Abstract:
From governments policy launching in 2007 supporting utilization of organic fertilizer in agriculture, Thailand Institute of Scientific and Technological Research (TISTR) was assigned to provide academic support for this policy and create some equipment for producing organic fertilizer as well as establish some factories to produce organic fertilizer throughout Thailand under the project called One Amphur One Fertilizer Plant. From the operation of each factory to produce such fertilizer, the important problem of production process was found, namely, organic fertilizer compress machine had short useful life considerably affecting the cost of fertilizer production. It was also found that, steel with low carbon amount was mostly preferred to make the mold of compress machine because it was easy to find with cheap price. However, such steel had never been processed with any thermal process. As a result, Thailand Institute of Scientific and Technological Research (TISTR) emphasized on the research aiming to extend the useful life of fertilizer compress machine in order to reduce the cost of organic fertilizer production. From initial study, it was found that main variables of organic fertilizer compress machines quality depended on types of steel and hardening. However, since there is limitation on supplying steel as mentioned above, it is necessary for this project to study on suitable hardening by selecting to study the hardening process with salt bath nitro carburizing method and the hardening process with gas carbonitriding method. The comparison is done between both methods at deep hard layer for 2 deep hard layers each. It is found that the hardening process by using gas carbonitriding method at deep hard layer of 0.5 millimeter can maximize the useful life of molding of no less than 3 times when compares to non-hardening process while the cost of molding manufacturing increases by 10%.