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 STRESS RELIEVING FOR A WELDED COMPONENT

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

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

CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY
[001] The present application claims priority from Indian Patent application no. (201941054269) filed on 27th December, 2019.
TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to a method of stress relieving for a welded component and more specifically a method to eliminate risk of Hydrogen induced crack in a welded component.
BACKGROUND
[003] Metals have many favorable properties, a primary advantage being their strength and resilience compared to other materials. However, metals are not as easily formed as many other materials, and in particular, while it is relatively straightforward to form sheets, plates, rods, and other symmetrical shapes, it is difficult to form shapes that are more complex. Thus, it is often necessary to join one or more pieces of stock metal to form a finalized product of an irregular shape. Of the available methods, welding provides the best compromise of efficiency and strength for joining most metals, especially steel. However, the welding process typically leaves unwanted stresses within the final part, especially around Heat-Affected Zone (HAZ), increasing the risk of a later failure of the part. For critical load-bearing pieces such as machine frames, beams, levers, and arms, the risk of failure should be minimized, both to avoid costly repair as well as to safeguard operators, nearby personnel and critical processes.
[004] In the past, it was known to heat treat metal to eliminate stresses, with the hopes that the stress-free metal would more easily resist cracking and breaking after a period of use. However, most of the time hardness of the metal cannot be controlled in the post weld heat treatment which results into unwanted breaking and cracking induced by Hydrogen. The above problems can be overcome by adopting a method of stress relieving for a welded component as disclosed by present subject matter.
OBJECT OF THE INVENTION
[005] Main object of the present invention is to reduce the hardness of the material post welding.
[006] Another object of the present invention is to improve toughness of the material.
[007] Another object of the present invention is to reduce risk of Hydrogen induced crack in the welded component.
SUMMARY
[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 of stress relieving for a welded component, 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] The present invention discloses a method of stress relieving for a welded component, wherein the method comprises steps of: pre-heating two or more components at 250°c and tack welding the two or more components by a suitable welding process to form the welded component; pre-heating the welded component at 250°c and completing the welding process; post-heating the welded component at 200°c and increasing the temperature of furnace to 550 °c at a step interval of 4°c per min; heating the welded component at 550°c for a predefined time interval; and oil quenching at 860°C and tempering procedure at 590°C for 1 hour.
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 a flow chart of steps for the method of stress relieving for a welded component, in accordance with an embodiment of the present subject matter.
[0013] Figure 2 illustrates a graph of Hardness values at Heat-Affected Zone (HAZ) in the welded component, in accordance with an embodiment of the present subject matter.
[0014] 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
[0015] 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.
[0016] 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.
[0017] The present subject matter discloses a method 100 of stress relieving for a welded component as illustrated in figure 1. Two or more components, configured to be of different materials, are welded to obtain a welded component. At first step of the present method, the two or more components are preheated at 250 °C. At second step, the two or more components are tack welded by any suitable welding process to form a welded component and again preheated at 250 °C. At next step, the welded component is fully welded as per the requirement.
[0018] At next step, the welded component is post heated at 200 °C and increasing the temperature of furnace to 550 °C at a predefined step increment of 4°C per min. Thereafter the temperature of the furnace is hold at 500°C for a predefined time interval. The predefined time interval is configured to be minimum 1 hour for each 1 inch thickness of the welded component. In an embodiment, the predefined time interval is configured to be. At next step, oil quenching at 860°C and tempering procedure at 590°C for 1 hour may be performed. The welded component achieved by the present method comprises reduced hardness and optimized toughness. Further the method also reduces risk of Hydrogen induced crack in the welded component.
[0019] The welded component is configured to maintain a hardness value below 350 BHN after the stress relieving method as disclosed above. The figure 2 illustrates a graph to show values of hardness (BHN) in the welded component with respect to the distance in the Heat-Affected Zone (HAZ) of the welded component. The welded component, after going the present stress relieving method, is configured to maintain a hardness below 350 BHN.
[0020] Further the welded component after cooling may be machined to obtain a final structure of the welded component.
[0021] In an exemplary embodiment, the two or more components are configured from a material SAE 4140H for tube and IS2062-E410 as plate material which are welded together and are configured to undergo the method of stress relieving as disclosed in the present subject matter. In another embodiment, a filler wire ER70S6 and CO2 as shielding gas may be selected for the welding process.
[0022] 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.
[0023] Some objects of the present invention enable to reduce the hardness of the material post welding.
[0024] Some objects of the present invention enable to improve toughness of the material post welding.
[0025] Some objects of the present invention enable to reduce risk of Hydrogen induced crack in the welded component.
[0026] Although implementations for the method of stress relieving for a welded component have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features described. Rather, the specific features are disclosed as examples of implementation for the method of stress relieving for a welded component.
,CLAIMS:
1. A method of stress relieving for a welded component, wherein the method comprises steps of:
pre-heating the components to be welded at 250°C and tack welding the two or more components by a suitable welding process to form the welded component;
pre-heating the welded component at 250°C and completing the welding process;
post-heating the welded component at 200°C and increasing the temperature of furnace to 550 °C at a predefined step increment;
heating the welded component at 550°c for a predefined time interval; and
quenching at 860°C and tempering at 590°C for 1 Hour.

2. The method as claimed in claim 1, wherein the welded component after cooling is configured to be machined to obtain a final structure of the welded component.

3. The method as claimed in claim 1, wherein the predefined step increment is configured for heating the welded component at a rate of 4°C per min.

4. The method as claimed in claim 1, wherein the predefined time interval is configured to be minimum 1 hour for each one inch thickness of the welded component.

5. The method as claimed in claim 1, wherein the predefined time interval is configured to be 1 hour 15 minutes.

6. The method as claimed in claim 1, wherein the components to be welded are configured from a material SAE 4140H for tube and IS2062-E410 as plate material.

7. The method as claimed in claim 1, wherein a suitable welding process is configured with a filler wire ER70S6 and CO2 as shielding gas.
8. The method as claimed in claim 1, wherein the welded component is configured to maintain a hardness below 350 BHN after stress relieving.