DESC:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See sections 10 & rule 13)
1. TITLE OF THE INVENTION
A METHOD FOR DETERMINATION OF CHEMICAL COMPOSITION OF LEADED BRONZE LAYER COMPACTED ON STEEL METAL STRIP
2. APPLICANT (S)
NAME NATIONALITY ADDRESS
BEML LIMITED IN BEML Soudha, No 23/1, 4th Main S.R. Nagar, Bengaluru- 560027, Karnataka, India.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION:
[001] The present invention relates to the field of leaded bronze layer compacted on steel metal strip. The present invention in particular relates to a method for determination of chemical composition of leaded bronze layer compacted on steel metal strip by Optical Emission Spectrometry Technique.
DESCRIPTION OF THE RELATED ART:
[002] In regular analysis, using optical emission technique, results will be obtained on each single excitation/ burn (i.e., one cycle of argon flush, pre-burn and exposure per parameters set in the program).
[003] Reference may be made to the following:
[004] Publication No. US2003064239 relates to a copper-based sintered sliding material comprising a steel back metal layer, and a sintered layer made of Cu or a Cu-based alloy which is bonded onto the steel back metal layer, the steel back metal layer having a hardness not less than 160 Hv and an elongation not less than 10%, the sintered layer having a hardness not more than 130 Hv and crystal grains each provided with a grain size not more than 45 mum, a method of producing the sliding material, and a sliding bearing formed of the sliding material.
[005] Publication No. CN202805787 relates to a lead-free bimetallic composite bearing plate, and aims at providing the lead-free bimetallic composite bearing plate which is simple in structure, good in process inheritance, excellent in lubricating property and reasonable in material use, and does not contain harmful ingredients. A layer of bronze powder layer is sintered at the surface of a low-carbon steel plate. The lead-free bimetallic composite bearing plate is characterized in that the bronze powder layer is sintered from CuSn8Ni1 or CuSn6Ni9 bronze powder. The lead-free bimetallic composite bearing plate does not contain lead, and can be prepared into a sliding bearing or a shaft bushing with a seam by mechanical machining such as clipping, pressing an oil groove, rolling, shaping and chamfering; the plates of a steel-copper alloy bimetallic bearing and the shaft bushing widely applied in the past are replaced; and the lead-free bimetallic composite bearing plate is a green metal plate which is harmless to a human body. The lead-free bimetallic composite bearing plate has the advantages that the lubricating bearing prepared from the lead-free bimetallic composite bearing plate has higher carrying capacity and decay resistance compared with the traditional copper-lead alloy composite plate besides the lead-free environmental protection property. The product can be widely applied to the fields such as the machining of automobiles, engineering plants, foods and medicines, and meets the lead-free requirements.
[006] Publication No. CN1664137 relates to a phos-bronze bimetal sheet used to make brass. The surface of steel sheet is adglutinated with alloying layer, of which component comprises 5.5`7wt% of tin, 0.1~0.4wt% of phosphor, 0.05~0.8wt% of 0.05~0.8wt% of zine and 91.3~94wt% of copper. Flow process comprises steel sheet degreasing derusting and coppering or preprocessing without coppering (roller leveling, bedding alloy powder, first clinkering (800~900 Deg. C), roll flattening, second clinkering (840~920 Deg. C) and finish roll flattening). Phos-bronze bimetal sheet used to make brass has properties of high-intensity and fine abradability to meet the need of automobile engine of high power and high speed. Further more, the invention in favor of environmental conservation and improving the operation quality of car.
[007] Patent No. US6746154 relates to a lead-free bearing includes a bronze matrix powder metal bearing layer bonded to a steel backing a fully densified. The bearing material has about 8 to 12% by weight tin, about 1 to less than 5% by weight bismuth, and about 0.03 to 0.08% by weight phosphorus, with the balance being copper. The tin is soluble in the copper to yield the bronze matrix, and the bismuth exists as finely dispersed, undissolved islands through the matrix. Such bearings exhibit physical properties comparable to or better than those of traditional bronze-lead bearings and improved wear in seizure properties.
