粉末射出成型(亦稱為金屬射出成型(MIM))係用於生產具有複雜形狀之高密度燒結組件之令人關注的技術。一般而言，此製程中使用精細羰基鐵粉末。所用其他類型之粉末係具有極精細粒度之經氣體霧化或水霧化者，其成本相對較高。為改良MIM製程之競爭力，期望降低所用粉末之成本。達此目的之一種方式係藉由利用較粗糙粉末。然而，粗糙粉末具有較精細粉末低之表面能且因此在燒結期間活性低得多。另一問題係使用粗糙及不規則粉末導致較低堆積密度且因此原料之最大粉末含量受限制。較低粉末含量在燒結期間產生較高收縮且可導致尤其在生產運行中所產生組件之間之高維散射。 WO2012089807揭示粗糙粉末之使用，其達成大於95%之理論密度。仍然需要可達成甚至更高密度之技術。 通常地，以鐵為主之MIM原料(即，準備好射出之以鐵為主之粉末與有機黏合劑之混合物)之固體負載(即，以鐵為主之粉末之部分)係約50體積%，此意味著為在燒結後達到高密度(高於理論密度之93%)，生坯組件必須收縮幾乎50體積%。此與藉助單軸壓縮產生之PM組件(其已呈生坯狀態)獲得相對高之密度形成對比。因此，MIM中通常使用具有高燒結活性之精細粉末。藉由升高燒結溫度，可使用較粗糙粉末。然而，此產生晶粒粗化，此進而給出並非最佳之機械性質。 已意外發現，金屬粉末具有某一組成之粗糙金屬粉末可在用於粉末射出成型之原料中使用，以獲得燒結密度為理論密度之至少96%之組件。Powder injection molding (also known as metal injection molding (MIM)) is an interesting technology for producing high-density sintered components with complex shapes. Generally speaking, fine carbonyl iron powder is used in this process. The other types of powders used are those with extremely fine particle size that are gas atomized or water atomized, and their cost is relatively high. In order to improve the competitiveness of the MIM process, it is desired to reduce the cost of the powder used. One way to achieve this is by using coarser powder. However, coarse powders have lower surface energy than fine powders and therefore have much lower activity during sintering. Another problem is that the use of coarse and irregular powder results in lower bulk density and therefore the maximum powder content of the raw material is limited. Lower powder content produces higher shrinkage during sintering and can lead to high-dimensional scattering between components, especially during production runs. WO2012089807 discloses the use of coarse powder to achieve a theoretical density greater than 95%. There is still a need for technologies that can achieve even higher densities. Generally, the solid load (ie, the part of the iron-based powder) of the iron-based MIM raw material (ie, the mixture of the iron-based powder and the organic binder ready for injection) is about 50% by volume This means that in order to achieve high density after sintering (higher than 93% of theoretical density), the green component must shrink by almost 50% by volume. This is in contrast to the relatively high density of PM components produced by uniaxial compression (which are already in a green state). Therefore, fine powders with high sintering activity are usually used in MIM. By increasing the sintering temperature, coarser powder can be used. However, this produces grain coarsening, which in turn gives sub-optimal mechanical properties. It has been unexpectedly discovered that the rough metal powder with a certain composition of the metal powder can be used in the raw material for powder injection molding to obtain a component with a sintered density of at least 96% of the theoretical density.
本發明之一個目標係提供相對粗糙之不銹鋼粉末組合物，其具有少量適用於金屬射出成型之合金元素。 本發明之另一目標係提供金屬射出成型原料組合物，其包含該相對粗糙之不銹鋼粉末組合物。 本發明之另一目標係提供自原料組合物生產射出成型之燒結組件之方法，該等組件之密度為理論密度之至少96%。 本發明之又一目標係提供根據MIM製程所生產之燒結組件，其在如此燒結而未硬化之情形下之密度為理論密度之96%及以上且拉伸強度高於800 MPa。 該等目標之至少一者係藉由以下實現： 一種用於金屬射出成型之以鐵為主之粉末組合物，其中值粒度為20-60 µm、較佳20-45 µm、最佳25-45 µm或甚至更佳25-35 µm。粒度係使用Sympatec Helos儀器藉由雷射繞射來測定。如上文所界定之中值粒度意味著粉末中50%之粒子大於此值。通常將此值稱為「X50」值。 一種金屬射出成型原料組合物，其包含經霧化之以鐵為主之粉末組合物，其中值粒度為20-60 µm、較佳20-45 µm、最佳25-45 µm或甚至更佳25-35 µm；及有機黏合劑。 一種用於生產燒結組件之方法，其包含以下步驟： a)製備如上文所建議之金屬射出成型原料； b)使原料成型為未燒結之坯料； c)去除有機黏合劑； d)在還原性氛圍中在1200-1400℃間之溫度下燒結所得坯料； e)使燒結組件冷卻，及； f)視情況使組件經受燒結後處理，例如沈澱硬化、表面硬化、滲氮、滲碳、氮碳共滲、碳氮共滲、感應硬化、表面滾壓及/或噴珠處理。 一種自原料組合物製得之燒結組件，該組件之密度為理論密度之至少96%且拉伸強度高於800 MPa。An object of the present invention is to provide a relatively rough stainless steel powder composition with a small amount of alloying elements suitable for metal injection molding. Another object of the present invention is to provide a metal injection molding raw material composition, which includes the relatively rough stainless steel powder composition. Another object of the present invention is to provide a method for producing injection-molded sintered components from the raw material composition, the density of which is at least 96% of the theoretical density. Another object of the present invention is to provide a sintered component produced according to the MIM process, the density of which is 96% or more of the theoretical density and the tensile strength is higher than 800 MPa under such sintered but unhardened condition. At least one of these goals is achieved by the following: An iron-based powder composition for metal injection molding, with a median particle size of 20-60 µm, preferably 20-45 µm, and optimally 25-45 µm or even better 25-35 µm. The particle size is measured by laser diffraction using Sympatec Helos instrument. The median particle size as defined above means that 50% of the particles in the powder are larger than this value. This value is usually called the "X50" value. A metal injection molding raw material composition comprising an atomized iron-based powder composition with a median particle size of 20-60 µm, preferably 20-45 µm, most preferably 25-45 µm or even more preferably 25 -35 µm; and organic binder. A method for producing sintered components, which includes the following steps: a) preparing the metal injection molding raw material as suggested above; b) forming the raw material into an unsintered blank; c) removing the organic binder; d) reducing The resulting blank is sintered at a temperature between 1200-1400°C in an atmosphere; e) cooling the sintered component, and; f) subjecting the component to post-sintering treatments as appropriate, such as precipitation hardening, surface hardening, nitriding, carburizing, nitrocarburizing Co-infiltration, carbonitriding, induction hardening, surface rolling and/or beading. A sintered component made from a raw material composition, the density of the component is at least 96% of the theoretical density and the tensile strength is higher than 800 MPa.
不銹鋼粉末組合物包括至少一種以鐵為主之粉末及/或純鐵粉末。以鐵為主之粉末及/或純鐵粉末可藉由水或氣體霧化鐵熔體及視情況合金元素來產生。經霧化粉末可進一步經受還原退火製程，並視情況進一步藉由使用擴散合金化製程來使其合金化。或者，鐵粉末可藉由還原氧化鐵來產生。 鐵粉末或以鐵為主之粉末組合物之粒度使得中值粒度為20-60 µm、較佳20-45 µm、最佳25-45 µm或甚至更佳25-35 µm。此外，較佳X99
應為至多120 µm、較佳至多100 µm。(X99
意指99%之粒子具有小於X99
之粒度) 銅(Cu)將藉助固溶硬化來增強強度及硬度。Cu亦將在燒結期間促進燒結頸之形成，此乃因銅在達到燒結溫度之前熔融，提供所謂的液相燒結。粉末可視情況與較佳呈Cu粉末形式之Cu以0-5 wt%或3-5 wt%之量混合。 可視情況將諸如硬質相材料及機械加工性增強劑(例如MnS、MoS2
、CaF2
、不同種類之礦物等)之其他物質添加至以鐵為主之粉末組合物。 原料組合物可藉由將上述以鐵為主之粉末組合物與黏合劑混合來製備。 呈至少一種有機黏合劑形式之黏合劑可以30-65體積%、較佳35-60體積%、更佳40-55體積%之濃度存在於原料組合物中。當在本說明書中使用術語黏合劑時，亦包括一般於MIM-原料中之其他有機物質，例如釋放劑、潤滑劑、潤濕劑、流變改質劑、分散劑。適宜有機黏合劑之實例係蠟、聚烯烴(例如聚乙烯及聚丙烯)、聚苯乙烯、聚氯乙烯、聚碳酸伸乙酯、聚乙二醇、硬脂酸及聚甲醛。 使原料組合物成型為坯料。然後將所得坯料熱處理或在溶劑中處理或藉由其他手段以如業內已知去除一部分黏合劑，並然後使其在還原性氛圍中在真空或減壓下在約1200-1400℃之溫度下進一步經受燒結。 燒結組件可(例如)藉由熱處理及藉由控制之冷卻速率經受熱處理製程以獲得期望之微結構。硬化製程可包括已知製程，例如沈澱硬化、淬火及回火、表面硬化、滲氮、滲碳、氮碳共滲、碳氮共滲、感應硬化及諸如此類。或者，可利用高冷卻速率之燒結-硬化製程。 可利用引入壓縮殘餘應力之其他類型之燒結後處理(例如表面滾壓或噴珠處理)，以增強疲勞壽命。 本發明之燒結組件之燒結密度達到理論密度之至少96%且拉伸強度高於800 MPa。 實例1 製備根據表1之以鐵為主之粉末組合物。
表1實例 2
將組合物壓縮至約4.5g/cm³之密度(理論密度之58%)，變成直徑25 mm及高度8 mm之圓柱體，且其後將A及E在1350℃下在100體積% H2
之氛圍中在1200分鐘期間內燒結。將試樣C在1380℃下120分鐘期間內100% H2
中燒結。使用如標準SS-EN ISO 3369:2010中所述之水置換法量測燒結密度。 表2顯示測試結果 實例 3
製備分別含有金屬粉末組合物A、B及D之原料並藉由將粉末組合物與有機黏合劑混合而與自組合物C製造之原料比較。黏合劑由47.5%聚乙烯、47.5%石蠟及5%硬脂酸構成。所有百分比係重量百分比。將有機黏合劑與粉末組合物以體積計53:47之金屬粉末:黏合劑之比率混合。 根據ISO- SS EN ISO 2740，使原料射出成型為標準MIM拉伸試棒。然後將試樣在60℃下於己烷中脫膠4小時以去除石蠟，隨後在1350℃下100%氫之氛圍中燒結120分鐘。 使用水置換法量測燒結密度。根據SS EN ISO 2740測試拉伸測試。結果顯示於表3中。標準值係自ISO22068獲得並顯示呈燒結狀態之標準合金17-4PH及316L之值。機械性質呈現為標準值之%以能夠比較兩種不同的合金。
表3The stainless steel powder composition includes at least one iron-based powder and/or pure iron powder. Iron-based powder and/or pure iron powder can be produced by atomizing iron melt with water or gas and alloying elements as appropriate. The atomized powder can be further subjected to a reduction annealing process, and optionally further alloyed by using a diffusion alloying process. Alternatively, iron powder can be produced by reducing iron oxide. The particle size of the iron powder or iron-based powder composition is such that the median particle size is 20-60 µm, preferably 20-45 µm, most preferably 25-45 µm, or even more preferably 25-35 µm. In addition, X 99 should preferably be at most 120 µm, preferably at most 100 µm. (X 99 means that 99% of the particles have a particle size smaller than X 99 ) Copper (Cu) will enhance strength and