Tool Steels: Processing of tool steels materials and
They are noble steels used for shaping.

The tool should often be harder, higher strength and wear resistant than the material it is machining. Therefore, the materials used for tool manufacturing should have as high hardness and strength as possible, but with sufficient ductility, in accordance with the conditions of their use, except for a few privileges. Especially in tools that are doing separation work, forming and changing form, impact or impact force, very high hardness, good wear resistance and together with these, high ductility and safety against breaking with the highest hardness that can be reached are required.

The most important factor in characterizing the usage characteristics of a tool is the hardness determined by Rockwell or Vickers methods. Hardness can also be measured by the bounce-back method when the print element traces are not desired on the surface. Knoop hardness measurement method can also be used for very hard and brittle materials. Although the elasticity limit, yield limit or 0.2 limit, tensile strength, elongation at break and shrinkage values ​​determined by the tensile test can be taken as criteria in evaluating the strength and deformability in the materials for the tools, the tool materials are hardly up to breakage. As little plastic deformation occurs, these are not sufficient to identify the material. Better evaluation of the mechanical properties can be made by determining the bending strength of 0.1, which is determined by the static bending test, and the elastic and plastic form change work. Torsion (torsion) and impact torsion tests can also be used to test tool materials in accordance with practical conditions. Although the life of the tool is determined by separating it from the breakage hazard, determining the quantitative value for ductility and fracture resistance creates problems.

To date, ductility is often determined on the basis of work up to fracture, in relation to the yield point and the breaking strength in bending. Accordingly, the ductility grades can be qualitatively classified as follows:

Fragile: Low strength, less plastic deformation work
Ductile soft: Low strength, high plastic deformation work
Ductile hard: High strength, high plastic deformation work

The determination of the ductility state of the high hardness material has been made mostly by impact bending and static bending tests on unnotched and notched samples until today. However, by improving fracture mechanics, new possibilities for characterizing ductility on fracture toughness base are also given for relatively fragile tool materials. Thus, the definition of this material characteristic as resistance to non-invasive crack expansion can also correlate with wear conditions.

The strength and life of the separating tools are determined primarily by the wear at the contact point between the tool and the material. Since temperatures up to 1000 ° C may arise during machining, thermal stresses as well as mechanical stresses also affect the wear mechanism. Thus, microscopic adhesion erosion and crack formation occur as a result of the adhesion that develops together with the decrease in thermal resistance and the rupture of the shear material.

Cutting edge wear seen in the rounding of the cutting edges is seen in cowhide very unalloyed and low alloyed steels. The formation of the wear surface, whose width is defined as the wear mark "B", is characterized as flank wear. Rarely, there is wear on the rake face, called rake face wear. This wear form is seen in the form of pitting wear (cratering - pitting), especially in tools made of speed steels and hard metals. Besides cutting, small flat craters are formed that deepen with the continuation of the cutting time and slide in the direction of the cutting edge, which causes rapid destruction and blinding.

As the wear definition size, the depth of the groove on the free surface and the distance of the groove axis to the cutting edge (Figure 155) are important. To determine this, a machining formability test is required. For this purpose, wear characteristic test is performed, in which the wear mark width B ‘is determined depending on the cutting time or cutting path. Acceptable wear mark width is dependent on material, type of tool, and economic viewpoint. At the very beginning, the optimization of the machining 'shaping method can be done by directly measuring the excess during the operation process.

In addition to demanding a good resistance against abrasive wear, a high strength with sufficient ductility is expected from the tools that make forming or changing form in the material. When using hot work tool steels for high temperature forming, they must withstand both mechanical and thermal stress. Except for good hardness and heat resistance, oxidation result 

They must have sufficient thermal resistance, which is expressed with sensitivity to tumble resistance and burning and hot cracking. If the tool is subjected to excessive temperature changes in the periodic workflow, such as die casting molds and forging molds, combustion cracks may occur. In direct contact with the heated material, the tool surface suddenly heats up and expands in a fraction of a second. Due to the less expansion of the colder layers inside the tool material, compression stresses occur, and the reverse situation occurs by generating tensile stress in the subsequent cooling. As a result of the elastic-plastic deformations associated with this, reticulated surface cracks occur (attrition wear). In addition to combustion cracks, especially in deep-grooved tools, cross-section changes and inner edges, hot cracks that also penetrate into the tool occur. The measure for susceptibility to cracking, which is also referred to as shock-heating resistance, is the notch impact strength and the heat flow limit as well as the heat conductivity and expansion coefficient of the material. In addition, for the estimation of tool behavior under operating conditions, it should be taken into account that there are often long lasting strains due to mechanical vibration or temperature effects. In such cases, continuous vibration resistance or time-continuous resistance of the material is determined.

