Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/24—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for saw blades
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the present invention is about a kind of steel to be used in cutting tools and machining of metals and other materials.
• the steel at issue has a composition which classifies it as a high speed-type tool steel, with its main feature being the use of a lower content of noble alloy elements, such as vanadium, tungsten and molybdenum, but with properties either equivalent or higher than those of less alloyed conventional high-speed steels and slightly inferior to those of more alloyed conventional high-speed steels.
• noble alloy elements such as vanadium, tungsten and molybdenum
• Cutting tools are applied in a large number of cutting and machining operations. Some examples are cutting operations' in tape, automatic or manual saws, drilling, turning, tapping, milling, . ; among other forms of machining steel, nonferrous alloys or other solid materials.
• An important example of operation for which the present invention is intended are saws, used in machines or saws for manual cutting, and both can be used under the hard form, entirely in high-speed steel, or bimetallic, with only the areas of high-speed steel teeth and the others made of low alloy mechanical construction steel.
• Other cutting tools typically employ high-speed steels and they may be made of the steel in the present invention, among them: helicoidal drills, top millings, profile tools, tacks, bit and special drills for high-resistance materials.
• thin cutting tools such as taps, dies and special mills.
• the same high-speed steels employed on those tools may be used as conforming tools.
• Examples are punches, tools for cold forging, blanking dies and plate cutting, coining dies, dies for conforming of postmetallic or ceramic, inserts and other tools for hot and warm forging, as well as tools in other applications in cold, warm or hot conforming, in which the conformed material has temperatures reaching up to 1300 0 C.
• Steels traditionally used in cutting tools are high-speed steels, whose main feature is high resistance to wear and preservation of hardness at high temperatures. Typical examples are the steels of series AISI M or AISI T, being steels AISI M2, M7 and Tl highlighted.
• alloyed steels may be used for less demanded tools; the main steels are DIN 1.3333 and steels AISI M50 and M52.
• Table 1 The chemical composition of such steels is shown in Table 1 , in which emphasis must be placed on tungsten, molybdenum and vanadium, which contribute with a large share to the final cost of the alloy.
• Table 2 The effect of these elements on the cost is presented in Table 2, as normalized by the cost of alloys in December 2005.
• the advantage of less alloyed steels over conventional steels is clear according to these amounts, in terms of alloy cost. • , : . . . Therefore, high-speed steels always had a. strong impact on ,. their cost associated with the. costs of raw materials (alloy. elements).
• Table 1 3% V steels comprehended in the Art (ET). Only the main allo elements are resented in mass ercenta e and balance in iron.
• the steel of the present invention meets such requirements.
• the objective of the invention was first of all to study the influence of silicon, aluminum and niobium elements in a composition with a low content of vanadium, molybdenum and tungsten.
• the important effect of niobium was identified in this study, however not sufficient to evolve hardness towards the levels necessary.
• Aluminum and especially silicon elements were then employed in the steel of the present invention, showing a significant effect.
• the definition of the contents of these elements and their adequate working range promotes, therefore, the reduction of costs and the achievement of the properties intended in the material. Such ranges are described and the effect of each element is outlined below.
• the steel of the present invention has a composition of alloy elements that, in mass percentage, consists of:
• 0.5 to 1.5 C preferably 0.8 to 1.1 C, typically 0.87 C.
• 1.0 to 7.0 C preferably 3.0 to 5.0 C 1 typically 4.0 C.
• Nb 0.5 to 3.0 Nb, preferably 0.8-1.8 Nb, typically 1.2 Nb, and Nb may be partially or fully replaced with Zr, Ti, Ta or V, in a relation in which 1.0% of Nb corresponds to 0.5% V or Ti, and 1.0% Nb corresponds to 1.0% Zr or Ta.
• V 0.3 to 2.0 V, preferably 0.5-1.0 V, typically 0.7 V, and V may be partially or fully replaced with Nb, in a ratio in which 1.0% Nb corresponds to
• Si 0.3 to 3.5 Si, preferably 0.7 to 2.0 V, typically 1.0 Si, and Si may be partially or fully replaced with Nb, at the 1 :1 ratio.
