US3854935A - Grain refining compositions and method of refining aluminum therewith - Google Patents

Abstract

Grain refining compositions for aluminium and aluminium alloys containing 15 - 85 percent by weight finely particulate Ti or high-Ti alloy, 2.5 - 70 percent by weight of an alkali metal complex fluoride and optionally a dense metal. The compositions are of density at least 2.4 g/cm3.

Description

United States Paten Snow 1 Dec. 17, 1974 GRAIN REFINING COMPOSITIONS AND [56] References Cited METHOD OF REFINING ALUMINUM UNITED STATES PATENTS THEREWITH 2,654,670 10/1953 Davis et al. 164/57 [75] Inventor: George Snow, Birmingham, England 3,144,323 8/1964 Watson et a1. 75/68 R [73] Assignee: Foseco International Limited, OREIGN PATENTS OR APPLICATIONS irmingh England 456,462 11/1936 Great Britain 75/68 R Filed g 9 1973 400,026 10/1933 Great Britain 75/68 R PP N 386,880 Primary ExaminerL. Dewayne Rutledge Related 1 8 Application Data Assistant ExaminerM. Andrews [63] Continuation-impart of Ser. No. 359,756, May 14, Agent or Flrm cushman Darby &

shman 1973, abandoned.

[30] Foreign Application Priority Data 7] ABSTRACT May 17, 1972 Great Britain 23219/72 Grain refining compositions for aluminium and alu- Aug. 8, 1972 Great Britain 36979/72 minium alloys containing 15 85 percent by weight finely particulate Ti or high-Ti alloy, 2.5 70 percent [52] US. Cl. 75/68 R, 75/93 AC, 75/135 by weight of an alkali metal complex fluoride and op- [51] Int. Cl C22b 21/06 tionally a dense metal. The compositions are of den- [58] Field of Search 75/93 R, 93 A, 93 E, 68 R, sity at least 2.4 g/cm 5 Claims, No Drawings GRAIN REFINING COMPOSITIONS AND METHOD OF REFINING ALUMINUM THEREWITH CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of my application Ser. No. 359,756 filed 14th May, 1973 now abandoned.

This invention relates to improved grain refining compositions containing titanium metal.

It has previously been proposed to use metallic titanium as a grain refiner for aluminium and aluminium alloys. However, titanium metal and known grain refining compositions containing titanium metal suffer from a number of disadvantages.

Titanium metal dissolves too slowly in molten aluminium at normal commercial operating temperatures, with the result that in the time available between the addition of a grain refiner and casting solution of the titanium is incomplete. It has also been found that dissolution and hence recovery of titanium in the cast aluminium is influenced by the condition of the surface of the molten aluminium, the presence of dross or fluxing agents causing an exothermic reaction to take place and titanium revovery to be reduced. Some improvement can be effected if the titanium metal containing grain refiner is plunged and held below the surface of the molten aluminium. However, the plunging operation involves an additional step on the part of the foundryman, and there is a danger that the aluminium can become contaminated from the plunging tool.

It has now been found that titanium metal can be used efficiently as a grain refiner for aluminium if the titanium is used in the form of particles less than 500 microns in size, and is compacted with a complex salt to give a composition having a density such that the composition when added to molten aluminium will sink below the surface of the molten aluminium.

According to the present invention there is provided a composition for the grain refinement of aluminium or aluminium alloys comprising:

i. 15 85 percent by weight metallic titanium and/or titanium alloy containing not less than 85 percent titanium,

ii. 2.5 70 percent by weight of one .or more of sodium borofluoride, potassium borofluoride, sodium titanofluoride, potassium titanofluoride, sodium zirconium fluoride and potassium zirconium fluoride, and

iii. 46 percent by weight of a metal having a density greater than 4.5 g/cm".

The content of said metal not exceeding the content of said titanium or titanium alloy, the content of component ii) being at least 12 percent of the content of said titanium or titanium alloy; said titanium and/or titanium alloy having a particle size not greater than 500 microns, and said composition having a density of at least 2.4 g/cm The metal having a density greater than 4.5 g/cm may be, for example, manganese, copper, iron, nickelchromium alloy or ferro-manganese. The actual metal and the amount used in the grain refining composition will be chosen such that the required specification of the cast aluminium or aluminium alloy is met. It is preferable to include at least percent by weight of dense metal in the composition to ensure self-sinking even if, as may happen in manufacture, the tablet is imperfectly pressed.

