| 摘要 |
PURPOSE:To raise durability of a tube and also to stabilize it, by forming in a tubular form a gray cast iron alloy containing C of a specified quantity, by means of vertical pouring. CONSTITUTION:A gray cast iron tube 2 which is formed by vertical pouring and has 3.8-4.0wt% C is installed to one end side of an SGP tube 1. When this gray cast iron tube 2 is cast and installed, a plug 5 having a suitable taper is installed to fit to the end part of the SGP tube 1, and also an end part covering layer 6 having thickness exceeding the inside diameter of the SGP tube 1 is formed from the end part of the tube concerned 1. Also, a black skin layer 3 is formed on the surface of this gray cast iron tube 2. In this way, when gray cast iron containing 3.8-4.0wt% C is used as a protecting tube, a comparatively large piece of graphite is deposited and formed comparatively densely in a cast iron texture, and erosion by Al in case of contacting with an Al molten metal can be obstructed by this piece of graphite whose surface area is large. In this way, durability of the protecting tube is raised remarkably, and also it can be stabilized sufficiently. |
