Title of Invention	A METHOD FOR WELDING THERMO-MECHANICALLY TREATED (TMT) REBAR
Abstract	This invention relates to a modified method of welding of thermomechanically treated (TMT) welded metal rebars for uniform strength maintaining throughout the thickness of welded rebars and welded rebars produced thereof comprising the steps of welding lap joint (single side) of TMT rebars of same or different diameter at horizontal, vertical or sloping position on striking electrode somewhere in the middle of and of the joint according to the procedure as laid down in paragraph 10.5.4 of IS 9417-1989 with actual welding current of 180 amperes as against proprietor specified current of 140/180 amperes; selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/IS0 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; sel ecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/ISO 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; carrying on determination of tensile properties before and after welding of the TMT rebar test specimens on conformation of uniform strength throughout the thickness of the welded rebars as specified in IS 9417-1989 after welding.

Title of Invention

A METHOD FOR WELDING THERMO-MECHANICALLY TREATED (TMT) REBAR

Abstract

This invention relates to a modified method of welding of thermomechanically treated (TMT) welded metal rebars for uniform strength maintaining throughout the thickness of welded rebars and welded rebars produced thereof comprising the steps of welding lap joint (single side) of TMT rebars of same or different diameter at horizontal, vertical or sloping position on striking electrode somewhere in the middle of and of the joint according to the procedure as laid down in paragraph 10.5.4 of IS 9417-1989 with actual welding current of 180 amperes as against proprietor specified current of 140/180 amperes; selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/IS0 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; sel ecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/ISO 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; carrying on determination of tensile properties before and after welding of the TMT rebar test specimens on conformation of uniform strength throughout the thickness of the welded rebars as specified in IS 9417-1989 after welding.

