FILLER MATERIALS FOR GMAW:
The current share of GMAW in the arc welding activity is likely to be about 30% to 35%. With increasing use of ER 70S-6 wire for welding of structural jobs in carbon steel, this has been rendered possible by availability of appropriate grade of steel wire rods by TATA Steel (Grade WR-3M). Apart from the major players, large numbers of SMEs are contributing to requisite production of filler wire ER 70S-6 leading to self sufficiency and self reliance in this important consumable. The growing competition has brought down the cost progressively and the user industry today has a wide choice of sources for the wire. The continuity in production & supply of ER 70S-6 wires to the welding industry, can be expected to be maintained, based on the production of the input material of steel wire rod coils by Tata Steel at 80,000 to 1,00,000 tonnes per year , and by Jindal Steel at 40,000 to 50,000 tonnes per year. What has to be mentioned as a special achievement of the steel producers is the elimination of the need for intermediate annealing of wire during drawing down from the 5.0 or 5.5 mm to the requisite size of finished wire, before copper coating and spooling. One can visualize the savings in cost & production time brought about by the elimination of intermediate annealing operation.
What is noteworthy is fairly rapid progress in setting up manufacturing units for FCAW wires. In technological terms there has been steady progress in the development and production of wires for stainless steel and hard facing, and the industry is on the right track preparing itself to face the increasing competition from imported products. The share of FCAW in the total welding activity may be at about 5% and moving towards 10% in the next five years.
TRENDS IN SHIELDED METAL ARC WELDING (SMAW):
(A) In SMAW the emerging trends relate to modifications with fine tuning for meeting increasingly stringent specification. Following are some of the examples:-
- E 7018-1 electrodes meeting all the test requirements after prolonged SR with holding periods of 12 hours or more.
2.Higher level of CVN impact values at -45oC or even -50o
3.Higher level of UTS well beyond code requirements after SR with holding period of 5 hours, i.e. 540 MPa as against 490 MPa required in SFA 5.1
4.E 8018B2 & E 7018-A1 – to achieve CVN impact values of 54 joules at -18 oC after different combination of temperature time PWHT cycles.
5. E 8018XX & E 9018XX classes for combination of high strength & high toughness, i.e. 600 MPa & 700 MPa UTS and CVN impact energy of 50 joules minimum at -50o This is required to weld HSLA steel developed for warship and air defence ships.
6. Progressively lower levels of diffusible hydrogen. What is significant is the growing awareness in the welding fabrication industry about the importance of control on hydrogen.
In many areas of special fabrications, SMAW becomes the choice, more so if it is for a limited number of jobs, many of them to be tackled for the first time. Change over to continuous wire processes will be attempted for repetitive jobs.
In short, it has to be ensured that welders use sound welding practices to minimise wastage and to prevent rework. We all have to try and bridge the gap between the high and the low in terms of quality standard.
(B) RECENT ADVANCES.
- While the electrode industry has been making steady advances for meeting new and stringent quality requirements, one of the most successful advances has been the outcome of a joint effort with total support from Indian Navy, coordinated through Naval Materials Research Laboratory (NMRL).This relates to development of consumables (SMAW, GMAW & SAW) for welding for warship using the indigenously developed steel “DMR249A” having exceptionally good properties (tensile, low temperature impact, and corrosion). Electrodes of AWS classification E 8018-C1 for higher levels of strength and toughness have been used successfully to the extent of more than 1000 tonnes by Naval Dockyards, Garden Reach Shipbuilders & Engineers, Cochin Shipyard Ltd. Capabilities of the electrode manufacturers as well as NMRL have been tested and utilized for technical and monetary advantage to Indian Navy to such a degree that this achievement can be looked upon as a milestone of Indian Navy – Industry partnership.
The success of the new developments has set the pattern of Indian Navy – Industry Partnership with a high level of mutual confidence. The welding consumables industry has played its part well and fulfilled the expectation of the Indian Navy. More such cooperative efforts are expected in the next few years.
DUPLEX AND SUPER DUPLEX STAINLESS STEELS.