Fluxing agents such as alkali metal or alkaline earth metal halides may be included in the grain refining composition. Carbonates may also be used. Examples of suitable fluxing agents are sodium chloride, potassium chloride, sodium fluoride, potassium fluoride, sodium aluminium fluoride and potassium aluminium fluoride. When used the content of the fluxing agent will not normally be more than 53 percent by weight.

The grain refining composition may be produced by any known method involving blending of the components and subsequent compaction to give a coherent mass having the required density. For example, the ingredients are mixed in a 1 ton capacity ribbon blade mixer and pressed to tablet form in a ton BIPEL press.

If desired other material may be incorporated in the grain refining composition to aid in the production of a coherent mass, or the mass may be preheated.

When used to treat molten aluminium or aluminium alloys the amount added should be at a weight ratio of 0.005 percent to 0.2 percent (of Ti) by weight.

The following examples will serve to illustrate the invention.

In all the examples, the following test procedure was used:

The grain refining composition to be tested was made by mixing the ingredients together in a planetary action mixer, and portions of mixture were then tabletted in a hydraulic tabletting press at a pressure of 1,000 kg/cm. The resulting tablets had a weight of about gms. and their density was then determined in the usual way.

The grain refining composition was tested for efficiency by adding the composition to molten LMO aluminium (99.8% AL), at a rate of 0.02 percent by weight of titanium. The LMO aluminium was held at 730C.

Samples were taken and cast into preheated sillmanite test moulds two minutes before, ten minutes after and forty minutes after the addition of the composition.

The castings, 2.5 cm. diameter and 7.5 cm. high, were sectioned transversely 2.5 cm. from the base. The cut face of the base was then polished to 600 micron silicon carbide paper using water as lubricant and then etched using a mixed acid solution.

In all cases, the grain size evident after etching was visually much smaller in the samples poured after the addition of the grain refining composition but there was no substantial difference between the sample at ten minutes and the sample at forty minutes. Accordingly, grain size determinations were than made only on the test specimen before addition and that at forty minutes after addition.

The following are the grain refining compositions tested. Thereafter, the table gives the results of the test procedures just described. Percentages are by weight.

Example 1:

titanium (less than 500 microns) 70% potassium borofluoride 30% Example 2:

titanium 30% nmnganese 20% potassium borofluoride 50% Example 3:

titanium 40% -Continued manganese 40%"- sodium boroiluoride 20% Example 4:

titanium 55% manganese potassium borotluoride l 1% potassium chloride 24% RESULTS RESULTS Example Density Grain Size before Grain Size No. (gm/cc) addition (microns) after addition (microns) The following are further examples of grain refining compositions according to the invention (weight percent):

Example 5 Potassium chloride 5.0% Potassium borofluoride 38.0% Manganese 20.0% Titanium 37.0% Example 6 Potassium chloride 5.0% Potassium borofluoride 28.0% Manganese 20.0% Titanium 47.0% Example 7 Potassium chloride 19.0% Potasium borofluoride 14.0% Manganese 20.0% Titanium 47.0% Example 8:

Potassium chloride 15.0% Potassium titanoiluoride 10.0% Manganese 20.0% Titanium 55.0%

I claim:

1. A composition for the grain refinement of aluminium or aluminium alloys consisting essentially of i. 85 percent by weight of a material selected from the class consisting of metallic titanium and titanium alloys containing not less than 85 percent titanium,

ii. 2.5 70 percent by weight of at least one component selected from the class consisting of sodium borofluoride, potassium borofluoride, sodium titanofluoride, potassium titanofluoride, sodium 5 zirconium fluoride and potassium zirconium fluoride, and

iii. 0 46 percent by weight of a metal having a density greater than 4.5 g/cm the content of said metal not exceeding the content of said component i), the content of component ii) being at least 12 percent of the content of said component i). said component i) having a particle size not greater than 500 microns, and said composition having a den sity of at least 2.4 g/cm".

2. A composition according to claim I wherein the metal of density greater than 4.5 g/cm is selected from the group consisting of manganese, copper, iron ferromanganese and nickel-chromium alloys.

3. A composition according to claim 1 and including up to 53 percent by weight of a compound selected from the group consisting of alkali and alkaline earth metal halides and carbonates as fluxing agent.

4. A method of treating molten aluminium and alloys thereof to effect grain-refinement, which comprises adding to said aluminium and alloys a composition consisting essentially of i. 15-85 percent by weight of a material selected from the class consisting of metallic titanium and titanium alloys containing not less than 85 percent titanium,

ii. 2.5 70 percent by weight of at least one component selected from the class consisting of sodium borofluoride, potassium borofluoride, sodium titanofluoride, potassium titanoi'luoride, sodium zirconium fluoride and potassium zirconium fluoride, and

iii. 0 46 percent by weight of a metal having a density greater than 4.5 g/cm,

the content of said metal not exceeding the content of said component i), the content of component ii) being at least l2 percent of the content of said component i), said component i) having a particle size not greater than 500 microns, and said composition having a density of at least 2.4 g/cm.

5. The method of claim 4 wherein the composition is added to the molten metal at a ratio of 0.005 to 0.2 percent of Ti by weight to said molten metal.

Claims (5)

1. A COMPOSITION FOR THE GRAIN REFINEMENT OF ALUMINUM OR ALUMINUM ALLOYS CONSISTING ESSENTIALLY OF I. 15 - 85 PERCENT BY WEIGHT OF A MATERIAL SELECTED FROM THE CLASS CONSISTING OF METALLIC TITANIUM AND TITANIUM ALLOYS CONTAINING NNOT LESS THAN 85 PERCENT TITANNIUM, II. 2.5 - 70 PERCENT BY WEIGHT OF AT LEAST ONE COMPONENT SELECTED FROM THE CLASS CONSISTING OF SODIUM BOROFLUORIDE, POTASSIUM BOROFLUORIDE, SODIUM TITANOFLUORIDE, POTASSIUM TITANOFLUORIDE, SODIUM ZIRCONIUM FLUORIDE AND POTASSIUM ZIRCONIM FLUORIDE, AND III. 0 - 46 PERCENT BY WEIGHT OF A METAL HAVING A DENSITY GREATER THAN 4.5 G/CM3, THE CONTENT OF SAID METAL NOT EXCEEDING THE CONTENT OF SAID COMPONENT I), THE CONTENT OF COMPOUND II) BEING AT LEAST 12 PERCENT OF THE CONTENT OF SAID COMPONENT I). SAID COMPONENT I) HAVING A PARTICLE SIZE NOT GREATER THAN 500 MICRONS, AND SAID COMPOSITION HAVING A DENSITY OF AT LEAST 2.4 G/CM3.

2. A composition according to claim 1 wherein the metal of density greater than 4.5 g/cm3 is selected from the group consisting of manganese, copper, iron ferromanganese and nickel-chromium alloys.

3. A composition according to claim 1 and including up to 53 percent by weight of a compound selected from the group consisting of alkali and alkaline earth metal halides and carbonates as fluxing agent.

4. A method of treating molten aluminium and alloys thereof to effect grain-refinement, which comprises adding to said aluminium and alloys a composition consisting essentially of i. 15-85 percent by weight of a material selected from the class consisting of metallic titanium and titanium alloys containing not less than 85 percent titanium, ii. 2.5 - 70 percent by weight of at least one component selected from the class consisting of sodium borofluoride, potassium borofluoride, sodium titanofluoride, potassium titanofluoride, sodium zirconium fluoride and potassium zirconium fluoride, and iii. 0 - 46 percent by weight of a metal having a density greater than 4.5 g/cm3, the content of said metal not exceeding the content of said component i), the content of component ii) being at least 12 percent of the content of said component i), said component i) having a particle size not greater than 500 microns, and said composition having a density of at least 2.4 g/cm3.

5. The method of claim 4 wherein the composition is added to the molten metal at a ratio of 0.005 to 0.2 percent of Ti by weight to said molten metal.