Full Text	-2- FIELD OF THE INVENTION The present invention relates to an improved method of welding on testing of strength of thermo mechanically treated (TMT) welded metal rebar. More specifically the proposed invention is related to develop a welding procedure to secure metal strength throughout its thickness including the welding zone after welding of TMT rebar through modified welding specification and procedure as laid down in IS 9417- 1989. BACKGROUND OF THE INVENTION The proposed invention has been developed by customer demand. The producer and supplier of TMT rebar are frequently been asked by their customer to advise for appropriate welding procedure as well as selection of welding electrode for welding of TMT rebar due to non-availability of any IS standard or in any prior published literature, in respect of using TMT welding rebar suitable for concrete reinforcement application without any failure, due to impairment of metal strength, weld bead, micro structural properties and heat affected zone at the weld. There is no specific procedure available for welding TMT bar. Welding procedure for cold twisted deformed (CTD) bars have been provided in IS- 1786-1985 and IS 9417-1989 as follows: i. Welding procedure -3.2.2 of IS 17864985 ii. Butt welding procedure by shielded metal are welding process- inter pass temperature to be maintained -10.3.4.1 (paragraph 1) of IS 9417-1989 iii. Electrodes -10.5.3 of IS 9417-1989 iv. Welding procedure for Lap Joint -10.5.4 of IS 9417-1989 3 The above standards kid down in IS standard was so far considered as the base level input as guidelines for strength characteristics to be maintained for welding of TMT bar. There has been always a controversy about the maximum interpass temperature to be maintained as provided by IS 9417-1989 which has indicated that the interpass temperature should be restricted within 250° C as stated in article 10.3.4.1 that "That temperature of the bars at a distance about one bar diameter from the joints shall not exceed 300° C immediately after the bead is made. Before commencing the next bead, the temperature shall not exceed 250° C". The said standard provided by IS as has not given a specific guideline in particular stages, has caused a serious concern to an industry in effect as if somehow to maintain interpass temperature around 300° C or slightly more. The said guideline being not sufficient for welding of TMT rebar, an upgraded testing procedure over the IS procedure of welding in this respect was a long felt need of the industry to be developed on investigation, recording and assessment on fresh practical welding condition for better understanding and securing of strength characteristics after welding of TMT rebar. The present invention has proposed to remove the above difficulties of prior state of art as laid down in IS guide lines by developing a testing procedure for evaluating strength characteristics of TMT rebar after welding to secure any failure in practical conditions of those welded TMT rebars in the above context. DESCRIPTION OF THE INVENTION It is well known that inter pass temperature is just as important, as if not more important than preheat temperature with regard to the mechanical and 4 micro structure properties of weld. For instance yield and ultimate tensile strength of the weld metal are both related with maintenance of inter pass temperature securely. High values of inter pass temperature tend to reduce the weld metal strength. It is important to impose control over the maximum inter pass temperature when certain mechanical weld metal properties are required. Those criterion are as follows: • The effects of the welding process, procedures, and sequence of welding must always be taken into account to maintain inter pass temperature within the proper range. • The effects of both minimum and maximum inter pass temperature should be considered with regard to the mechanical and micro structure properties of the weld metal and the heat affected zone (HAZ). The inter pass temperature should be maintained throughout the full thickness of the base metal and some reasonable distance away from the weld, approximately equal to one inch, unless the codes specify otherwise. One object of the invention is to carry out welding of TMT rebar maintaining interpass temperature within the range of 234 to 310°C through out the thickness of the test bar specimens along with the effect of minimum and maximum interpass temperature with regard to the mechanical and micro structural properties of the weld metal and the heat affected zone. Another object of the invention is to study the input of higher interpass temperature than that mentioned in IS 9417, on tensile properties of the TMT rebar before and after welding and the interpass temperature being monitored by CMSS 200 infrared the rmometer SKF. A further object of the invention is to determine appropriate electrode specification and TMT bar composition for welding of TMT bars without leading any defect in the welded zone. 5 Yet another object of the invention is to provide welding procedure for obtaining uniform cross-sectional mechanical properties of welded TMT rebar accordingly to guidelines provided in 10.3.4.1 (paragraph 1) [IS 9417- 1989] for inter-pass temperature, 10.5.3[IS9417-1989] for Electrodes and 10.5.4[IS 9417-1989] for welding procedure followed for lap joint (single side) with actual current 180 amperes against current 140/180 amperes, specified by proprietor. A still another object of the invention is to carry out testing procedure during welding of TMT rebar on maintaining after evaluating, electrode specification confirming AWS/SFA 5.5 E 8018. The invention will he better understood from the following description with examples and accompanying drawing in which. Figure 1 shows a welding of TMT test piece following welding procedure for CTD bars (IS 9417:1989). Figure 2 shows the sequence of welding beads according to paragraph 10.3.4.1 of IS 9417-1989. Figure 3 shows the manner of welding in horizontal and vertical position as specified in paragraph 10.5.4 of IS 9417-1989. Figure 4 to 7 shows manner of welding various lap joints with specified dimension as laid down in paragraph 10.5.4 of IS 9417-1989. Chemical composition of the TMT rebar is examined as follows according to the specification as laid down in IS 1608: 2005/ISO 6892: 1998 'Metallic Materials Tensile Testing At Ambient Temperature' through YS, UTS and % elongation on inspection before welding. 6 Chemical Composition of the steel (TMT rebar) samples: % C Mn s P Si %(S+P) Specified 0.30 max 0.06 max 0.06 max 0.11 max Actual 0.15 0.060 0.018 0.016 0.141 0.034 Tensile properties before welding of TMT rebar of the above mentioned composition is tested as follows: - Table 1 Tensile Properties: (Before welding) YS(N/min2) UTS (N/mm2) % Elongation Specified 415 min 485 min 14.5 Actual 494 592 21 The chemical composition and tensile properties of the TMT rebar test specimens conformed to IS 1786:1985 for grade of Fe 415. Welding procedure was maintained as follows: The following guidelines were followed during welding: 10.3.4.1 (paragraph 1) [IS 9417-1989] for inter-pass temperature, 10.5.3 [IS 9417-1989] for Electrodes and 10.5.4 [IS 9417-1989] for welding procedure were followed for lap joint (single side) with actual current 180 amperes against current 140/180 amperes, specified by proprietor. 