Sindo Kou - Welding Metallurgy

Figure E2.2Transverse cross‐sections of welds.

1 (a) No, with 2D heat flow the temperature distribution changes little in the depth direction.

2 (b) With 3D heat flow, the temperature distribution changes significantly in the depth direction.

3 (c) 2D equation works better because the weld width is essentially uniform in the depth direction, suggesting 2D heat flow.

4 (d) 3D equation works better because the weld width changes significantly in the depth direction, suggesting 3D heat flow.

5 (e) Increasing preheating temperature increases the weld width but decreases the cooling rate.

Example 2.3Consider the transverse cross‐section of the weld pool based on Rosenthal's 3D heat flow equation. What is the shape of the transverse cross‐section of a weld based on Rosenthal's 3D equation?

From Rosenthal's 3D equation

(2.20)

At a fixed value of x , x = c , where c is a constant. For a given material under a given welding condition, T o , k, Q, V , and α are all constant. Furthermore, T = T m(the melting point) at the fusion boundary. Therefore, everything in Eq. (2.20) is constant, and the radial distance R between the origin and a point at the fusion boundary must, therefore, also be constant.

(2.21)

Since R and x are both constant, y 2+ z 2= constant. Thus, the transverse cross‐section of the weld pool is round. In reality, however, the transverse cross‐section of a bead‐on‐plate weld is often not round, even when the plate is very thick.

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