CA1080309A - Submerged arc welding process for nickel containing steel - Google Patents
Submerged arc welding process for nickel containing steelInfo
- Publication number
- CA1080309A CA1080309A CA274,358A CA274358A CA1080309A CA 1080309 A CA1080309 A CA 1080309A CA 274358 A CA274358 A CA 274358A CA 1080309 A CA1080309 A CA 1080309A
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Abstract
ABSTRACT OF THE DISCLOSURE
Submerged arc welding for nickel containing steel such as steel containing 3.5 weight percent of nickel. The process uses a bond type of flux of specific composition to suppress the oxygen content in the weld metal. Further, the process utilizes a cored welding wire including a core material of specific composition. As the result, it is possible to obtain a weld metal of high impact-resistance at low temperature such as minus 100°C. The welding electrode is a cored wire consist-ing of a mild steel and core material, the core material includ-ing, on the basis of weight to the total weight of the welding electrode, 5 to 25 percent of CaF2, 2.5 to 5.5 percent of nickel, O to 0.5 percent of Mo, 0 to 0.5 percent of Ti. The flux is a bond type flux having a composition of, by weight percent, 10 to 30 percent of SiO2, 8 to 20 percent of A12O3, 25 to 45 per-cent of MgO, 10 to 30 percent of CaO, 7 to 20 percent of CaF2, and at least one member selected from the group consisting of metallic Si, Fe-Si, Fe-Si-Mn, the amount of Si in all cases being 6 percent or less calculated in terms of metallic Si. The flux has a basicity B higher than 1.5, the basicity being defined on the basis of weight by the following equation:
Submerged arc welding for nickel containing steel such as steel containing 3.5 weight percent of nickel. The process uses a bond type of flux of specific composition to suppress the oxygen content in the weld metal. Further, the process utilizes a cored welding wire including a core material of specific composition. As the result, it is possible to obtain a weld metal of high impact-resistance at low temperature such as minus 100°C. The welding electrode is a cored wire consist-ing of a mild steel and core material, the core material includ-ing, on the basis of weight to the total weight of the welding electrode, 5 to 25 percent of CaF2, 2.5 to 5.5 percent of nickel, O to 0.5 percent of Mo, 0 to 0.5 percent of Ti. The flux is a bond type flux having a composition of, by weight percent, 10 to 30 percent of SiO2, 8 to 20 percent of A12O3, 25 to 45 per-cent of MgO, 10 to 30 percent of CaO, 7 to 20 percent of CaF2, and at least one member selected from the group consisting of metallic Si, Fe-Si, Fe-Si-Mn, the amount of Si in all cases being 6 percent or less calculated in terms of metallic Si. The flux has a basicity B higher than 1.5, the basicity being defined on the basis of weight by the following equation:
Description
V309 ~ :
The present invention relates to a submerged arc -welding process and more particularly to a submerged arc welding process for nickel containing steel. More specifi-cally, the present invention pertains to a submerged arc weld-ing process for nickel containing steel which can provide a weld metal having an improved toughness. The present invention is particularly suitable for welding 3.5% nickel containing steel but is not limited to such purpose.
Conventionally, 3.5% nickel containing steel has been -utilized for constructing vessels which are used for storing liquefied gas such as liquefied nitrogen, liquefied oxygen or the like. Since such vessels are constructed from the steel material by means of welding and subjected in use to an extreme cold temperature, it is very important to provide an adequate impact-resistant property at low temperature such as below minus lOO~C even at the welded portion. From the viewpoint of manufacture, it is of course desirable to perform the welding operation automatically making use of a submerged arc welding technique, however, since it has been difficult to ensure a satisfactory impact-resistant property through a conventional submerged arc welding, manually operated welding technique has ; been employed for the manufacture of such vessels so that thermal input at the welding portion can be maintained as low as possible to provide a weld metal of high toughness.
It has previously been proposed and actually been -~
' practiced, in order to obtain an increased tou~hness in the `~I weld metal, to increase the amount of nickel content in the '~ weld metal. However, experiences have shown that the increase in the nickel content does not provide any improvement in the ; 30 toughness but there have rather been an adverse effect thereon when the nickel content exceeds 3%. The reason of this tendency is understood that the increased nickel content serves to pro-- 1 ~
.
vide the weld metal of brittle structures such as bainite. Thus, according to prior art, it has been very difficult to ensure an impact-resistant property at low temperatures such as below minus 100C.
The present invention has therefore an object to pro-vide a submerged arc welding process which can provide a weld metal of improved toughness.
Another object of the present invention is to provide a novel submerged arc welding process for nickel containing steel which uses flux and welding electrode of specific composi-tion.
A further object of the present invention is to pro-vide a submerged arc welding process which is particularly suitable, although not limited, to the welding of 3.5% nickel . -containing steel.
