Effect Of Titanium On The Quality Of Gray Iron Castings
Under the condition of high carbon equivalent (above 4.10% CE) of gray cast iron, a small amount of titanium can improve the mechanical properties of the cast iron and improve the uniformity of different sections of the cast. In this paper, under the condition of medium and low carbon equivalent (3.65% ~ 3.85% CE), the influence of different titanium content on the quality of gray iron castings, such as microstructure, mechanical properties and compactness.
The test results show that: titanium promotes the formation of D-type graphite in iron castings; when the D-type graphite reaches a certain proportion, especially when the Si/C is high, its mechanical properties increase significantly; with the increase of titanium and aluminum content, The compactness of gray iron castings decreases, and the probability of shrinkage porosity increases.
In the production process of iron castings, with the extensive use of metal furnace materials such as pig iron and scrap steel, titanium more or less enters the molten iron. A large number of research data indicate that after titanium is added to gray cast iron, most titanium compounds exist in the metal matrix, but some titanium nitrides or carbonitrides still exist in the interface layer between ferrite and graphite. Titanium compounds with a hardness of 3200 HV or higher greatly reduce the machinability of cast iron.
In addition, too high titanium content (0.096%) produces hot cracks when cutting castings. However, D-type graphite iron castings with titanium addition have good oxidation resistance, growth resistance and thermal fatigue resistance. Under the working condition of 500-700 ℃, compared with common CrMoCu cast iron, the service life can be increased by 3 times. Titanium is strictly prohibited as an interfering element in ductile iron.
However, in some vermicular cast irons, titanium is added to the vermicular agent as a beneficial element to expand the range of vermicular treatment. Under the condition of high carbon equivalent, micro-titanium alloying can improve the strength and hardness of gray iron castings, and improve the cross-sectional uniformity of castings. Trace amounts of titanium can also neutralize excess nitrogen in cast iron to reduce the frequency of crack-like nitrogen pores.
