Title of Invention

"AN IMPROVED PROCESS FOR PREPARATION OF COPPER-TITANIUM ALLOYS"

Abstract An improved process for the preparation of copper titanium alloys, wherein the said process comprises of refining commercialpurity cathodecopper insitu by pickling with dilute hydrochloric acid, washing thoroughly in water, cleaning in acetone and drying following by melting in the graphite crucible of air induction melting furnace (AIM) at 1200-1230°C for 10-20 minutes and stirring the melted copper well by carbon monoxide gas bubbles and a graphite rod characterized by; preparing the copper titanium alloy by cleaning commercial grade titanium in acetone and adding 1 to 6 wt% of this cleaned titanium to the copper melt obtained in step (a) then melting it for 10-20 minutes till the temperature reaches 1200-1230°C followed by pouring the liquid copper titanium alloy into graphite mould and allowing it to cool in air, homogenizing the Cu-Ti alloy ingots obtained in step (b) at 800-900 °C for 8-12 hours, soaking them at 750-900 °C for 2-3 hours then forging/rolling to break the solidification microstructure followed by heating again to 750-900 °C for about 2 hours then quenching rapidly into water to obtain uniform grain size of 75 microns, cold working the homogenized Cu-ti alloy ingots obtained in step (c) by rolling at room temperature to desired amount of deformation to fabricate specific tools, aging at 380-480 °C for 1-16 hours then cleaning with 10-20% diluted HC1 acid, washing thoroughly in water and then drying with acetone.
Full Text FIELD OF INVENTIONS
The present invention relates to Air Induction Melting (AIM) of Cu-Ti Alloy. The resultant alloy made by AIM possesses high strength and sufficient electrical conductivity for specific application but without implying any limitation thereto, for preparation of non-sparking tools besides beneficial applications in other areas like springs, valves, connectors and contacts.
PRIOR ART
Non-sparking tools require very high strength and good electrical conductivity and are used in the areas of mining, gas and petroleum industries and explosive filling in ordnance stores to avoid likelihood of occurrence of unwarranted explosions. Unlike applications for electric conduction such as in wires and strips, the non-sparking tools require making of thicker sections so as to enable manufacture of hammers, chisels, knives, blades etc. typically used in the explosive, petroleum and mining industries. Non sparking characteristics are obtained in a material, if there is sufficient resistance for formation of ultra-fine abraded particles during impact/sliding of the tool and adequate conductivity to allow withdrawal and dissipation of heat generated during the impact or contact.
Conventionally, Cu-Be alloys are used for making non-sparking tools. However, the manufacture and processing (hot forging and rolling, heat treatment and pickling) of the alloys containing beryllium metal poses health hazard which leads to a disease of lungs known as 'Berylliosis' which is caused due to the toxicity of beryllium metal, Recently, the use of Cu-Ti alloys is being explored extensively as a replacement for Cu-Be alloys, as Cu-Ti alloys are non-sparking and do not suffer from the drawback of toxicity associated with Cu-Be alloys. Besides, titanium ores are in abundance compared to those beryllium and therefore, Cu-Ti alloys cost less than the Cu-Be alloys.
One of the processes known in the art is by Saarivirta (US, patent 2,943,960) wherein Oxygen Free copper and Ti sponge are used and melting and casting are carried out under inert gas cover, followed by hot working and cold working. Solution treatment, cold working and aging treatments were utilized to obtain strengths of 1440 Mpa and electrical conductivity of 10% lACS.
The main disadvantage of the process is that it uses high purity copper which is very costly.
Another disadvantage of the process is that it uses protective atmosphere even for heating prior to hot working and other heat treatments.
Another process known in the art by Ikushima et al (US Patent Nos. 4,566,915 and 4,599,119) relate to the preparation of Cu-Ti alloys needed for strip conductors having an average crystal grain size of 25 microns and tensile strength of 1100 Mpa.
The main disadvantage of the above process is that it does not specify the exact melting and casting procedures, which affect the physical and mechanical properties of the resultant alloy.
Another limitation of this process is that the Cu-Ti alloy obtained is not suitable for preparation of non-sparking tools such as chisels etc., which require material of higher thickness.
OBJECTS OF PRESENT INVENTION
