Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C37/00—Cast-iron alloys
  • C22C37/04—Cast-iron alloys containing spheroidal graphite

Definitions

• the invention relates to a nodular cast iron alloy for cast iron products having a high mechanical strength, a high wear resistance and at the same time a high toughness, comprising as non-iron constituents 2.5 to 3.8 wt.% C, 2.4 to 3.4 wt. % Si, 0.02 to 0.08 wt% P, 0.02 to 0.06 wt% Mg, 0.01 to 0.05 wt% Cr, 0.002 to 0.02 wt% Al, 0 , 0005 to 0.015 wt% S, 0.0002 to 0.002 wt% B and the usual impurities.
• GB 832 666 is a cast iron alloy with as non-iron constituents 1, 0 to 2.5 wt.% C, 1, 5 to 3.2 wt.% Si, less than 1, 15 wt.% Mn, less than 0 , 5% by weight of S and 0.001 to 0.05% by weight of B are known.
• the graphite part is formed in a compact form. Because the alloy does not contain any Mg, nodular graphite or vermicular graphite, it has predominantly a graphite formation that looks similar to the tempered carbon knot of malleable cast iron.
• the alloy contains 5 to 10% carbides in a predominantly pearlitic matrix, with the result that the elongation at break is relatively low.
• tellurium and bismuth are added as alloying elements. Higher fracture strain values are achieved by a subsequent heat treatment.
• a further cast iron alloy is known from US 2004/0112479-A1, which preferably contains 3.7% by weight of C, 2.5% by weight of Si, 1.85% by weight of Ni, 0.85% by weight of Cu and 0, Contains 05 wt.% Mo.
• This material is characterized by an elongation of 20 to 16% at a tensile strength of 500 to 900 MPa and by a
• Brinell hardness from 180 to 290 HB. These properties are achieved after a time-consuming heat treatment, which comprises in succession: 10 to 360 minutes austenitizing at temperatures between 750 and 790 0 C, rapid cooling in a salt bath at a temperature between 300 and 400 0 C, 1 to 3 hours annealing at Temperatures between 300 and 400 0 C and cooling to room temperature. After this treatment, the material has a structure with an austenitic and ferritic microstructure. The material is characterized by a lighter machinability than a cast iron, which was subjected in the usual way to an austempering.
• a nodular cast iron alloy for cast iron products with a high mechanical strength, a high wear resistance and at the same time a high toughness, comprising as non-iron constituents 2.5 to 3.8 wt.% C, 2.4 to 3.4 wt.
• the alloy contains 3.0 to 3.7% by weight of C, 2.6 to 3, 4 wt% Si, 0.02 to 0.05 wt% P, 0.025 to 0.045 wt% Mg, 0.01 to 0.03 wt% Cr, 0.003 to 0.017 wt% Al, 0.0005 to 0.012 wt.% S and 0.0004 to 0.002 wt.% B.
• the alloy has the best possible wear behavior. This is achieved in that the alloy 0.1 to 1, 5 wt.% Cu, preferably 0.5 to 0.8 wt.% Cu and 0.1 to 1, 0 wt.% Mn, preferably 0.15 to 0.2 wt.% Mn. This is also achieved in that the alloy 0.1 to 1, 5 wt.% Mn, preferably 0.5 to 1, 0 wt.% Mn and 0.05 to 1, 0 wt.% Cu, preferably 0.05 contains up to 0.2 wt.% Cu.
• the core idea of the invention is to specify a cast iron alloy which has a Brinell hardness of more than 220 and which is worn as uniformly as possible when used as a brake disk.
• Lamellar graphite discs are inexpensive, but have less resistance to temperature changes. This can lead to so-called fire cracks after a short period of use, which continue to grow rapidly and lead to uneven surfaces. An uneven surface in turn leads to uneven temperature load, irregular wear and so-called Bremsrubbeln.
• axle and chassis parts for trucks and passenger cars such as wishbones, wheel and pivot bearings, which are exposed to high mechanical and dynamic loads and which must deform plastically in the event of a collision of the motor vehicle and must not break.
• a brake disk was manufactured from the ductile iron alloy according to the invention.
• the chemical composition was 3.34 wt.% C, 2.92 wt.% Si, 0.62 wt.% Cu, 0.17 wt.% Mn, 0.038 wt.% Mg, 0.025 wt.% P, 0.021 wt % Cr, 0.01% by weight Al, 0.001% by weight S and 0.0008% by weight B 1 balance Fe and the usual impurities.
• the brake disk was tested for spherulite number, graphite content, graphite shape and graphite size, perlite content and Brinell hardness. Samples from the brake disc were subjected to a tensile test to determine the strength-elongation behavior. The
• Spärolitheniere is 384 +/- 76 spherulites per mm 2 .
• the graphite content 9.7 +/- 0.7%.
• the graphite mold according to DIN EN ISO 945 is 97.9% of the form VI.
• the size distribution according to DIN EN ISO 945 is 45% of the size 8, 42% of the size 7 and 13% of the size 6.
• the perlite content is 84 +/- 1%.
• the Brinell hardness is 248 +/- 3 HB. In the tensile test, the following values were determined:
• the weight gain in grams per square meter and day by oxidation at 700 0 C in air is shown.
• the inventive material shows a weight gain of about 9 g / m 2 .d compared to a cast iron material for conventional brake discs with a weight gain of about 21 g / m 2 .D.
• test for fire crack formation were carried out as follows: A sample measuring 40 ⁇ 20 ⁇ 7 mm is subjected to at least 100 cycles consisting of heating for 7 seconds to 700 ° C. and quenching in water for 6 seconds. Then cross-sections are made and examined under the microscope and photographed.
• FIG. 2 shows a microfoto of a commercially available brake disk with a fire crack of 0.4 mm depth.
• FIG. 3 shows a further microfoto of the brake disk according to the invention with the same magnification with a fire crack of 0.14 mm depth.
• a wishbone for passenger cars was made from the nodular cast iron alloy according to the invention.
• the chemical composition was 3.5 wt% C, 2.85 wt% Si, 0.63 wt% Cu, 0.18 wt% Mn, 0.038 wt% Mg, 0.026 wt% P, 0.029 wt % Cr, 0.004% by weight Al, 0.001% by weight S and 0.0007% by weight B, remainder Fe and the usual impurities.
• Tensile strength R p 0.2 465 MPa
• tensile strength Rm 757 Mpa
• elongation at break A5 11, 1%
• elastic modulus E 165 to 170 kN / mm 2 .
• the Brinell hardness is 258 +/- 3 HB.
• a wheel carrier for passenger cars was manufactured from the ductile iron alloy according to the invention.
• the chemical composition was 3.43 wt% C, 3.38 wt% Si, 0.71 wt% Cu, 0.2 wt% Mn, 0.037 wt% Mg, 0.047 wt% P 1 0.043 wt % Cr, 0.012% by weight Al, 0.004% by weight S and 0.0008% by weight B, remainder Fe and the usual impurities.
• Tensile strength R p 0.2 558 MPa
• tensile strength Rm 862 MPa
• elongation at break A5 6.1%.
• the Brinell hardness is 288 HB.
• the number of spherulites in the microstructure was found to be 455 spherulites per mm 2 .
• FIG. 4 shows the breaking elongation A5 as a function of the tensile strength Rm.
• the solid line indicates the minimum values according to standard EN 1563 for ductile iron castings of as-cast grades.
• the measurements of the inventive material are listed according to the above examples 1 to 3.
• FIG. 5 shows the elongation at break A5 as a function of the yield strength R p 0.2.
• the solid line indicates the minimum values according to standard EN 1563 for spheroidal graphite cast iron of as-cast grades.
• the measurements of the inventive material are listed according to the above examples 1 to 3.
• FIG. 6 shows the strength ranges with respect to the elongation at rupture of the materials cast aluminum alloys, spheroidal graphite cast iron, ADI and the material according to the invention with the registered examples 1 to 3.
• the uniformity of the structure is also achieved by a new casting process.
• the mold is divided horizontally instead of vertically, with the brake discs are arranged horizontally and the filling of the mold is carried out from the center to the edge of the brake disc. This has the consequence that the mold is filled rotationally symmetrical and that the brake disc cools evenly after casting from inside to outside. This creates over the entire circumference of the brake disc a uniform, homogeneous structure. Subsequent heat treatment, which is time consuming and incurs costs, is no longer required.

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• 2004
  • 2004-11-22 DE DE102004056331A patent/DE102004056331A1/de not_active Withdrawn
• 2005
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