7 Paragraph 10.3.4.1 of IS 9417-1989 for interpass temperature has stated as the sequence of weiding beads as shown in Fig. 2. The runs 1 to 4 are made in the position of welding best suited for the quality of the weid. Besides the interruption in weiding required for cleaning of each bead, a pause shall be made after every second bead and the bar is allowed to cool. The temperature of the bars at a distance of about one bar diameter from the joints shall not exceed 300oC immediately after the bead is made. Before commencing the net bead, the temperature shall not exceed 250°C. The temperature may be checked approximately by using temperature indicating crayons. However, in the absence of temperature indicating devices, the bar may be allowed to cool down to handhot temperature before the next bead is deposited. After completing bead 4, the bars are turned through 180o and the beads 5 to 7 are made in the same manner as described above. The top bead 8 is deposited as joint is continuously rotated and the size of the reinforcement should be approximately as indicated in Fig. 2. Paragraph 10.5.3 of IS 9417-1989 for electrode has specified the size of electrodes according to the diameter of the bar to be welded shall be as follows: Nominal Diameter of bar, d mm Size of Electrode, Max Up to and including 10 2.5 Over 10 up to and 3.15 Including 18 Over18 up to and 4.0 Including 28 Over 28 5.0 Paragraph 10.5.4 of IS 9417-1989 for welding procedure of lap joint has specified that the arc should be struck as shown in Fig. 3 somewhere in the middle of the joint and not at its beginning. 8 The movement of the electrode for welding lap joints in the horizontal and vertical position is indicated in Fig. 3. The various lap joints used to connect cold-worked bars are shown in Fig. 4 to 7. In Fig. 4 to 6, the dimensions indicated as '5d' for single side welding should be halved to '2.5d' if the welds are deposited from the opposite side also. The single-strap arrangement shown in Fig. 7 is not recommended where access is from one side only. In the case of joints illustrated in Fig. 6 and 7, the strap cross sectional area must, at least, equal that of the bar to be joined. Welding electrode is maintained confirming specification AWS/ SF A 5.5. E 8018 with composition in weight % C-0.05-0.10, Mn-1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48 and Ni-0.45-0.80 and size 4 mm x 450 mm Tensile properties inspected after welding of TMT rebar is narrated as follows in table 2. Table 2 Tensile properties after welding: Sample Id. Inter-pass Temperature (oC) YS (N/mm2) UTS (N/mm2) Breaking Load in KN 1. 310 487 582 184 2. 294 497 592 186 3. 272 490 582 183 4. 270 503 596 187 5. 240 500 589 185 6. 234 497 592 186 9 It was observed that no TMT rebar sample 1 to 6 above broke from the welded region while maintained with interpass temperature from 234oC to 310° C. The welding of TMT test piece following welding procedure for CTD bars according to IS 9417:1989 is shown in Figure 1. The above test procedure for welding test of TMT rebar was carried out with inspection stages of i. Preliminary stage i.e. before commencing fabrication of welding, ii. In process stage i.e. during fabrication by welding and iii. After welding, followed by evaluation of mechanical properties after welding. From the test investigations as narrated above it is assessed and concluded that Conclusion: The above test results show that TMT rebar can be welded following the above process without any detrimental impact. Welding electrode: AWS/ SF A 5.5. E 8018 was found appropriate for welding of TMT rebar. The material can be welded satisfactorily even at the interpass temperature of 310° C without any detrimental effect on tensile properties. The invention as narrated though described with a particular embodiment should not be read and construed in a restrictive manner as some modifications, alterations and changes are possible within the scope and limit of the invention as defined in the encompassed appended claims. 10 We claim: 1. A modified method of welding of thermomechanically treated (TMT) welded metal rebars for uniform strength maintaining throughout the thickness of welded rebars comprising the steps of • welding lap joint (single side) of TMT rebars of same or different diameter at horizontal, vertical or sloping position on striking electrode somewhere in the middle of the joint and not at its beginning and in the groove between the welded bars at an angle of 75° for horizontal and 80°-85° for vertical position, performing welding operation from the forward and of the upper bar to the end point of the lower bar in case of horizontal lap joint and from bottom to top in case of vertical lap joint according to the procedure as laid down in paragraph 10.5.4 of IS 9417- 1989 with actual welding current of 180 amperes as against proprietor specified current of 140/180 amperes; • selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S-0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/ISO 6892:1998 and electrode specification confirming to AWS/SFA 5.5 E 8018 having composition in weight % C-0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45-0.80 and size of 4 mm x 450 mm; • carrying on determination of tensile properties before and after welding of the TMT rebar test specimens and confirming tensile properties obtained after welding without any detrimental impact on conformation of uniform strength throughout the thickness of the welded rebars as specified in IS 9417-1989. 2. A modified method of welding as claimed in claim 1 wherein the welding procedure for welding of test pieces of TMT rebar was carried out with inspection stages of 11 i. preliminary stage i.e. before commencing fabrication of welding, ii. in process stage i.e. during fabrication by welding and iii. after welding, followed by evaluation of mechanical properties after welding. 3. A modified method of welding as claimed in claim 1 wherein compative tensile properties of YS 487n/mm2 UTS 582 n/mtn2 and breaking load 184 KN are achieved after welding of the said test rebar specimens even at interpass temperature of 310° C. 4. A modified method of welding as claimed in claim 1 and 3 wherein all the welded TMT rebar test specimens broke from welded region during breaking load determination thus satisfying the IS specification in this respect. 5. A modified method of welding as claimed in the preceding claims wherein improved welding characters of TMT rebars are secured with expanded interpass temperature range of 234-310° C between bead to bead formation than that of the range of 250-300°C as laid down in the IS specification. 6. A modified method of welding as claimed in the proceeding claims wherein the chemical composition and tensile properties of the TMT rebar test specimens conform to IS 1786:1985 for grade of Fe 415. 7. A modified method of welding as claimed in the proceeding claims wherein the electrode as specified in AWS/SFA 5.5 E 8018 was selected after carrying out test and evaluating suitable performance of welding of lap joint TMT rebar specimens with other standards for electrode as specified in IS for CTD bars. 8. A modified method of welding as claimed in claim 1 wherein the interpass temperature was monitored by CMSS 2000 infrared thermo meter SKF. 9.A lap jointed TMT rebars as obtained according to the method of claim 1. This invention relates to a modified method of welding of thermomechanically treated (TMT) welded metal rebars for uniform strength maintaining throughout the thickness of welded rebars and welded rebars produced thereof comprising the steps of welding lap joint (single side) of TMT rebars of same or different diameter at horizontal, vertical or sloping position on striking electrode somewhere in the middle of and of the joint according to the procedure as laid down in paragraph 10.5.4 of IS 9417-1989 with actual welding current of 180 amperes as against proprietor specified current of 140/180 amperes; selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/IS0 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; sel ecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/ISO 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; carrying on determination of tensile properties before and after welding of the TMT rebar test specimens on conformation of uniform strength throughout the thickness of the welded rebars as specified in IS 9417-1989 after welding.

