molibdenum, and vanadium tailors the steel’s properties:

• • Hrom enhances hardenability, otpornost na habanje, i otpornost na koroziju.
  • Vanadijum forms hard carbides, improving wear resistance.
  • Tungsten and Molybdenum increase toughness and heat resistance.

Rezime Tabela: Key Properties of Tool Steel

Nekretnina	Opis	Key Grades
Tvrdoća	Resistance to deformation under pressure	D2, O1, H13
Žilavost	Ability to withstand impact without cracking	S7, A2
Otpornost na habanje	Longevity under abrasive conditions	D2, M2
Heat Resistance	Retains properties at high temperatures	H13, H21
Obratnost	Ease of cutting and shaping	O1, A2
Stabilnost dimenzija	Minimal distortion during use or heat treatment	A2, H13
Otpornost na koroziju	Resistance to oxidation and rust	A2, D2
Impact Resistance	Withstands heavy mechanical shocks	S1, S7
Toplotna provodljivost	Efficient heat dissipation during operation	H-series
Fatigue Resistance	Performance under repeated stress cycles	O-series, S-series

4. Heat Treatment of Tool Steel

Heat treatment is a critical process in tool steel manufacturing, transforming the steel’s microstructure to develop the desired mechanical properties.

Here’s a detailed look at the heat treatment processes:

Importance of Heat Treatment:

• • Heat treatment enhances tool steel’s hardness, žilavost, i otpornost na habanje, tailoring these properties to suit specific applications.
    Na primjer, a drill bit requires high hardness to cut effectively, while a hammer needs toughness to withstand impacts.

Basic Heat-Treating Processes:

• • Gašenje: This involves heating the steel to a temperature above its critical transformation point, followed by rapid cooling in a quenching medium like water, ulja, or air.
    The rapid cooling traps carbon in a hard, brittle martensite structure. Na primjer, O1 steel might be quenched in oil to achieve a hardness of 60-64 HRC.
  • Kaljenje: Nakon gašenja, the steel is brittle. Tempering involves reheating the steel to a lower temperature, typically between 300°F to 600°F, to reduce brittleness while maintaining some of the hardness.
    Tempering at 400°F for A2 steel, na primjer, can yield a hardness of 55-59 HRC with improved toughness.
  • Case Hardening: This process adds a hard, wear-resistant outer layer while keeping the core tough.
    It’s done by carburizing, nitrizam, or cyaniding, where carbon or nitrogen atoms diffuse into the surface layer. M2 steel can achieve a surface hardness of over 70 HRC through this method.
  • Kriogeni tretman: Beyond traditional heat treatments, cryogenic treatment involves cooling the steel to very low temperatures (often below -300°F)
    to further enhance hardness and wear resistance by reducing retained austenite, a softer phase in steel.

Effects of Heat Treatment:

• • Tvrdoća: Heat treatment significantly increases the steel’s hardness, making it capable of maintaining a sharp edge or resisting indentation.
    Na primjer, D2 steel can achieve a Rockwell C hardness of 57-62 after proper heat treatment.
  • Žilavost: While hardness is increased, toughness can be compromised if not properly balanced.
    Tempering is crucial here, as it reduces brittleness by allowing some of the martensite to transform into tougher microstructures like tempered martensite.
  • Otpornost na habanje: The formation of hard carbides during heat treatment, especially in high-speed steels, greatly improves wear resistance,
    allowing tools to cut or form materials for extended periods.
  • Stabilnost dimenzija: Proper heat treatment ensures that tools maintain their shape under stress or temperature changes,
    which is vital for precision tools like gauges and measuring instruments.

Ključna razmatranja:

• Heat Treatment Atmosphere: The atmosphere during heat treatment can affect the steel’s properties.
  Na primjer, a nitrogen-rich atmosphere can enhance surface hardness through nitriding.
• Quenching Medium: The choice of quenching medium affects the cooling rate and, samim tim, the final properties of the steel.
  Water provides the fastest cooling rate, but oil or air might be used for less distortion and cracking.
• Kontrola temperature: Precise control of heating and cooling temperatures is essential to achieve the desired properties without introducing defects like cracking or warping.
• Post-Heat Treatment: After heat treatment, tools often undergo additional processes like stress relieving,
  which can reduce internal stresses, or surface treatments like coating or polishing to further enhance performance.

5. Applications of Tool Steel

Alati za rezanje

• Bušilice: Used for creating holes in various materials. High-speed steel (HSS) bušilice, such as M2, are commonly used for drilling hard metals.
• Reamers: Used to enlarge and smooth existing holes. HSS reamers provide precise and smooth finishes.
• Saw Blades: Used for cutting wood, metal, and other materials. Cold work tool steels like D2 are often used for saw blades due to their high wear resistance.

Dies and Punches

• Stamping: Used to form sheet metal into specific shapes. Cold work tool steels like D2 and A2 are ideal for stamping dies due to their high hardness and wear resistance.
• Kovanje: Used to shape metal by compressing it under high pressure. Hot work tool steels like H13 are suitable for forging dies due to their excellent heat resistance.
• Ekstruzija: Used to force metal through a die to create specific cross-sectional profiles.
  Hot work tool steels are often used for extrusion dies due to their ability to withstand high temperatures.