According to the present invention, the above and other objects can be accomplished by a submerged arc welding process for weldi.ng nickel containing steel with a welding electrode in the presence of a flux, said welding process ::
being characterized in that:
A) said welding electrode is a cored wire consisting of a mild steel and core material, the core material including, on the basis of weight to the total weight of the welding electrode, 5 to 25 :
percent of CaF2, 2.5 to 5.5 percent of nickel, 0 to 0.5 percent of Mo, 0 to 0.5 percent of Ti, B) said flux is bond type flux having a composition of, by weight percent, 10 to 30 percent of SiO2, .
~: . . . . .
` ~080309 8 to 20 percent of A1203, 25 to 45 percent of MgO, 10 to 30 percent of CaO, 7 to 20 percent of CaF2, and at least one me~ber selected from the group con-sisting of metallic Si, Fe-Si, Fe-Si-Mn, the amount of . Si in all cases being 0.6 percent or less calculated - in terms of metallic Si, and having a basicity B higher . than 1.5, the basicity being defined on the basis of weight by the following equation: ~:
B CaO + MaO
SiO2 + Ai2o3 Through extensive investigations in obtaining an improved toughness through a submerged arc welding of steel material of high nickel content, the inventors have found that ::
: the Si and C contents in the weld metal have an important effect on the property. More specifically, in case of a weld metal having nickel content exceeding 2 percent, a decrease in silicon content and also a decrease in carbon content are effective to provide a high toughness at low temperatures~ Particularly, with a weld metal having a silicon content not exceeding 0.20 percent and a carbon content not exceeding 0.08 percent, it has been ensured that a high impact-resistant property can be attained even at an extremely low temperature around minus 100C. The reasons for such an improvement in toughness through the decreased carbon and silicon contents of weld metal have not been fully clarified but it i9 understood that the reducing in the carbon and silicon amounts is effective to suppress the ., ~trength of the weld metal including a relatively high per-centage of nickel.
However, in welding processes utilizing a melt type flux, it is very difficult to maintain the silicon content of the weld metal lower than 0.20 percent because the flux normally contains a large amount of SiO2 and the basicity of the flux cannot be as high as desirable, whereby there will be . -,. ~ , : :
~0803V9 a tendency that the SiO2 content will be reduced in the slagwhich will be formed during the welding process, and the silicon content in the weld metal will correspondingly be increased.
Thus, it is impractical to use such melt type flux for the pur-pose of the present invention and it is therefore essential for the present invention to utilize a bond type flux having a high basicity and less SiO2 content.
The use of such bond type flux of high basicity may also be effective to decrease the oxygen content in the weld metal but there still exists surplus oxygen so that it is required to add deoxidizing agents such as silicon, metallic silicon, Fe-Si, Fe-Si-Mn, metallic manganese and Fe-Mn. The amount of such de-oxidizing agents is very important because, when the agents are added excessively, they will cause an increase in the silicon content but if the amount is insuffi-cient there will be produced welding defects such as blow-holes and there will also be a decrease in the toughness due to insufficient de-oxidization. Thus, in order to decrease the silicon content in the weld metal and to achieve an adequate de-oxidization, it is necessary to utilize a bond type flux having a low silicon content and a high basicity and, at the same time, to decrease the oxygen content in the pool of the molten metal produced during welding operation.
.~ According to the present invention, a welding elec-trode of cored wire is employed because it provides a stable welding arc with a relatively large input. The welding elec-trode may be manufactured by turning over a mild steel hoop to ~ -form an elongated wire or tube and then incorporating the above-mentioned core material in the space defined in the tube. The hoop is preferably of a composition by weight of less than 0.15 percent of carbon, less than 1.0 percent of manganese and the balance of iron because of its workability. ~ -.. .
.. - . . . . . .. .
~08U309 It has been found that CaF2 is very effective to de-crease the oxygen content in the welding pool of the molten metal. The inventors found that the oxygen content in the molten metal could substantially be decreased in a submerged arc welding through a use of a bond type flux of high basicity in combination with a welding electrode of cored wire including CaF2. The weld metal thus produced has been found substantially free from any defects such as blow-holes.
It is understood that CaF2 in the core material of the welding electrode is subjected to a high temperature of the welding arc and vaporized and decomposed as soon as the electrode is molten, to produce a large amount of fluoric gas which serves to shield the arc space and the surface of the molten metal so as to prevent air or other gaseous impurities from reaching the molten metal. Thus, CaF2 is effective to decrease the amounts of oxygen and other impurities in the molten metal.
Thus, it has been ensured that through a submerged arc welding utilizin~ a bond type flux of high basiclty and a weld-ing electrode of cored wire containing CaF2, it is possible to produce a welded metal of low carbon and low silicon contents without causing any defects such as blow holes. Further, it has ' also been ensured that the silicon content in the weld metal can be maintained below 0.20% and the oxygen content below 400 ppm.