Full Text

-2-
FIELD OF THE INVENTION
The present invention relates to an improved method of welding on testing of
strength of thermo mechanically treated (TMT) welded metal rebar.
More specifically the proposed invention is related to develop a welding
procedure to secure metal strength throughout its thickness including the
welding zone after welding of TMT rebar through modified welding
specification and procedure as laid down in IS 9417- 1989.
BACKGROUND OF THE INVENTION
The proposed invention has been developed by customer demand. The
producer and supplier of TMT rebar are frequently been asked by their
customer to advise for appropriate welding procedure as well as selection of
welding electrode for welding of TMT rebar due to non-availability of any IS
standard or in any prior published literature, in respect of using TMT welding
rebar suitable for concrete reinforcement application without any failure, due
to impairment of metal strength, weld bead, micro structural properties and
heat affected zone at the weld.
There is no specific procedure available for welding TMT bar. Welding
procedure for cold twisted deformed (CTD) bars have been provided in IS-
1786-1985 and IS 9417-1989 as follows:
i. Welding procedure -3.2.2 of IS 17864985
ii. Butt welding procedure by shielded metal are welding process- inter
pass temperature to be maintained -10.3.4.1 (paragraph 1) of IS
9417-1989
iii. Electrodes -10.5.3 of IS 9417-1989
iv. Welding procedure for Lap Joint -10.5.4 of IS 9417-1989

