1. The type of heat performed on the steel is called annealing which involves the heating of a metal to a suitable temperature for a certain time called “ soaking “, and gradually cooling.
The soaking time is calculated using this formula:
Soaking Time = (1Hr)(tmax)
Where tmax is the maximum thickness (in inches) of the steel.
And our tmax for this experiment = 0.372in as shown in Table 3.
Therefore, Soaking time = (1hr)(0.372") = 0.372hr = 22.32minutes
Shorter soaking times can be used during an annealing heat treatment if an increase in material hardness and less ductility is desired.

2. The micrometer was used to measure the cross-sectional dimensions of the steel before and after the heat treatment and values where recorded as shown in Table 3. And it was observed that there was an increase in the workpiece (steel) size after the heat treatment when compared with the dimensions before the heat treatment as shown in Table 3, this simply means that there was an increase in ductility after the heat treatment was performed.
3. In terms of mechanical properties after this heat treatment, a softer material was obtained, there was an increase in ductility which improves machinability and formability.
If a slightly harder workpiece is desired, the workpiece should be: * Heated to the austenite phase and then quenched with water or oil. This rapid cooling results in a hard and brittle workpiece. * The soaking time should be shorter.

Table 1. The Rockwell B Hardness for the steel before and after treatment Rockwell B Hardness Before Heat Treatment (HRB-1) | Rockwell B Hardness After Heat Treatment (HRB-2) | 53.9 | 41.4 | 58.6 | 44.6 | 63.4 | 44.6 | 59.2 | 43.3 | 61.1 | 45.2 | 67.3 | 47.8 | 58.2 | 48.5 | 64.7 | 45.9 | 64.9 | 42.9 |

Table 2. The Mean and Standard deviation of the Rockwell B hardness values in Table 1 Mean ± Standard Deviation of HRB-1 | Mean ± Standard Deviation of HRB-2 | 61.26 ± 4.199 | 44.91 ± 2.276 |

Table 3. Cross-sectional dimensions of the steel (work piece) Dimensions ( in inches) Of steel before heat treatment | Dimensions ( in inches) of steel after heat treatment | Length = 1.9955in | Length = 2.001in | Width = 1.4715in | Width = 1.4775in | Thickness = 0.372in | Thickness = 0.375in |

Using the Hardness Conversion Chart; based on the Rockwell B hardness, the Brinell Hardness Number (BHN) for the steel was obtained at 500kg and values recorded as shown in Table 4.
Table 4. Brinell Hardness Number of the steel before and after treatment BHN Before heat Treatment at 500kg | BHN Before heat Treatment at 500kg | 96 BHN | 79 BHN |

Using the following, we calculate the percent carbon content before and after heating the work piece:
BHN = BHNf(0.77 - %C / 0.77) + BHNc(%C / 0.77)
Where BHN = Brinell Hardness Number for final microstructure BHNf = Brinell Hardness Number for Ferrite = 80 BHNc = Brinell Hardness Number of Cementite %C = Percent carbon content (by weight) of steel
Table 5. The BHNc values Cementite Type | BHNc | Process | Coarse | 240 | Furnace Cool | Medium | 280 | Air Cool | Fine | 380 | Quench |

Percent Carbon Content:
BEFORE HEAT TREATMENT
BHN = 96 BHN at 500kg as shown in Table 4
BHNf = 80
BHNc = 240 because the work piece will undergo a furnace cooling process as shown in Table 5
96 = 80(0.77 -%C / 0.77) + 240(%C /0.77)
%C = 0.077 ≅ 0.08%C
This means the steel is a hypoeutectoid steel because it contains less than 0.8% carbon in its composition.
AFTER HEAT TREATMENT
BHN = 79 BHN at 500kg as shown in Table 4
BHNf = 80
BHNc = 240 because the work piece was furnace cooled as shown in Table 5
79 = 80(0.77 -%C / 0.77) + 240(%C /0.77)
%C = -0.0048 ≅ -0.005%C
This means there was no carbon in the steel after the heat treatment.

Percent dimensional change:
Using the values shown in Table 3, we calculate the percent dimensional change in the steel after the heat treatment.
Length = (2.001 – 1.9955) / 1.9955 x 100 ≅ 0.28% increase
Width = (1.4775 – 1.4715) / 1.4715 x 100 ≅ 0.41% increase
Thickness = (0.375 – 0.372)/ 0.372 x 100 ≅ 0.81% increase