, The inventors have further made investigations on the influence of Ni, Mo and/or Ti contents in the welding electrode on the weldability, the strength and the impact-resistant pro-perty at minus 100C. As the result, the inventors have found that adequate impact-resistant property at minus 100C cannot be stably provided unless the Ni content in the cored wire is ;~
maintained above 2.5%. On the other hand, it has also been found that excessive nickel content has a tendency of producing bainite structure even where the silicon content in the weld metal is .
` 10~1~J3(~
very low, resulting in an unstable impace-resistant property at low temperatures. It is of course true that, even in this in-stance, the decrease in the toughness is not as significant as in the case where the weld metal contains more than 0~2 percent of silicon, however, in view of an expensive cost of nickel and in view of the fact that an excessive nickel content may be a cause of cracks at a high temperature, it is recommendable to maintain the nickel content in the welding electrode between 2.5 and 5.5 percent.
Molybdenum may be incorporated into the welding elec-trode in order to secure the strength of the welded part because -there is a tendency that the strength of the welded part is relatively low with low carbon and silicon contents. However, the Mo content should be limited lower than 0.5 percent because an increased Mo content has a tendency of producing a weld metal of bainite structure resulting in a remarkable decrease in the impact-resistant property at low temperatures.
Titaniummay be also incorporated to the welding elec-trode as a de-oxidizing agent and further serves to make the weld metal of fine crystals and fine structures which are effective to improve the toughness of the weld metal. Although thetitanium is thus effective to improve the toughness of the weld metal, the content must be maintained lower than 0.5 per-cent because the titanium content exceeding this value has a ;~
tendency of increasing the silicon content in the weld metal and of producing a bainite structure resulting in a decrease in the impact-resistant property at low temperatures.
With respect to the flux, the basicity is of impor-tance because, under the basicity less than 1.5, the SiO2 in ;"
the flux will be increased and the Si content in the weld metalis correspondingly increased. Further, with the basicity less than 1.5, there is also a tendency that the oxygen content in ' :
108030~
the weld metal is increased and blow holes are produced. ;~
The SiO2 has an influence on the melting point of the flux and where the SiO2 content is less than 10 percent there will be an increase in the melting point of the flux so that adverse effects will be seen in the performance of the welding operation and also in the appearance of the welded beads. With the SiO2 content exceeding 30 percent, the SiO2 will be chemi-cally reduced and there will be an increase in the Si content in the weld metal resulting in a poor toughness of the weld metal.
The A1203 has an influence on the appearance of the welded beads and an acceptable range is between 8 and 20 per-cent. With the MgO content less than 25 percent, it will be difficult to maintain the basicity at a desirable level but where the content is greater than 45 percent the melting point of the flux will be increased to an unacceptable level. The CaO content should be greater than 10 percent in order to main-tain the basicity within the desired range but it will have an adverse effect on the workability if it is increased beyond 30 percent.
The CaF2 content should be greater than 7 percent in order to provide a satisfactory appearance on the welded beads.
However, excessive addition of CaF2 causes an unstable welding arc so that the content should be lower than 20 percent. In order to maintain the silicon content in the weld metal below 0.20 percent, it is required to maintain the silicon content of metallic Si, Fe-Si and Fe-Si-Mn in the flux to lower than 0.6 percent. Otherwise, there will be an adverse effect on the toughness at low temperatures due to an increase in the silicon content in the weld metal. As mentioned above, silicon contain-ing de-oxidizing agent may be metallic Si, Fe-Si, Fe-Mn-Si. It is of course possible to use a material other than silicon as -~.
: - :
. - . - .: . .
the de-oxidi~ing agent. For example, manganese may be used for the purpose. Thus, the flux of the present invention may con-tain de-oxidizing agent in an amount of less than 0.6% calculated in terms of silicon.
Regarding the cored wire, it has been found that the ~ -CaF2 content should be greater than 5 percent to the total weight of the wire. Otherwise, blow-holes are apt to be pro-duced in the weld metal and there will be a decrease in the toughness. With the CaF2 content greater than 5 percent, there is a remarkable decrease in the oxygen content in the molten metal so that blow holes are prevented and the toughness is improved. However, the CaF2 content should not exceed 25 per-cent because an excessive CaF2 content makes the welding arc unstable and causes apoor workability.
In order to ensure an adequate impact-resistant pro-perty at minus 100C, it is necessary to maintain the nickel content in the core wire in an amount of higher than 2.5 per-cent, however, where the content increases beyond 5.5 percent, it may cause cracks under high tempera-ture.
Molybdenum may be incorporated to the cored wire for obtaining an increased strength of the weld metal but the con-tent shall not exceed 0.5 percent because it may have an adverse effect on the impact-resistant property at low temperatures where the Mo content is above this value.
Titanium may be also incorporated to the cored wire because it is effective to produce fine crystalline structures which serve to provide an improved impact-resistant property under low temperature. However, the titanium may be omitted because it is possible to obtain a satisfactory impact-resistant property around minus 100C. Where the Ti content is greater than 0.5 percent, there will be a decrease in the toughness due to an increase in the silicon content in the weld metal.