Successful development and marketing of electrodes for welding DSS and SDSS is another noteworthy achievement. For several years AWS A 5.4 provided classifications of E 2209 and E 2553 in the duplex category. Production and supplies of the SDSS grades on an increasing scale during the period 1995 – 2005, was duly recognized by AWS in revising and issuing A 5.4 in 2006. The classifications for SDSS are E 2594 & E 2595 to cover the new grades of steel with higher levels of nitrogen and addition of W & Cu. The higher levels of YS & UTS of the DSS were combined with higher corrosion resistance, especially pitting corrosion resistance indicated by pitting resistance equivalent number (PREN) at 40 or higher, as compared to PREN at 35 – 36 (38 max) for DSS.
(PREN = % Cr + 3.3 X %Mo + 16 X %N + 3.3 X half the % W)
The classes E 2594 & E 2595 achieving PREN of 40 – 42 have already come into use, especially in the foundry industry. Availability of indigenous grades has helped to reduce dependence on imported products, and the choice is determined by cost competitiveness. In technological terms, there has been significant advancement in this group of consumables.
NICKEL BASE ALLOYS:
This is another area in which there has been good progress in development of several grades of electrodes to the satisfaction of fabrication industry. On the basis of the satisfactory experience several indigenous brands are rated at par with the imported ones, thereby giving opportunity to the manufacturers to compete.
Electrodes E 9015/9018-B91 As Per SFA 5.5 for welding of P-91 grade of Steel:
This is the latest consumable which has engaged the attention of several Indian manufacturers to offer an acceptable equivalent against imported brands which have been well accepted by the power sector on the basis of fairly long experience abroad and then in India. The foreign brands have the advantage of being backed by data relating to creep properties, which is time related, to the extent of 30,000 hours and more. Indian manufacturers have made considerable headway in securing approval of BHEL, the leading high pressure boiler manufacturer.
While approval and satisfactory performance are a matter of time, but not in doubt, there will remain a question mark on the commercial viability due to the high cost of the imported raw materials combined with the aggressive marketing of the established imported brands.
The next one in this group will be the electrode E 9015/9018-B92 for welding of P-92 grade. This grade is now attracting the attention of the power sector and hence also of consumable manufacturers. Requirement of these two put together may be in excess of 200 tonnes per year, with progressive rise linked with the growth of the power sector. This serves to underline the importance of this particular group of electrodes.
The share of SAW is at 5 – 6% in line with the situation for most of the highly developed countries. While the application of SAW for involving CrMo steels, low alloy steels, and even stainless steels continues to rise in the shops of leading fabrications such as L & T, BHEL, Godrej, ISGEC, it has to be noted that the major part of consumable requirement is met through imports. For that matter even in the area of saw pipes with huge production the welding flux used is imported. Thus, development and production of flux for such special application has not kept pace with the needs, in an area which does call for more intense attention. The requirement of flux for this application may go up to about 5000 tonnes per year.
In reviewing the progress of the consumable manufacturing in India, we may state that;
- Developments in SMAW have kept pace with the needs of the industry to the extent of, may be, 90% in technical terms.
- In development in GMAW – MAG, the industry has done extremely well.
- In FCAW progress has been good despite keen competition from imported products.
- Developments of SAW have not kept pace with the needs of the industry in several applications even in carbon steel, especially in the welding of pipes. Reasons have to be looked into.
FUTURE REQUIREMENTS & OBJECTIVES:
In reviewing the current status and trends we have to accept the harsh reality of huge imports at highly competitive prices. We are already witnessing the adverse effect on Indian Steel industry which has made this country proud by displacing the USA from the third place in the year 2015 with a production of 89.6 Million Tonnes and, furthermore, recording an increase of 2.6% over the previous year 2014 at a time when all the other countries in the top ten category have recorded a drop, with 2.3% in China and 10.5% in USA. If such a strong and well-built sector of steel industry has suffered the adverse effect of indiscriminate imports, how can one expect the welding consumable and equipment industry to withstand this trend, especially with its fragmented structure. Such a situation gets aggravated because as the industry is moving into new grades of materials of construction, Indian industry has to depend heavily on imported steel grades for developing the appropriate consumables. The typical latest example is of SMAW electrodes (AWS E 9015-B91) for welding of P-91 grade steel which is being consumed in increasing quantities by the power sector, to the extent of, may be 200 tonnes per year. Hence, in planning for the future development and growth of industry, technological development can be and will be achieved by Indian industry but at prices which may not be acceptable to the fabrication industry which has ready access to cheaper imported products. This vital issue has to engage our attention and this is where we need to take active cooperation of Indian steel industry. Let us start with the most common grade of carbon steel for core wire which is covered by Indian Standard IS:2879.