• aluminum may be added to the steel of the present invention, promoting property advantages.
• compositions with no addition of aluminum can also be employed in the steel of the present invention, since it is easier in terms of alloy manufacture. Therefore, the aluminum content should be dosed as follows:
• Al at maximum preferably 0.5 Al at maximum, typically 0.2 Al at maximum for compositions with Al as residual element.
• Al should be treated as impurity.
• 1.5 Mn at maximum preferably 0.8 Mn at maximum, typically 0.5 Mn at maximum.
• 0.10 S at maximum preferably 0.020 S at maximum, typically 0.008 S at maximum.
• 0.1 N at maximum preferably 0.05 N at maximum, typically 0.5 N at maximum.
• 0.5 Ce at maximum or other rare-earth elements The elements of the lanthanoid or actinoid families in the periodic table, as well as La, Ac, Hf and Rf elements are considered rare-earth elements.
• the Ce content should be preferably lower than 0.1 and typically lower than 0.06.
• Carbon is the main responsible for the response to heat treatment and the formation of primary carbides. Its content should be lower than 1.5%, preferably 1.1% at maximum, so that the presence of austenite retained is not very high after quenching. This is important in- less alloyed steels, as the one of the present invention, because carbon tends to form less carbides of alloy elements, in the form of primaries and eutectics; thus, a higher content of free carbon is obtained after quenching, contributing to a significant increase in the fraction of retained austenite. However, the carbon content should be sufficient to form primary carbides, especially in combination with niobium, as well as secondary carbides during tempering and promote the hardening of martensite after quenching.
• the carbon content should not be lower than 0.5%, being carbon higher than 0.8% preferable.
• Cr The chromium content should be higher than 1%, preferably higher than 3%, because this element contributes to quenching characteristics and precipitation of secondary carbides during tempering and annealing. Together with carbon, chromium also determines the formation of M 7 C 3 -type primary carbides, which are not desirable for high-speed steels, since they reduce rectification capacity and toughness. Thus, the chromium content should be limited to 10%, preferably lower than 7%.
• W and Mo Tungsten and molybdenum have analog effects on high-speed steels, present especially in M2C- or M6C-type primary carbides and secondary carbides of the same type, being the latter formed during tempering or under gross solidification condition. Thus, they may be jointly specified through the equivalent tungsten relation (W eq ), given by the sum W + 2Mo, that normalizes the differences of atomic weight of both elements.
• W eq equivalent tungsten relation
• W eq equivalent tungsten relation
• W eq equivalent tungsten relation
• W eq the content of W eq should be lower than 10.0%, preferably lower than 8.0%.
• vanadium should have a function equivalent to the one described for molybdenum and tungsten-action on the secondary hardening, forming thin carbides at tempering. Vanadium also can form primary carbides, but this is not the main purpose of its addition to the steel in the present invention. Vanadium also has, further, a significant influence on the control of growth of austenitic grains, during austenitization. For such effects, vanadium should be higher than 0.3%, preferably higher than 0.5%. Since this is also an important agent in the alloy cost, the content of vanadium in the present invention should be lower than 2.0%, preferably lower than 1.0%.
• Niobium has an important effect for the steel of the present invention. This element forms mainly MC-type highly hard eutectic carbides and, therefore, they are important for resistance to the wear of the tools produced. Another interesting effect of niobium is that the MC carbides formed dissolve a little tungsten, molybdenum and vanadium, enabling these elements to be free, after austenitization and quenching, for secondary precipitation. Thus, the highspeed steel linked to niobium allows for the use of a lower amount of molybdenum, tungsten and vanadium and, therefore, this element operates significantly to reduce the alloy cost. However, its performance is ensured by the fraction of thin and highly hard MC carbides, formed by niobium.
• the content of niobium cannot be higher than 3%, because it forms primary and coarse carbides under these situations, hardly refined by the hot conforming process. So, an excessive content of niobium may harm toughness and rectification capacity of the alloy, in addition to increasing its cost. Therefore, the niobium content in the steel of the present invention should be between 0.5 and 3.0%, preferably between 0.8 and 1.8%.
