# Homework Help: Welding Coursework Problem

1. Mar 5, 2007

### Fowler_NottinghamUni

1. The problem statement, all variables and given/known data
Given, the density, specific heat per unit volume, latent heat of fusion, melting point and thermal conductivity - calculate the energy needed to melt a cubic mm of carbon steel, starting at 20 celcius.

Hence find the minimum power needed to generate a bead on a plate weld of 15 mm square cross sectional area at a welding speed of 4mm/s.

2. Relevant equations
density ro = 7900 kg/m^3
specific heat per unit mass Cm = 0.45kJ/Kg/K
Melting Temperature of Carbon steel Tm= 1535 deg C
Latent heat of melting deltaHf = 270 kJ/Kg
deltaT = Tm-starting temp
3. The attempt at a solution

Am I right in saying that there are two energies, one to heat the metal up and another energy to overcome the latent heat of fusion?

If so, I used Q = (mXCmxdeltaT) + (mxdeltaHf).

When substituting the numbers I got out 7.5 J, which seems a little low.
As for the second part, I'm not sure how to go about it.
If anyone is any the wiser please let me know where I have gone wrong?!

Many thanks, Gavin.