3
The above standards kid down in IS standard was so far considered as the
base level input as guidelines for strength characteristics to be maintained for
welding of TMT bar.
There has been always a controversy about the maximum interpass
temperature to be maintained as provided by IS 9417-1989 which has
indicated that the interpass temperature should be restricted within 250° C as
stated in article 10.3.4.1 that "That temperature of the bars at a distance about
one bar diameter from the joints shall not exceed 300° C immediately after the
bead is made. Before commencing the next bead, the temperature shall not
exceed 250° C".
The said standard provided by IS as has not given a specific guideline in
particular stages, has caused a serious concern to an industry in effect as if
somehow to maintain interpass temperature around 300° C or slightly more.
The said guideline being not sufficient for welding of TMT rebar, an upgraded
testing procedure over the IS procedure of welding in this respect was a long
felt need of the industry to be developed on investigation, recording and
assessment on fresh practical welding condition for better understanding and
securing of strength characteristics after welding of TMT rebar.
The present invention has proposed to remove the above difficulties of prior
state of art as laid down in IS guide lines by developing a testing procedure
for evaluating strength characteristics of TMT rebar after welding to secure
any failure in practical conditions of those welded TMT rebars in the above
context.
DESCRIPTION OF THE INVENTION
It is well known that inter pass temperature is just as important, as if not more
important than preheat temperature with regard to the mechanical and

4
micro structure properties of weld. For instance yield and ultimate tensile
strength of the weld metal are both related with maintenance of inter pass
temperature securely. High values of inter pass temperature tend to reduce the
weld metal strength. It is important to impose control over the maximum inter
pass temperature when certain mechanical weld metal properties are required.
Those criterion are as follows:
• The effects of the welding process, procedures, and sequence of
welding must always be taken into account to maintain inter pass
temperature within the proper range.
• The effects of both minimum and maximum inter pass temperature
should be considered with regard to the mechanical and micro structure
properties of the weld metal and the heat affected zone (HAZ).
The inter pass temperature should be maintained throughout the full thickness
of the base metal and some reasonable distance away from the weld,
approximately equal to one inch, unless the codes specify otherwise.
One object of the invention is to carry out welding of TMT rebar maintaining
interpass temperature within the range of 234 to 310°C through out the
thickness of the test bar specimens along with the effect of minimum and
maximum interpass temperature with regard to the mechanical and
micro structural properties of the weld metal and the heat affected zone.
Another object of the invention is to study the input of higher interpass
temperature than that mentioned in IS 9417, on tensile properties of the TMT
rebar before and after welding and the interpass temperature being monitored
by CMSS 200 infrared the rmometer SKF.
A further object of the invention is to determine appropriate electrode
specification and TMT bar composition for welding of TMT bars without
leading any defect in the welded zone.

5
Yet another object of the invention is to provide welding procedure for
obtaining uniform cross-sectional mechanical properties of welded TMT rebar
accordingly to guidelines provided in 10.3.4.1 (paragraph 1) [IS 9417-
1989] for inter-pass temperature, 10.5.3[IS9417-1989] for Electrodes and
10.5.4[IS 9417-1989] for welding procedure followed for lap joint (single
side) with actual current 180 amperes against current 140/180 amperes,
specified by proprietor.
A still another object of the invention is to carry out testing procedure during
welding of TMT rebar on maintaining after evaluating, electrode specification
confirming AWS/SFA 5.5 E 8018.
The invention will he better understood from the following description with
examples and accompanying drawing in which.
Figure 1 shows a welding of TMT test piece following welding procedure for
CTD bars (IS 9417:1989).
Figure 2 shows the sequence of welding beads according to paragraph
10.3.4.1 of IS 9417-1989.
Figure 3 shows the manner of welding in horizontal and vertical position as
specified in paragraph 10.5.4 of IS 9417-1989.
Figure 4 to 7 shows manner of welding various lap joints with specified
dimension as laid down in paragraph 10.5.4 of IS 9417-1989.
Chemical composition of the TMT rebar is examined as follows according to
the specification as laid down in IS 1608: 2005/ISO 6892: 1998 'Metallic
Materials Tensile Testing At Ambient Temperature' through YS, UTS and %
elongation on inspection before welding.

6
Chemical Composition of the steel (TMT rebar) samples:

% C Mn s P Si %(S+P)
Specified 0.30
max 0.06
max 0.06 max 0.11 max

Actual 0.15 0.060 0.018 0.016 0.141 0.034
Tensile properties before welding of TMT rebar of the above mentioned
composition is tested as follows: -
Table 1
Tensile Properties:
(Before welding)

YS(N/min2) UTS (N/mm2) % Elongation
Specified 415 min 485 min 14.5
Actual 494 592 21
The chemical composition and tensile properties of the TMT rebar test
specimens conformed to IS 1786:1985 for grade of Fe 415.
Welding procedure was maintained as follows:
The following guidelines were followed during welding:
10.3.4.1 (paragraph 1) [IS 9417-1989] for inter-pass temperature, 10.5.3 [IS
9417-1989] for Electrodes and 10.5.4 [IS 9417-1989] for welding procedure
were followed for lap joint (single side) with actual current 180 amperes
against current 140/180 amperes, specified by proprietor.

