CN1023492C - Copper alloy for coin and its metallugical process - Google Patents

Abstract

The present invention relates to a copper alloy for manufacturing coins. The chemical component of the alloy is composed of the following elements: copper, zinc, tin, nickel, manganese and boron. The alloy has the advantages of beautiful appearance which presents golden yellow, corrosion resistance, strong anti-discoloring capability, good plasticity, easy processing, batch production, low production cost, rich resources and good counterfeit prevention.

Description

Copper alloy for coin and its metallugical process

The present invention is a kind of copper alloy that is used to make coin.

At present, nickel coin, zinc coin, aluminium coin, the steel coin of the metal coin adularescent of countries in the world circulation are yellow or red copper coin, but most of coins lose the form and aspect that itself have at circulation period gradually because of various ambiance corrosion such as sweat, air.Zinc content is that about 30% copper zinc binary alloy has flavous color and luster.People often like the metal coin of this color and luster, but it is corrosion-resistant, anti-tarnishing ability is poor, so be unsuitable for making metal coin with it.Nineteen eighty-three coinage scientific and technological information is " corrosion-resistant, the tarnishproof copper alloy coinage materials of energy " literary composition introduction in the first phase, in copper zinc alloy, add of the influence of other element: add aluminium in the copper zinc alloy to resistance to corrosion, because zinc and aluminium degenerate in conjunction with causing significantly, the result that the adding of nickel then produces, close nickel 1% and be referred to as nickel brass usually, can improve etch resistant properties, but still sense is not enough.In order to obtain obviously improvement aspect the corrosion resisting property, nickel content need rise to 7-8%, preferably to 9%, patent PL105132, PL145133, PL145134 has introduced the coin copper alloy that contains Ni19-21%, yet high like this nickel content has just left flavous scope significantly, and the coinage materials cost is improved.Copper zinc alloy is why not anti-corrosion mainly to be because Dezincification corrosion easily takes place its contained zinc.People are devoted to study the generation and the evolution of Dezincification corrosion and prevent the dezincify measure for many years, find to add trace element and can suppress dezincify as AS, P, Sb, Sn etc., especially AS only needs to add ten thousand/several AS and then can suppress Dezincification corrosion basically in the brass.But because the oxide compound of arsenic is poisonous, harmful, so should not adopt.

The objective of the invention is to develop a kind of alloy that is used to make metal coin, it not only has golden yellow, and corrosion-resistant in monetary field of circulation, anti-discolouring, can keep the color and luster of alloy itself for a long time.

The present invention is the copper zinc-nickel tin manganese multicomponent alloy that contains trace B.For keeping the golden yellow of alloy, can only add its unit of a small amount of base in the Cu70Zn30 alloy and usually improve corrosion stability, though it is remarkable to add the micro AS effect, should not use but its oxide compound is harmful, through a large amount of experimental studies, find that B also has the similar effect with AS to improving the brass etch resistant properties, zinc optimum solvation stays a lot of rooms in the brass corrosion process, zinc atom will be diffused into the surface by these rooms and continue dissolving, the little and easy diffusion (r of boron atom in the boracic brass _B=0.88A °) it will fight for these rooms with zinc atom, so the part room after the dezincify will occupy by the boron atom and stop up the diffusion admittance of some zinc atoms, and increase its diffusional resistance, thereby suppress brass dezincification corrosion.Test shows: just can play positive effect even add in the Cu70Zn30 alloy less than 0.01%B.Ni and Mn can further improve alloy under damp and hot, salt fog, industrial gasses environment stability and the wearing quality in the process of circulation, simultaneously Ni and Mn element also come crystal grain in refinement ingot casting and the converted products as adjusting material.Improve materials processing and coinage performance.Prevent to produce when alloy from annealing coarse grain in the standard national currency process.

Alloying constituent of the present invention is: Cu70-75%, and Sn0.5-1.5%, Ni0.5-1.5%, Mn0.1-0.8%, B＜0.04%, surplus is Zn, optimal components is Cu71-73%, Sn0.8-1.2%, Ni0.8-1.3%, Mn0.1-0.5%, B0.003-0.01%, surplus is Zn.

Production technique of the present invention is as follows: Cu, Ni, Mn add in the smelting furnace according to a certain percentage, take high temperature, fusing fast, add charcoal simultaneously as in the stove topped dose, add Sn again and Zn stirs, all fusing back copper water temp rises to and adds the P-Cu master alloy more than 1080 ℃ and give deoxidation, add the B-Cu master alloy then, through stirring, when furnace temperature reaches 1100 ℃-1200 ℃, cast again, adopt expanded borax topped in the crystallizer, be cast into desired shape and specification.Ingot casting carried out hot rolling in 50-100 minute through 680 ℃-780 ℃ heating, and hot rolling is carried out cold working behind certain specification, and the process annealing temperature is that 550 ℃ of-650 ℃ of total working moduluses of twice process annealing are no more than 50%.The finished product working modulus preferably is controlled at 25-35%.

Alloy of the present invention has golden yellow attractive in appearance, and is corrosion-resistant, anti-tarnishing ability is strong.Through hand perspiration simulation test and discoloration-resistant performance test, the result shows that every performance obviously is better than other brass, bronze coinage materials both at home and abroad, and cost is low, and plasticity is good, easily the processing impression is shaped, and antifalsification is good.

Illustrate alloy of the present invention and production technique thereof:

With 715 kilograms of Cu, 10 kilograms of Ni, 5 kilograms of Mn and charcoal are in line frequency furnace, heat fused, add 10 kilograms of Sn and surplus Zn again, treat that all slag is dragged in the stirring of fusing back, rise to more than 1100 ℃ until the copper water temp, add 1 kilogram of P-Cu master alloy containing P12%, 4 kilograms of B-Cu master alloys that contain B3%, through fully stirring, cast with semicontinuous method, crystallizer is topped with expanded borax, and pouring speed is controlled in 45-55 second/100mm scope, ingot casting heated 60-90 minute in 710 ℃ ± 20 ℃ after face is milled in sawing, carry out hot rolling, carry out cold working after being rolled to 12mm, until required trimmed size, the process annealing temperature is 590 ℃ ± 10 ℃, soaking time is 60-90 minute, and working modulus is controlled at 25-35% between twice annealing.

Claims (5)

1, a kind of copper alloy that is used to make coin is golden yellow, it is characterized in that chemical ingredients is Cu70-75%, Sn0.5-1.5%, and Ni0.5-1.5%, Mn0.01-0.8%, B＜0.04% (not comprising zero), surplus is a zinc.

2, by the described copper alloy of claim 1, it is characterized in that chemical ingredients is Cu71-73%, Sn0.8-1.2%, Ni0.8-1.3%, Mn0.1-0.5%, B0.003-0.01%, surplus is a zinc.

3, a kind of method of making claim 1 or 2 described copper alloys comprises operations such as founding, hot-work, cold working and process annealing, it is characterized in that,

A. melting this alloy takes quick fusing, fully stirs;

B. use charcoal as topped dose in the stove, crystallizer is topped with expanded borax;

C.B adds with the B-Cu master alloy, adds the P-Cu master alloy earlier and give deoxidation before adding the B-Cu master alloy;

D. furnace temperature reaches 1100 ℃-1200 ℃ and pours into the desired shape specification;

E. ingot casting carried out hot-work in 50-100 minute in 680 ℃-780 ℃ heating;

F. alloy cold working process annealing temperature is 550 ℃-650 ℃;

G. total working modulus is no more than 50% in the middle of the twice annealing.

4,, it is characterized in that working modulus is 25-35% before the finished product as manufacture method as described in the claim 3.

5, as method as described in the claim 3, it is characterized in that,

A. adopt the line frequency furnace melting, cast with semicontinuous method, pouring speed is controlled in 45-55 second/100mm scope;

B. ingot casting carried out hot-work in 60-90 minute in 710 ℃ ± 20 ℃ heating, and cold working process annealing temperature is 590 ℃ ± 10 ℃, and soaking time is 60-90 minute, and working modulus is controlled at 25-35% between twice annealing.