• Si Silicon is one of the main element for the steel of the present invention.
• This element has an usually undesirable effect on both primary and secondary carbides of more alloyed high-speed steels.
• the increase in the volume of primary carbides is one of the main effects, harming the rectification capacity and the response to heat treatment, and the decrease in the resistance to tempering. This occurs for the effect of silicon on the volume of delta ferrite during solidification, and the reduction in the volume of high-stability MC- and MC2-type secondary carbides. So 1 it is not added higher than 0.5% in usual compositions.
• the steel of the present invention does not have negative problems as for the introduction of silicon, since it is a less alloyed steel. On the contrary, this element causes a significant increase in the temper hardness.
• the increase in silicon content in the steel of the present invention promotes the recovery and elevation of hardness, until values acceptable for high-speed steels.
• the content of silicon must be higher than 0.3%, preferably higher than 0.7%.
• the content of this element must be lower than 3.5%, since it reduces the austenitization range and causes an expressive hardening of ferrite when annealed.
• the content of silicon must be preferably lower than 2.0%
• Al The addition of aluminum is optional for the steel of the present invention. Slight property gains, such as resistance to tempering, may be achieved with content higher than 0.3%, preferably higher than 0.7%.
• Slight property gains such as resistance to tempering, may be achieved with content higher than 0.3%, preferably higher than 0.7%.
• aluminum in order to promote high hardening of ferrite, high reactivity in liquid steel and increase of ACi and AC 3 temperatures, aluminum must be lower than 3.5%, preferably lower than 2.0%. Even in content close to 1.0%, aluminum still causes these undesirable effects.
• the variatign of ACi and AC 3 temperatures makes the conditions for annealing of material especially difficult, requiring significantly higher temperatures.
• the reactivity of the liquid metal makes the works of steel mills and cleaning difficult, in term of nonmetallic inclusions of the end steel obtained.
• the steel of the present invention can be also produced with residual contents of aluminum. In this case, aluminum must be lower than 1.0%, preferably lower than 0.5%.
• Residuals Other elements, such as manganese, nickel and copper and those usually obtained as typical residuals from the preparation process of liquid steel, must be regarded as impurities, related to the process of deoxidation in steel mill or inherent to manufacturing processes. Therefore, the content of manganese, nickel and copper is limited to 1.5%, preferably lower than 1.0%. Elements such as phosphorus and sulfur segregate on grain contours and other interfaces. Thus, phosphorus must be lower than 0.10%, preferably lower than 0.5%, and sulfur must be lower than 0.050%, preferably 0.020% at maximum.
• the alloy can be produced in the form of products rolled or forged by whether conventional or special processes, such as powder metallurgy, spray conforming or continuous casting, in products such as wire rod, bars, wire, plates and strips.
• Figure 1 shows the fusion gross microstructure of the alloy in the art, ET1, showing the X-ray mappings of vanadium, tungsten and molybdenum elements. At the mapping, the higher the density of points, the higher the relative concentration of the chemical element. Microstructure obtained through scanning electronic microscopy (SEM), secondary electrons; X-ray mapping obtained through WDS.
• SEM scanning electronic microscopy
• Figure 2 shows the fusion gross microstructure of the alloy in the art, ET2, showing the X-ray mappings of vanadium, tungsten and molybdenum elements. At the mapping, the higher the density of points, the higher the relative concentration of the chemical element. Microstructure obtained through scanning electronic microscopy (SEM), secondary electrons; X-ray mapping obtained through WDS.
• SEM scanning electronic microscopy
• Figure 3 shows the fusion gross microstructure of the alloy in the present invention, PH , showing the X-ray mappings of vanadium, tungsten, molybdenum and niobium elements. At the mapping, the higher the density of points, the higher the relative concentration of the chemical element.
• Microstructure obtained through scanning electronic microscopy (SEM), secondary electrons; X-ray mapping obtained through WDS.
