CN101516549A

CN101516549A - Iron-based powder

Info

Publication number: CN101516549A
Application number: CNA2007800269533A
Authority: CN
Inventors: O·H·莫斯; I·豪尔
Original assignee: Hoganas AB
Current assignee: Hoganas AB
Priority date: 2006-07-21
Filing date: 2007-06-20
Publication date: 2009-08-26
Also published as: ATE525156T1; JP2009544841A; EP2051826B1; WO2008010767A1; EP2051826A1; US20080019858A1; ES2375159T3; TW200808982A; DK2051826T3

Abstract

The present invention relates to an atomised pre-alloyed iron-based powder which comprises by weight-% 10,5-30 Cr 3-15 Al 5-20 Cu max 0,1 C max 0,2 N max 3.0 Mn max 2.5 Si max 3.0 Mo balance essentially only iron and unavoidable impurities.

Description

Iron-based powder

Technical field

The present invention relates to have the atomizing iron-based powder of good high-temperature oxidation resistance, relate more specifically to and chromium and the pre-alloyed powder of aluminium.

Background technology

A kind of ferrous alloy commonly used comprises Fe, 10 to 30% Cr and 1 to 10% Al usually, it is so-called FeCrAl alloy, found that this alloy has very high using value owing to good non-oxidizability under multiple high temperature, and can be used for temperature up to 1200 to 1400 ℃.For example, these materials are used to make the carrier material of resistive element and automobile catalyst.Because its aluminium component, this alloy can form substantially by Al in high temperature and most of atmosphere ₂O ₃The oxide on surface of non-that ooze, the tack that constitutes.This oxide protection metal is avoided further oxidation, and avoids the corrosion of many other forms, for example carburizing, sulfuration etc.

Yet a problem in the powder metallurgy is above-mentioned FeCrAl powder is difficult to sintering because aluminium oxide than chromium oxide difficulty be reduced.The oxidized aluminium of the formation of the sintering neck by diffusion weakens, and is favourable if this problem can overcome.

US 5,970, and 306 disclose the method for being made resistant to elevated temperatures molded component by high temperature insostatic pressing (HIP) (HIP) by the FeCrAl powder.

DE 4,235, and 141 disclose and a kind ofly wherein at first powder are exposed in the oxygen-containing atmosphere by the method based on the hot pressed powder manufacture component of FeCrAl alloy, to form chromium oxide around particle.

US 6,761,751 disclose a kind of method by aerosolization manufactured FeCrAl material, this material not only contains iron (Fe), chromium (Cr) and aluminium (Al), also contains in a spot of molybdenum (Mo), hafnium (Hf), zirconium (Zr), yttrium (Y), nitrogen (N), carbon (C) and the oxygen (O) one or more.

US 6,569,221 disclose a kind of powder metallurgy FeCrAl alloy, its in weight % comprise carbon less than 0.02%, greater than 0.0 and≤0.5% silicon, greater than 0.0 and≤0.2% manganese, 10.0 to 40.0% chromium ,≤0.6% nickel ,≤0.01% copper, 2.0 to 10.0% aluminium, amount are one or more among 0.1 to 1.0 Sc, Y, La, Ce, Ti, Zr, Hf, V, Nb and the Ta, all the other are iron and unavoidable impurities.

Goal of the invention

The purpose of this invention is to provide a kind of metal dust, this powder can provide good sintered component when at the sintering process of routine (for example loose sintering, cold pressing or temperature and pressure) sintering, and the parts of sintering have the good high-temperature oxidizing property.More specifically, the purpose of this invention is to provide a kind of powder of stainless steel, it comprises above the chromium of 10.5 weight % and the aluminium of 3 to 15 weight %, but this powder is than the easier sintering of known powder of prior art.

Brief summary of the invention

Iron-based powder by atomizing has been realized above-mentioned purpose, and the Cu of the Cr of this powder and 10.5 to 30 weight %, the Al of 3 to 15 weight % and 5 to 20 weight % is pre-alloyed.Powder and copper is pre-alloyed, can sinter them into parts with common sintering process, and keep the gratifying material property of this sintered component, these parts also have the excellent high-temperature non-oxidizability.

In second embodiment, proposed and the Cu of Al, 5 to the 20 weight % of Cr, 3 to the 15 weight % of 10.5 to 30 weight % and the pre-alloyed iron-based powder of Ni of 8 to 20 weight %.

Powder of the present invention is preferably as follows manufacturing: the melt of iron and described alloying element is provided, and with this melt water atomization, thus, the molten drop through solidifying by atomizing forms powder type.

Can as described belowly make sintered component: a) provide the agglomerated material that comprises powder of the present invention by powder of the present invention; B) form green compact by described agglomerated material; C) in reduction or neutral atmosphere, in atmospheric pressure or pressure below atmospheric pressure, in the temperature that is higher than 1100 ℃, with described green sintering.

For example, can be with the agglomerated material loose sintering, cold pressing or temperature and pressure.

Relate to and colding pressing or temperature and pressure, agglomerated material is the mixture of binding agent and/or lubricant and powder of the present invention.

Cold pressing be lower than 100 ℃ temperature, preferably the pressure between 100 to 1000MPa carries out.

Temperature and pressure are 100 to 200 ℃ temperature, preferably the pressure between 300 to 1000MPa carries out.

Loose sintering is not carry out under the situation to the green compact pressurization.Here, agglomerated material can be the mixture of binding agent and/or lubricant and powder of the present invention, also can be powder self, promptly not with powder and binding agent and/or mix lubricant.For example, when not using binding agent, agglomerated material can be poured in the model, the model that this agglomerated material wherein will be housed inserts in the sintering furnace.For example, by with powder loose sintering of the present invention, can make filter with excellent high temperature oxidation resistance.

In addition, find, the sintered component that can have the excellent high-temperature non-oxidizability by powder manufacturing of the present invention, this sintered component has the 6.5g/cm of being higher than ³Sintered density, be higher than 500MPa tensile strength, be higher than the 400MPa yield strength.

Description of drawings

Fig. 1 shown the Fe-Cu phasor and

Fig. 2 A shown the test bar that comprises Cr, Al, Cu and Fe metallograph and

Fig. 2 B shown the test bar that comprises Cr, Al and Fe metallograph and

Fig. 3 A shown the test bar that comprises Cr, Al, Cu, Ni and Fe metallograph and

Fig. 3 B has shown the metallograph of the test bar that comprises Cr, Al, Ni and Fe.

Detailed Description Of The Invention

The present invention relates to pre-alloyed iron-based powder, it comprises the chromium that surpasses 10.5 % by weight, and The aluminium of specified quantitative and copper. As mentioned above, the FeCrAl alloy has demonstrated and has had good high-temperature oxidation resistant Property, but lamentedly, under atmospheric pressure or lower pressure (vacuum) sintering difficulty. Here it is Compound based on the FeCrAl powder will pass through HIP method (for example, such as US 5,970,306 is described) The reason of making. By also pre-alloyed with copper, reduced the problem that sintering brings, with cupric not Contrast material is compared, and sintering structure improves. Can find out that from appended metallograph the copper component has Be beneficial to the formation of sintering neck. We believe that the generation of this effect is because the copper of liquefaction has destroyed oxidation Aluminium lamination. Also with copper with test after the FeCrAl powder mixes, but sintering does not have in this case Improve significantly.

Powder of the present invention is made with the melt of the alloying element that needs by making iron. Then should The melt atomizing forms powder by the molten drop that solidifies by atomizing thus. By routine techniques (gas for example Atomizing or water atomization) atomize. In fact, highly preferably with the melt blend water atomization, because The powder of water atomization is than the easier compacting of the powder of aerosolization. When forming powder owing to water atomization, Powder is oxidized, and forms thin chromium oxide and alumina layer on the surface of powder particle.

Effective range as described below, as to have tested aluminium content found that, and is anti-for what need to obtain Oxidisability, aluminium content should be higher than 3%, and preferably, aluminium content should be higher than 5%. Yet, if aluminium Too high levels, fusing point will reduce, and material is strength decreased at elevated temperatures. Can think that also aluminium is super Cross a certain amount of after, the not obvious raising of non-oxidizability further increases aluminium content and only can slightly improve anti-oxidant The property. Therefore, according to the present invention, the upper limit of aluminium content is 15 % by weight, and in fact, preferred aluminium contains Amount is lower than 12 % by weight.

Obtained the scope of copper content by following test. Correspondingly, copper content should surpass 5 % by weight, Be beneficial to the formation of sintering neck, and the sintered component with good high-temperature oxidation resistance is provided. In addition, Copper content should be lower than 20 % by weight, and the powder with high copper content may have for some application very much With, but they are not in protection scope of the present invention.

Fig. 1 has shown the Fe-Cu phasor, but believes that Cu will affect system in a similar manner. For Reduce/destroy alumina layer, believe to form a certain amount of liquid phase, namely make us in (γ Fe+L) zone Pay close attention to. Because this phasor is pure Fe-Cu system, the information that therefore therefrom obtains only has directiveness. What attract people's attention especially is the amount of the liquid phase that forms in the sintering process. Need to form liquid phase to destroy oxidation Aluminium lamination, but excessive liquid phase then can be destroyed structure in sintering. Amount and the chemical group of the liquid phase that forms Become relevant with sintering temperature. It is copper that liquid phase is formed the element with significant effects. Here it is at oxygen Copper content in changing before the test per sample applies the reason of different sintering temperatures.

