Title of Invention

AN IRON BASE ALLOY HAVING HIGH WEAR RESISTANCE AT HIGH TEMPERATURE

Abstract An Iron base alloy having high wear resistance at high temperature comprising of the following: Elements (wt %) Carbon(C) : 3.0-4.5 Silicon (Si) : 0.0-1.0 Manganese (Mn) : 1.0-3.0 Nickel (Ni) optional : 0.0 - 4.0 Chromium (Cr) ; 8.0 - 18. Molybdenum (Mo) : 1.0- 4.0 Niobium (Nb) : 2.0 - 8.0 Tungsten (W) : 1.0-4.0 Balance Iron (Fe) : 53.5 to 84
Full Text
FORM 2
THE PATENTS ACT. 1970
(39 OF 1970)
&
THE PATENT RULES. 2003
COMPLETE SPECIFICATION
[SECTION 10; RULE 13]
"AN IRON BASE ALLOY HAVING HIGH WEAR RESISTANCE AT HIGH TEMPERATURE"
EWAC ALLOYS LIMITED, L & T HOUSE, BALLARD ESTATE, N. M. MARG, MUMBAI - 400 001.
THE FOLLOWING SPECIFICATION DISCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED:-


FIELD OF INVENTION
The present invention relates to an iron base alloy having high wear resistance at high temperature and plates, bars and parts made therefrom. The said alloy and said parts made therefrom are especially useful in industrial applications where resistance to wear at high temperature is required such as baffle plates used in burner nozzle assembly in a power generation plant, furnace liner plates, sinter and clinker crushers etc.
PRIOR ART
Iron base high temperature wear resistant alloys are known in the prior art. However they are expensive due to high content of expensive material like cobalt and nickel. This invention therefore proposes inexpensive iron base high temperature wear resistant alloy. The micro structure and properties of said alloy differ with change in proportions of constituent elements. The percentage of constituent elements therefore assumes importance.
U.S. Patent No 5674449 describes a similar alloy for internal combustion (IC) engine valve seat inserts. However, the alloy described therein cannot be used to manufacture the baffle plates used in burner nozzle assembly in power generation plant. The alloy described in the said U.S. Patent contains between 1.6 and 2 wt%. carbon whereas the alloy according to this invention contains higher carbon

content (3 to 4.5 wt%). The said higher carbon content provides more carbides and hard but slightly brittle matrix which are useful in resisting erosive/abrasive wear. However such hard but slightly brittle matrix would fail early in adhesive wear environment of the type contemplated in the said U.S. patent as the brittle matrix would crack and give way making carbides fall out. Therefore said U. S. patented alloy is not suitable in erosive wear resistant applications. Further, alloy described in the U. S. patent uses Cobalt (Co) to give high strength at high temperature. However, in the alloy of the present invention Co is not used as it does not react with carbon to from carbides which are useful in improving erosive wear resistance. Instead, in the alloy according to mis invention are present numerous metal carbides which resist the erosion and abrasion. Still further, alloy described in the U. S. Patent contains higher percentage of Tungsten (W) and Molybdenum (Mo) which is required for resisting adhesive wear whereas the alloy according to this invention is not used for adhesive wear resistance but is used for erosive wear resistance and hence does not contain higher percentage of W and Mo but contains high percentage of Niobium (Nb).
OBJECT OF THE PRESENT INVENTION
The present invention proposes an iron base high temperature wear resistant alloy having enhanced hardness, strength and wear resistance properties that is useful in industrial applications such as the baffle plates which are used in burner nozzle

assembly in a power generation plant, furnace liner plates, sinter and clinker crushers etc.
DESCRIPTION OF THE PRESENT INVENTION
The present invention is based on Fe-Cr-C type alloys that are classified as high carbon, high chromium cast irons. Carbon as an interstitial alloying addition provides hardness to steel and cast iron. However, beyond certain limits the said carbon becomes useless, as it cannot be dissolved in iron and forms free graphite in cast irons. To bind this additional carbon into useful constituents that provide additional hardness and wear resistance, other alloying elements are used in the present invention. The said alloying elements used in this alloy design and their purpose are as mentioned under:
• Chromium (Cr) is kept between 8 wt% & 18 wt% in this design. This Cr content gives hard (Cr, Fe)7 C3 carbides that provide additional wear resistance. In the present design the carbon content is from 3.0 wt% to 4.5 wt%.
• Molybdenum (Mo) is in the range of 1.0 wt% to 4.0 wt%. The Mo acts to suppress pearlite formation and increases hardenability by inhibiting secondary carbide precipitation during cooling. Mo enhances the effect of the other alloying elements such as Nickel (Ni) in delaying pearlite