• Figure 4 shows the fusion gross microstructure of the alloy in the present invention, PI2, showing the X-ray mappings of vanadium, tungsten, molybdenum and niobium elements. At the mapping, the higher the density of points, the higher the relative concentration of the chemical element.
• FIG. 5 shows the fusion gross microstructure of the alloy in the present invention, PI3, showing the X-ray mappings of vanadium, tungsten, molybdenum and niobium elements. At the mapping, the higher the density of points, the higher the relative concentration of the chemical element.
• Microstructure obtained through scanning electronic microscopy (SEM), secondary electrons; X-ray mapping obtained through WDS.
• Figure 6 shows the alloy tempering curves.
• ET2 PH , PI2 and PI3 alloys curves for two austenitization temperatures were studied, identified at the right upper comer of each curve.
• ET1 alloy was compared to austenitization at 1200 0 C, since this is its usual austenitization temperature. Results for test specimens with approximately 15 mm of suction, submitted to austenitization at the temperature indicated, for 5 minutes at temperature, quenching in oil and double tempering for 2 hours.
• Figure 7 compares the size distributions of carbides for ET2, PH , PI2 and PI2 alloys, in a) absolute values and b) percentage.
• Table 2 shows the significant reduction in the elements of steel alloy of the present invention, which are converted into a lower cost alloy-as compared in Table 3, calculated for amounts of December 2005.
• the reduction which occurs from the steel of art ET1 to ET2 can be observed, as well as the reduction at the same proportion of steel ET2, since this is a less alloyed steel, for the steels of the present invention.
• the steel of this invention is a second step towards the reduction of alloy costs, concerning already existing less alloyed steels, such as steel ET2.
• the difference in alloy cost is twice as large.
• the ingot fusion was made at a close procedure for such five alloys, in a vacuum induction oven, and poured into iron cast moulds, resulting in a 55-kg ingot. After solidification, the ingots were subcritically annealed and such five compositions were initially classified concerning the fusion gross microstructure. Firstly, one can see the higher quantity of primary carbides in ET1 alloy, a result from its higher content of alloy elements. Secondly, the concentration of vanadium, molybdenum and tungsten elements is clear, in accordance with the density of points in the X-ray image, and it is significantly higher at primary carbides in ET1 and ET2 alloys, concerning PH , PI2 and PI2 alloys.
• niobium carbides are MC type, and highly hard: therefore, they can replace well carbides of higher cost elements, such as tungsten, molybdenum and vanadium. And, added to such effect, niobium carbides have an interesting feature: they do not have expressive amounts of other elements, especially molybdenum, tungsten and vanadium.
• Figures 1 through 5 show that the primary carbides of PH , PM and PI3 alloys are predominantly MC type and rich in niobium. They consume lower amounts of tungsten, molybdenum and vanadium than primary carbides of the steels of the art and, thus, they allow for the reduction in the total content of such elements in the alloy, what is intended through the steel of the present invention.
• Table 2 Chemical compositions of four steels of the art (ET1 to ET 4) and the steel of the present invention (Pl)
• the hardness after the heat treatment is essential for high-speed steels. Therefore, the experimental ingots were rolled for 34-mm diameter round bars and annealed, with level at 85O 0 C for ET1 , ET2 and ET3 alloys, and level at 98O 0 C for PI3 alloy. Afterwards, they were submitted to quenching treatment, with austenitization between 1185 and 1200 0 C for 5 minutes and two temperings, between 450 and 600 0 C for 2 hours each.
• Table 3 Cost of metallic load, that is, the alloy metal contained in ET1, ET2, PH, PI2 and PI3 alloy. Values normalized by the cost of the metallic load of alloy ET1 and for ET2. The calculations were related to production through electric steel mill, in December 2005.
• Table 4 shows hardness after quenching and tempering of
• ET1, ET2, PM , PI2 and PI3 steels which, in form of a chart, is presented in
• Table 4 Response to heat treatment of steels of the art (ET1 and ET2) and steel of the present invention. Results of HRC hardness aster austenitization at 1185 and 1200 0 C, quenching in oil and double two-hour tem erin at the temperature indicated.