~0~30309 Nickel, molybdenum and titanium in the core material may be incorporated in the welding electrode in the form of ferrous alloy thereof, for example Fe-Ni, Fe-Mo and Fe-Ti.
Fe-Ni, Fe-Mo or Fe-Ti may be incorporated to the electrode in the above mentioned amount calculated in term of nickel, molyb-denum or titanium. It is of course that nickel, molybdenum or titanium may be added to the electrode in the form of elementary metal.
It has been found that, when a submerged arc welding using the aforementioned flux and welding electrode of cored wire is applied to 3.5% Ni containing steel, it is possible to pro-duce a weld metal having an excellent toughness at low tempera-tures. It should be noted, however, that the submerged arc welding process in accordance with the present invention can also be applied to other types of nickel containing steel such as 3.5% Ni containing steel. Further, it should also be noted that the welding conditions may suitably be selected in prac-tice.
The present invention will now be described by way of examples.
Examples:
Butt welding operations were performed in specimens of 3.5% Ni containing steel (ASTMA 203D) of 25 mm thick with a welding current of 600 A under 40 V and a welding speed of 40 cm/min. to form multiple layers of weld metal. The operations were performed in accordance with conventional process as well as in accordance with the present invention. In the welding operations, metal sheets were shaped to have edges sloped by an angle of 20 degrees, and a pair of such sheets were placed at a minimum distance of 10 mm.
The welded specimens were subjected to tests for weld-ing defects. The specimens were then formed with V-shaped notches _ g _ 1~80309 and subjected to Charpy impact test at minus 100C. The results are shown in the following table.
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: Example of the Invention o .
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10~0309 In the above table, the wire composition designates the constituents of core material in weight percentages with respect to the wire as a whole. Mild steel in the Table had a composition by weight, of 0.06 percent of carbon, 0.50 percent of manganese and the balance of iron. In the table, it will be noted that the specimen A shows unsatisfactory toughness because the welding employed a melt type flux with a low basicity. The specimen B shows blow holes due to insufficient deoxydization because the flux does not contain silicon. The specimen C does not have a satisfactory toughness because the process employed for for the specimen uses a welding electrode of solid wire which did not provide adequate amount of oxygen~ The specimen D shows unqatisfactory toughness due to insufficient nickel content.
The specimen E has blow holes due to insufficient deoxydization because the flux used for the specimen had lower basicity.
The specimens J through N which have been welded in accordance with the present invention show satisfactory impact resistance under low temperature. In the specimen L, the flux did not contain Si but deoxydization was effected due to the existence of Ti.
The specimen F had blow holes which have produced due to insufficient content of CaF2 in the welding wire. The speci-men G had been welded with a welding wire containing excessive amount of nickel. As the result, the weld metal did not possess a satisfactory toughness. ~he ~pecimen H had been welded with the welding wire containing excessive titanium and as the result the weld metal had insufficient toughness. The specimen I had unacceptable appearance of welded beads due to excessive amount of CaF2 in the welding wire.
The invention has thus been shown and described with reference to examples but it should be noted that modifications may be made without departing from the scope of the appended claims.
., . . ......................... .. -.:
The present invention relates to a submerged arc -welding process and more particularly to a submerged arc welding process for nickel containing steel. More specifi-cally, the present invention pertains to a submerged arc weld-ing process for nickel containing steel which can provide a weld metal having an improved toughness. The present invention is particularly suitable for welding 3.5% nickel containing steel but is not limited to such purpose.
Conventionally, 3.5% nickel containing steel has been -utilized for constructing vessels which are used for storing liquefied gas such as liquefied nitrogen, liquefied oxygen or the like. Since such vessels are constructed from the steel material by means of welding and subjected in use to an extreme cold temperature, it is very important to provide an adequate impact-resistant property at low temperature such as below minus lOO~C even at the welded portion. From the viewpoint of manufacture, it is of course desirable to perform the welding operation automatically making use of a submerged arc welding technique, however, since it has been difficult to ensure a satisfactory impact-resistant property through a conventional submerged arc welding, manually operated welding technique has ; been employed for the manufacture of such vessels so that thermal input at the welding portion can be maintained as low as possible to provide a weld metal of high toughness.
It has previously been proposed and actually been -~
' practiced, in order to obtain an increased tou~hness in the `~I weld metal, to increase the amount of nickel content in the '~ weld metal. However, experiences have shown that the increase in the nickel content does not provide any improvement in the ; 30 toughness but there have rather been an adverse effect thereon when the nickel content exceeds 3%. The reason of this tendency is understood that the increased nickel content serves to pro-- 1 ~
.
vide the weld metal of brittle structures such as bainite. Thus, according to prior art, it has been very difficult to ensure an impact-resistant property at low temperatures such as below minus 100C.