formation. Another advantage of Molybdenum is that it has little effect on Ms (Martensite Start) temperature and does not over stabilize austenite.
• Nickel (Ni) & Manganese (Mn) are added between 0.0 and 4.0 wt% and 1.0 and 3.0 wt% respectively, to improve hardenability and inhibit pearlite formation. Ni is mainly dissolved in the matrix and when added in conjunction with Molybdenum is most effective in avoiding pearlite formation.
• Silicon (Si) content in this alloy is limited to maximum 1 wt% as higher silicon contents enhance pearlite formation and decrease hardenability.
• Niobium (Nb) is a strong carbide-forming element and is added between 2 to 8 wt%. Nb helps in making the microstructure fine with equiaxed grains. This factor helps to improve the wear resistance of Alloy. Nb carbides also provide high temperature resistance to the alloy as they retain sufficient hardness up to 600° C.
• Tungsten (W) is added between 1.0 and 4.0 wt% in the present design. W is also strong carbide former and forms WC or W2C type of carbides. Tungsten carbides have very high hardness and the ability to retain their hardness at elevated temperatures upto 600° C. This combination of properties provides the high temperature wear resistance to this present alloy system.

• A small amount of Vanadium (V) may also be added to increase hardenability.
The chemistry of the alloy according to this invention is as follows:-
Elements (wt%)
Carbon(C) : 3.0-4.5
Silicon (Si) : 0.0-1.0
Manganese (MJI) : 1.0-3.0
Nickel (Ni) optional : 0.0 - 4.0
Chromium (Cr) : 8.0-18.0
Molybdenum (Mo) : 1.0 - 4.0
Niobium (Nb) : 2.0-8.0
Tungsten (W) 1.0-4.0
Balance Iron (Fe) : Balance
And wherein (Mo) and (W) together are in the range of 2.0 - 6.0 wt%.
The present invention will now be explained with the help of its micro structure shown in the drawing accompanying the provisional specification. However the said microstructure is only illustrative and in no way limits the invention.
In the drawing accompanying the provisional specification, Figure No.l shows the microstructure of the invented design, comprising of primary chromium carbides (1) that are large and orthogonal; primary niobium carbides (2) that are

small and rhomboidal. As will be seen the said chromium and niobium carbides are distributed uniformly in a eutectic matrix (3).
According to this invention, the alloy is made in the following manner: Mild Steel Scrap + Ferro Chromium metal lumps + Pure Molybdenum metal + Ferro Manganese metal lumps + Petroleum coke + Pure Nickel are charged into a suitable melting equipment and are melted to near pouring temperature which is between 1500 to 1600° C. At 1500° C, add pure Tungsten metal, Ferro Niobium lumps, Ferro Silicon. The aforesaid molten alloy is deoxidized with Pure Aluminum metal powder. The slag is then removed by adding Calcium Silicide.
ADVANTAGES:
Following are some of the advantages of the present invention:
• The alloy described herein can be easily melted and cast in the form of plates despite lower Silicon contents (less than 1%). This in turn helps to improve wear resistance (Higher Silicon contents are detrimental to high wear resistance as it reduces the hardenability and eventually the wear resistance of the alloy). It is fluid.
• A casting can be produced in the form of plates (for burner assembling), sinters/clinker crushers, furnace liners etc. without much distortion and warpage and with a reasonably smooth surface.

• Due to the elimination of Cobalt and lower % of Nickel which are expensive elements, the alloy is less expensive.
The following comparative table/bar-chart illustrates the superiority of the invented alloy in its erosive wear properties against conventional alloys.


We Claim:
1. An iron base alloy having high wear resistance at high temp, comprising of 3 to 4.5. wt% Carbon (C) and 2 to 6 wt% combined Molybdenum (Mo) and Tungsten (W).
2. An iron base alloy claimed in claim 1 further comprising of 2 to 8 wt% Niobium (Nb).
3. An iron base alloy claimed in claim 1 further comprising of 8 to 18 wt% Chromium (Cr).
4. An iron base alloy claimed in claim 1 further comprising of 1 to 3 wt% Manganese (Mn).
5. An iron base alloy claimed in claim 1 further comprising of 0 to 1 wt% Silicon (Si) and 0 to 4 wt% Nickel (Ni).
6. An iron base alloy claimed in claim 1 further comprising of 1 to 4 wt% Molybdenum (Mo).
7. An iron base alloy claimed in claim 1 further comprising of 1 to 4 wt% Tungsten (W).
8. An iron base alloy claimed in claim 1 further comprising of the following:-