For die cutting and measuring tools, dimensional stability is also important. This event includes both the change in size, which cannot be prevented as a result of the change in form due to thermal stresses and transformation events during heat treatment, which is defined as change in size, and the changes in the form that can not be corrected in the heat treatment that is not done in accordance with the rule. Dimensional variations can be studied very complex and depend on the amount of alloy, heat treatment technology, and tool form and size.

It is very important that the melting, alloying and heat treatment technology of tool or work steels change within wide limits and meet very different demands with this. Conventionally, steels can be classified in the following style:

Unalloyed tool steels
Alloyed cold work steels
Hot work steels
Speed ​​steels

There is no clear boundary between construction and tool steels in terms of chemical composition. For example, a steel containing the same amount of chromium can be used for both rolling bearing (Section 9.6.I.) and cold rolling mill. On the other hand, the case hardening steels described in Section 5.6 are the most important materials for tools used in the processing of high polymers.

In addition to steels, cast hard alloys, sintered hard metals and oxide ceramics, hard casting, diamond (diamant) and synthetic hard materials are also used. Non-ferrous metals and alloys can only be used in special places: For example, nickel-based hot cutting blade and injection molding, Cu-Be alloy spark-free inserts.

Since tool steels are important for nearly all machining methods, besides the introduction of materials, their production and machinability are explained below. In addition, in addition to the heat treatment information specified in Chapter 4, additional information that is important for tool steels is also given.

MELTING AND SHAPING
Tool steels are principally produced as noble steels and more commonly in basic arc furnaces. The most important approach for good quality is to use clean scrap containing small amounts of Cr, Ni and Cu. The production of high quality tool steel, where melting is performed under vacuum, in electron bombarded multi-chamber furnace (EMO) and under slag melting (ESU) fashion, is also becoming widespread. In the EMO method, the improvement of the cattle is achieved by solidification in the crystallizer cooled with low pressure and water, while in the ESU method, it is achieved by the refining of the reactive slag from which the steel drops. The structure of ui-pure (UA) steels produced in this manner is void-free, bubble-free, non-porous and seed-free, and due to little tendency to precipitate, they show better chemical homogeneity. The good core properties obtained in this way are particularly beneficial for large sized tools. Another advantage of ultra-moment steels is the significantly reduced amount of gas. Thus, by reducing the oxygen content to about 70% and the nitrogen content to 30 to 50% in the EMO method. By also reducing the amount of sulfur, the amount of non-metallic bonding is greatly reduced, and the degree of microscopic purity is significantly improved. In addition, when re-flushed under vacuum, easily volatile elements such as Pb, Bi, Sb and As, which reduce hot formability and hot ductility, can also be completely removed from the steel. Polishability in the tool manufacturing process from ultra-refined steels (production of high polymer materials and cold rolling tools), improved abrasion resistance (increased hot wear resistance) and elevated hot weathering 

The plurality (reduced yanniî es: U ~ danger) is of great importance. The lifetime of tools made of ultra-an steel is 20 to 100% higher than that of conventionally produced steels, depending on the tool type and j.srr conditions.

The determination of the ductile state of the high hardness material has been made mostly by impact bending and static bending tests on unnotched and notched samples. However, by improving fracture mechanics, new possibilities for characterizing ductility on some fracture toughness Kje (See Section 7.2.3.) Are also given for relatively fragile tool materials. Thus, the definition of this material characteristic as resistance to non-invasive crack expansion can also correlate with wear conditions.

With an additional development of the I SiS method, the appearance of crystal separations was also prevented and the steels were given isotropic properties. As a result of providing a single phase structure, it rises in the direction perpendicular to the rolling direction, improves rupture strength and reduces notch sensitivity in multi-axis stress situations. Cold work and hot work tool steels produced according to this method have two to three times higher life.

After the billets are cast, they are processed again by rolling or forging. Care should be taken to maintain the hot forming temperature exactly, as cementite mesh may form in high carbon steels and black fracture may occur at low temperatures.
Materials produced by cast steel or investment casting are preferred only to a limited extent, as they can be economical for tools produced in large numbers. If steel casting is used, the strength and wear resistance of the tool in heat increases and better isotropy is provided in mechanical properties.

The strength and life of the separating tools are determined primarily by the wear at the contact point between the tool and the material. Since temperatures up to 1000 ° C may arise during machining, thermal stresses as well as mechanical stresses also affect the wear mechanism. Thus, microscopic adhesion erosion and crack formation occur as a result of the adhesion that develops together with the decrease in thermal resistance and the rupture of the shear material. The characteristic wear views for the turning tool are seen in Figure 154.

Cutting edge wear seen in the rounding of the cutting edges is seen in cowhide very unalloyed and low alloyed steels. The formation of the wear surface, whose width is defined as the wear mark "B", is characterized as flank wear. Rarely, there is wear on the rake face, called rake face wear. This wear form is seen in the form of pitting wear (cratering - pitting), especially in tools made of speed steels and hard metals. Besides cutting, small flat craters are formed that deepen with the continuation of the cutting time and slide in the direction of the cutting edge, which causes rapid destruction and blinding.

As the wear definition size, the depth of the groove on the free surface and the distance of the groove axis to the cutting edge (Figure 155) are important. To determine this, a machining formability test is required. For this purpose, wear characteristic test is performed, in which the wear mark width B ‘is determined depending on the cutting time or cutting path. Acceptable wear mark width is dependent on material, type of tool, and economic viewpoint. At the very beginning, the optimization of the machining 'shaping method can be done by directly measuring the excess during the operation process.

EFFECT OF ALLOY ELEMENTS
With the addition of the alloying element, the properties of tool steels can be changed to multiple layers. Alloy elements dissolved in iron cage or added for special carbide formation improve hardenability, temper strength, hardness, strength, ductility and wear resistance to a different extent. In summary, the special effect of each of the major alloying elements in tool steels is as follows:

Carbon: With sudden cooling hardening, it is possible to reach a hardening depth of 1 to 4 mm in alloyed steels. Above I% carbon, the highest achievable hardness is constant, but with increasing carbide the wear resistance gradually increases.

Manganese: Increases hardenability due to the decrease in conversion rate and thus provides hardenability in larger cross-sections. However, it also makes the grain coarse and causes tempering brittleness. There is a tendency for cold hardening, which increases the wear resistance in impact and compression forces.

Silicon; It increases resistance to oxidation, but also increases the tendency to decarburize.
Due to the increase in elasticity limit, silicon alloy steels are used for tools with good spring properties. In Hot Work tool steels, the adhesion tendency is reduced with the amount of 1% SI.

Chromium: It decreases the critical cooling rate and thus increases the hardenability. Since special carbides are formed, wear resistance 

increases resistance to cold. It is one of the most important alloying elements in tool steels.

Tungsten: It acts as a grain thinner, reduces sensitivity to overheating and produces special hard carbides that improve wear resistance, heat resistance and tempering strength. The downside is that it decreases the heat conducting capability and, in turn, increases the tendency to crack formation in heat treatment.

Molybdenum: It prevents temper brittleness and increases the hardness, wear resistance and temper strength as a strong carbide maker.

Vanadium: As a result of the formation of hardly soluble carbides, it prevents grain growth at high austenitization temperatures and increases wear resistance. Hence, the polishability of the tool deteriorates with high vanadium amounts.

Cobalt: Increases the solubility of carbide-forming elements in austenite and also increases the heat resistance, hot hardness, temper strength and heat conductivity.

Nickel: It improves the hardening depth and refines the grain. The addition of nickel is particularly important in increasing the ductility of tools working with impact and impact forces.

In addition to demanding a good resistance against abrasive wear, a high strength with sufficient ductility is expected from the tools that make forming or changing form in the material. When using hot work tool steels for high temperature forming, they must withstand both mechanical and thermal stress. Apart from good heat hardness and heat resistance, they should have sufficient thermal resistance, expressed in sensitivity to tumble resistance resulting from oxidation and against burning and hot cracking. If the tool is subjected to excessive temperature changes in the periodic workflow, such as the die-casting die and the forging die, combustion cracks may occur. In direct contact with the heated material, the tool surface suddenly heats up and expands in a fraction of a second. Due to the less expansion of the colder layers inside the tool material, compression stresses occur, and the reverse situation occurs by generating tensile stress in the subsequent cooling.

Team Steel FEATURES
Hardenability A certain hardness ability after hardening.
Abrasion Resistance Resistance to abrasion at room temperature or higher
Toughness Resistance to breaking with force
Hot Hardness and
Strength Hardness or strength does not change at room temperature Ability to hold significantly at higher (red) temperatures
Temper Permanence Little decrease in hardness at high tempering temperatures
Size Retention Uncontrollable dimensional changes during hardening.

What is Team Ceiling?
Tool steels are high-quality steels that form the workpiece in hot or cold state using one or more of the cutting, forging and compression methods used in machining or non-machining.

usage areas

Cutting tools, Drawing tools, Machining tools (for processing ferrous or non-ferrous metals), Gear sets, Machine knives, Hand tools.