The present invention has therefore an object to pro-vide a submerged arc welding process which can provide a weld metal of improved toughness.
Another object of the present invention is to provide a novel submerged arc welding process for nickel containing steel which uses flux and welding electrode of specific composi-tion.
A further object of the present invention is to pro-vide a submerged arc welding process which is particularly suitable, although not limited, to the welding of 3.5% nickel . -containing steel.
According to the present invention, the above and other objects can be accomplished by a submerged arc welding process for weldi.ng nickel containing steel with a welding electrode in the presence of a flux, said welding process ::
being characterized in that:
A) said welding electrode is a cored wire consisting of a mild steel and core material, the core material including, on the basis of weight to the total weight of the welding electrode, 5 to 25 :
percent of CaF2, 2.5 to 5.5 percent of nickel, 0 to 0.5 percent of Mo, 0 to 0.5 percent of Ti, B) said flux is bond type flux having a composition of, by weight percent, 10 to 30 percent of SiO2, .
~: . . . . .
` ~080309 8 to 20 percent of A1203, 25 to 45 percent of MgO, 10 to 30 percent of CaO, 7 to 20 percent of CaF2, and at least one me~ber selected from the group con-sisting of metallic Si, Fe-Si, Fe-Si-Mn, the amount of . Si in all cases being 0.6 percent or less calculated - in terms of metallic Si, and having a basicity B higher . than 1.5, the basicity being defined on the basis of weight by the following equation: ~:
B CaO + MaO
SiO2 + Ai2o3 Through extensive investigations in obtaining an improved toughness through a submerged arc welding of steel material of high nickel content, the inventors have found that ::
: the Si and C contents in the weld metal have an important effect on the property. More specifically, in case of a weld metal having nickel content exceeding 2 percent, a decrease in silicon content and also a decrease in carbon content are effective to provide a high toughness at low temperatures~ Particularly, with a weld metal having a silicon content not exceeding 0.20 percent and a carbon content not exceeding 0.08 percent, it has been ensured that a high impact-resistant property can be attained even at an extremely low temperature around minus 100C. The reasons for such an improvement in toughness through the decreased carbon and silicon contents of weld metal have not been fully clarified but it i9 understood that the reducing in the carbon and silicon amounts is effective to suppress the ., ~trength of the weld metal including a relatively high per-centage of nickel.
However, in welding processes utilizing a melt type flux, it is very difficult to maintain the silicon content of the weld metal lower than 0.20 percent because the flux normally contains a large amount of SiO2 and the basicity of the flux cannot be as high as desirable, whereby there will be . -,. ~ , : :
~0803V9 a tendency that the SiO2 content will be reduced in the slagwhich will be formed during the welding process, and the silicon content in the weld metal will correspondingly be increased.
Thus, it is impractical to use such melt type flux for the pur-pose of the present invention and it is therefore essential for the present invention to utilize a bond type flux having a high basicity and less SiO2 content.
The use of such bond type flux of high basicity may also be effective to decrease the oxygen content in the weld metal but there still exists surplus oxygen so that it is required to add deoxidizing agents such as silicon, metallic silicon, Fe-Si, Fe-Si-Mn, metallic manganese and Fe-Mn. The amount of such de-oxidizing agents is very important because, when the agents are added excessively, they will cause an increase in the silicon content but if the amount is insuffi-cient there will be produced welding defects such as blow-holes and there will also be a decrease in the toughness due to insufficient de-oxidization. Thus, in order to decrease the silicon content in the weld metal and to achieve an adequate de-oxidization, it is necessary to utilize a bond type flux having a low silicon content and a high basicity and, at the same time, to decrease the oxygen content in the pool of the molten metal produced during welding operation.
.~ According to the present invention, a welding elec-trode of cored wire is employed because it provides a stable welding arc with a relatively large input. The welding elec-trode may be manufactured by turning over a mild steel hoop to ~ -form an elongated wire or tube and then incorporating the above-mentioned core material in the space defined in the tube. The hoop is preferably of a composition by weight of less than 0.15 percent of carbon, less than 1.0 percent of manganese and the balance of iron because of its workability. ~ -.. .
.. - . . . . . .. .
~08U309 It has been found that CaF2 is very effective to de-crease the oxygen content in the welding pool of the molten metal. The inventors found that the oxygen content in the molten metal could substantially be decreased in a submerged arc welding through a use of a bond type flux of high basicity in combination with a welding electrode of cored wire including CaF2. The weld metal thus produced has been found substantially free from any defects such as blow-holes.
It is understood that CaF2 in the core material of the welding electrode is subjected to a high temperature of the welding arc and vaporized and decomposed as soon as the electrode is molten, to produce a large amount of fluoric gas which serves to shield the arc space and the surface of the molten metal so as to prevent air or other gaseous impurities from reaching the molten metal. Thus, CaF2 is effective to decrease the amounts of oxygen and other impurities in the molten metal.
