DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
A METHOD OF OPTIMIZING PROCESS PARAMETERS FOR MIG BRAZING OF ROLLING STOCK

Applicant:
BEML Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
BEML Soudha, 23/1, 4th Main,
Sampangirama Nagar, Bengaluru,
Karnataka - 560 027, India

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

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[001] This patent application claims priority from Indian Provisional Application 201941053721 filed on 24th December 2019.

TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to a method of optimizing process parameters for brazing and more specifically method of optimizing process parameters for brazing of LHB coaches.
BACKGROUND
[003] Generally, a rolling stock is manufactured using ferritic stainless steel. The side and roof joints of the rolling stock are joined by MIG brazing. In order to ensure aesthetic appearance of the rolling stock and leak proof joints, the MIG brazing finish needs to be upmost quality. However, it is observed that a large amount of defects/rejections are observed with the conventional MIG brazing process due to non-establishment of the process parameters of MIG brazing. Hence, it leads to poor aesthetic appearance and leakage of water from the side and roof joints.
OBJECT OF THE INVENTION
[004] It is an object of the present invention to optimize process parameters for MIG brazing of rolling stock.
[005] It is an object of the present invention to manufacture defect free and leak proof joint between the side and roof joints.
[006] It is an object of the present invention to ensure superior quality weld between the side and roof joints.
[007] It is an object of the present invention to improve aesthetic appearance of the rolling stock.
STATEMENT OF INVENTION
[008] Before the present system and method are described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in

the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a method for optimizing process parameters for mig brazing of rolling stock, and the aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[009] A method for optimizing process parameters for MIG brazing of rolling stock comprises identifying, controlling and determining process parameters including, but not limited to, braze size, visual defects, brazing current, brazing voltage, feed rate and type of shielding gas. The determined parameters are then used to achieve good quality weld.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawing:
[0011] The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0012] Figure 1 illustrates sidewall structure, in accordance with one embodiment of the present subject matter.
[0013] Figure 2 illustrates cantrail, in accordance with one embodiment of the present subject matter.
[0014] Figure 3 illustrates a method for optimizing process parameters for mig brazing of rolling stock, in accordance with one embodiment of the present subject matter.
[0015] Figure 4 illustrates combination of variables to get desired output, in accordance with one embodiment of the present subject matter.

[0016] Figure 5 illustrates combination of interactions to get desired output, in accordance with one embodiment of the present subject matter.
[0017] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0018] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0019] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[0020] Referring now to Figure 1 and Figure 2, a sidewall (A) structure and cantrail (B), in accordance with one embodiment of the present subject matter, is disclosed. Sidewall is a fundamental structure comprising of two major parts i.e. the sidewall structure (A) and cantrail (B).
[0021] Figure 3 illustrates a method for optimizing process parameters during mig brazing of rolling stock, in accordance with one embodiment of the present subject matter.
[0022] The method discloses a flow chart of the brazing operation carried out on sidewalls of LHB coaches. In order achieve defect free brazing operation on LHB sidewalls,

the process is carried out into two parallel stages to ensure zero defects while carrying out brazing operation.
[0023] In the first stage, the machine parameters and functionalities are periodically checked (after every 5 Sets) to perform brazing on test pieces (material), secondly the test samples are self-inspected and later lab inspected.
[0024] In the second stage, the sidewall (A) structure and the cantrail (B) are placed on the inspection table to ascertain straightness and defects on the welding surfaces/edges. Further, the sidewall (A) and the cantrail (B) are placed on the jig to check alignment to maintain root gap (2 mm) between the welding surfaces and accordingly clean the welding areas. Furthermore, the sidewall (A) and the cantrail (B) are inspected to confirm straightness and alignment followed by cleaning to avoid any welding defects during brazing. The sidewall (A) structure and the cantrail (B) are then subjected to tack weld in series on the joint at equal intervals followed by complete brazing over the entire length. This operation critically depends on the brazing process parameters which are accordingly optimized for the brazing operation.
[0025] To improve the process and to understand the effect of certain parameters of MIG Brazing, a design of experiments was conducted. Following factors were taken for experiment: -
Experimental factors Brazing current, brazing voltage, feed rate and type of shielding gas
Control factors Welding machine parameters, filler material, gas flow, parent material
Noise factors Ambient conditions (Temp., Humidity etc.), Operator fatigue, etc.
No. of factors 4
Levels 3 Levels for Brazing current & voltage &
2 Levels for feed rate & Type of shielding Gas
Type of experiment full factorial, replicates: 1
Centre points Nil
No. of blocks 1
No. Of experimental runs 36
[0026] Total 36 experiments were conducted and data were collected for braze size and visual defects, brazing current, brazing voltage, feed rate and type of shielding gas. Large effects were determined using pie chart and normal plot. Significant factors are found to be current, voltage, feed rate and type of shielding gas. Subsequently main effect plot was plotted and found that there is a significant change in MIG brazing output when current, voltage, feed rate and type of shielding gas is changed.
[0027] Referring now to figure 4, in one aspect of present invention, various parameters such as type of gas, feed rate, current and voltage are established to get the desired output. By controlling the above-mentioned parameters during brazing, a finish of superior quality can be achieved.
[0028] Referring now to figure 5, in one aspect of present invention, various parameters such as type of gas, feed rate, current and voltage displaying combinations of interactions to get the desired output. The combinations of various parameters can be monitored to achieve the desired finish.
[0029] In one example, a method of optimizing process parameters for MIG brazing of rolling stock carried out by welding machine with 99% Argon as shielding gas and filler rod material of specification DIN 1733-SG-CuAl8 for parent material (Stainless Steel) with specification RDSO/SPEC. C-K201 X2 Cr Ni12 (409M) of thickness 2 mm for optimizing brazing process parameters. To make defect free MIG brazing in sidewall for a rolling stock, a sidewall structure and a cantrail is levelled on an inspection table for determining straightness and defects on welding surface for fitting and aligning the said sidewall structure and said cantrail on a jig to maintain root gap of 2 mm between the welding surface.
[0030] Further, the method comprises cleaning, said sidewall structure and said cantrail to avoid any welding defects during brazing and tack brazing at pre-determined intervals along the length of the welding surface to position the joint between said sidewall structure and said cantrail. Furthermore, the method comprises brazing said sidewall structure and cantrail along the entire length of the welding surface for optimizing process parameters; and inspecting said rolling stock.