7
Paragraph 10.3.4.1 of IS 9417-1989 for interpass temperature has stated as the
sequence of weiding beads as shown in Fig. 2. The runs 1 to 4 are made in the
position of welding best suited for the quality of the weid. Besides the
interruption in weiding required for cleaning of each bead, a pause shall be
made after every second bead and the bar is allowed to cool. The temperature
of the bars at a distance of about one bar diameter from the joints shall not
exceed 300oC immediately after the bead is made. Before commencing the net
bead, the temperature shall not exceed 250°C. The temperature may be
checked approximately by using temperature indicating crayons. However, in
the absence of temperature indicating devices, the bar may be allowed to cool
down to handhot temperature before the next bead is deposited.
After completing bead 4, the bars are turned through 180o and the beads 5 to 7
are made in the same manner as described above. The top bead 8 is deposited
as joint is continuously rotated and the size of the reinforcement should be
approximately as indicated in Fig. 2.
Paragraph 10.5.3 of IS 9417-1989 for electrode has specified the size of
electrodes according to the diameter of the bar to be welded shall be as
follows:
Nominal Diameter of bar, d mm Size of Electrode, Max
Up to and including 10 2.5
Over 10 up to and 3.15
Including 18
Over18 up to and 4.0
Including 28
Over 28 5.0
Paragraph 10.5.4 of IS 9417-1989 for welding procedure of lap joint has
specified that the arc should be struck as shown in Fig. 3 somewhere in the
middle of the joint and not at its beginning.

8
The movement of the electrode for welding lap joints in the horizontal and
vertical position is indicated in Fig. 3.
The various lap joints used to connect cold-worked bars are shown in Fig. 4 to
7.
In Fig. 4 to 6, the dimensions indicated as '5d' for single side welding should
be halved to '2.5d' if the welds are deposited from the opposite side also. The
single-strap arrangement shown in Fig. 7 is not recommended where access is
from one side only. In the case of joints illustrated in Fig. 6 and 7, the strap
cross sectional area must, at least, equal that of the bar to be joined.
Welding electrode is maintained confirming specification AWS/ SF A 5.5. E
8018 with composition in weight % C-0.05-0.10, Mn-1.4-1.85, S-0.030 Max,
P-0.030 Max, Si-0.20-0.48 and Ni-0.45-0.80 and size 4 mm x 450 mm
Tensile properties inspected after welding of TMT rebar is narrated as follows
in table 2.
Table 2
Tensile properties after welding:

Sample
Id. Inter-pass
Temperature
(oC) YS (N/mm2) UTS (N/mm2) Breaking
Load in KN
1. 310 487 582 184
2. 294 497 592 186
3.
272 490 582 183
4. 270 503 596 187
5. 240 500 589 185
6. 234 497 592 186

9
It was observed that no TMT rebar sample 1 to 6 above broke from the
welded region while maintained with interpass temperature from 234oC to
310° C.
The welding of TMT test piece following welding procedure for CTD bars
according to IS 9417:1989 is shown in Figure 1.
The above test procedure for welding test of TMT rebar was carried out with
inspection stages of
i. Preliminary stage i.e. before commencing fabrication of welding,
ii. In process stage i.e. during fabrication by welding and
iii. After welding, followed by evaluation of mechanical properties after
welding.
From the test investigations as narrated above it is assessed and concluded that
Conclusion:
The above test results show that TMT rebar can be welded following the
above process without any detrimental impact.
Welding electrode: AWS/ SF A 5.5. E 8018 was found appropriate for
welding of TMT rebar.
The material can be welded satisfactorily even at the interpass temperature of
310° C without any detrimental effect on tensile properties.
The invention as narrated though described with a particular embodiment
should not be read and construed in a restrictive manner as some
modifications, alterations and changes are possible within the scope and limit
of the invention as defined in the encompassed appended claims.

10
We claim:
1. A modified method of welding of thermomechanically treated (TMT)
welded metal rebars for uniform strength maintaining throughout the
thickness of welded rebars comprising the steps of
• welding lap joint (single side) of TMT rebars of same or different
diameter at horizontal, vertical or sloping position on striking electrode
somewhere in the middle of the joint and not at its beginning and in the
groove between the welded bars at an angle of 75° for horizontal and
80°-85° for vertical position, performing welding operation from the
forward and of the upper bar to the end point of the lower bar in case of
horizontal lap joint and from bottom to top in case of vertical lap joint
according to the procedure as laid down in paragraph 10.5.4 of IS 9417-
1989 with actual welding current of 180 amperes as against proprietor
specified current of 140/180 amperes;
• selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06,
S-0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as
laid down in IS 1608:2005/ISO 6892:1998 and electrode specification
confirming to AWS/SFA 5.5 E 8018 having composition in weight %
C-0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48,
Ni-0.45-0.80 and size of 4 mm x 450 mm;
• carrying on determination of tensile properties before and after welding
of the TMT rebar test specimens and confirming tensile properties
obtained after welding without any detrimental impact on conformation
of uniform strength throughout the thickness of the welded rebars as
specified in IS 9417-1989.
2. A modified method of welding as claimed in claim 1 wherein the
welding procedure for welding of test pieces of TMT rebar was carried
out with inspection stages of

11
i. preliminary stage i.e. before commencing fabrication of welding,
ii. in process stage i.e. during fabrication by welding and
iii. after welding, followed by evaluation of mechanical properties
after welding.
3. A modified method of welding as claimed in claim 1 wherein compative
tensile properties of YS 487n/mm2 UTS 582 n/mtn2 and breaking load 184
KN are achieved after welding of the said test rebar specimens even at
interpass temperature of 310° C.
4. A modified method of welding as claimed in claim 1 and 3 wherein all the
welded TMT rebar test specimens broke from welded region during breaking
load determination thus satisfying the IS specification in this respect.
5. A modified method of welding as claimed in the preceding claims wherein
improved welding characters of TMT rebars are secured with expanded
interpass temperature range of 234-310° C between bead to bead formation
than that of the range of 250-300°C as laid down in the IS specification.
6. A modified method of welding as claimed in the proceeding claims wherein
the chemical composition and tensile properties of the TMT rebar test
specimens conform to IS 1786:1985 for grade of Fe 415.
7. A modified method of welding as claimed in the proceeding claims wherein
the electrode as specified in AWS/SFA 5.5 E 8018 was selected after carrying
out test and evaluating suitable performance of welding of lap joint TMT
rebar specimens with other standards for electrode as specified in IS for CTD
bars.
8. A modified method of welding as claimed in claim 1 wherein the interpass
temperature was monitored by CMSS 2000 infrared thermo meter SKF.
9.A lap jointed TMT rebars as obtained according to the method of claim 1.

This invention relates to a modified method of welding of
thermomechanically treated (TMT) welded metal rebars for uniform
strength maintaining throughout the thickness of welded rebars and welded
rebars produced thereof comprising the steps of welding lap joint (single
side) of TMT rebars of same or different diameter at horizontal, vertical or
sloping position on striking electrode somewhere in the middle of and of
the joint according to the procedure as laid down in paragraph 10.5.4 of IS
9417-1989 with actual welding current of 180 amperes as against
proprietor specified current of 140/180 amperes;
selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S-
0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid
down in IS 1608:2005/IS0 6892:1998 and electrode specification
confirming to AWS/SFAS.SE 8018 having composition in weight % C-
0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45-
0.80 and size of 4 mm x 450 mm;
sel ecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S-
0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid
down in IS 1608:2005/ISO 6892:1998 and electrode specification
confirming to AWS/SFAS.SE 8018 having composition in weight % C-
0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45-
0.80 and size of 4 mm x 450 mm;
carrying on determination of tensile properties before and after welding of
the TMT rebar test specimens on conformation of uniform strength
throughout the thickness of the welded rebars as specified in IS 9417-1989
after welding.

A METHOD FOR WELDING THERMO-MECHANICALLY TREATED (TMT) REBAR

Documents:

Inventors:

PCT Conventions: