TW200808982A - Iron-based powder - Google Patents

Abstract

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

200808982 IX. Description of the Invention: [Technical Field] The present invention relates to an atomized iron-based powder having good high temperature oxidation resistance, and more particularly to a powder pre-alloyed with chromium and aluminum. [Prior Art] It has been found that a conventional iron-based alloy (so-called FeCrA1 alloy) typically containing Fe and 10_30〇/〇Cr and bWWAi has good oxidation resistance and can be used at temperatures as high as 120 (M40〇t; It is highly useful in a variety of high temperature applications. Therefore, this material has been used in the manufacture of resistive elements and as a carrier material in automotive catalysts. Due to its aluminum composition, the alloy can be formed at high temperatures and in most atmospheres. An impermeable and adhesive surface oxide consisting essentially of 〇2〇3. This oxide protects the metal against further oxidation and also against many other corrosion formations, such as carbonization, vulcanization, etc. But in powder metallurgy The problem is that FeCrAi powder is difficult to sinter, which is difficult to reduce due to the fact that alumina is more difficult to reduce than chromium oxide. The sintered neck formed by diffusion is weakened by the aluminum oxide layer, which is advantageous if it can overcome this problem. US 597〇3〇6Description A method for producing a south-resistant shaped part from FeCrA1 powder by thermal pressure equalization (mp). DE 4235141 describes a crucible based on FeCrA1 alloy under thermal compression. Finally, a method of making the article is obtained, wherein the powder is initially exposed to an oxygen-containing oxygen atmosphere to produce a chromium oxide protective layer around the particles. US 6,761,751 describes a method for producing FeCrA1 material by gas atomization, which includes In addition to iron (Fe), chromium (Cr) and aluminum (A1), 6 200808982 Λ ' This material also includes less than one or more of the following materials: molybdenum (Mo), helium (Hf), helium (Zr), (Y), nitrogen (N), carbon (C), and oxygen (0). US 6569221 describes a powder metallurgy FeCrAl alloy comprising (by weight percent) less than 0.02% carbon, more than 〇〇 <=〇5%矽, more than 0·0 and <-0 2% violent, 10·0-40·0% way, <==〇·6. /. Nickel, <=Q 〇1 〇/〇 copper, 2·〇·10·〇% aluminum; the amount of Mo is Se, γ, La,

One or more of Hf, V, Nb, and Ta; the remainder is iron and unavoidable impurities. SUMMARY OF THE INVENTION The object of the present invention is to provide a metal powder which can be sintered when sintered by a conventional firing method (for example, pressureless sintering, cold press forming or warm press forming), and this is sintered. The structural member has good high temperature oxidation properties. . More specifically, it is an object of the present invention to provide a stainless iron powder comprising more than 1 5% by weight of chromium and 3 to 15% by weight of aluminum, but this powder is easier to sinter than the materials well known in the prior art. . Dan. This target consists of a kind of atomized and 1〇·5_3〇 weight. Re-introduction: A1 and 5_2 〇 weight 0 / core pre-alloyed iron-based powder. By pre-sintering, this powder and Cu can be sintered by a sintering method which is known, and maintains the material properties of the sintered member which also has excellent high-temperature oxidation resistance. Further, in the second embodiment, an iron-based powder having an alloy of W yoke = r, 3.7 wt% A1, 5, wt% c weight has been proposed. 7 200808982 The powder of the present invention is preferably formed by providing a melt of iron and alloying elements, atomizing the melt, thereby forming a powder from the atomized droplets after solidification. & A sintered member can be produced from the powder of the present invention by: providing a sintered material comprising the powder of the present invention; b) forming a sintered material therefrom; and C) in a reducing or neutral atmosphere At or below atmospheric pressure, and at temperatures above 1100. (: The green body is sintered.

This sintered material can be formed, for example, by pressureless sintering, cold press forming or warm press forming. Regarding cold press forming or warm press forming 'this sintered material is - a binder... or a mixture of a lubricant and the powder of the present invention. - Cold forming is carried out at a temperature below 10 CTC, preferably in the range of 100-1000 MPa (MPa). The warm press forming is carried out in a temperature range of 100_20 (rc, preferably in the range of compaction pressure of 300-1000 MPa). The pressureless sintering is not compacted. Here, the sintered material may be a binder. And/or a mixture of a lubricant and a powder of the invention, but the same can be used for the powder itself (ie 'no mixing of the powder with the binder and/or lubricant). For example, when no binder is used, the sintered material can be used. Pour into a shape to insert the sintered material into the sintering furnace after containing the shape. For example, a powder having excellent high temperature oxidation resistance can be produced by pressureless sintering of the powder of the present invention. It is shown that a sintered member having excellent high temperature oxidation resistance can be produced from the powder of the present invention, the sintered member having a sintered density of more than 6.5 g/cm 3 , a tensile strength of more than 5 MPa and a yield strength of 8 200808982 t , greater than 400 MPa. [Embodiment] The present invention relates to a prealloyed iron-based powder comprising aluminum and steel in excess of weight I / chrome and 疋i. As described above, FeCrAl alloy has Display It has excellent oxidation resistance at high temperatures, but unfortunately it is difficult to sinter at atmospheric pressure or below atmospheric pressure (vacuum). This is the reason why the Hip method is used to manufacture compounds based on FeCrA1 powder (as described in For example, in US 5,970,306), the result of reducing the sintering problem and improving the sintered structure by pre-alloying with copper (the copper composition is shown to promote the formation of a sintered neck compared to a reference material without copper, as can be seen from the accompanying metallographic photographs. It is believed that this effect occurs because the oxidized layer is broken up by the liquefied copper. The mixed copper and FeCrA1 powders are also tested, but the sintering is not significantly improved in this example. The powder of the present invention is produced by the iron and the desired alloying elements. The melt "atomizes the (four) material after the °" to thereby form a powder from the atomized droplets after solidification. The atomization is preferably performed according to a conventional technique (for example, gas or water atomization). It is water atomizing the melt mixture because the water atomized powder is denser than the gas atomized powder. When the powder is formed by water atomization, '(4) is oxidized and A thin layer of chromium oxide and aluminum oxide is formed on the surface of the powder particles. The effective range of the aluminum content is tested as described in the following table, and it is inferred that the aluminum content should be greater than 3% and the content of the content should preferably be greater than 5%. Obtain the desired antioxidant properties. However, if the content of the melamine becomes too high, the melting point is reduced and the material loses its strength at the temperature of 9 200808982 2 . Again, this can be assumed to be more than the amount of anti-oxidation. It is not necessary to add a, and the increase of the content of the _ step will only be called micro-improvement oxidative. Therefore, according to the present invention, the upper limit of the ing content is set to 15 mph, and the aluminum content is less than 12% by weight. 。 From the test described below, the limit of copper content is introduced. Therefore, copper is used at a weight of 5 liters to promote the formation of a sintered neck and to provide a sintered member having good oxidizing properties at south temperature. Further, the cu content should be less than 2 Å. Powders having a souther Cu content may be useful for some applications, but they are not within the scope of the present invention. $ ! shows the Fe_Cu phase diagram 'but the salt letter Cu will be similar to the square ~ denier / play the layer of emulsified aluminum, the salt must form a liquid phase 'that is (called the area of interest. Because this figure For the 妒e-Cu system, the information obtained from it can only be used as a guideline. = Interest is the amount of liquid phase formed during sintering. The liquid phase needs to be formed: the political phase, but the excess liquid phase The amount of liquid phase formed by this structure during sintering is related to the chemical composition and sintering temperature. The element that affects the formation of liquid is copper. This is why different sintering temperatures are applied depending on the copper content of the sample before the oxidation test. Other alloying elements may also be of interest. In particular, the composition of the powder can also be formed with the Worth field (especially the word) to the 'but can also be recorded as equivalent. 35 for the Worth field Forming; ^ has also been known to have a beneficial effect on antioxidant properties, which of course is desired in the application of the application. If you want to use this product in the range of (4) weight%, the shovel can also be Extra = 200808982 4 The body forms an alloying element, Good manganese content is less than 3% by weight. It is not used under 苇 because it is relatively expensive. 軚乜 軚乜 Keep the slave content low, because carbon has a tendency to cause intergranular corrosion. Less than 〇·1% by weight of carbon. In the sample of :::, the carbon content is about 〇·〇2% by weight or less. Keeping nitrogen-曰 is low and better, and the nitrogen content is less than 0% by weight. Preferably, embodiment 1

A powder of seven compositions which have a composition of 纟i is prepared by making a molten iron of the desired alloying element. Thereafter, the melt is atomized by water' thereby forming a powder from the atomized droplets after solidification. Atomization is carried out according to conventional water atomization techniques. The resulting powder is extracted by providing a grid with a maximum diameter of 75 microns. For each powder, a sintered test sample was prepared. The sintered test sample and the reference sample containing the 31 Å B composition (25 wt% heart + 2 〇 wt% shame + 25 wt% remaining A Fe) were subjected to the following high temperature oxidation test. Choice (4) should be used as a reference because it is well known to have good resistance to high temperature oxidation. Test samples and reference samples were prepared by filling the powder of interest into a shape (diameter 10 mm and thickness 2 mm) followed by smoothing the surface without compacting the powder. This procedure provides samples with a high specific area (approximately 45% porosity). The temperature was determined according to the Cii content. In a 100% hydrogen atmosphere, the test sample was sintered for 30 minutes according to the following table: 5% Cu

1150°C 200808982

* 10%Cu 1320〇C 15%Cu 135〇〇c

20% Cu 1320〇C at _. The reference sample was sintered at mot: for 3 minutes in a hydrogen atmosphere. The prepared test and reference samples are then ready for high temperature testing. Oxidation tests were carried out in air in a laboratory furnace (Lenton 12/50/300) at a temperature of 8 〇〇t:. Connect the balance (Mettler T〇led〇 ae26〇) to the computer to automatically store the data. Six samples can be tested simultaneously by placing the sample on the sample holder, and two samples are reference samples for each test run. The sample was weighed before being introduced into the furnace. For a short period of time, each cycle consisted of 2 minutes of heating and 3 seconds of cooling, which was sufficient to cool the sample to less than 150C. Repeat this cycle 15 times, resulting in 3 minutes in the furnace. In the heated zone, the sample is weighed every 3 minutes and the weight gain is stored each time. The test was stopped after 2 hours in the heated zone. 12 200808982

The results showed that the oxidation resistance of φ, I observed with ΑβΓ5 7 was worse than that of the reference powder 8. Can be seen ~ content: 5,5 wt% of the sample (ie, powder 2, 4'5 and Ο ^ ^, b;, 7i / 〇e! ^ " : ° 4 *% (^ ^ 4) highest resistance Oxidizing property: Cu content: 5 cc% (powder 2) when oxidation resistance is obtained" and the progress is increased to 20% by weight (powder); fruit such as powder having 10% by weight of Cu (powder 4). ^ 3里丨5 /. The best knot for the anti-temper temperature oxidation provides 'indicated at 1. It is visible, however, that during the sintering, the powder 5 shrinks considerably and Cu contains more than about 20% by weight to form too much liquid phase. ~Comparative powder 4 with powder 3 and comparative powder 2 with powder 攸 5.5 wt% increase A1 content slightly increase oxidation resistance. 13 200808982 Example 2 The following table shows the notes to further test powder 2 at different oxidation temperatures and relative to the reference 31 0B weight increase. Table 2_ Test temperature powder 3 powder 2 degrees [°C] relative to the reference weight increase relative to the reference (%) Weight increase 800 46 24 850 43 22 900 21 21 950 14 14 1000 _20 13 The " table shows the difference in oxidation resistance between the sample containing CuA1 and the reference sample at temperatures above 800 °C Obviously, the composition having an A1 content of 5.5% and a Cu content of 15% seems to have better oxidation resistance as compared with the composition having 1% by mass of A1 and i〇% Cu. Example 3 In order to evaluate the addition of Cu The effects of sintered density, tensile strength and yield strength 'compare four different powders. These powders are water atomized powders as in Examples 1 and 2. This powder is combined with ι% Αα_χι. The mixture was compacted into a tensile test rod under MPa. The test rod 3 () was sintered in a 1GG% hydrogen atmosphere at 132 °C. The sintered density, tensile strength and yield strength were measured. The results are shown in the table. 3 中. 14 200808982 Table 3 Chemical composition wt%, residual sintered density [gram tensile strength yield strength part Fe / cubic centimeter] [million kPa] [million kPa] 22Cr+5.5Al+10Cu 6.87 582 522 22Cr+5.5 Al (Reference) 5.74 295 259 22Cr+18Ni + 5.5Al + 8Cu 6.70 507 412 22Cr+18Ni + 5.5Al (Reference) 4.96 87 69 Table 3 shows that if the powder is pre-alloyed with Cu, Cr or Cr-containing A1 The density and mechanical properties of Ni stainless steel powder have increased considerably. This indicates a greater change. Good sintering activity. Further metal inspection on tensile test bars. See Figure 2 A, 2B and Figure 3 for metallographic photographs of A and 3B, which clearly show that Cu is incorporated into Cr or Cr-Ni containing A1. The stainless steel powder considerably increases the sintering of the material. Figure 2A shows a metallographic photograph of a test stick comprising 22 (^ + 5.5 八 1 + 10 (^ + remaining Fe) and Figure 2B showing a corresponding reference test stick containing 22Cr + 5.5 Al + remaining Fe. 3 A shows the metallographic photograph of the test rod containing 22Cr+5.5Al+18Ni + 8Cu+ remaining Fe and FIG. B shows the metallographic photograph of the corresponding reference test rod containing 22Cr+5.5Al+18Ni+ remaining Fe. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a Fe-Cu phase diagram; and FIG. 2A shows a metallographic 15 of a test rod containing Cr, Al, Cu, and Fe. 200808982. Photographs; and FIG. 2B shows Cr, A1, and Fe. Metallographic photographs of the test bars; and Figure 3A shows metallographic photographs of test bars containing Cr, Al, Cu, Ni, and Fe; and Figure 3B shows metallographic photographs of test bars containing Cr, A, Ni, and Fe. [Main component symbol description] No reference 16