In the group of carbon steel grades IS : 2062, IS : 2002, ASTM A 516 Gr.60 & 70 and 537 Cl.1 steels continue to dominate in welded fabrication, Indian consumable manufacturers have the capability to meet increasingly stringent specifications of welded fabrication as required by service conditions. This calls for fine tuning and tighter controls in E 7018 & E 7018-1 classes and hence the need for a superior grade of steel for core wire in the Indian Standard IS: 2879. I have strongly advocated in my Misra Memorial Lecture of 1979 and Lifetime Achievement Award lecture of 2003 that Indian steel majors ought to accept this challenge of producing the superior grade of steel to help the consumable industry to meet the requisite higher standards. I have proposed to the Bureau of Indian Standards to initiate action for this exercise to motivate the steel industry to produce the superior grade. Success in doing so will be a very significant step in our technological advancement, and great benefit will accrue to consumable manufacturers through use of indigenously produced superior grade.
In the highly competitive business world today, one has to pay attention to the scale of production to make the effort viable in monetary terms. This is a valid point which cannot be ignored, and yet the need is of technological advancement in the field of welding, as a part of overall manufacturing activity, based on “Make in India” objective. The Government departments concerned viz: Science & Technology and Industry, have to find a way to financially support the effort to indigenise any important / vital raw material through a funding mechanism, if effort of any steel producer in the development and production of special grade of base material, calls for such incentive. Over the past several decades subsidies for several consumer items became a practice regardless of the huge losses, with the sole objective of benefit to the society at large. Suitable incentive on the lines already mentioned, is not out of place or irrelevant because it will help to motivate the effort and thereafter consolidate technological advancement in the manufacturing sector with emphasis on indigenous production and job creation.
We have only to look at Indian Nuclear capabilities developed through closely monitored advancement with availability of funds for indigenous development. Funds and an appropriate mechanism are required to promote such development efforts of manufacturers with proven technical capability. This is an area in which we ought to consider steel industry and consumable manufacturing industry together because the two have to work together with the twin objective;
a) producing the grade of steel required for the welding consumable for critical application such as;
- superior grades of stainless steel (with low impurities).
- low alloy steel grades such as for welding of P-91, P-92.
- high alloy steel such as duplex stainless steels
b) motivating consumable manufacturers to develop indigenous welding consumables which in turn will promote marketing of the respective new grade of steel, in India and abroad.
For technological advancement to promote and strengthen the “Make in India” drive on continuous long term basis, the need is for the steel industry and the welding consumables industry to join hands for cooperative effort aimed at these stated objectives, and then for the Central Government to back it up with whatever is required for implementation. We, members of the welding fraternity have to hope for this to happen.
THE FUTURE OF JOINING TECHNOLOGY
The 21st Century holds out vast, exciting s cope for research in the science of arc welding – physics of the arc, chemistry of fluxes, metallurgy of metals and alloys (base materials and filler materials), thermal cycles, role of interstitial elements, inclusions. Such research will lead to a very much better understanding of the related aspects, thereby facilitating new flux formulation based on scientific study, instead of findings based on a series of experiments with only limited understanding of the role of each ingredient or radical, as has been the case for over fifty years. We know that the efforts and investments in manpower and money necessitate these findings to be treated as trade secrets to face competition and make profits. These studies will facilitate development of flux formulation. The R & D work will be propelled by:
- The need to join materials of progressively superior strength, cryogenic toughness, elevated temperature properties, corrosion resistance, resistance to stress corrosion cracking;
- Increasing stringency of specification even for the existing filler materials;
- Higher productivity levels in existing processes GMAW, SAW, & even GTAW through innovations.
The next few years will witness wider application of plasma, electron beam, laser, and the latest one – friction stir welding – which has been generating tremendous amount of interest and development work to extend its scope for wider application.
The new materials of construction will keep researchers, designers, welding technicians, inspection agencies & standardization bodies busy in their respective areas of activity.
The next decade will witness a concerted massive effort, & growing cooperation among nations at different levels in a globalized economy. It will offer to welding personnel opportunities to participate in & contribute to advancement of welding technology and welded fabrication in a wider working environment, aided by rapid sharing of knowledge and information through modern electronic gadgets. As far as welding consumables are concerned development in power sources will continue to enhance the scope for using of GMAW in terms of productivity as well as innovative applications, thereby widening the role of joining technology.