Laser Welding of Grey Cast Iron with Spheroidal Graphite-Influence of Process Parameters on Crack Formation and Hardness

Abstract

In the investigation at hand, sheets of ferritic and pearlitic grey cast iron with spheroidal graphite are welded using a fiber-laser. The influence of varying laser power and welding speed on the macroscopic characteristics of the weld seam and crack formation are analyzed and discussed. Substantial crack formation with crack densities of up to 2.93/cm are found. Furthermore, hardness measurements are conducted to evaluate the formation of brittle phases within the weld metal and heat-affected zone. Peak hardness values of up to 860 HV0.3 and 975 HV0.3 are identified in EN-GJS-400-15 and EN-GJS-700-2, respectively. Subsequently, a proposition on the dependence of crack formation on weld seam width is given. Furthermore, the influence of nickel-containing filler material on the microstructure, crack formation and hardness is studied. It can be derived from the results that laser-beam welding of grey cast iron with spheroidal graphite requires further research in order to achieve crack-free weld seams and hinder the formation of undesirable, brittle phases.

Bead Geometry Prediction Model for 9% Nickel Laser Weldment, Part 1: Global Regression Model vs. Modified Regression Model

“…In this study, to estimate the performance of the prediction developed using various methods, the sum of the square error (SEE), R-square (R 2 ), and the standard error (SE) were calculated as expressed in Equations ( 14) and (15).…”

“…Excessive gap opening causes welding defects such as depression of the bead after welding, therefore cracking the welding bead during the forming process or shortening the product fatigue life [13]. In addition, since the temperature gradient of the weld is very large compared to other welding techniques, there is a high probability of high temperature cracking in the center of the weld zone [14,15]. Management of welding conditions, etc., is very important in order to suppress the high-temperature cracking of such a weld zone.…”