• the size of austenitic grains for ET2, PH , PI2 and PI3 alloys was also evaluated for several austenitization temperatures. The results are shown in Table 5.
• Steels PH , PI2 and PI3 have grain size slightly larger than steel ET2, because it has a high vanadium content-quite efficient to control the growth of the size of austenitic grains.
• PH , PI2 and PI3 alloys have grain size still refined, especially until 1185 0 C, and considering that 33-mm ga ⁇ ge is relatively large for high-speed steels. Therefore, this austenitization temperature seems the most suitable for the steel of the present invention.
• Table 5 Size of austenitic grains, as measured by the Snyder- Graff intercept method, for steels austenitized between 1185 and 1200 0 C.
• the indexes ⁇ indicate the standard deviation of the measures.
• Steel ET2 has a total volumetric fraction of carbides equivalent to the one of steels PU and PI3; steel PU has a slightly higher volumetric fraction. As for size, steel ET2 has fewer total carbides, but it has a higher number of coarse carbides (over 8 ⁇ m).
• the steels described in the present invention especially steels ET2 and ET3, have properties quite adequate for high-speed steel tools used in low demanding situations.
• Manual saws or saws used in machines are examples, in addition to cutting tools such as drills and milling devices, employed in situations with low working life demands.
• the properties of the steel of the present invention allows for its use as replacement for steels such as ET2 in all of such applications, with equivalent properties and a significant cost reduction (see Table 3).
• the steel of the present invention can also replace more alloyed steels, herein represented by steel ET1 , probably with lower performance, but the cost reduction is extremely significant.
• the steel of the present invention were tested in performance tests.
• Cutting tools of the "hard manual saws” type were manufactured and cutting tests were carried out.
• Such testes were performed in accordance with standard BS 1919, in three blades of each one of ET2, PU , PI2 and PI3 alloys.
• the alloys of the present invention, PH , PI2 and PI3, were produced from 55-kg experimental ingots, hot rolled until 2.8 * 12 mm 2 dimensions and, then, rolled again for the final dimension of the saw.
• Steel ET2 was obtained from an industrial batch for reference purposes. Alloy ET2 was chosen for comparison purposes, because this is the material traditionally employed in manual saw blades.
• the test consisted of 10 cuts per blade on a bundle of stainless steel UNSS304,00, with dimensions of 2.60 x 25.00 mm 2 , 180-HV hardness. The speed was constant, 70 strokes per minute, and the cutting powers were precalibrated equally for all the saw blades. The tests were carried out in a proper machine. The performance indicators were: average wear rate and total average cutting time.
• the wear rate is characterized by the evolution in the number of strokes required to make each cut. It is calculated through the first order derivative of the chart on number of strokes per cut in view of the number of cuts. A lower rate of wear means that the saw cuts with fewer strokes, what is felt by users as better performance. The same thing occurs for cutting time-the shorter, the better the saw blade performance.
• the results obtained at the performance test are shown in Table 7, for the materials under two tempering conditions.
• Table 7 Results of the performance of saw blades made of steels ET2, PH , PI2 and PI3, divided between two tempering conditions. The best performance is related to the reduction in wear rate and cutting time.
• the most important condition is 54O 0 C, since this is the most used in saws produced currently.
• the results achieved are interesting for the alloys of the present invention, once they show results either equivalent or even higher than those of the steel of the art (ET2), especially for PI2 and PI3 alloys.
• ET2 steel of the art
• the alloy with PI3 has the lowest wear rate; and, as well as PI2 alloy, it results in shorter cutting time than ET2 alloy.
• PI2 and PI3 alloys can be deemed as interesting for application, since they result in a significant reduction in the content of alloy elements and, notwithstanding, they promote a suitable cutting performance.
• Such performance may be even higher than the steels of the art. As discussed in Example 1, this occurs by means of the proper development of the chemical composition-especially through the combination of Nb and Si elements, something that promotes high hardness and refined carbides, entailing the total reduction of the more expensive alloy elements Mo, W and V.

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