Elements (wt%)
Carbon(C) : 3.0-4.5
Silicon (Si) : 0.0-1.0
Manganese (Mn) 1.0 - 3.0
Nickel (Ni) optional : 0.0 - 4.0
Chromium (Cr) : 8.0-18.0
Molybdenum (Mo) 1.0- 4.0
Niobium (Nb) : 2.0-8.0
Tungsten (W) : 1.0-4.0
Balance Iron (Fe) : Balance
9. An iron base alloy claimed in claim 8 above further comprising 53.5 to 84
wt%ofIron(Fe).
10. An iron base alloy claimed in claim 8 above substantially described herein
and shown in the drawing accompanying the provisional specification.
Dated this 7 day of February, 2008.


Documents:

837-MUM-2007-ABSRACT(GRANTED)-(10-8-2011).pdf

837-MUM-2007-ABSTRACT(14-1-2011).pdf

837-mum-2007-abstract(7-2-2008).doc

837-mum-2007-abstract(7-2-2008).pdf

837-MUM-2007-CANCELLED PAGES(26-7-2011).pdf

837-mum-2007-claims(7-2-2008).doc

837-mum-2007-claims(7-2-2008).pdf

837-MUM-2007-CLAIMS(AMENDED)-(14-1-2011).pdf

837-MUM-2007-CLAIMS(AMENDED)-(26-7-2011).pdf

837-MUM-2007-CLAIMS(GRANTED)-(10-8-2011).pdf

837-mum-2007-correspondence(7-2-2008).pdf

837-MUM-2007-CORRESPONDENCE(IPO)-(10-8-2011).pdf

837-mum-2007-correspondence-received.pdf

837-mum-2007-description (provisional).pdf

837-mum-2007-description(complete)-(7-2-2008).pdf

837-MUM-2007-DESCRIPTION(GRANTED)-(10-8-2011).pdf

837-mum-2007-drawings.pdf

837-mum-2007-form 18(7-2-2008).pdf

837-mum-2007-form 2(7-2-2008).doc

837-mum-2007-form 2(7-2-2008).pdf

837-MUM-2007-FORM 2(GRANTED)-(10-8-2011).pdf

837-MUM-2007-FORM 2(TITLE PAGE)-(14-1-2011).pdf

837-mum-2007-form 2(title page)-(7-2-2008).pdf

837-MUM-2007-FORM 2(TITLE PAGE)-(GRANTED)-(10-8-2011).pdf

837-MUM-2007-FORM 2(TITLE PAGE)-(PROVISIONAL)-(27-4-2007).pdf

837-mum-2007-form 3(27-4-2007).pdf

837-mum-2007-form 5(7-2-2008).pdf

837-mum-2007-form-1.pdf

837-mum-2007-form-2.doc

837-mum-2007-form-2.pdf

837-mum-2007-form-26.pdf

837-MUM-2007-OTHER DOCUMENT(18-7-2011).pdf

837-MUM-2007-REPLY TO EXAMINATION REPORT(14-1-2011).pdf

837-MUM-2007-REPLY TO HEARING(18-7-2011).pdf

837-MUM-2007-REPLY TO HEARING(26-7-2011).pdf

837-MUM-2007-SPECIFICATION(AMENDED)-(14-1-2011).pdf


Patent Number 248719
Indian Patent Application Number 837/MUM/2007
PG Journal Number 32/2011
Publication Date 12-Aug-2011
Grant Date 10-Aug-2011
Date of Filing 27-Apr-2007
Name of Patentee EWAC ALLOYS LIMITED
Applicant Address L&T HOUSE, BALLARD ESTATE, N. M. MARG, MUMBAI 400 001,
Inventors:
# Inventor's Name Inventor's Address
1 P. N. JOGLEKAR B-301, Sarena, Shanti Park Vallabhbaug Road Extension, Ghatkopar (East), Mumbai 400077
2 VILAS G. HIPPARGI 303, Windsor, Hiranandani Estate, Off Ghodbunder Road, Thane (West), 400607
3 YOGESH S. SOMAN 3/53, M.I.G.Colony, Rajawadi, Mumbai 400077
4 KEDAR A. BHIDE Row House No.5, Deen Dayal Nagar, Behind Bharti Vidyapeeth, Katraj-Pune 411046
PCT International Classification Number C22C33/02
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA