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 SYSTEM AND METHOD FOR WELDING THE ENRICHED CARBON SURFACE COMPONENT TO A LOW OR MEDIUM CARBON STEEL COMPONENT
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 welding. The present invention in particular relates to a system and method for welding low carbon steel with enriched surface carbon.
DESCRIPTION OF THE RELATED ART:
[002] After gas carburize, quench and low tempering the component has martensitic structure in the component. During welding this enriched carbon surface having martensitic structure is very difficult to weld the enriched surface component with martensitic structure creates high tensile stress in the weld metal and causing cracks in the weld bead. Root cause for the cracks are due to the presence of martensitic structure in the component. Structure changes from austenite to martensite is formed during quenching of enriched carbon components and also the Surface hardness of the material is very high (60HRc) which is not suitable for welding process.
[003] Reference may be made to the following:
[004] Publication No. US2017157692 relates to a method of welding a ferritic stainless steel part to a carbon steel part. The method comprises arc welding (e.g. GTAW welding) the ferritic stainless steel part to the carbon steel part using a duplex stainless steel filler metal. Welded article made in this way is useful for industrial electrolyzers and particularly for corrosion resistant cathode and carrier plate assemblies in a sodium chlorate electrolyzer. Welding material is different ferritic stainless steel is used and GTAW welding is used. GMAW welding is used by present invention to weld enriched carbon surface to a medium carbon steel.
[005] Publication No. US2006243353 relates to a weld joins a thin overlay of low carbon steel to a base that contains high carbon steel, at least at its surface along which the weld is formed. The weld may be effected by fusion (melting) or by solid-state diffusion. With either it creates a heat affected zone (HAZ) in the base around the weld. The HAZ contains enough austenite, and perhaps bainite as well, to render the HAZ relatively ductile and also crack resistant. Weld joint are made using thin overlay on low carbon steel to a base of high carbon steel. The present invention uses GMAW welding thick overlay on enriched carbon steel to a base of medium carbon steel
[006] Publication No. CN112063964 relates to an energy-saving and environment-friendly stainless steel surface hardening process method. The method is mainly a process for carburizing by utilizing glow discharge generated between a workpiece (cathode) and an anode in a carburizing atmosphere lower than one atmospheric pressure, and is called an ion carburizing technology. This publication states energy saving and environment friendly stainless surface hardening by carburizing process and no where related to welding procedures.
[007] Existing methods of welding the enriched carbon surface is done by masking the local area with anti carburizing paint during carburizing which prevents the deposition of carbon in the material.
[008] The local area with anti carburizing paint is cleaned and it is welded which results in weld cracks in the weld bead of the local anti carburizing area and the weld is removed by gouging and re-welded to the component.
[009] In order to overcome above listed prior art, the present invention aims to provide a system and method to weld the enriched carbon surface component to a low or medium carbon steel component.
OBJECTS OF THE INVENTION:
[010] The principal object of the present invention is to provide system and method to weld the enriched carbon surface component to a low or medium carbon steel plates component.
[011] Another object of the present invention is to transform the martensitic structure to pearlitic structure by local annealing.
[012] Yet another object of the present invention is to provide good quality of welding process and system which eliminates cracks in the weld bead.
[013] Still another object of the present invention is to provide welding process and system which avoids gouging and eliminates the welder fatigue.
[014] Yet another object of the present invention is to eliminate weld cracks of the enriched carbon surface with martensitic structure.
SUMMARY OF THE INVENTION:
[015] The present invention relates to a system and method to weld the enriched carbon surface component to a low or medium carbon steel component plates. This invention eliminates weld cracks of the enriched carbon surface with martensitic structure by local annealing of the component during Induction annealing the martensite structure transformed to pearlitic structure which is more favourable for welding process.
BREIF DESCRIPTION OF THE INVENTION
[016] 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.
[017] Figure 1a shows system to weld the enriched carbon surface component to a low or medium carbon steel component plates.
[018] Figure 1b shows process flowchart according to the present invention.
[019] Figure 2 shows Martensite structure.