Thus, it has been ensured that through a submerged arc welding utilizin~ a bond type flux of high basiclty and a weld-ing electrode of cored wire containing CaF2, it is possible to produce a welded metal of low carbon and low silicon contents without causing any defects such as blow holes. Further, it has ' also been ensured that the silicon content in the weld metal can be maintained below 0.20% and the oxygen content below 400 ppm.
, The inventors have further made investigations on the influence of Ni, Mo and/or Ti contents in the welding electrode on the weldability, the strength and the impact-resistant pro-perty at minus 100C. As the result, the inventors have found that adequate impact-resistant property at minus 100C cannot be stably provided unless the Ni content in the cored wire is ;~
maintained above 2.5%. On the other hand, it has also been found that excessive nickel content has a tendency of producing bainite structure even where the silicon content in the weld metal is .
` 10~1~J3(~
very low, resulting in an unstable impace-resistant property at low temperatures. It is of course true that, even in this in-stance, the decrease in the toughness is not as significant as in the case where the weld metal contains more than 0~2 percent of silicon, however, in view of an expensive cost of nickel and in view of the fact that an excessive nickel content may be a cause of cracks at a high temperature, it is recommendable to maintain the nickel content in the welding electrode between 2.5 and 5.5 percent.
Molybdenum may be incorporated into the welding elec-trode in order to secure the strength of the welded part because -there is a tendency that the strength of the welded part is relatively low with low carbon and silicon contents. However, the Mo content should be limited lower than 0.5 percent because an increased Mo content has a tendency of producing a weld metal of bainite structure resulting in a remarkable decrease in the impact-resistant property at low temperatures.
Titaniummay be also incorporated to the welding elec-trode as a de-oxidizing agent and further serves to make the weld metal of fine crystals and fine structures which are effective to improve the toughness of the weld metal. Although thetitanium is thus effective to improve the toughness of the weld metal, the content must be maintained lower than 0.5 per-cent because the titanium content exceeding this value has a ;~
tendency of increasing the silicon content in the weld metal and of producing a bainite structure resulting in a decrease in the impact-resistant property at low temperatures.
With respect to the flux, the basicity is of impor-tance because, under the basicity less than 1.5, the SiO2 in ;"
the flux will be increased and the Si content in the weld metalis correspondingly increased. Further, with the basicity less than 1.5, there is also a tendency that the oxygen content in ' :
108030~
the weld metal is increased and blow holes are produced. ;~
The SiO2 has an influence on the melting point of the flux and where the SiO2 content is less than 10 percent there will be an increase in the melting point of the flux so that adverse effects will be seen in the performance of the welding operation and also in the appearance of the welded beads. With the SiO2 content exceeding 30 percent, the SiO2 will be chemi-cally reduced and there will be an increase in the Si content in the weld metal resulting in a poor toughness of the weld metal.
The A1203 has an influence on the appearance of the welded beads and an acceptable range is between 8 and 20 per-cent. With the MgO content less than 25 percent, it will be difficult to maintain the basicity at a desirable level but where the content is greater than 45 percent the melting point of the flux will be increased to an unacceptable level. The CaO content should be greater than 10 percent in order to main-tain the basicity within the desired range but it will have an adverse effect on the workability if it is increased beyond 30 percent.
The CaF2 content should be greater than 7 percent in order to provide a satisfactory appearance on the welded beads.
However, excessive addition of CaF2 causes an unstable welding arc so that the content should be lower than 20 percent. In order to maintain the silicon content in the weld metal below 0.20 percent, it is required to maintain the silicon content of metallic Si, Fe-Si and Fe-Si-Mn in the flux to lower than 0.6 percent. Otherwise, there will be an adverse effect on the toughness at low temperatures due to an increase in the silicon content in the weld metal. As mentioned above, silicon contain-ing de-oxidizing agent may be metallic Si, Fe-Si, Fe-Mn-Si. It is of course possible to use a material other than silicon as -~.
: - :
. - . - .: . .
the de-oxidi~ing agent. For example, manganese may be used for the purpose. Thus, the flux of the present invention may con-tain de-oxidizing agent in an amount of less than 0.6% calculated in terms of silicon.
Regarding the cored wire, it has been found that the ~ -CaF2 content should be greater than 5 percent to the total weight of the wire. Otherwise, blow-holes are apt to be pro-duced in the weld metal and there will be a decrease in the toughness. With the CaF2 content greater than 5 percent, there is a remarkable decrease in the oxygen content in the molten metal so that blow holes are prevented and the toughness is improved. However, the CaF2 content should not exceed 25 per-cent because an excessive CaF2 content makes the welding arc unstable and causes apoor workability.
In order to ensure an adequate impact-resistant pro-perty at minus 100C, it is necessary to maintain the nickel content in the core wire in an amount of higher than 2.5 per-cent, however, where the content increases beyond 5.5 percent, it may cause cracks under high tempera-ture.
Molybdenum may be incorporated to the cored wire for obtaining an increased strength of the weld metal but the con-tent shall not exceed 0.5 percent because it may have an adverse effect on the impact-resistant property at low temperatures where the Mo content is above this value.
Titanium may be also incorporated to the cored wire because it is effective to produce fine crystalline structures which serve to provide an improved impact-resistant property under low temperature. However, the titanium may be omitted because it is possible to obtain a satisfactory impact-resistant property around minus 100C. Where the Ti content is greater than 0.5 percent, there will be a decrease in the toughness due to an increase in the silicon content in the weld metal.
~0~30309 Nickel, molybdenum and titanium in the core material may be incorporated in the welding electrode in the form of ferrous alloy thereof, for example Fe-Ni, Fe-Mo and Fe-Ti.
Fe-Ni, Fe-Mo or Fe-Ti may be incorporated to the electrode in the above mentioned amount calculated in term of nickel, molyb-denum or titanium. It is of course that nickel, molybdenum or titanium may be added to the electrode in the form of elementary metal.
It has been found that, when a submerged arc welding using the aforementioned flux and welding electrode of cored wire is applied to 3.5% Ni containing steel, it is possible to pro-duce a weld metal having an excellent toughness at low tempera-tures. It should be noted, however, that the submerged arc welding process in accordance with the present invention can also be applied to other types of nickel containing steel such as 3.5% Ni containing steel. Further, it should also be noted that the welding conditions may suitably be selected in prac-tice.
The present invention will now be described by way of examples.
Examples:
Butt welding operations were performed in specimens of 3.5% Ni containing steel (ASTMA 203D) of 25 mm thick with a welding current of 600 A under 40 V and a welding speed of 40 cm/min. to form multiple layers of weld metal. The operations were performed in accordance with conventional process as well as in accordance with the present invention. In the welding operations, metal sheets were shaped to have edges sloped by an angle of 20 degrees, and a pair of such sheets were placed at a minimum distance of 10 mm.
The welded specimens were subjected to tests for weld-ing defects. The specimens were then formed with V-shaped notches _ g _ 1~80309 and subjected to Charpy impact test at minus 100C. The results are shown in the following table.
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10~0309 In the above table, the wire composition designates the constituents of core material in weight percentages with respect to the wire as a whole. Mild steel in the Table had a composition by weight, of 0.06 percent of carbon, 0.50 percent of manganese and the balance of iron. In the table, it will be noted that the specimen A shows unsatisfactory toughness because the welding employed a melt type flux with a low basicity. The specimen B shows blow holes due to insufficient deoxydization because the flux does not contain silicon. The specimen C does not have a satisfactory toughness because the process employed for for the specimen uses a welding electrode of solid wire which did not provide adequate amount of oxygen~ The specimen D shows unqatisfactory toughness due to insufficient nickel content.
The specimen E has blow holes due to insufficient deoxydization because the flux used for the specimen had lower basicity.
The specimens J through N which have been welded in accordance with the present invention show satisfactory impact resistance under low temperature. In the specimen L, the flux did not contain Si but deoxydization was effected due to the existence of Ti.
The specimen F had blow holes which have produced due to insufficient content of CaF2 in the welding wire. The speci-men G had been welded with a welding wire containing excessive amount of nickel. As the result, the weld metal did not possess a satisfactory toughness. ~he ~pecimen H had been welded with the welding wire containing excessive titanium and as the result the weld metal had insufficient toughness. The specimen I had unacceptable appearance of welded beads due to excessive amount of CaF2 in the welding wire.
The invention has thus been shown and described with reference to examples but it should be noted that modifications may be made without departing from the scope of the appended claims.
., . . ......................... .. -.:
Claims (11)
1. A submerged arc welding process for welding nickel con-taining steel with a welding electrode in the presence of a flux, said welding process being characterized in that;
A. said welding electrode is a cored wire consisting of a mild steel and core material, the core material including, on the basis of weight to the total weight of the welding electrode, 5 to 25 percent of CaF2, 2.5 to 5.5 percent of nickel, 0 to 0.5 percent of Mo, 0 to 0.5 percent of Ti, and B. said flux is bond type flux having a composition of, by weight percent, 10 to 30 percent of SiO2, 8 to 20 percent Al2O3, 25 to 45 percent of MgO, 10 to 30 percent of CaO, 7 to 20 percent of CaF2, and at least one member selected from the group consist-ing of metallic Si, Fe-Si, and Fe-Si-Mn, the amount of Si in all cases being 0.6 percent or less calcu-lated in terms of metallic Si, and having a basicity B higher than 1.5, the basicity being defined on the basis of weight by the following equation:
A. said welding electrode is a cored wire consisting of a mild steel and core material, the core material including, on the basis of weight to the total weight of the welding electrode, 5 to 25 percent of CaF2, 2.5 to 5.5 percent of nickel, 0 to 0.5 percent of Mo, 0 to 0.5 percent of Ti, and B. said flux is bond type flux having a composition of, by weight percent, 10 to 30 percent of SiO2, 8 to 20 percent Al2O3, 25 to 45 percent of MgO, 10 to 30 percent of CaO, 7 to 20 percent of CaF2, and at least one member selected from the group consist-ing of metallic Si, Fe-Si, and Fe-Si-Mn, the amount of Si in all cases being 0.6 percent or less calcu-lated in terms of metallic Si, and having a basicity B higher than 1.5, the basicity being defined on the basis of weight by the following equation:
2. A submerged arc process as claimed in claim 1, wherein said electrode consists of a mild steel hoop turned over to form an elongated tube, and the core material is contained in the space defined by the turned mild steel hoop.