The main object of the present invention is to propose an improved process for the preparation of Cu-Ti alloy by air induction melting (AIM) with Ti content preferably from 4 to 6 weight percent, which possess high strength as well as sufficient electrical conductivity specifically suitable for preparation of non-sparking tools, besides other applications.
Another object of the present invention is to propose an improved process for preparation of Cu-Ti alloys, which uses commercial grade copper and titanium.
One more object of the present invention is to propose an improved process for preparation of Cu-Ti alloys, which is cost-efficient and economical.
Still another object of the present invention is to propose an improved process for preparation of Cu-Ti alloys wherein insitu refining of commercial grade copper is carried out by carbon monoxide gas bubbles generated insiiu during melting in the graphite crucible in air induction melting furnace.
Still another object of the present invention is to propose an improved process for preparation of Cu-Ti alloys • vhich uses titanium extracted from the abundantly available ores as compared to conventional processes which use costly and toxic Be metal whose resources (ores) are limited.
Further object of the present invention is to propose an improved process for preparation of Cu-Ti alloys, which is trouble-free, non-toxic and does not pose health hazard during the process of preparation as compared to the conventional processes for preparation of Cu-Be alloys used for making non-sparking tools.
Still further object of the present invention is for obtaining Cu-Ti alloys having grain size of 70-80 µm.
Yet further object of the present invention is for obtaining Cu-Ti alloy capable of being worked for obtaining large size implements used in explosive, mining and petroleum industries.
Further object of the present invention is to propose an improved process, for the preparation of Cu-Ti alloys wherein Ti content could be from 1 to 6 wt% which may be hot/cold worked for obtaining characteristics suitable for use as springs, valves, connectors and contacts.
Yet further object of the present invention is to propose an improved process for the
preparation of Cu-Ti alloys, which is energy-efficient requiring solution treatment
schedules for very short durations.
DESCRIPTION OF INVENTION
According to this invention there is provided an improved process for the preparation of
copper titanium alloys, wherein the said process comprises of:
(a) refining commercial purity cathode copper insitu by pickling with dilute hydrochloric acid, washing thoroughly in water, cleaning in acetone and drying following by melting in the graphite crucible of air induction melting fumace (AIM) at 1200-123 0°C for 10-20 minutes and stirring the melted copper well by carbon monoxide gas bubbles and a graphite rod,
(b) preparing the copper titanium alloy by cleaning commercial grade titanium in acetone and adding 1 to 6 wt% of this cleaned titanium to the copper melt obtained in step (a) then melting it for 10-20 minutes till the temperature reaches 1200-123 0°C followed by pouring the liquid copper titanium alloy into graphite mould and allowing it to cool in air.
(c) homogenizing the Cu-Ti alloy ingots obtained in step (b) at 800-900°C for 8-12 hours, soaking them at 750-900°C for 2-3 hours then forging/rolling to break the solidification microstructure followed by heating again to 750-900°C for about 2 hours then quenching rapidly into water to obtain uniform grain size of 75 microns,
(d) cold working the homogenized Cu-ti alloy ingots obtained in step (c) by rolling at room temperature to desired amount of deformation to fabricate specific tools, aging at 380-480°C for 1-16 hours then cleaning with 10-20% diluted HCl acid, washing thoroughly in water and then drying with acetone.
The process of the present invention involves solution treatment at temperatures in the range of 750-900°C, preferably in the range of 840-900°C for a period of about 2 hours only as compared to the process of the known art which require heating at 500 to 700°C for long durations extending over to about 20 hours. The process follows cold working schedules that lead to formation of deformation twins that enhance strength without decreasing the electrical conductivity compared to that of dislocation cells. During aging carried out at temperatures of 380-480°C preferably at 400-450°C, double precipitation
occurs which further enhances electrical conductivity. Cu-Ti alloy obtained by the process of the present invention has grain size of 75 microns, strength varying from 1000-1480 Mpa, 465 Hv hardness and 20% lACS (International Annealed Copper Standard) electrical conductivity. Further, Cu-Ti alloy obtained by the process of the present invention is highly cost-efficient thus, requiring only air induction melting furnace and reduced manpower.
DESCRIPTION OF PROCESS
According to the present invention, the process of preparation of Cu-Ti alloy comprises of the following steps:
a) Institu refinement of copper
For insitu refinement of copper, commercial purity cathode copper is pickled using dilute hydrochloric acid, washed thoroughly in water, cleaned in acetone and dried in air. This copper is melted and refined insitu in a graphite crucible of air induction melting (AIM) furnace at 1200-1230°C for 10 to 20 minutes. The melt is stirred well by the
escaping carbon monoxide gas bubbles insitu and also using a graphite rod, which removes all the gaseous and volatile impurities, thus resulting in purity-enhanced copper.
b) Preparation of Cu-Ti Alloy
For making Cu-Ti alloys, commercial grade titanium is taken in the range of 1 to 6wt% for general applications and 4 to 6 wt% for non-sparking tools. The titanium is cleaned in acetone and is then added to the copper melt obtained by step (a) and the melting process is continued for 10-20 minutes till the temperature reaches 1200-1230°C, the liquid alloy is poured into graphite mould and allowed to cool in air.
c) Hot forging and rolling of ingots to wrought forms
The ingots so obtained were homogenized at 800-900°C for 8-12 hours. Hot forging/rolling is carried out to break the solidification microstructure, after soaking at 750-900.°C for 2 to 3 hours, into sizes customized for making specific non-sparking tools or strips etc.
d) Solution Treatment
Wrought materials are then heated for 2 hours at hig.'t temperatures of 750 to 9G0°C and quenched rapidly into water to obtain uniform grain size of about 75 microns.
e) Cold working/Fabrication of specific tools
Solution treated alloys are cold worked by rolling at room temperature to the desired amounts of deformation so as to fabricate specific tools. Cold working of Cu-4.5 Ti and Cu-5.4Ti alloys results in deformation twins, which lead to enhanced strength without drastically decreasing the electrical conductivity.
f) . Aging treatment
Cold worked alloys as obtained above, are aged at 380-480°C preferably at 400 to 450°C, for 1-16 hours to get double precipitation which results in further enhancement of electrical conductivity and strength.
g) Surface Cleaning
The aged tools are then cleaned using 10-20% diluted HCl acid, washed thoroughly in water and dried with acetone for obtaining bright surface.
The process of the present invention will now be illustrated by specific examples. It is to be understood that the examples given herein are by way of illustration and are not intended to be taken restrictively to imply any limitation on the scope of the present invention.
WORKINVG EXAMPLES: Example 1
The charge is prepared by taking 28.65 kgs of cathode.copper and 1.35 kgs of commercial grade titanium metal. The copper cathodes were cut to small sizes to fit into
the crucible. The cut cathode copper pieces were pickled using dilute hydrochloric acid, washed thoroughly in water, cleaned in acetone and dried in air. The titanium metal pieces were also cleaned in acetone. The cleaned cathode copper.pieces were charged in the graphite crucible of the air induction melting (AIM) fiirnace, melted by induction heating and refined for 10-20 minutes at I200°C wherein insitu carbon monoxide gas bubbling is generated for refining'the copper. The surface of the copper melt was covered by a thick layer of graphite pieces of assorted sizes. The titanium metal pieces were then added to the liquid copper and the crucible was covered with an asbestos sheet. The insitu carbon monoxide gas bubbling ensures uniform dissolution of Ti in the melt. The liquid alloy was also stirred well using a graphite rod. After allowing the temperature to reach 1230°C, the liquid alloy was poured at 1230°C into a graphite mould and cast (the melting practice described herein can be used to cast ingots of varying sizes weighing 30 kgs on a lab scale). The ingots were homogenized at 850°C for 12 hours and hot forged and rolled after soaking at 850°C for 2 hours, mto-suitable sizes. Samples from the wrought products are solution treated and quenched rapidly into water to obtain 75 micron grain size as well as fine scale precipitation in Cu-4.5Ti and Cu-5.4Ti alloys. When they are cold worked and aged at 400 to 450°C for 1-16 hours, tensile strengths as high as 1200-1480 MPa as well as electrical conductivity as high as 20% lAGS are imparted. To determine electrical conductivity, the hot rolled rod samples were drawn to 2 mm diameter wires with intermittent solution treatments. The electrical conductivity of the alloy was computed from the resistivity values calculated from the experimentally measured resistance of the wires using "Phillips PM 6303 RCL meter". These observations are listed in Table-1 displayed hereafter.
Table 1 Hardness, Tensile properties and Electrical Conductivity of air induction melted (AIM) Cu-4.5Ti alloy.

(Table Removed)
: Conductivity and tensile strength achieved when the deformed alloy was aged at 450'c/24h.
A test for certification of Cu-Ti alloy for non-sparking characteristics was carried out at Central Mining Research Institute (CMRI) Dhanbad in an explosion chamber fabricated for the purpose. The Cu-Ti alloy samples on subjection to abrasive action as per specification laid vide Indian Standard specification IS: 4595-1969, with the environment inside the chamber consisting of 50% each gasoHiie and oxygen mixture niaintained at 28°C, did not result in an explo.sion. CMRI therefore, issued the certification of "non-
sparking" conforming to Indian Standard specification, IS 4595-1969 to the Cu-Ti alloy samples prepared by the process of this invention.
The average grain size of the order of 75 microns is obtainable after solution treatment at 750°C for Cu-1.5Ti, 800°C for Cu-2.7Ti, 860°C for Cu-4.5Ti and 880°C for Cu-5.4Ti alloy. Reduction in grain size either with intermediate annealing or with cold rolling followed by solution treatment gave hardly any incremental improvements. Further treatments carried out to reduce the grain size below 75 microns resulted in recrystallised grains of about 75 microns only even in short duration anneals. Therefore, the process of this invention enables one-step solution treatment to obtain above grain size, even for thicker sections required for making non-sparking tools like hammer etc. For subsequent processing 75 microns average crystal grain size was utilized.
The strength of Cu-Ti alloys is increased by the presence of Ti in solution and cold working, whereas the electrical conductivity decreases due to the above phenomena. In the process of the present invention, the structure obtained after solution treatment and cold work is significantly different which does not reduce the electrical conductivity drastically. The solution treated Cu-1.5Ti and Cu-2.7Ti alloys resulted in microstructure consisting of high density of dislocation cells on cold working by 90%, which reduced electrical conductivity of these alloys significantly. In the case of Cu-4.5Ti and Cu-5.4Ti alloys, the presence of fine scale precipitates formed during quenching itself, results in the formation of deformation twins on cold working which while contributing to enhanced precipitation, does not reduce electrical conductivity compared to that by dislocation cells
The aforesaid processing conditions involving deliberate utilization of prior fine scale precipitation are obtainable in Cu-Ti alloys with Ti contents ranging from 4 to 6 wt%. The properties of Cu-Ti alloys having Ti in the range of 4 to 6 wt% and processed by the above said methods compare favorably with those disclosed in the prior art (US patents 2,943,960; 4,566,915; 4,599,119) as well as Cu-2.0 Be-0.6 Co alloys, as illustrated in Table 2.

able 2 Comparison of the properties of air induction melted Cu-4.5Ti alloy vvitii
those ofconvenrionai Cu-2.0Be-0.5Co alloy and Cu-Ti alloys of prior art.

(Table Removed)


1
2 3 4
SCA

: Alloy of Preset Invention
: Vacuum melted eu-4.5Ti alloy (Patent filed on 09.12.1999).
: Alloy of US patent 2,943,960
: Alloy ofUS patent 4,566,915 and 4,599,119. NR .Not reported
: ST + Cold work (90%) + peak aged (400OC/lh). The time, temperature and % Cold work given here correspond to air melted Cu-Ti alloy of present invention
and vacuum melted Cu-Ti alloy of prior art (patent filed on 09.12.1999). : Conductivity and tensile strength achieved When the deifonned alloy was aged at
4500C/24h. : .
: Conductivity and tensile strength achieved when the deformed alloy was aged at
4000C/17h



It is to be understooa that the ,process of the present invention is susceptibl modifications, changes, - adaptions by those skilled in the art Scuh modification,














WE CLAIM;
1. An improved process for the preparation of copper titanium alloys, wherein the said process comprises of:
(a) refining commercial purity cathode copper insitu by pickling with dilute hydrochloric acid, washing thoroughly in water, cleaning in acetone and drying following by melting in the graphite crucible of air induction melting furnace (AIM) at 1200-1230°C for 10-20 minutes and stirring the melted copper well by carbon monoxide gas bubbles and a graphite rod characterized by;
(b) preparing the copper titanium alloy by cleaning commercial grade titanium in acetone and adding 1 to 6 wt% of this cleaned titanium to the copper melt obtained in step (a) then melting it for 10-20 minutes till the temperature reaches 1200-1230°C followed by pouring the liquid copper titanium alloy into graphite mould and allowing it to cool in air,
(c) homogenizing the Cu-Ti alloy ingots obtained in step (b) at 800-900°C for 8-12 hours, soaking them at 750-900°C for 2-3 hours then forging/rolling to break the solidification microstructure followed by heating again to 750-900°C for about 2 hours then quenching rapidly into water to obtain uniform grain size of 75 microns,
(d) cold working the homogenized Cu-ti alloy ingots obtained in step (c) by rolling at room temperature to desired amount of deformation to fabricate specific tools, aging at 380-480°C for 1-16 hours then cleaning with 10-20% diluted HC1 acid, washing thoroughly in water and then drying with acetone.

2. An improved process as claimed in claim 1 wherein in step (b) 4 to 6 wt.% to cleaned titanium is added to the upper met.
3. An improved process as claimed in claim 1 wherein step (d) the aging is carried out at 400-450°C.
4. An improved process for the preparation of copper titanium alloys as substantially described and exemplified herein.


Documents:

264-del-2004-Abstract-(18-10-2010).pdf

264-del-2004-abstract.pdf

264-del-2004-Claims-(18-10-2010).pdf

264-del-2004-claims.pdf

264-del-2004-Correspondence-Others-(18-10-2010).pdf

264-del-2004-correspondence-others.pdf

264-del-2004-correspondence-po.pdf

264-del-2004-description (complete).pdf

264-del-2004-form-1.pdf

264-del-2004-form-2.pdf

264-del-2004-Form-3-(18-10-2010).pdf

264-del-2004-Form-5-(18-10-2010).pdf

264-del-2004-GPA-(18-10-2010).pdf


Patent Number 247901
Indian Patent Application Number 264/DEL/2004
PG Journal Number 22/2011
Publication Date 03-Jun-2011
Grant Date 31-May-2011
Date of Filing 23-Feb-2004
Name of Patentee DIRECTOR GENERAL,DEFENCE RESEARCH & DEVELOPMENT ORGANISATION
Applicant Address DEFENCE RESEARCH & DEVELOPMENT ORGANISATION MINISTRY OF DEFENCE, GOVT OF INDIA, WEST BLOCK-VIII, WING-1, SECTOR-1, RK PURAM, NEW DELHI-110066, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 NAGARJUNA SETTIVARI DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH-P.O., HYDERABAD-500 058, INDIA.
2 BANDARU RAJENDRA PRASAD DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH-P.O., HYDERABAD-500 058, INDIA.
3 KRISHAN KUMAR SHARMA DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH-P.O., HYDERABAD-500 058, INDIA.
PCT International Classification Number C22C 45/10
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA