Microwave Sintering – A Novel Approach to Powder Technology

2010 ◽  
Vol 636-637 ◽  
pp. 946-951 ◽  
Author(s):  
Teresa Marcelo ◽  
João M.G. Mascarenhas ◽  
Fernando A. Costa Oliveira
Keyword(s):  
Stainless Steel ◽  
Microwave Radiation ◽  
Energy Savings ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Steel Powder ◽  
Powder Technology ◽  
Metal Powders ◽  
Novel Approach ◽  
Microstructural Evaluation

The present paper focus on preliminary work carried out at INETI concerning the use of microwave radiation applied to sintering of both ceramic and metal powders. Due to the characteristics of materials-radiation interaction, microwaves can become an interesting power source in powder technology and other processing routes, since it is possible to lower the sintering temperature and shorten the sintering cycles, leading to time and energy savings. Alumina, hydroxyapatite, titanium and stainless steel powder compacts were sintered in a modified commercial oven of 2.45GHz and 1000W nominal power. Microwave susceptors were used to enable temperature rise during the initial stage of the sintering cycles. Results on densification and microstructural evaluation of microwave sintered samples are reported and compared to conventionally sintered ones, when available. For similar porosity levels upon sintering, microwave radiation generally reduces sintering times from several hours to minutes. The results obtained so far are quite encouraging since in the case of alumina and stainless steel compacts, a decrease of about 200°C in the sintering temperature was achieved. It was also found that the green density plays a key role in the densification of both metallic and ceramic powders.

Effects of Sintering Conditions on Properties of a Warm Compacted Stainless Steel Powder

2012 ◽  
Vol 217-219 ◽  
pp. 483-486
Author(s):  
Mei Yuan Ke
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Sintered Density ◽  
Sintering Temperature ◽  
Steel Powder ◽  
Stainless Steel Powder ◽  
Sintering Atmosphere ◽  
Comprehensive Properties ◽  
Ammonia Atmosphere ◽  
Sintering Conditions

Effects of Sintering atmosphere and temperature on properties of warm compacted 410L stainless steel powder were studied. Sintered density, hardness, tensile strength and elongation were measured. Results showed that in order to achieve high comprehensive properties, the optimal sintering temperature was 1230°C for 410L stainless steel powder. At the same sintering temperature, density and hardness sintered in vacuum were much higher than that sintered in cracked ammonia while tensile strength sintered in cracked ammonia were much higher than that in vacuum. When sintered in vacuum at 1230°C, sintered density was 7.45 g•cm-3, hardness was 65 HRB, tensile strength was 410 MPa and elongation was 29.5%. When sintered in cracked ammonia atmosphere at 1230°C, sintered density was 7.26 g•cm-3, hardness was 97 HRB, tensile strength was 515 MPa and elongation was 3.8%.

Dry Mixing of Feedstock for injection Moulding of 316L Stainless Steel Powder

2012 ◽  
Author(s):  
Mohd. Afian Omar
Keyword(s):  
Stainless Steel ◽  
Injection Moulding ◽  
316L Stainless Steel ◽  
Steel Powder ◽  
Model Material ◽  
Stainless Steel Powder ◽  
Metal Powders ◽  
Wet Process ◽  
Moulding Machine ◽  
Dry Mixing

Bahan pengikat pengacuan yang terdiri daripada polietilina glikol (PEG) dan polimetil metakrilate (PMMA) telah dihasilkan untuk proses pengacuan suntikan logam. Penyediaan bahan suapan adalah secara kaedah basah di mana PMMA adalah dalam bentuk emulsi dengan saiz serbuk antara 0.1 µm hingga 0.2 µm. Oleh itu, untuk menghindarkan proses pengeringan, satu kaedah baru penyediaan bahan suapan dalam bentuk percampuran kering telah dilakukan. Untuk ini, PMMA yang digunakan adalah terdiri daripada serbuk PMMA komersial berjenama Elvacite yang mempunyai saiz serbuk 100 µm dan juga serbuk PMMA yang didapati daripada proses pengeringan emulsi yang dikisar dan diayak hingga ke saiz serbuk 53 µm. Bahan suapan tersebut telah dicampur ke dalam mesin pencampur bilah sigma selama dua jam pada suhu 120°C. Bahan suapan kemudian disemperit panas sebelum dilakukan proses pengacuan. Keputusan uji kaji menunjukkan dalam semua kes, didapati PMMA telah menyerak secara tidak sekata. Ini seterusnya meningkatkan lagi bahan teracu untuk mengampul semasa proses pengurasan dan menyebabkan bahan tersinter mempunyai banyak keliangan. Walau bagaimanapun, adalah dirumuskan bahawa dengan menggunakan serbuk PMMA yang bersaiz lebih kecil, produk yang lebih baik akan diperolehi. Kata kunci: Percampuran kering, pengacuan suntikan logam, pengsinteran, bahan suapan, serbuk keluli tahan karat 316L An injection moulding binder, which is composed of poly ethylene glycols (PEGs) of various molecular weights and poly methylmethacrylate (PMMA), has been developed for injection of metal powders. Feedstocks have been prepared using a wet process with PMMA introduced in the form of an emulsion with particles of 0.1 to 0.2 µm in size. To eliminate the drying process, an attempt has been made to prepare the feedstock using a dry mixing process using 316L stainless steel powder as a model material. For this, the PMMA used was either a commercial powder, Elvacite, with a particle size of up to 100 m or a powder obtained by drying the emulsion and grinding the resultant cake, followed by classification using 53 µm sieves. The feestock constituents were mixed into a sigma blade mixer for 2 hours at mixing temperature of 120°C. The feedstock was then hot extruded using piston injection moulding machine prior to being moulded. It was found in all cases that PMMA was poorly dispersed. This resulted in an increased tendency for the moulded bars to swell on being leached and the sintered bars to have a substantial residual porosity. This study suggests that by using small particles of PMMA powder, an acceptable product could be obtained. Key words: Dry mixing, metal injection moulding, sintering, feedstock, 316L stainless steel powder

scholarly journals Microwave Sintering and Microwave Dielectric Properties of (1–x)Ca0.61La0.26TiO3-xNd(Mg0.5Ti0.5)O3 Ceramics

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 438
Author(s):  
Shuwei Yang ◽  
Bingliang Liang ◽  
Changhong Liu ◽  
Jin Liu ◽  
Caisheng Fang ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Mobile Communications ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Microwave Dielectric Properties ◽  
Conventional Heating ◽  
Sintering Process ◽  
Microwave Dielectric ◽  
Sintering Time ◽  
Frequency Temperature

The (1–x)Ca0.61La0.26TiO3-xNd(Mg0.5Ti0.5)O3 [(1–x)CLT-xNMT, x = 0.35~0.60] ceramics were prepared via microwave sintering. The effects of sintering temperature and composition on the phase formation, microstructure, and microwave dielectric properties were investigated. The results show that the microwave sintering process requires a lower sintering temperature and shorter sintering time of (1–x)CLT-xNMT ceramics than conventional heating methods. All of the (1–x)CLT-xNMT ceramics possess a single perovskite structure. With the increase of x, the dielectric constant (ε) shows a downward trend; the quality factor (Qf) drops first and then rises significantly; the resonance frequency temperature coefficient (τf) keeps decreasing. With excellent microwave dielectric properties (ε = 51.3, Qf = 13,852 GHz, τf = −1.9 × 10−6/°C), the 0.65CLT-0.35NMT ceramic can be applied to the field of mobile communications.

Behavior of Microwave Heating of 316 Stainless Steel Green Body

2014 ◽  
Vol 936 ◽  
pp. 1694-1700
Author(s):  
Zhi Wei Li ◽  
Kai Yong Jiang ◽  
Fei Wang ◽  
Ji Liang Zhang
Keyword(s):  
Particle Size ◽  
Stainless Steel ◽  
Microwave Heating ◽  
Powder Particle ◽  
Microwave Power ◽  
Arc Discharge ◽  
Steel Powder ◽  
Powder Particle Size ◽  
Auxiliary Heating ◽  
316 Stainless Steel

This paper mainly introduces the mechanism of microwave heating: electric conduction loss, eddy current loss and arc discharge. The microwave heating behavior of 316 stainless steel powder body which made by gel casting was investigated in the paper. Experiments on different microwave power, powder particle size, and the content of auxiliary heating material showed that the smaller the powder particle size, the larger microwave power and auxiliary heating materials help 316 stainless steel body for sintering.

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