Diseño y construcción de una máquina automatizada para ensayos Jominy de acuerdo a la normativa ASTM A255 para la determinación de curvas de templabilidad en aceros

Abstract

The objective of this project was to design, build and automate a Jominy testing machine according to the ASTM A-255 standard, to perform hardenability tests on steels. Initially, the QFD was deployed, to know that the experimental requirements established in the ASTM A-255 standard are to obtain a column of cooling fluid 2.5 in of eight and maintain it for 10 min. The design of the machine was divided into three parts: hydraulic, structural, and electronic. In the hydraulic part it was designed the tanks, the cooling nozzle and a pipe bypass, which consists of: a “cooling” line and a “drainage” line. In the electronics, the control algorithm was programmed and 8.46 liters per minute was established as the reference flow, a value that must be read by the flow sensor installed in the cooling line to start the test; otherwise, the PLC activates the valve installed in the drain line until reaching the reference flow. The structure was designed as compact as possible, and its resistance was verified with a static simulation carried out in ANSYS. To verify the functionality of the machine once built, the theoretical hardenability curve shown in (Callister, 1995, p.344) was contrasted with the experimental curve obtained for AISI 4340 steel; and it was observed that it follows the same trend as the theoretical one and the hardness values do not vary significantly. In addition, a micrographic analysis of the tempered specimen was carried out, where it was found that the tempered end has a 100% martensitic structure as predicted in the CCT diagrams. Analyzing the results obtained, it was concluded that the design proposed for the Jominy machine meets the experimental requirements established in the ASTM A-255 standard and is suitable for use in the laboratory.