US 3001869 A
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United States Patent 3,001,869 NODULAR RON MANUFACTURE William G. Longstreth, Pontiac, and Royal A. Van Patten, Dearborn, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware No Drawing. Filed Aug. 7, 1959, Ser. No. 832,142 3 Claims. (Cl. 75130) This invention relates to the siderurgical arts and more particularly to that portion of the ferrous technology relating to the production of nodular cast iron. This invention is especially concerned with a process for the conservation and more eflicient and reliable utilization of the nodularizing adjuvants.
In current practice, a cast iron base metal of the proper chemistry is rendered nodular by the addition of a small amount of magnesium. The actual addition of magnesium to molten cast iron is complicated by the fact that magnesium exhibits at molten iron pouring temperatures a vapor pressure far in excess of atmospheric pressure. Magnesium is highly flammable and this fact coupled with its volatility render it an extremely fugacious additive from the view point of the iron founder.
In an effort to circumvent this evanescent characteristic of magnesium, the art has had recourse to the addition of magnesium to the molten iron in the form of an alloy containing about eight percent magnesium alloyed with about forty percent silicon and the remainder iron. Even with this comparatively dilute magnesium alloy, the recoveries are undependable and average only about fifteen percent of theory.
We have discovered that this very low yield of magnesium can be at least doubled by the use of a very simple and effective expedient without altering the foundry operation objectionably. This result is obtained by adding the magnesium metal to a ladle prior to the filling of the ladle with molten cast iron, and protecting this magnesium metal by at least partially covering it with a layer of ferrous metal. The composition, mass and temperature of this protecting mass of ferrous metal is not critical as long as objectionable alloys are not introduced, and the mass of the ferrous metal and its temperature are so regulated that the thermal inertia of the ferrous metal is adequate to provide a temporary protection to the magnesium metal. It is to be understood that a cold layer of ferrous metal will provide the maximum protection with the least mass, and that the mass must be increased if the ferrous metal is added hot or permitted to long remain in the hot ladle prior to the addition of the molten cast iron.
The layer of magnesium metal may be added to the empty ladle, or a portion of the ferrous protecting metal may be first added followed by the magnesium metal and finally the remainder of the ferrous protecting metal.
A typical example of the execution of this invention may be outlined as follows. A ladle capable of containing six hundred pounds of metal is preheated and an addition of one hundred and sixteen grams of magnesium clippings is made directly into the empty ladle. The magnesium clippings are covered by an addition of seven percent of steel punchings about one-eighth inch thick. On the basis of a six hundred pound heat, the steel punchings would weigh forty-two pounds. The analysis of the base metal is a conventional one for nodular iron and contains about 3.9 percent carbon and 2.0 percent silicon. This charge is heated to 28-00 F. in an electric furnace and then poured promptly into the prepared ladle containing the magnesium clippings and the protecting mass of steel punchings.
The solution of the magnesium in the molten iron was prompt and substantially devoid of pyrotechnics and violent reactions. The product was poured into chill blocks and appeared to be satisfactorily nodular.
The term metallic magnesium as used herein is intended to include alloys of magnesium sufdciently rich in this metal to be hazardous for direct addition to molten iron, as well as pure metallic magnesium.
1. The process of imparting a nodularizing addition of magnesium to a cast iron base metal comprising placing within a ladle a layer of metallic magnesium, superimposing upon this layer of metallic magnesium a layer of ferrous metal at a temperature substantially below the temperature of molten cast iron, and pouring molten cast iron base metal into the ladle.
2. The process of imparting a nodularizing addition of magnesium to a cast iron base metal comprising placing within a ladle a layer of ferrous metal at a temperature substantially below the temperature of molten cast iron, superimposing upon this layer of ferrous metal a layer of metallic magnesium, superimposing upon this layer of metallic magnesium a further layer of ferrous metal at a temperature below the temperature of molten cast iron, and pouring molten cast iron base metal into the ladle.
3. The process of imparting a nodularizing addition of magnesium to a cast iron base metal comprising placing within a ladle a layer of metallic magnesium, superimposing upon this layer of metallic magnesium a layer of ferrous metal having suflicient mass and sufliciently low temperature to protect the metallic magnesium from excessive loss from the ladle, and pouring molten cast iron base metal into the ladle.
References Cited in the file of this patent UNITED STATES PATENTS 1,922,037 Hard Aug. 15, 1933