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Iron-based powder

a technology of iron-based powders and atomised iron, which is applied in the direction of transportation and packaging, metal-working apparatuses, etc., can solve the problems of difficult sintering of fecral-powders, and achieve the effects of easy sintering, good high temperature oxidation properties, and good sintered structur

Inactive Publication Date: 2008-01-24
HOGANAS AB
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010]This object is solved by an atomised iron based powder pre-alloyed with 10.5-30 wt % Cr, 3-15 wt % Al and 5-20 wt % Cu. By pre-alloying the powder with Cu it is possible to sinter a component in conventional sintering processes and maintaining satisfactory material properties of the sintered component which component also have excellent high temperature oxidation resistance.

Problems solved by technology

A problem in powder metallurgy however is that that FeCrAl-powders are difficult to sinter, due to the fact that the aluminium oxide is harder to reduce than the chromium oxide.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0033]Seven different water atomised powders having the compositions of Table 1 were made by making a melt of iron and the desired alloying elements. The melt was thereafter water atomised whereby the powder formed from the atomized droplets upon solidification. The atomization was performed according to conventional water atomization technology. The resulting powders were extracted through a grid providing a maximum diameter of 75 μm.

[0034]For each powder sintered test samples were prepared. The sintered test samples and a reference sample having a 310B composition (25 wt % Cr+20 wt % Ni+2.5 wt % Si+bal. Fe) were subjected to a high temperature oxidation test described below. The material 310B was chosen as reference since it is known to possess good high temperature oxidation resistance.

[0035]The test samples and the reference sample were produced by filling a form (10 mm diameter and 2 mm thickness) with the powder of interest, followed by smoothing out the surface without compac...

example 2

[0045]Powder 2 and 3 were further tested at different oxidation temperatures. The following table shows the increase in weight relative to the reference 310B.

TABLE 2Powder 3Powder 2TestIncrease in weightIncrease in weighttemperaturerelative referencerelative reference[° C.](%)(%)REMARKS800462485043229002121950141410002013Terminated after 16hours

[0046]Table 2 shows that difference in oxidation resistance between samples containing Cu and Al and reference samples is further pronounced at temperatures above 800° Celcius. Furthermore, the composition having a Al content of 5.5% and a Cu content of 15% seems to have better oxidation resistance compared to the composition having 10 Al and 10% Cu.

example 3

[0047]In order to evaluate the effect of added Cu-content with regard to sintered density, tensile strength and yield strength, four different powders having were compared. The powders were as in example 1 and 2 water atomized powders. The powders were mixed with 1% of Acrawax®. The mixes were compacted at a compacting pressure of 600 MPa into tensile test bars. The test bars were sintered for 30 minutes at 1320° Celsius in an atmosphere of 100% hydrogen. Sintered density, tensile strength and yield strength were measured. The results are shown in table 3.

TABLE 3ChemicalSinteredTensileYieldcomposition wt %,densityStrengthstrengthbalance Fe[g / cm3][MPa][MPa]22Cr + 5.5Al + 10Cu6.8758252222Cr + 5.5Al (ref.)5.7429525922Cr + 18Ni + 5.5Al + 8Cu6.7050741222Cr + 18Ni + 5.5Al (ref.)4.968769

[0048]The table 3 shows that the density and the mechanical properties of Al-containing Cr or Cr—Ni stainless steel powders increases considerably if the powder are pre-alloyed with Cu. This indicates much ...

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Abstract

An atomised pre-alloyed iron-based powder which comprises by weight-%10.5-30Cr  3-15Al  5-20Cumax 0.1Cmax 0.2Nmax 3.0Mnmax 2.5Simax 3.0Mobalance essentially only iron and unavoidable impurities.

Description

[0001]This application claims priority to U.S. Patent Application No. 60 / 840,457, filed 28 Aug. 2007, and to Swedish Patent Application No. 0601601-8, filed 21 Jul. 2006, the complete disclosures of which are incorporated herein by reference.TECHNICAL FIELD[0002]The invention concerns atomised iron based powders having good high temperature oxidation resistance, more particular powders which are pre-alloyed with chromium and aluminium.BACKGROUND[0003]Conventional iron based alloys containing typically Fe and 10-30% Cr and 1-10% Al, so-called FeCrAl-alloys, have been found highly useful in various high temperature applications, due to their good oxidation resistance and can be used at temperatures as high as 1200-1400° C. Thus, such materials have been used in the production of electrical resistance elements and as carrier materials in motor vehicle catalysts. As a result of its aluminium content, the alloy is able to form at high temperatures and in the majority of atmospheres an im...

Claims

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Application Information

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IPC IPC(8): C22C38/20B22F1/00B22F9/06
CPCB22F3/1007B22F9/082C22C38/42C22C38/20C22C38/06C22C33/0285B22F2999/00B22F2998/10B22F2009/0828B22F1/0059B22F3/02B22F2003/145B22F2201/01B22F2201/10B22F1/10
Inventor MARS, OVE H.HAUER, INGRID
Owner HOGANAS AB
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