3. A submerged arc welding process as claimed in claim 2, wherein said mild steel hoop has a composition of, by weight percent, less than 0.15 percent of C, less than 1.0 percent of Mn and the balance consisting essentially of Fe except the inevit-able amount of impurities.
4. A submerged arc welding process as claimed in claim 2, wherein said core material consists essentially of CaF2, metal-lic Ni, Fe-Mo, and Fe-Ti.
5. A submerged arc welding process as claimed in claim 1, wherein said nickel containing steel contains about 3.5 per-cent by weight of nickel.
6. A submerged arc welding process for welding steel con-taining nickel comprising welding the steel with a welding elec-trode in the presence of a bond-type flux, (a) said welding electrode being a cored wire consisting of a mild steel and a core material, the core material containing, in percent by weight based on the total weight of the welding electrode, from 5 to 25 percent of CaF2, from 2.5 to 5.5 percent of Ni, from 0 to 0.5 percent of Mo, and from 0 to 0.5 percent of Ti; and (b) said bond-type flux having a composition containing, in percent by weight, from 10 to 30 percent of SiO2, from 8 to 20 percent of Al2O3, from 25 to 45 percent of MgO, from 10 to 30 percent of CaO, from 7 to 20 percent of CaF2, and at least one deoxidizing agent selected from the group consisting of metallic Si, Fe-Si, Fe-Si-Mn, metallic Mn, and Fe-Mn, the amount of Si in all cases being 0.6 percent or less calculated in terms of metallic Si, said flux having a basicity (B) higher than 1.5, the basicity being defined, on a weight basis, by the following equation;
thereby to produce a weld metal having a high impact-resistant property at a temperature below minus 100°C, and having a silicon content not exceeding 0.20%, a carbon content not exceeding 0.08%, and an oxygen con-tent not exceeding 400 ppm.
thereby to produce a weld metal having a high impact-resistant property at a temperature below minus 100°C, and having a silicon content not exceeding 0.20%, a carbon content not exceeding 0.08%, and an oxygen con-tent not exceeding 400 ppm.
7. The process of claim 6 wherein the welding electrode consists of a mild steel hoop turned over to form an elongated tube, and the core material is contained in the space defined by the turned mild steel hoop.
8. The process of claim 7 wherein the mild steel hoop contains, in percent by weight, less than 0.15% of carbon, less than 1.0% of manganese, with the remainder consisting essent-ially of iron.
9. The process of claim 6 wherein the nickel, molybdenum, and titanium are each present in the core material in its metallic form or in the form of its ferrous alloy.
10. The process of claim 9 wherein the core material consists essentially of CaF2, metallic Ni, Fe-Mo, and Fe-Ti.
11. The process of claim 6 wherein the steel contains about 3.5% by weight of nickel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA274,358A CA1080309A (en) | 1977-03-21 | 1977-03-21 | Submerged arc welding process for nickel containing steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA274,358A CA1080309A (en) | 1977-03-21 | 1977-03-21 | Submerged arc welding process for nickel containing steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1080309A true CA1080309A (en) | 1980-06-24 |
Family
ID=4108205
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA274,358A Expired CA1080309A (en) | 1977-03-21 | 1977-03-21 | Submerged arc welding process for nickel containing steel |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1080309A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114227063A (en) * | 2021-12-23 | 2022-03-25 | 锦州公略焊接技术有限公司 | Welding wire for submerged arc welding, welding flux and preparation method thereof, submerged arc welding material and application thereof, welding joint and welding method |
-
1977
- 1977-03-21 CA CA274,358A patent/CA1080309A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114227063A (en) * | 2021-12-23 | 2022-03-25 | 锦州公略焊接技术有限公司 | Welding wire for submerged arc welding, welding flux and preparation method thereof, submerged arc welding material and application thereof, welding joint and welding method |
| CN114227063B (en) * | 2021-12-23 | 2023-08-11 | 锦州公略焊接技术有限公司 | Submerged arc welding material suitable for low-carbon high-manganese steel, preparation method, application and welding joint |
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