Kalupi

• Injection Molding: Used to produce plastic parts by injecting molten plastic into a mold.
  Special-purpose tool steels like P20 and 718 are commonly used for injection molds due to their good polishability and corrosion resistance.
• Die Casting: Used to produce metal parts by forcing molten metal into a mold. Hot work tool steels like H13 are ideal for die-casting molds due to their high strength and heat resistance.

Gauges and Measuring Instruments

• Calipers: Used to measure the dimensions of objects. Cold work tool steels like A2 are often used for calipers due to their dimensional stability.
• Micrometers: Used to measure precise distances. Cold work tool steels with high dimensional stability are ideal for micrometers.
• Gauges: Used to check the dimensions of parts. Cold work tool steels like D2 are commonly used for gauges due to their high wear resistance.

Mining and Oil Well Tools

• Drill Bits: Used to drill holes in rock and soil. High-speed steels like M2 are often used for drill bits due to their ability to cut at high speeds.
• Downhole Tools: Used in oil and gas extraction. Hot work tool steels like H13 are suitable for downhole tools due to their excellent heat resistance and strength.

Other Tools

• Noževi: Used for cutting various materials. Cold work tool steels like D2 and A2 are often used for knives due to their high hardness and wear resistance.
• Scissors: Used for cutting paper, fabric, and other thin materials. Cold work tool steels like A2 are ideal for scissors due to their balance of hardness and toughness.
• Dleta: Used for carving and shaping wood and stone. Shock-resisting tool steels like S7 are suitable for chisels due to their high toughness and ability to withstand impact.

6. Selecting the Right Tool Steel

Factors to Consider

• Type of Operation: Cutting, formiranje, or other specific operations.
• Uslovi rada: Temperatura, stres, and environmental factors.
• Material Being Worked On: The properties of the material being processed.
• Cost vs. Performance Analysis: Balancing the cost of the tool steel with the performance requirements.

Guide on How to Choose Based on Specific Needs

1. Identify the Application: Determine the specific use of the tool.
2. Assess Operating Conditions: Evaluate the temperature, stres, and environmental factors.
3. Consider Material Properties: Understand the properties of the material being worked on.
4. Evaluate Cost and Performance: Compare the cost of different tool steels with their performance benefits.
5. Consult Experts: Seek advice from metallurgists or tool steel suppliers to ensure the best selection.

8. Challenges and Considerations

Trošak

• Expensive Material: Tool steel can be costly, especially for high-performance grades.
  Međutim, the initial investment often pays off in terms of longer tool life and reduced downtime.
• Economic Impact: Consider the overall cost-effectiveness of using tool steel in your application.
  Na primjer, while D2 steel may be more expensive than W1 steel, its superior wear resistance can lead to lower maintenance costs over time.

Održavanje

• Regular Inspection: Regularly inspect tools for signs of wear and damage to prevent unexpected failures.
• Proper Storage: Store tools in a dry, controlled environment to prevent rust and corrosion. Proper storage can extend the lifespan of your tools.
• Cleaning and Lubrication: Clean and lubricate tools to maintain their performance. Regular maintenance can significantly improve the longevity of your tools.

Uticaj na životnu sredinu

• Recycling: Consider recycling old tool steel to reduce waste and environmental impact. Many tool steel manufacturers offer recycling programs.
• Disposal: Follow proper disposal guidelines to minimize environmental harm. Proper disposal ensures that hazardous materials are handled safely.

9. Budući trendovi

Advances in Tool Steel Metallurgy

• New Alloys: Development of new alloys with enhanced properties, such as improved wear resistance and heat resistance.
  Na primjer, researchers are exploring the use of nanotechnology to create ultra-fine grain structures in tool steels.
• Microstructure Control: Advanced techniques for controlling the microstructure of tool steel to optimize performance.
  Microalloying and controlled cooling rates are being used to achieve specific microstructures.

Development of New Alloys or Treatments

• Površinski tretmani: New surface treatments to enhance wear resistance and corrosion resistance. Plasma nitriding and diamond-like carbon (DLC) coatings are gaining popularity.
• Aditivna proizvodnja: Use of 3D printing to create complex tool steel parts with precise geometries.
  Additive manufacturing allows for the creation of intricate designs that are difficult to achieve with traditional manufacturing methods.

10. Zaključak

Tool steel is a vital material in manufacturing and industry, offering exceptional hardness, otpornost na habanje, and strength.
Understanding the different types of tool steel, their properties, and their applications is crucial for selecting the right material for your specific needs.
By considering factors such as the type of operation, operating conditions, i svojstva materijala, you can make informed decisions that ensure optimal performance and cost-effectiveness.
As technology continues to advance, the future of tool steel looks promising, with new alloys and treatments enhancing its capabilities even further.

We hope this article has provided valuable insights into the world of tool steel and encourages you to explore its potential in your projects.
If you have any questions or need further assistance, feel free to reach out to us.