LAB REP?RT

Lab Rep?rt

[Name ?f the Writer]

[Name ?f the Instituti?n]

Lab Rep?rt

I.?bjective

In this particular lab, we c?nducted experiments in ?rder t? learn ab?ut h?w different thermal treatments affected the micr?structure and material pr?perties ?f several steel specimens. We perf?rmed hardness and bending tests in ?rder t? analyze h?w furnace-c??led, n?rmalized, and ?il-quenched specimens reacted under stress. In d?ing s?, we gained s?me insight int? h?w thermal meth?ds can bring ab?ut desired macr?sc?pic pr?perties in certain materials. Additi?nally, we learned h?w these heat treatments affected the materials at a micr?sc?pic level.

II.Experimental Meth?ds

Heat Treatments

In ?rder t? discuss the macr?sc?pic pr?perties ?f these steel specimens, it is imp?rtant t? pr?vide f?rmal definiti?ns f?r the thermal treatments that will be referenced thr?ugh?ut. Pri?r t? the experiments, the f?ll?wing thermal treatments were perf?rmed ?n the steel specimens:

An annealed specimen is a specimen that has been put int? a furnace at 850 degrees Celsius, which is the austenitic range f?r the metal. It is held f?r ?ne h?ur, and then furnace-c??led at a steadily-decreasing temperature f?r 10 h?urs.

A specimen that has been austentized and quenched has been put int? a furnace at ar?und 850 degrees Celsius, held in the furnace f?r an h?ur, and immediately placed int? a large reserv?ir ?f ?il ?r water at r??m temperature.

A specimen that has been austentized, quenched and tempered underg?es the same pr?cess as the austentized and quenched meth?d, but after it is c??led in the large reserv?ir ?f ?il, it is re-heated t? its tempering temperature (~250( C), held f?r 2 h?urs and c??led at r??m temperature.

All ?f the thermal meth?ds defined ab?ve have different implicati?ns ?n the micr?sc?pic structure ?f materials that underg? these meth?ds. As will be discussed at length later in this rep?rt, engineers can utilize these meth?ds in ?rder t? m?dify the mechanical pr?perties ?f a metal s? that they are better suited f?r a particular applicati?n.

Manual Bending Test

Specimens ?f 4140 Steel (each with a diameter ?f r?ughly 6.3 mm) that had been annealed, quenched, and quenched/tempered were tested f?r their tensile yield strength by being subjected t? an end l?ad perpendicular t? the plane ?f the specimen. Preparati?n f?r this experiment inv?lved placing ?ne end ?f the specimen int? a jig and clamping it d?wn t? the table. A l?ng, cylindrical metal tube ab?ut ~1 meter l?ng was placed ?n the ?ther end ?f the specimen, and a screw was tightened t? secure it ?nt? the specimen. A pict?rial representati?n ?f this experiment can be f?und in Figure E-1 in the appendices ?f this rep?rt. In c?nducting the experiment, we used tw? f?rce gauges t? apply an ?rth?g?nal l?ad t? the free end ?f the specimen, all the while measuring the m?ment arm ?f the f?rce with a tape measure. We applied a c?ntinually increasing l?ad until the specimen seemed t? def?rm at a c?nstant applied l?ad (its yield strength), ?r in ?ther cases, failed. We rec?rded the l?ad that caused the material t? reach yield strength, as well as the length ?f the m?ment arm, after ...