Certainly, also can pay close attention to other alloying element. Especially, if need to obtain austenitic structure, Also can make powder and form austenitic element (nickel particularly, and the manganese that is equal to nickel) prealloy Change. Nickel is not only and is formed austenitic element, and also known have beneficial effect to non-oxidizability, this It also is desirable that the expection of powder of the present invention is used certainly. If also contain nickel in the powder, preferably, Nickel content is 8 to 20 % by weight. Manganese also can be the austenitic alloying element of formation that adds, and is preferred Ground, manganese content is lower than 3 % by weight.

Usually do not use cobalt, because it is relatively expensive.

Also preferably that the content maintenance of carbon is lower, because carbon may cause intergranular corrosion, therefore, carbon Content should be preferably less than 0.1 % by weight. In the sample of testing, carbon content is about 0.02 % by weight Or lower. Also preferably nitrogen content is kept as much as possible low, nitrogen content preferably is lower than 0.2 % by weight.

Embodiment 1

Have seven kinds of different water atomized powder of composition as shown in table 1 by making the melt of iron and required alloying element, making.Then with the melt water atomization, thereby the molten drop through solidifying by atomizing forms powder.Atomizing is undertaken by the water atomization technology of routine.The net grid of the maximum gauge by 75 μ m are provided extract the powder that obtains.

For each powder, the specimen of preparation sintering.Specimen to sintering is carried out following high-temperature oxydation test with the comparative sample with 310B composition (Fe of 25 weight %Cr+20 weight %Ni+2.5 weight %Si+ surpluses).Selecting the 310B material to do contrast is because it has the good high-temperature non-oxidizability.

Fill model (diameter 10mm, thick 2mm) with relevant powder, make its surfacing then,, make specimen and comparative sample thus not with powder pressing.This operation provides the have high specific area sample of (about 45% porosity).

With specimen sintering 30 minutes in 100% nitrogen atmosphere, the content that sintering temperature depends on Cu is with reference to following table:

5％Cu 1150℃

10％Cu 1320℃

15％Cu 1350℃

20％Cu 1320℃

With comparative sample in 100% nitrogen atmosphere 1320 ℃ of sintering 30 minutes.

After this, specimen that makes like this and comparative sample have been ready for the high-temperature oxydation test.

The oxidation test is carried out in air at 800 ℃ in experimental furnace Lenton 12/50/300.Balance Mettler Toledo AE 260 is linked to each other with storing data automatically with computer.Can test 6 samples simultaneously by 6 samples are placed on the specimen holder, when testing, 2 in the sample is comparative sample at every turn.

With samples weighing, be placed in the stove then.Carry out the short period circulation, each cycle comprises 2 minutes heating and 30 seconds cooling, and this cooling procedure is enough to sample is cooled to below 150 ℃.This repeats 15 times in cycle, thereby in stove 30 minutes.Whenever in the thermal treatment zone, after 30 minutes,, write down the weight increase that each time weighed with samples weighing.Test after 20 hours in the thermal treatment zone and to stop.

Table 1

The result shows, powder 6 and 7 non-oxidizability comparison are poorer than powder 8.Observing aluminium content is the sample of 5.5 weight %, and promptly powder 2,4,5 and 6, can see when copper content non-oxidizability when 5 weight % (sample 6) bring up to 10 weight % (powder 4) and obviously improving; When copper content was 15 weight % (powder 2), non-oxidizability had reached peak.When further increase copper content reached 20 weight % (powder 5), non-oxidizability result was identical with the powder that contains 10 weight % copper (powder 4).

As can be seen, copper content is 15% o'clock high-temperature oxidation resistance that can offer the best.

But powder 5 obviously shrinks when sintering, shows to have formed too much liquid phase when copper content is higher than about 20 weight %.

Relatively powder 4 and 3, powder 2 and 1, as can be seen, when aluminium content when 5.5 weight % increase, non-oxidizability improves slightly.

Embodiment 2

Further in different oxidizing temperature test powders 2 and 3.Following table has shown that the weight with respect to contrast sample 310B increases.

Table 2

Table 2 shows, in the temperature that is higher than 800 ℃, the difference that contains the sample of copper and aluminium and the non-oxidizability between the comparative sample is more obvious.In addition, the chemical composition of 5.5% aluminium and 15% bronze medal looks better than the non-oxidizability of the chemical composition of 10% aluminium and 10% bronze medal.

Embodiment 3

For the influence of the copper content of estimating interpolation, 4 kinds of different powder have been compared to sintered density, tensile strength and yield strength.These powder are identical with 2 water atomized powder with embodiment 1.With these powder and 1%

Mix.Pressing pressure at 600MPa is pressed into tensile test bars with mixture.With prod 1320 ℃, in 100% nitrogen atmosphere sintering 30 minutes.Measure sintered density, tensile strength and yield strength.The result is as shown in table 3.

Table 3

Table 3 shows that pre-alloyed if Al-contains Cr or Cr-Ni powder of stainless steel and Cu, its density and engineering properties obviously improve.This shows that sintering activity improves greatly.

Further tensile test bars being carried out metallicity detects.Metallograph Fig. 2 A, 2B and Fig. 3 A, 3B clearly show, copper contained Cr with Al-or Cr-Ni base powder of stainless steel combines the agglutinating property that has obviously strengthened material.Fig. 2 A has shown the metallograph of the prod that comprises the 22Cr+5.5Al+10Cu+ balance iron.Fig. 2 B has shown the metallograph of the corresponding contrast test rod that comprises the 22Cr+5.5Al+ balance iron.Fig. 3 A has shown the metallograph of the prod that comprises the 22Cr+5.5Al+18Ni+8Cu+ balance iron.Fig. 2 B has shown the metallograph of the corresponding contrast test rod that comprises the 22Cr+5.5Al+18Ni+ balance iron.

Claims

1, a kind of prealloy iron-based powder of atomizing, it comprises in weight %:

10.5 Cr to 30

3 to 15 Al

5 to 20 Cu

Maximum 0.1 C

Maximum 0.2 N

Maximum 3.0 Mn

Maximum 2.5 Si

Maximum 3.0 Mo

All the other substantially only are iron and unavoidable impurities.

2, powder according to claim 1, wherein the content of Al is 5 to 12 weight %.

3, according to the described powder of aforementioned each claim, wherein the content of Cu is 7 to 17 weight %.

4, according to the described powder of aforementioned each claim, wherein the content of Cr is 15 to 30 weight %.

5, powder according to claim 4, wherein the content of Cr is 20 to 30 weight %.

6, according to the described powder of aforementioned each claim, wherein this powder also comprises the Ni of 8 to 20 weight %.

7, according to the described powder of aforementioned each claim, wherein this powder is made by water atomization.

8, make the method for the prealloy iron-based powder of water atomization, wherein this iron-based powder comprises in weight %:

10.5 Cr to 30

3 to 15 Al

5 to 20 Cu

Maximum 0.1 C

Maximum 0.2 N

Maximum 3.0 Mn

Maximum 2.5 Si

Maximum 3.0 Mo

All the other substantially only are iron and unavoidable impurities,

Described method comprises the melt that iron and described alloying element are provided, with described melt water atomization, thereby by the atomizing molten drop through solidifying to form powder.

9, method according to claim 8, wherein said iron-based powder also comprises the Ni of 8 to 20 weight %.

10, make the method for sintered component, comprising:

A) provide the agglomerated material of the prealloy iron-based powder that contains water atomization, described iron-based powder comprises in weight %:

10.5 Cr to 30

3 to 15 Al

5 to 20 Cu

Maximum 0.1 C

Maximum 0.2 N

Maximum 3.0 Mn

Maximum 2.5 Si

Maximum 3.0 Mo

All the other substantially only are iron and unavoidable impurities;

B) make green compact by described agglomerated material; With

C) in reduction or neutral atmosphere, in atmospheric pressure or pressure below atmospheric pressure, be higher than 1100 ℃ temperature with described green sintering.

11, method according to claim 10, wherein in a), the agglomerated material that is provided is the mixture of the prealloy iron-based powder of lubricant and/or binding agent and described water atomization.

12, method according to claim 11 is wherein at b) in, described green compact are made by the described mixture of colding pressing, and wherein preferably, pressing pressure is between 100 to 1000MPa, and preferably, temperature is lower than 100 ℃.

13, method according to claim 11 is wherein at b) in, described green compact are made by the described mixture of temperature and pressure, and wherein preferably, pressing pressure is between 300 to 1000MPa, and preferably, temperature is between 100 to 200 ℃.

14, method according to claim 10, wherein in a), the agglomerated material that is provided only is the prealloy iron-based powder of described water atomization.

15,, described green compact are shaped according to claim 11 or 14 described methods.

16, the sintered component of being made by each method of claim 10 to 14, the sintered density of wherein said parts is higher than 6.5g/cm ³

17, the sintered component of being made by each method of claim 10 to 14, the tensile strength of wherein said parts is higher than 500MPa.

18, the sintered component of being made by each method of claim 10 to 14, the yield strength of wherein said parts is higher than 400MPa.