[0031] The process parameters optimized using the above method are experimental factors, welding machine parameters and noise factors, wherein the method is based on simulation of the experimental factors, welding machine parameters and noise factors. The optimized experimental factors are brazing current, brazing voltage, feed rate and type of shielding gas whereas the optimized control factors are welding machine parameters, filler material, gas flow and parent material and the optimized noise factors are ambient conditions such as temperature, humidity and operator fatigue.
[0032] The optimized brazing process parameters are experimental factors on the welding machine, side wall skin length of 8.5 meter and noise factors.
[0033] The method is based on full factorial design of experiments of factors (3 Levels for Brazing current & voltage, 2 Levels for feed rate & Type of shielding Gas) on the said welding machine.
[0034] The optimized experimental factors are brazing current (112 amp to 117 Amp), brazing voltage (18.5 Volt), feed rate (8.5meter/min) and type of shielding gas (Argon (Ar): 99.99%)
[0035] The optimized control factors are filler material (Type: Cu-Alloy (Cu-Al Bronze) wire Specification: DIN 1733/88SG-Cu-AL8, Size:0.8mm Dia), gas flow (3.6kg/cm2), parent material (Sidewall-Ferritic SS AISI 409M, Roof End Part-Ferritic SS to AISI 409M, Thickness:2.00mm) and welding position (LAP Joint: Horizontal).
[0036] The welding machine with 99% argon as shielding gas is used for optimizing brazing process parameters.
[0037] The optimized brazing process parameters are experimental factors, welding machine parameters and noise factors.
[0038] The method is based on full factorial design experimental factors conducted on a welding machine.
[0039] The optimized experimental factors are brazing current, brazing voltage, feed rate and type of shielding gas.
[0040] The brazing current is in the range of 112 ampere to 117 ampere, said brazing voltage is 18. Volt, said feed rate is 8.5 metre/min and type of shielding gas is argon: 99.99%

[0041] The said optimized control factors are welding machine parameters, filler material, gas flow and parent material.
[0042] The filler material is a copper alloy and parent material is from one of a ferritic stainless steel.
[0043] The optimized noise factors are ambient conditions such as temperature, humidity and operator fatigue.
[0044] Further, the invention can be used, but not limited to, in the following applications.
[0045] One embodiment of the invention can be used for optimizing process parameters during MIG brazing of rolling stock.
[0046] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0047] Some object of the present invention ensures good quality weld.
[0048] Some object of the present invention reduces defects. ,CLAIMS:

1. A method of optimizing process parameters for MIG brazing of rolling stock
comprises:
inspecting, a sidewall structure and a cantrail on an inspection table for determining straightness and defects on welding surface;
fitting and aligning said sidewall structure and said cantrail on a jig to maintain root gap of 2 mm between the welding surface;
cleaning, said sidewall structure and said cantrail to avoid any welding defects during brazing;
tack brazing at pre-determined intervals along the length of the welding surface to position the joint between said sidewall structure and said cantrail;
brazing said sidewall structure and cantrail along the entire length of the welding surface for optimizing process parameters; and
inspecting said rolling stock.

2. The method as claimed in claim 1, wherein a welding machine with 99% argon as shielding gas is used for optimizing brazing process parameters.

3. The method as claimed in claim 1, wherein said optimized brazing process parameters are experimental factors, welding machine parameters and noise factors.

4. The method as claimed in claim 1, wherein said method is based on full factorial design experimental factors conducted on a welding machine.

5. The method as claimed in claim 2, wherein said optimized experimental factors are brazing current, brazing voltage, feed rate and type of shielding gas.
6. The method as claimed in claim 5, wherein said brazing current is in the range of 112 ampere to 117 ampere, said brazing voltage is 18. Volt, said feed rate is 8.5 metre/min and type of shielding gas is argon: 99.99%
7. The method as claimed in claim 2, wherein said optimized control factors are welding machine parameters, filler material, gas flow and parent material.
8. The method as claimed in claim 7, wherein said filler material is a copper alloy and parent material is from one of a ferritic stainless steel.
9. The method as claimed in claim 2, wherein said optimized noise factors are ambient conditions such as temperature, humidity and operator fatigue.