The Development And Application Of Powder Nodulizer

The nodulizer demand is increasing gradually year after year with the development of ductile cast iron. At present, the main disadvantage of nodulizer accession technics is that the absorptivity of Mg element is low (about 30-50%), and the soot pollute is serious. In this paper, aim to problem that NPT5 air compressor crankshafts have the defect of graphite sphere in all the while, powder nodulizer as a new kind of nodulizer was investigated to improve graphite structure of ductile cast iron, increase coefficient of utilization of nodulizer, reduce environmental pollution and production cost, and spheroidizing process was investigated to make application for production.The effects of powder nodulizer and massive nodulizer on graphite structure and mechanical properties of QT700-2 were analyzed. And the effects of spheroidizing process and adding quantity of powder nodulizer on microstructures and mechanical properties were investigated. The results are as follows:1. The graphite size was smalle and the distribution was uniformity with the same spheroidizing process and adding quantity of powder nodulizer compared with massive nodulizer. And the tensile strengthen, yield strength and hardness of ductile cast iron were improved used powder nodulizer compared with massive nodulizer. The graphite size of NPT5 air compressor crankshaft produced by ductile cast iron used powder nodulizer was smalle and mechanical properties of that were improved.2. Graphite modality was piece or dendritic, and the graphite was not sphered almostly with adding 1.0% powder nodulizer packed by aluminum foil. With increasing powder nudolizer content to 2.0%, the graphite modality was not changed compared 1.0% powder nodulizer with 2.0% powder nodulizer. Based on the above discussion, the nodulizer packed by aluminum foil process is not feasibility.3. The graphite modality was sphered, graphite size was smalle and the distribution was uniformity with adding 1.0% powder nodulizer packed by tinplate. Compared with ductile cast iron casting, the graphite modality accord with the require. The integrative mechanical properties of ductile cast iron is good, the strengthen, the hardness and the specific elongation were improved respectively. Based on the above discussion, the nodulizer packed by tinplate process is feasibility.4. The graphite sphere grade, graphite sphere distribution level and the mechanical properties increase firstly and then decrease with increasing adding quantity of powder nodulizer. By contraries, the graphite sphere size decrease firstly and then increase. When the adding quantity of powder nodulizer reach to 1.3%, the graphite sphere grade reach to second. And the graphite modalify, tensile strengthen, yield strength and the hardness reach to better value. Compared with standard casting production in the manufactory, the microstructure andmechanical properties were improved. When the adding quantity is over 1.5%, the graphitemodality was deteriorate and the mechanical properties decreased. It will provide thetheoretical basis and technicology support for producing ductile cast iron with highermechanical properties in the future.