This Research is a Development of 8k White Gold low Alloy Metal Components for Jewelry Pieces. By Study and Analyze the Influence of Silver Alloy Gold Alloy Bronze Alloy Zinc Alloy and Tin Alloy. Which Affect Microstructure and Mechanical Properties. (The Different of Color Scales) And Resistance Behavior of Lowered 8k White Gold Alloy in Varies Ratio. The Results Showed that Tests and Analysis to Find the Quantities of Elements has found out that Chemical Components of 8k White Gold Low Alloy Metal had a Little Different Quantities when Compared Between Before and After Centrifugal Casting Process. The Tests and Analysis Results of Mechanical Properties of Test Pieces Showed that the Hardness and Tensile Strength of 8k White Gold Low Alloy Metal with Mixture of 33.33%Au+50.67%Ag+10%Cu+5%Zn+1%Sn had Minimum Ultimate Tensile Strength Equal 0.54 kN/mm2 Minimum Elongation Percentage of 55% and Maximum Hardness of 137.0 HV. The Test Results also Show that the Mechanical Properties of the Material are Brittle Material. When Perform a Forming Process the Pieces will be Easily Broken which was Meant that the Forming Process would be Difficult. But The Color Level of the Test Pieces at this Composite Ratio had the Best Metal Color Level. The Brightness L * = 74.87 was a * = -0.89 b * = 13.74 and the Value of ΔE with the Lowest Color Difference Level of 1.35. Compared to other Varies Ratio. It Showed that 8k White Gold Low Alloy Metal Test Pieces were Very Green and Came out Slightly Yellow Compared to the Blue Line that Approached the Standard Line. These Properties were the Physical Properties Required in 8k White Gold Low Alloy Metal Jewelry Pieces Production. Also there were the Results of 8k White Gold Low Alloy Metal in Two Formulas 8k 33.33%Au+50.67%Ag +8%Cu+7%Zn+1%Sn 33.33%Au+50.67%Ag+8%Cu+8%Zn+0%Sn. These Formulas had Tensile Strength in the Range of 1.10 0.60 kN /mm2 Elongation Percentage in the Range of 70 61% and Hardness of 115.6 123.3HV Respectively. The Results of the Mechanical Properties Test of the Test Pieces Showed that 8k White Gold Low Alloy Metal 33.33% Au+50.67%Ag+8%Cu+7%Zn+1%Sn has Similar Tensile Strength but Maximum Elongation Percentage of 70% and Minimum Hardness of 115.6HV. Which was Suitable for Forming Because of good Ductility and Stretchness Properties (Ductile Material). Forming would be Easy. These were Good Mechanical Properties for Forming Precious Metals.

This study developed the cemented tungsten carbide by steadily sintering at 1430 °C for one hour. The tungsten carbide structure is a long shape. Its grain size has a difference between width and length and there are high distribution of sizes and shapes. In comparison with the work piece which has the similar size of grain structure the milling duration of tungsten carbide is less even though the condition of WC-Co is the same (95% WC – 5% Co). When the sintering of 1400 °C with the identical milling duration is performed. It turned out that both grain structures of the tungsten carbide and the work piece are similar and their grain sizes are slightly different. However when the grain structures are almost the same and sphericity is increased the hardness and wear resistance will also be improved. Therefore the size of grain structure between 1.00 – 3.00 μm with the milling duration of 100 hours will provide a work piece that has a wear resistance according to international standard

การวิจัยนี้เป็นการศึกษาสมบัติของโลหะเงินเจือต่า 58.33% ที่มีธาตุทองแดง (Cu) และดีบุก (Sn) เป็นธาตุผสม ซึ่งมีปริมาณการผสมอยู่ในช่วงระหว่าง 36.66 - 41.57% และ 0.10-5.01% ตามล่าดับ โดยท่าการเปรียบเทียบกับสมบัติของโลหะเงินสเตอร์ลิง 925 และโลหะเงินเจือต่า 58.33% เพื่อศึกษา วิเคราะห์อิทธิพลของธาตุเจือทองแดงและดีบุกที่มีผลต่อสมบัติทางกลและโครงสร้างจุลภาของโลหะเงินเจือ ต่า 58.33 wt% AgCuSn และหาปริมาณของธาตุเจือทองแดงและดีบุกที่เหมาะสมในการผลิต เครื่องประดับเงินเจือต่า 58.33% ผลจากการศึกษาโลหะเงินเจือต่า 58.33 % ที่ประกอบด้วยเงิน (Ag) และทองแดง (Cu) เมื่อ น่ามาเปรียบเทียบกับโลหะเงินสเตอร์ลิง 925 จากการศึกษาเปรียบเทียบพบว่าโลหะเงินผสมเจือต่า 58.33Ag + 36.66Cu +5.01Sn มีค่า Yield Strength 195.2 Mpa Ultimate tensile strength 345.25 MPa Breaking point 301 MPa และ Elongation 61.58 % ซึ่งเป็นอัตราส่วนผสมของแต่ละ ธาตุที่เหมาะสมที่สุด ค่าความแข็งของโลหะเงินเจือต่า 58.33Ag + 41.57Cu + 0.10Sn มีค่าความแข็ง น้อยที่สุด เท่ากับ 93.03 HV ซึ่งปริมาณดีบุก (Sn) ที่ผสมเข้าไปในอัตราส่วน 0.10Sn จะท่าให้โครงสร้าง ของเงินเจือต่า เป็น β-phase เกิดการเปลี่ยนแปลงจาก β phase ที่มีขนาดเล็กลงเป็นโครงสร้าง Eutectic phase ที่มี α-phase และ β-phase ขนาดเล็กและละเอียด ผลจากการวิเคราะห์ส่วนผสมทางเคมีของโลหะเงินเจือต่า 58.33% พบว่าส่วนผสมทางเคมี ของโลหะเงินเจือต่าในแต่ละอัตราส่วนผสมมีสัดส่วนของธาตุใกล้เคียงกับอัตราส่วนผสมจริง จึงท่าให้โลหะ เงินเจือต่าที่ได้ท่าการทดลองมีค่าที่เป็นไปตามมาตรฐานของเครื่องประดับเงินตามมาตรฐานอุตสาหกรรม การผลิตเครื่องประดับทั้งของในประเทศและต่างประเทศ

The research involved the characterization of the properties of silver alloys -bearing copper and zinc. The alloys composed of 58.4% silver 20.85-41.76% copper and 0-20.83% zinc respectively. When comparing the characteristics of this alloy and sterling silver 925 the alloy specimen had mechanical properties better than the sterling silver 925. The alloy tests presenting the mechanical values of the hardness shear bond strength elasticity of the specimen were in a range of 54.6-95.3 HV1 209.5-379.3 MPa. 100.6-193.8 MPa. and 32.1-51.7% respectively. While the mechanical values of sterling silver 925 were 52.8 HV1 193.5MPa. 96.0 MPa. and 29.8% respectively. Besides these the microstructure of the alloy specimen showed the dendrite structure. We found that this structure decreased when the concentration copper in the specimen increased. After adding zinc into the alloys the high amount of zinc caused the zinc-rich (alpha) phase changed to Eutectic phase together with the significantly increased area of alpha phase. These effects therefore brought up the better various mechanical properties of the alloys. At the same time the another test specimen composed 58.67% Ag 39.20% Cu and 2.14% zinc. The color level of this specimen was close typically to the sterling silver 925 with the difference of Da at 0.236 and Db only at 5.268. Additionally the higher copper concentration in the alloy provided a value tentatively increased but b value decreased. However more remarkable results were that the zinc showed opposite effects from the copper.

Drying an agricultural product with hot air (HA) method causes a long drying time and results in high specific drying energy consumption (SEC). The dried product has high shrinkage percentage and low rehydration. Therefore this research aims to develop dried shiitake mushroom using belt-conveyor combined microwave-hot air drying method (MHB). The shiitake mushroom was dried by MHB at microwave power of 300 W 400 W 500 W and 600 W and air temperature of 65 oC with air velocity of 0.3 m/s and recycled air of 80% and by the HA drying method at air temperature of 65 oC. The samples were dried until their final moisture content less than 11.1% dry basis. The drying kinetics SEC of drying process and quality of dried shiitake mushroom were evaluated. The quality of dried product was considered in terms of color shrinkage rehydration texture water activity and microstructure. The results showed that the shiitake mushroom drying using MHB gave higher drying rate than that of HA drying method leading to short drying time and resulting in low SEC. The drying rate of un-blanched shiitake mushroom was higher than that of blanched shiitake mushroom. Dried shiitake mushroom from MHB drying gave lower values in shrinkage percentages and hardness but higher rehydration and larger pore size than that dried by HA drying. However the color values (L* +a* and +b*) of dried shiitake mushroom in all cases were not significantly different. Meanwhile dried shiitake mushroom from un-blanched case gave lower values in shrinkage percentage and hardness but higher values in all colors and rehydration and larger pore size than those of blanched case.