[020] Figure 3 shows Martensite structure at the weld area transformed to pearlite structure F.
DETAILED DESCRIPTION OF THE INVENTION:
[021] The present invention provides a system and method to weld the enriched carbon surface component to a low or medium carbon steel component plates. This invention eliminates weld cracks of the enriched carbon surface with martensitic structure by local annealing of the component during Induction annealing the martensite structure transformed to pearlitic structure which is more favorable for welding process.
[022] Present invention states that material is low carbon steel 0.18 to 0.20% with enriched surface of 0.8% Carbon is welded to 0.45% carbon steel using GMAW process.
[023] Low carbon steel is carburized, quenched and Low tempered to get martensite structure in the component. The martensite present in the microstructure is the root cause for cracking of the component the martensite is formed due to the presence of enriched carbon in the material.
[024] Present invention shows the presence of martensite structure in the base metal which is the main root cause for weld cracks. Present technology indicates the prevention carbon deposit can eliminate the cracks. The martensite structure remains same all over the component except the local annealing area. It is easy to transform the microstructure from martensite to pearlite by local annealing without affecting the properties of the component on the other surfaces. Hardness of the weld surface is less than 60Hrc. No pre heating or post heating is required. Figure 1b shows process flowchart according to the present invention.
[025] To eliminate the presence of martensite in the welded area a local annealing is done in the weld area. The microstructure from martensite is transformed to pearlite in the local annealed area of the component. During welding the components or the weld bead are not cracked.
[026] The low carbon steel is carburized to get surface carbon of 0.8%C. Hardening and low tempering to achieve required hardness. Anneal the local area which is to be welded and checked for microstructure at the local annealing or hardness at the local anneal. The weld surface is prepared for welding done using GMAW process and it check for any cracks. Fig-1a is a eccentric bush of low carbon material after carburizing both the faces of the bush will be welded to the structure. During welding weld cracks and delay cracks are noticed.
[027] Martensite structure Fig-2 is formed during carburize, quench and temper and component is pre heated before welding at 150? during pre-heating the martensite structure does not transform and it retains in the component which is creating tensile stress during welding and causing crack formation during the welding.
[028] After carburizing the surface of the component are enriched with high carbon (0.8%), during quenching the enriched carbon surface transforms to martensite which is unfavourable for welding.
[029] Martensite structure generates high tensile stress during welding which leads to crack formation in the weld. Martensite structure at the weld area is transformed to pearlite structure (Fig-3) by local annealing and it is the most favourable structure for welding.
[030] Thus the carbon is enriched during carburizing process (0.8%C). Martensite structure is formed during quenching and low tempering. Martensite structure on the component is removed by induction annealing at temperature above 700°C to get pearlite structure in the component. The component is subjected to welding.
[031] 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 system and method to weld the enriched carbon surface component to a low or medium carbon steel component plates comprises two dissimilar steels wherein one is enriched carbon steel and other is medium carbon steel characterized in that during welding of two dissimilar steel weld cracks are generated which is removed by local annealing and martensite is transformed to pearlite structure.
2. The method to weld the enriched carbon surface component to a low or medium carbon steel component plates includes following steps:
a) Forming Martensite during quenching and low tempering,
b) Creating tensile stress in the weld area generating cracks during welding,
c) Removing Martensite by local annealing, martensite transforms to pearlite,
d) Welding Pearlite structure and no cracks are generated.
3. The system and method to weld the enriched carbon surface component to a low or medium carbon steel component plates, as claimed in claim 1, where in local annealing of the component during Induction annealing the martensite structure transformed to pearlitic structure.
4. The system and method to weld the enriched carbon surface component to a low or medium carbon steel component plates, as claimed in claim 1, wherein low carbon steel is carburized to get surface carbon of 0.8% C.
5. The system and method to weld the enriched carbon surface component to a low or medium carbon steel component plates, as claimed in claim 1, wherein low carbon steel 0.18 to 0.20% with enriched surface of 0.8% Carbon is welded to 0.45% carbon steel using GMAW process.