[008] Patent No. US5429876 relates to a copper-lead based bearing material having excellent corrosion resistance, comprising a steel back metal and a bearing layer of a copper-lead based bearing alloy, the latter consisting essentially, by weight, 0.5 to 10% Bi, 0.5 to 8% Sn, 15 to 30% Pb, 2 to 10% Ni, not greater than 0.2% P, the balance Cu and incidental impurities. By adding Bi in a copper-lead based bearing alloy it becomes possible to obtain excellent corrosion resistance without impairing the conformability and seizure resistance of the bearing material in comparison with the conventional copper-lead based bearing alloys.
[009] Publication No. US2003161751 relates to high-density composite materials comprising tungsten and bronze are useful as lead replacements in the production of ammunition, weights and other high density articles. The composition of the composite, articles manufactured using the composite, and a process for making the composite are disclosed.
[010] Publication No. EP0143449 relates to an improved process and an improved composite bearing material produced thereby comprising a hard metal backing strip having leaded-bronze bearing lining tenaciously bonded to at least one face surface thereof and wherein the bearing lining is characterized by having the lead constituent thereof substantially uniformly distributed throughout the lining matrix in the form of extremely fine sized particles providing improved operating characteristics to the bearing materials fabricated therefrom. In accordance with the process aspects of the present invention, the steel backing strip is provided with a metallic plating composed predominantly of nickel to at least the face on which a prealloyed leaded-bronze powder of a controlled composition is applied and is thereafter sintered at a controlled temperature for a short period of time sufficient to effect a liquid phase sintering of the powder together and the formation of a bond between the powder layer and the metallic plating on the face of the backing strip where after the sintered composite strip is cooled and is compacted usually at temperatures below about 300 DEG F. (149 DEG C) to effect a substantially complete densification of the powder layer. The composite strip is again reheated at a controlled temperature and for a brief period of time sufficient to further enhance the physical properties of the bearing lining and to further enhance the strength of the bond between the lining and backing strip under controlled conditions to inhibit growth of the fine sized lead particles into undesirable larger particles. The composite strip is thereafter again cooled and may be subjected to a further compaction at moderate warm temperatures to achieve still further densification and to improve the physical properties and sizing of the composite strip.
[011] Patent No. US4904537 relates to an improved process and an improved composite bearing material produced thereby comprising a hard metal backing strip having leaded-bronze bearing lining tenaciously bonded to at least one face surface thereof and wherein the bearing lining is characterized by having the lead constituent thereof substantially uniformly distributed throughout the lining matrix in the form of extremely fine-sized particles providing improved operating characteristics to the bearing materials fabricated therefrom. In accordance with the process aspects of the present invention, the steel backing strip is provided with a metallic plating composed predominantly of nickel to at least the face on which a prealloyed leaded-bronze powder of a controlled composition is applied and is thereafter sintered at a controlled temperature for a short period of time sufficient to effect a liquid phase sintering of the powder together and the formation of a bond between the powder layer and the metallic plating on the face of the backing strip where after the sintered composite strip is cooled and is compacted usually at temperatures below about 300 DEG F. to effect a substantially complete densification of the powder layer. The composite strip is again reheated at a controlled temperature and for a brief period of time sufficient to further enhance the physical properties of the bearing lining and to further enhance the strength of the bond between the lining and backing strip under controlled conditions to inhibit growth of the fine-sized lead particles into undesirable larger particles. The composite strip is thereafter again cooled and may be subjected to a further compaction at moderate warm temperatures to achieve still further densification and to improve the physical properties and sizing of the composite strip.
[012] Publication No. US2003072670 relates to a method of fabricating multi-layer bronze bearings includes laying down a first layer of copper-based powder metal material of a first composition onto a steel backing strip. At least a second layer of copper-based powder metal material of a second composition different than that of the first is laid down on the first layer, without significantly densifying the first layer. The layers are then sintered, cooled, and roll compacted to bond them to one another and to the backing, after which the layers are further sintered.
[013] Publication No. GB929072 relates to electrically butt welding the edges of pieces of ferrous strip having a non-ferrous metal surface layer the pieces are arranged such that when the non-ferrous metal melts on application of welding current it is substantially removed from the weld locality by gravity. In welding pieces of steel coated with leaded bronze a fixed copper jaw holds one piece and a movable jaw holds the other with the steel uppermost, A.C. current is supplied between the jaws and as the abutting edges melt the moving jaw is advanced. The non-ferrous layer is melted and falls from the steel and any lead is volatilized. A blast of compressed air or hot or cold inert gas may assist removal. When the non- ferrous metal is removed from the weld area the current is cut off and the moving jaw is advanced to force the cleaned steel edges together to form weld. The coating may comprise copper based bearing alloy containing 3-30% lead and 0-15% tin.
[014] The expert in these arena are still content with Wet method or the high end industries, deploy Inductively Coupled Plasma - Optical Emission Spectrometer (ICP-OES), for which sample preparation is carried out by digestion technique using hazardous chemicals.
[015] In order to overcome above listed prior art, the present invention aims to provide a method for determination of chemical composition of leaded bronze layer compacted on steel metal strip by sintering process using optical emission spectrometer by iterative stabilized & homogenized burning technique.
OBJECTS OF THE INVENTION:
[016] Processes used for manufacturing bi-metal strips for copper based Bushings (Bush bearings)
[017] The principal object of the present invention is to provide a method for determination of chemical composition of leaded bronze layer compacted on steel metal strip by sintering process.
[018] Another object of the present invention is to provide a non-hazardous alternate test method using direct reading optical emission spectrometer for determination of Lead (Pb), Tin (Sn) & Copper (Cu) in Copper base alloys compacted on steel metal strip by sintering process.
[019] Yet another object of the present invention is to provide a method for determination of chemical composition of leaded bronze layer compacted on steel metal strip which eliminates dissolution, boiling, filtration, ignition, Furnace, Desiccator, electrolysis using Electro Analyzer, Platinum electrodes and distilled water and minimizes testing time, consumption of high cost Certified Reference Materials in chip form and prevents usage of hazardous chemicals (concentrated Nitric Acid).
SUMMARY OF THE INVENTION:
[020] The present invention relates to a method for determination of chemical composition of leaded bronze layer compacted on steel metal strip by sintering process using optical emission spectrometer (point to plane technique) by iterative stabilized & homogenized burning technique.
[021] Quantitative analysis of leaded bronze (Specification: JIS – LBC-3 / SAE – 797) compacted on steel metal strip by sintering process of minimum 0.7mm thickness is carried out on direct reading optical emission spectrometer. Leaded bronze (copper base) program, ultra high pure argon, set-up standards and certified reference materials in disc form are used for this technique.
BREIF DESCRIPTION OF THE INVENTION
[022] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.
[023] Figure 1 shows processes used for manufacturing bi-metal strips for copper based bushings.
DETAILED DESCRIPTION OF THE INVENTION:
[024] The present invention provides a method for determination of chemical composition of leaded bronze layer compacted on steel metal strip by sintering process using direct reading optical emission spectrometer (point to plane technique) by iterative stabilized & homogenized burning technique.
[025] Referring to figure 1 which shows processes used for manufacturing bi-metal strips for copper based bushings.
[026] Fig. 2a shows section of bimetallic bushing with leaded bronze sintered layer and steel backing plate. Fig 2b shows Sample Preparation i.e., Surface of Leaded Bronze Sintered Layer before analysis (excitation).
[027] Selection of relevant Cu base Leaded Bronze is done on Optical Emission Spectrometer. Standardization of OES Instrument is done using Cu base Set-up Standards.
[028] Verification of Certified Reference Materials (Cu base leaded bronze) certification is verified and the sample is placed on excitation table of OES Instrument:
[029] The excitation is continuous excitation till homogeneity of sintered layer is attained (Cu, Pb and Sn).
Table 1: Optical Emission Spectrometer - Results in Mass Fraction %
Burn Sl. No. Program Sample No Cu Pb Sn
1 Cu101 LBC-3
175TF24006 76.79 16.19 6.46
2 76.94 16.04 6.52
3 79.17 13.87 6.47
4 79.05 13.83 6.64
5 77.66 15.62 6.38
6 77.78 15.68 6.27
7 77.62 15.67 6.46
8 79.56 12.50 7.75
9 80.94 10.63 8.26
10 80.79 10.45 8.58
11 81.65 9.21 8.96
12 81.32 10.18 8.33
13 81.82 9.17 8.84
14 82.62 8.62 8.56
15 82.17 8.83 8.81
16 82.23 8.64 8.96
17 82.42 8.63 8.76
18 82.49 8.38 8.97
19 82.45 8.49 8.89
20 82.22 8.50 9.11
[030] Readings of Cu, Pb & Sn (from 15 to 20) in shaded shells reveals sintered layer attained homogeneity due to continuous excitation.
Table 2: Test Results/ burns exhibiting repeatability to be considered for reporting:
Burn Sl. No. Program Sample No Cu Pb Sn
15 Cu101 LBC-3
175TF24006 82.17 8.83 8.81
16 82.23 8.64 8.96
17 82.42 8.63 8.76
18 82.49 8.38 8.97
19 82.45 8.49 8.89
20 82.22 8.50 9.11
[031] Readings of Cu, Pb & Sn (Sl. No. from 15 to 20) in shaded shells exhibiting repeatability to be considered for reporting.
[032] Figure 3 shows Surface of Leaded Bronze Layer after analysis (excitation).
Table 3: Average / Mean value of elements exhibiting repeatability in results / burns to be reported
Burn Sl. No. Program Sample No Cu Pb Sn
15 Cu101 LBC-3
175TF24006 82.17 8.83 8.81
16 82.23 8.64 8.96
17 82.42 8.63 8.76
18 82.49 8.38 8.97
19 82.45 8.49 8.89
20 82.22 8.50 9.11
Average Test Result in Mass Fraction % 82.33 8.58 8.92
[033] Mean / Average value to be reported:
[034] Cu: 82.33%, Pb: 8.58% & Sn 8.92%
[035] Quantitative analysis of leaded bronze (Material Specification: JIS – LBC-3 / SAE – 797) compacted on steel metal strip by sintering process of minimum 0.7mm thickness is carried out by using direct reading optical emission spectrometer. Leaded bronze (copper base) program, ultra high pure argon (99.9995%), set-up standards, certified reference materials in disc form are used for this technique.
[036] Standardization of the instrument (direct reading optical emission spectrometer) is to be carried out in accordance with Instrument Operation Manual and Test Method Standard BS EN 15079 and analysis is done on dirt and dust free sintered layer by taking minimum of 20 no. of continuous burns on the same spot and the same to be repeated on other locations too. Due to continuous sparks, the surface of the sintered layer exposed to high power discharges and melts the surface layer and makes the sintered layer more homogeneous (Table 4: Burn Sl. No. 15 to 20).
Table 4:
Optical Emission Spectrometer - Results in Mass Fraction %
Burn Sl. No. Program Sample No Cu Pb Sn
1 Cu101 LBC-3
175TF24006 76.79 16.19 6.46
2 76.94 16.04 6.52
3 79.17 13.87 6.47
4 79.05 13.83 6.64
5 77.66 15.62 6.38
6 77.78 15.68 6.27
7 77.62 15.67 6.46
8 79.56 12.50 7.75
9 80.94 10.63 8.26
10 80.79 10.45 8.58
11 81.65 9.21 8.96
12 81.32 10.18 8.33
13 81.82 9.17 8.84
14 82.62 8.62 8.56
15 82.17 8.83 8.81
16 82.23 8.64 8.96
17 82.42 8.63 8.76
18 82.49 8.38 8.97
19 82.45 8.49 8.89
20 82.22 8.50 9.11
[037] Due to repetitive excitation on the same spot, approximately after 14th reading (in some case more than 14th reading), repeatability in readings are observed due to sintered layer attains homogeneity. Results with good repeatability can only be considered and bad burn reflecting vague readings are to be deleted. Average of Minimum 05 No. of burns with repeatability (shaded cells) to be considered for reporting the results (Pl. refer Table5).
Table 5:
Burn Sl. No. Program Sample No Cu Pb Sn
15 Cu101 LBC-3
175TF24006 82.17 8.83 8.81
16 82.23 8.64 8.96
17 82.42 8.63 8.76
18 82.49 8.38 8.97
19 82.45 8.49 8.89
20 82.22 8.50 9.11
Average Test Result in Mass Fraction % 82.33 8.58 8.92
[038] Validation of method to be carried out by comparing the test results obtained by both wet (Referee Method) and OES (Reference Method) and calculated Z-Score to be within in ±2 (2 Sigma limit).
Method Validation
Comparison of LBC- 3 Sintered Layer Results obtained by
OES New Technique and Wet Method
Details of Artifacts:
Description: Chemical Analysis of Bimetallic Bushing by different methods
Table 6 : Analysis of Copper (Cu)
Sl. No. Laboratory Name Material Grade Results Z Score
Wt % (x) (x-X)/s
01 OES Method (New Technique) BSB LBC-3 82.33 0.707
02 By Wet Method 82.40 0.707
a Average (X) 82.37
b Std. Dev. (s) 0.05
Table 7 : Analysis of Lead (Pb)
Sl. No. Laboratory Name Material Grade Results Z Score
Wt % (x) (x-X)/s
01 OES Method (New Technique) BSB LBC-3 8.58 0.707
02 By Wet Method 8.80 0.707
a Average (X) 8.69
b Std. Dev. (s) 0.16

Table 8 : Analysis of Sn (Tin)

Sl. No. Laboratory Name Material Grade Results Z Score
Wt % (x)
(x-X)/s
01 OES Method (New Technique) BSB LBC-3 8.92 0.707
02 By Wet Method 8.80 0.707
a Average (X) 8.86
b Std. Dev. (s) 0.09
[039] a. Z-Score observed for Cu, Pb & Sn by new technique = 0.707
[040] Interpretation of Results: As per ISO/IEC 17043 & ISO 13528

Table 9 Results comparison between two methods by percentage method:
Element Result by
New Technique
Wt % (x) Result by
Wet Method
Wt % (y) % Variation with respect to New Technique
((x-y)/x)*100
Cu 82.33 82.40 0.09
Pb 8.58 8.80 2.56
Sn 8.92 8.80 1.35
[041] Present invention, uses direct reading optical emission spectrometer to carry out quantitative chemical analysis on leaded bronze (Cu base) sintered layer in place of wet analysis. Minimizes testing time (it requires approximately 120 minutes) to complete an analysis against 8 hours (i.e., 480 minutes) required to complete the same by wet method. The invention uses the OES (point to plane technique), continuous repetitive excitation / burns on the same spot till the homogeneity of sintered layer is attained.
[042] Results of good repeatable readings are for reporting, with permissible levels of standard deviation.
[043] Numerous modifications and adaptations of the system of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of this invention.
,CLAIMS:WE CLAIM:
1. A method for determination of chemical composition of leaded bronze layer compacted on steel metal strip by sintering process using optical emission spectrometer (point to plane technique) includes following steps.
a) Sample Preparation with Surface of Leaded Bronze Sintered Layer before analysis (excitation).
b) Selection of relevant Cu base Leaded Bronze is done on Optical Emission Spectrometer.
c) Standardization of OES Instrument is done using Cu base Set-up Standards.
d) Verification of Certified Reference Materials (Cu base leaded bronze) certification is verified and the sample is placed on excitation table of OES Instrument.
e) The excitation is continuous excitation till homogeneity of sintered layer is attained (Cu, Pb and Sn).
2. The method for determination of chemical composition of leaded bronze layer compacted on steel metal strip, as claimed in claim 1, wherein the Quantitative analysis of leaded bronze compacted on steel metal strip by sintering process of minimum 0.7mm thickness is carried out on direct reading optical emission spectrometer.