Claims (1)

200808982 X. Patent application scope: 1 · An atomized prealloyed iron-based powder containing the following by weight: 10.5-30 Cr 3_15 A1 5-20 Cu up to 0.1 C up to 0.2 N • up to 3.0 Μη up to 2.5 The remainder of Si up to 3.0 Mo is essentially iron and unavoidable impurities. 2. The powder of claim 1 wherein the A1 content is in the range of 5 to 12% by weight. 3. A powder according to claim 1 or 2, wherein the Cu content is in the range of 7 to 17% by weight. 4. A powder according to claim 1 or 2, wherein the Cr content is in the range of 15 to 30% by weight. 5. A powder according to item 4 of the patent application, wherein the Cr content is in the range of 20 to 30% by weight. 6. A powder according to claim 1 or 2, wherein the powder further comprises 8-2 Torr. 7. The powder of claim 1 or 2, wherein the powder is produced by water atomization. 17 200808982 8 - A method for producing a water atomized prealloyed iron-based powder comprising, by weight %, 10.5-30 Cr 3-15 A1 5_20 Cu up to 0.1 C up to 0.2 N Up to 3.0 Μη up to 2.5 Si up to 3.0 Mo The remainder is essentially only iron and unavoidable impurities; s "wide: the method consists of providing a melt of iron and alloying elements, which atomizes this melting t, thereby The droplets form a powder after solidification. 9. The method of claim 8, wherein the iron-based powder advance comprises 8-20% by weight of Ni. 10 - A method of manufacturing a sintered component, comprising: A pre-alloy comprising water atomization comprising the following in weight percent: 10.5-30 Cr 3-15 A1 5-20 Cu up to 0.1 C up to 0.2 N up to 3.0 Mn 18 200808982 - up to 2.5 Si up to 3.0 Mo remainder Basically only iron and unavoidable impurities; b) forming a green body from the sintered material, and C) sintering the raw material in a reducing or neutral atmosphere at atmospheric or subatmospheric pressure and at a temperature higher than 11001 η. The method of claim 1 (), wherein the sintered material provided in a) is a mixture of a lubricant and/or a binder and a water atomized prealloyed iron, a base powder. 12. The method of applying for patent scope item u Wherein in b) the preparation is formed by cold forming the mixture, wherein the house pressure ranges from 100 to 1000 MPa and the temperature is below 1 〇 (rc. 13. as claimed in the scope of claim u The method wherein, in b), the preparation is formed by warm-forming the mixture, wherein the compaction pressure ranges from 300 to 1000 MPa and the temperature ranges from 1 〇〇 2 〇〇 ec. The method of claim 1, wherein the sintered material provided in the kitchen is only a water atomized prealloyed iron-based powder. 15. The method of claim 2, wherein the green body The green body is not compacted. 16. A sintered member produced by the method of any one of the preceding claims, wherein the sintered density of the member is greater than 6 gram / Cubic centimeters. 17. A sintered component produced by the method of any one of claims 10 to 14, wherein the tensile strength of the member is greater than 5 〇〇 19 200808982, MPa. A sintered member manufactured by the method of any one of claims 10 to 14, wherein the member has a yield strength of more than 400 MPa. Η•1, schema: as the next page 20