hardness by solid solution hardening. Cu will also promote the formation of sintering necks during sintering, because copper melts before reaching the sintering temperature, providing so-called liquid phase sintering. The powder may be mixed with Cu, preferably in the form of Cu powder, in an amount of 0-5 wt% or 3-5 wt% as appropriate. Other substances such as hard phase materials and machinability enhancers (such as MnS, MoS 2 , CaF 2 , different types of minerals, etc.) can be added to the iron-based powder composition as appropriate. The raw material composition can be prepared by mixing the above-mentioned iron-based powder composition with a binder. The binder in the form of at least one organic binder may be present in the raw material composition at a concentration of 30-65% by volume, preferably 35-60% by volume, more preferably 40-55% by volume. When the term binder is used in this specification, it also includes other organic substances commonly found in MIM-materials, such as release agents, lubricants, wetting agents, rheology modifiers, and dispersants. Examples of suitable organic binders are waxes, polyolefins (such as polyethylene and polypropylene), polystyrene, polyvinyl chloride, polyethylene carbonate, polyethylene glycol, stearic acid, and polyoxymethylene. The raw material composition is formed into a blank. The resulting blank is then heat-treated or treated in a solvent or by other means to remove a part of the binder as known in the industry, and then subjected to a further step in a reducing atmosphere at a temperature of about 1200-1400°C under vacuum or reduced pressure. Withstand sintering. The sintered component can, for example, undergo a heat treatment process by heat treatment and by a controlled cooling rate to obtain the desired microstructure. The hardening process may include known processes such as precipitation hardening, quenching and tempering, surface hardening, nitriding, carburizing, nitrocarburizing, carbonitriding, induction hardening, and the like. Alternatively, a sinter-hardening process with a high cooling rate can be used. Other types of post-sintering treatments (such as surface rolling or beading) that introduce compressive residual stresses can be used to enhance fatigue life. The sintered density of the sintered component of the present invention reaches at least 96% of the theoretical density and the tensile strength is higher than 800 MPa. Example 1 A powder composition based on iron according to Table 1 was prepared. Table 1 Example 2 The composition was compressed to a density of about 4.5g/cm³ (58% of the theoretical density), and it became a cylinder with a diameter of 25 mm and a height of 8 mm, and then A and E were placed in 100 volumes at 1350℃ Sintering within 1200 minutes in an atmosphere of% H 2 . Sample C was sintered in 100% H 2 at 1380°C for 120 minutes. The sintered density is measured using the water displacement method described in the standard SS-EN ISO 3369:2010. Table 2 shows the test results Example 3 Prepared raw materials containing metal powder compositions A, B, and D, and compared them with raw materials made from composition C by mixing the powder composition with an organic binder. The adhesive is composed of 47.5% polyethylene, 47.5% paraffin wax and 5% stearic acid. All percentages are percentages by weight. Mix the organic binder and the powder composition at a ratio of 53:47 metal powder: binder by volume. According to ISO-SS EN ISO 2740, the raw materials are injection molded into standard MIM tensile test bars. The sample was then degummed in hexane at 60°C for 4 hours to remove paraffin, and then sintered in a 100% hydrogen atmosphere at 1350°C for 120 minutes. The sintered density is measured by the water displacement method. The tensile test is tested according to SS EN ISO 2740. The results are shown in Table 3. The standard value is obtained from ISO22068 and shows the value of standard alloy 17-4PH and 316L in a sintered state. The mechanical properties are presented as% of the standard value to be able to compare two different alloys. table 3
