Classifications

• • 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
• • 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
• • 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
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • 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
  • C22C38/40—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
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy

Definitions

• Patent Descriptive Report of the Invention "STEEL FOR TOOLS
• the present invention relates to a steel for use in various hot forming dies and tools for metals, principally for extrusion of aluminum alloys or other non-ferrous metals. Even initially developed for the extrusion process, the material may also be employed in other hot forming processes, where the metal to be formed has temperatures above 600 ° C, although processes at lower temperatures or even at room temperature may be used. used with said steel.
• the steel in question has a composition that classifies it as a hot working tool steel, having as its main feature the lower use of costly alloy elements, such as molybdenum and vanadium, and yet reaching levels of tempering resistance (or hardness loss) superior to conventional state-of-the-art steels.
• hot work tools is used for a large number of hot forming operations, employed in various industrial branches and focused on the production of parts intended for mechanical applications and especially automotive parts.
• the processes The most well-known hot-forming products are steel forging, and extrusion or casting of non-ferrous alloys.
• Other high temperature applications typically above 500/600 ° C, can also be classified as hot work.
• molds, dies, punches, inserts and other forming devices are classified by the generic term: hot work tools. These tools are usually made of steel, which require special properties to withstand the high temperatures and mechanical stresses of the processes in which the tools are employed.
• hot work steels high temperature hardness resistance, hardness loss resistance called tempering resistance, toughness, temperability and physical properties such as thermal conductivity and heat. specific.
• Non-ferrous alloy extrusion dies mainly aluminum
• the segment of these matrices is important for the tool steel market, both in Brazil and abroad.
• steels are very standardized, based on steels such as ABNT H13 (see Table 1), with lower quality requirements than other applications such as die casting die cast, but with strong pressure for lower cost.
• Table 1 Typical chemical composition of state of the art steels. The sum Mo + V + Co is entered because these elements have the highest cost and are closely related to the final cost of the tool steel. Content in percentage by mass and balance in Fe. For all W content is low, usually below 0.1%.
• a third problem of the invention US 2009/0191086 concerns the core hardness of the dies, which may be reduced due to reduced temperability by reducing Cr and Mo contents.
• the alloys of the invention US 2009/0191086 apply higher Mn content, which leads to higher temperability, but can lead to segregation (banding) problems and excess retained austenite. These two effects can compromise the hardness and final toughness and thus the tool life.
• a final aspect can also be raised in relation to the high Mn content: the problem of scraps of this steel can hardly be incorporated into the production of conventional hot work steels with low Mn content.
• the steel of the present invention has an alloying element composition which, by weight percentage, consists of:
• Mo can be replaced by W in a ratio where 2 parts by mass of W equals 1 part Mo.
• Al may be added concomitantly to the alloys of the present invention, promoting advantages in terms of hardness after nitriding, but disadvantages in terms of toughness and complexity of the steelmaking process.
• Al contents should be measured as a percentage by mass as follows:
• compositions presented should have a Fe balance and metallic or non-metallic impurities unavoidable to the steelmaking process, wherein said non-metallic impurities include, but are not limited to the following elements, by weight:
• Carbon is primarily responsible for hardening martensite at low temperatures. However, along with the alloying elements, carbon also acts on secondary hardening, which is important for high temperature hardening. In these cases the C content is more important for hardness at temperatures below 600 ° C, where the hardness still depends on the hardness of martensite or the formation of cementite or carbides from Cr. In addition, carbon is an important element in promoting temperability and does not cause cost increases. For these purposes, especially for raising the hardness above 45 HRC, carbon contents of at least 0.40% are indicated, preferably above 0.45%. Very high grades, on the other hand, promote excessive carbide precipitation in grain boundaries at the time of quenching (especially when Mo and V levels are high), and promote higher hardness and increased secondary carbide volume.
• the C content should be limited to a maximum of 0.60%, preferably below 0.55%. This limitation also contributes to reducing the amount of retained austenite, avoiding problems of dimensional instability and brittleness.
