Quench and temper - Lab Report Example

Mechanical Engineering Technology Materials Testing Laboratory Experiment Quench and temper Experiment Number: Section: of Principal Author: Names of Contributors: Instructor Name: Quench and temper Abstract This experiment explores the effect of tempering and the tempering temperature on hardness and strength of steel. Three pieces of steel were subjected to different tempering temperatures while one piece was neither quenched nor tempered. The results indicate significant difference due to the temperatures to the conclusion that lower temperatures are recommended for the tempering stage.

Objective This paper seeks to investigate the effects of quenching and tempering on hardness and impact properties of steel. It experimentally subjects different pieces of steel to different tempering conditions to determine the effects of quenching, and tempering temperature on steel’s impact strength and hardness. Results The following tables summarize the results for the materials’ hardness readings and impact strength. Rockwell hardness readings unmarked 19.4 19.7 19.9 20.4 20.1 19.9 red 30.5 31.1 31.4 31.2 30.4 30.92 blue 48.4 48.3 48.2 48.1 48.2 48.24 yellow 54 54.4 54.7 49.8 54.4 53.

46 Material impact strength material impact strength (ft lb) unmarked 14 red 61.5 blue 17.8 yellow 18 Discussion The experiment selected four pieces of steel and designated them as unmarked, red, blue, and yellow. The unmarked piece was left untreated while the red designate was quenched and then tempered for three hours at a temperature of 1000 F. The blue designate was quenched and then tempered for three hours at a temperature of 600 F while the yellow designate was quenched, and tempered for three hours at a temperature of 350 F.

The procedure was repeated several times for each condition. The results show different values for every experimental reading on Rockwell’s hardness. There is also an identified difference between results in each treatment as can be identified from the means per treatment as shown bellow. treatment mean unmarked 19.9 red 30.92 blue 48.24 yellow 53.46 A further analysis of variance with the null hypothesis that there is no significant difference on gained strength due to treatment yields the following results.

ANOVA Source of Variation SS df MS F P-value F crit Between Groups 4329.228 3 1443.076 1567.539 6.85E-24 3.098391 Within Groups 18.412 20 0.9206 Total 4347.64 23         The small probability value identifies significant difference between groups for each of the material treatments, leading to the conclusion that the temprature to which a material is subjected during tempering determines its attained hardness. The results also show that the attained hardness is inversely proportional to temperature at the tempering stage.

The resultant material impact effect is also inversely proportional to the temperature at the tempering stage, though a deviation is at 1000 F. This can however be attributed to experimental error. Quenching and tempering is one of the approaches to achieving strength within materials such as steel. Quenching involves heating a metal to very high temperatures followed by a sudden cooling for increased strength. The tempering process that reduces the material’s brittleness to ensure strength and durability then follows this.

The first step in a quench and temper process is the intense heating that that aims at ensuring homogeneity of the steel’s elements and requires a temperature that is above the component’s transformation potential. This therefore eliminates possible asymmetries that reduce strength of normal steel. The sudden cooling then yields a “body centered ‘martensite’, which is hard” but is brittle (Black and Kohser, p. 133). The temper process however, defines a reheating of the material, at moderate temperatures to reduce the brittleness towards more malleable material (Palmer and King, p. 61). The achieved strength of the material however depends on a number of factors.

One of the factors that determine the achieved strength, and toughness, of a material from a quench and temper process is the level of orientation of microelements of the materials. Quenching and tempering process aligns the microelements to a level of homogeneity, a process that is done at the tempering process. Homogeneity can however only be achieved if the material is heat to a higher temperature, above the transformation level of each element of the material. A lower temperature exposure, relative to the elements’ transformation temperature is therefore expected to have little impacts on the achieved level of toughness and strength of a material while a high temperature heating is likely to achieve an increased level of toughness and strength.

This factor directly relates to the nature of treatment (Shah, p. 58). The nature of treatment that a material is subjected to also plays a role in the acquired strength. Inappropriate processes are for instance identified with lower gained strength and hardness. In some cases however, poor treatment conditions even worsen a material’s strength and hardness to make it weaker than its original condition. Other factors that affect the effects of quenching and tempering are “rate of loading,” “notch sensitivity,” “orientation,” and the adopted technique of loading the material (Shah, p. 58, 59). Conclusion The report therefore concludes that tempering should be done at lower temperatures.

This is because lower temperatures identify higher attained strength and hardness. Appendix Data analysis ANOVA table Anova: Single Factor SUMMARY Groups Count Sum Average Variance Row 1 6 119.4 19.9 0.116 Row 2 6 185.52 30.92 0.1576 Row 3 6 289.44 48.24 0.0104 Row 4 6 320.76 53.46 3.3984 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 4329.228 3 1443.076 1567.539 6.85E-24 3.098391 Within Groups 18.412 20 0.9206 Total 4347.64 23         Reference list Black, J and Kohser, Ronald.

DeGarmo’s materials and processing in manufacturing. New Jersey, NJ: John Wiley & Sons, 2011. Print. Shah, Vishu. Handbook of plastics testing and failure analysis. New Jersey, NJ: John Wiley & Sons, 2007. Print. Palmer, Andrew and King, Roger. Subsea pipeline engineering. Oklahoma, OK: PennWell Books, 2008. Print.