• Chromium content should be higher than 2.5%, preferably higher than 3.0%, because this element contributes to temperability, which is important for large tool applications. However, the content should be limited.
• the concept of reducing the Cr content to promote a greater effect of tempering resistance was developed in the present invention. The mechanisms of this effect are not fully understood, but must be related to the formation of the secondary Cr carbides, type M7C3, which dissolve Mo and V and are the first carbides to form. Therefore, the lower the Cr content, the lower the volume of M7C3 carbides and thus the greater the amount of Mo and V available for the formation of M 2 C and MC fine carbides, important for secondary hardening. The end result is significantly higher tempering resistance in steels with lower Cr, enabling the reduction of Mo content in relation to state-of-the-art steels.
• Mo and W Low Mo contents are employed in the alloy of the present invention to reduce the cost, but, associated with the Cr and C contents, still promote the secondary hardness peak and equivalent tempering resistance. even higher than steel H13.
• the alloy of the present invention should be at least 0.30%, preferably above 0.50%.
• very high Mo contents may impair toughness due to precipitation of pro-eutectic carbides at quenching, and may significantly increase the cost of the alloy, contrary to the cost reduction objective of the present invention. Therefore, the Mo content should be limited to 0.90%, preferably below 0.70%.
• tungsten and molybdenum have similar effects on the tool steel of the present invention, forming secondary carbides type M2C or MeC. Thus, they can be specified together through the equivalent tungsten ratio (Weq), given by the sum W + 2Mo, which normalizes the atomic weight differences of the two elements.
• V Vanadium is of prime importance for the formation of MC type secondary carbides. Because they are very thin, these carbides act as barriers to the movement of lines of disagreement, increasing the mechanical resistance. It also aids in contouring grain growth, allowing high austenitization temperatures (above 1000 ° C). For these effects the V should be above 0.1%, preferably above 0.3%.
• V content should be below 1.0%, preferably below 0.6%.
• Si Silicon has a strong effect on secondary hardening and toughness. When at low levels, Si promotes better toughness by generating a better distribution of secondary carbides. Therefore, the material of the present invention should have Si content below 1.0%, typically below 0.5%.
• Mn for promoting intense microsegregation, generating bandages with different hardness, and for increasing the austenite content Therefore, high Mn contents may be considered undesirable and this element is treated as impurity in the present invention.
• the Mn content should be limited to 1.0%, preferably below 0.8%, typically below 0.50%.
• the alloys may have a high Al content. However, the levels should be limited in these situations to 1.0% because they cause lower toughness. Thus, aluminum contents between 0.40% and 0.60% may be interesting for this purpose. However, for applications where the hardness of the nitrided layer may be slightly lower than H13 steel, but high toughness is required, the alloy of the present invention may have aluminum content below 0.1%, typically below 0.05%. .
• Residuals Other elements, such as Ni and Co, should be understood as impurities, related to steelmaking deoxidation processes or inherent to manufacturing processes. Therefore, the Ni and Co content is limited to 1.5%, preferably below 1.0%. In terms of formation of inclusions, one should control the S content, as such inclusions facilitate fracture during work; thus, the S content should be below 0.050%, preferably below 0.020%. Also for increased toughness, embrittling elements such as P should be avoided, with P below 0.030%, preferably P below 0.015%, typically below 0.010% being desired. In fact, the low Cr content also facilitates the reduction of the P content in the electric steelmaking processes, thus leading to non-contradictory conclusions to the desired cost reduction.
• the alloy as described may be produced in the form of rolled or forged products by conventional or special processes such as powder metallurgy, spray forming or continuous casting such as wire rod, bars, wires, sheets and strips.
• Figure 1A shows the effect of Mo content on hardness after tempering at 600 ° C
• Figures 1 B and 1 C show the effect of Cr content with 0.60% molybdenum for usual carbon contents ( Figure 1 B) and for higher contents (Figure 1 C); where the dashed horizontal line in figures 1A, 1 B and 1 C indicates the Minimum Hardness of application.
• Figures 2A, 2B and 2C show the effect of molybdenum (fig. 2A) and chromium (fig. 2B and fig. 2C) on tempering resistance.
• Figures 3A and 3B show the TRC curve of the compositions of the present invention with two Cr contents. Quantitative temperability results can be obtained by the amount of phases formed (perlite and bainite) and, most importantly, by the final hardness obtained at each rate.
• the summary compositions are shown in Table 1, base 3, with 3% and 4% Cr contents chosen for comparison.
• Figure 3A illustrates the TRC curve for the composition with 0.50% C and 3.00% Cr; and
• Figure 3B illustrates the TRC curve for the composition with 0.50% C and 4.00% Cr.
• alloys with the final composition of the present invention are compared in terms of hardness after tempering (fig. 5A) and loss of hardness as a function of time (fig. 5B). 600 ° C (referred to in the tempering resistance text).
• - Figure 6 compares impact toughness on two types of transverse specimens: non-notched (7 mm x 10 mm cross-section according to NADCA) or Charpy V, 10mm x 10mm cross section and V-notch. All materials were treated to hardness of 45 HRC according to the parameters of Figure 5a.
• - Figure 7 shows the hardness profile of the nitrided layer of PM, PI 2 and PI 3 alloys compared to H13 steel. The nitriding was conducted in the usual process of H13 steel, in plasma process. Prior to nitriding, samples of all alloys were hardened and tempered for hardness of 45 HRC.
• Hardness after tempering at 600 ° C is shown in Figure 1, showing the effects of the reduction of Mo, Cr and also the effect of the higher C content. decreased hardness of tempering. However, when Cr also reduces, the hardness of tempering is increased. Probably the lower Cr content reduces the amount of M 7 C 3 which in turn dissolves Mo. Thus, a higher free Mo content must exist in the lower Cr alloys, justifying the most intense tempering response.
• the temperature of 600 ° C is considered typical for tempering.
• Table 1 Chemical compositions used to study samples taken from the same run with the variation of one element. The asterisk signs, placed on the Cr and Mo contents, indicate that several compositions with this base were produced in the same race, increasing the content of this element but maintaining the base composition of the race.
• C is related to the higher formation of secondary carbides and, when associated with the reduction of Cr, promotes the hardness necessary for starting work, even in lower Mo alloys (half of H13). In higher C alloys, the same effect as Cr.
• Table 2 50 kg experimental ingots produced for the alloys of the present invention (PI) and H13 steel.
• PI 1 alloy is more suitable, also showing nitriding behavior close to H13, reaching over 1000 HV on the surface, which is normally specified for extrusion tools.
• PI 1 alloy also exhibits better hot strength properties.
• the alloys of the present invention point to results equivalent or superior to those of H13 steel. Such results are especially relevant for non-ferrous alloy extrusion dies, such as aluminum for example, or hot forging dies.
• PI 1 alloy has higher tempering strength but nitride hardness and H13 equivalent toughness
• PI 2 alloy has lower toughness but significantly superior tempering strength and nitriding hardness compared to H13 steel. The choice of alloy should thus shed light on the most critical properties for the application. However, in all cases, significant cost reductions can be obtained due to the low Mo and V content of the alloys of the present invention.

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• 2010
  • 2010-03-08 BR BRPI1003185-5A patent/BRPI1003185A2/pt not_active Application Discontinuation
• 2011
  • 2011-03-04 KR KR1020127026298A patent/KR20130004591A/ko not_active Withdrawn
  • 2011-03-04 JP JP2012556347A patent/JP2013521411A/ja active Pending
  • 2011-03-04 WO PCT/BR2011/000059 patent/WO2011109881A1/pt not_active Ceased
  • 2011-03-04 CA CA2792615A patent/CA2792615A1/en not_active Abandoned
  • 2011-03-04 CN CN2011800200854A patent/CN103097562A/zh active Pending
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  • 2011-03-04 US US13/583,288 patent/US20130243639A1/en not_active Abandoned
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