BR102016009658A2

BR102016009658A2 - processo para reduzir a porosidade de um cordão de solda usando um elétrodo t5 blindado fluxado, e, elétrodo t5 blindado fluxado

Info

Publication number: BR102016009658A2
Application number: BR102016009658A
Authority: BR
Inventors: M Keegan James
Original assignee: Lincoln Global Inc
Priority date: 2015-05-01
Filing date: 2016-04-29
Publication date: 2017-01-31
Also published as: JP2016209931A; KR20160130168A; US20160318115A1; DE102016005310A1; CN106077991A

Abstract

a invenção descrita aqui diz geralmente respeito a um processo melhorado na área de soldagem usando distâncias bico de contato-peça mais longas do que o recomendado acopladas com caudais de gás de proteção efetivamente reduzidos por adição de entre 0,25 ? 10 partes de pelo menos um agente de redução da porosidade à composição de elétrodos compreendendo uma escória à base de fluoreto de cal, selecionado do grupo consistindo em: (a) pelo menos um formador de nitreto metálico selecionado do grupo consistindo em ti, zr, ca, ba e al, incluindo suas ligas metálicas ou ligas que incorporam pelo menos um dos metais identificados, e adicionalmente em que, quando nenhum al está presente no pelo menos um formador de nitreto metálico, um composto de li está substituído; ou (b) pelo menos um metal de terra rara selecionado do grupo consistindo em la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, sc e y, incluindo combinações de (a) e (b).

Description

PROCESSO PARA REDUZIR A POROSIDADE DE UM CORDÃO DE SOLDA USANDO UM ELETRODO T5 BLINDADO FLUXADO, E, ELETRODO T5 BLINDADO FLUXADO

Technical Field [0001] The invention described herein pertains generally to an improved process for welding using longer than recommended contact-to-work-distances coupled with reduced shielding gas flow rates and welding compositions to achieve the same.

Background of the Invention [0002] When welding and joining heavy section plates using excessive contact-to-work-distance ("CTWD") in comparison to the recommended distance (e.g., as high as 2.5" when a recommended distance would be for example, 1H") and using excessive voltage (e.g., as high as 36 volts) and higher than recommended shielding gas rates (resulting in an effectively lowered shielding gas rate due to turbulence), all of the above resulting in internai weld bead porosity when using a T5 welding electrode.

[0003] Without being held to any one theory or mode of operation, it is believed that at least one of the causes of this porosity is excessive nitrogen in the molten weld puddle.

Summary of the Invention [0004] In accordance with the present invention, there is provided a process to reduce the porosity of a weld bead which is made outside of the recommended contact-to-work distance using a flux-cored shielded electrode comprising the step of adding at least one porosity reducer selected from the group consisting of (a) at least one metallic nitride former or (b) at least one rare earth compound to the electrode composition, the preceding "or" used in the disjunctive sense as well as combinations of (a) and (b) , the preceding "and" used in the conjunctive sense.

[0005] In one aspect of the invention, the at least one metallic nitride former is selected from the group consisting of Ti, Zr, Ca, Ba and Al, including metallic alloys thereof or alloys which incorporate at least one of the identified metais.

[0006] In another aspect of the invention, the metallic alloys of the at least one nitride former comprise an Al/Zr powder alloy (50/50) and a Ca/Si/Ba powder alloy (4-19% Ca / 45-65% Si / 8-18% Ba / 9% max Fe / 1% max Al).

[0007] It is further noted in yet another aspect of the invention, that the addition of a rare earth metal improves the nitriding characteristics. As used in this application, rare earth metais, often in the silicide or oxide form, include: a set of seventeen Chemical elements in the periodic table, specifically the fifteen lanthanides: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb & Lu; as well as Sc and Y. Scandium and yttrium are considered rare earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar Chemical properties. Despite their name, rare earth elements are - with the exception of radioactive promethium - relatively plentiful in Earth's crust. They tend to occur together in nature and are difficult to separate from one another. However, because of their geochemical properties, rare earth elements are typically dispersed and not often found concentrated as rare earth minerais in economically exploitable ore deposits.

[0008] In a further aspect of the invention, there is provided an electrode composition for a T5 flux-cored shielded electrode which meets H4 diffusible hydrogen leveis as illustrated in Table I. The electrode compositions which have a designation of T5, as used in this application, will be used with a CO2 shielding gas, although the electrodes may be used with a blend of CO2 and Ar to reduce spatter. It should be further noted that as used in this application, these electrodes have a lime-fluoride base slag (CaF2) .

Table I

[0009] What is described herein is a process to reduce the porosity of a weld bead which is made outside of the recommended contact-to-work distance using a flux-cored shielded T5 electrode, the weld made from the T5 electrode having a diffusible hydrogen as measured in mL/lOOg weld deposit of less than or equal to 4.0 comprising the step of: adding between 0.25 - 10 parts of at least one porosity reducing agent to the electrode composition comprising a lime-fluoride based slag, selected from the group consisting of: (a) at least one metallic nitride former selected from the group consisting of Ti, Zr, Ca, Ba and Al, including metallic alloys thereof or alloys which incorporate at least one of the identified metais, and further wherein when no Al is present in the at least one metallic nitride former, a Li compound is substituted; or (b) at least one rare earth metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y, including combinations of (a) and (b) .

[0010] In the above process, the Li compound is selected from the group consisting of LÍ2CO3 and LiF, preferably LiF. In the process, the metallic alloys of the at least one nitride former include an Al/Zr powder alloy and a Ca/Si/Ba powder alloy. In one aspect of the invention, the process of claim will include the addition of at least one rare earth metal is selected from the group consisting of cerium and lanthanum.

[0011] In composition, a flux-cored shielded electrode having a diffusible hydrogen in a weld derived from the electrode of less than or equal to 4.0 mL/lOOg weld deposit, the electrode comprising at least one porosity reducing agent, the electrode forming a lime-fluoride based slag, the at least one porosity reducing agent selected from the group consisting of (a) at least one metallic nitride former selected from the group consisting of Ti, Zr, Ca, Ba and Al, including metallic alloys thereof or alloys which incorporate at least one of the identified metais, and further wherein when no Al is present in the at least one metallic nitride former, a Li compound is substituted; or (b) at least one rare earth metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y, including combinations of (a) and (b).

[0012] The Li compound is selected from the group consisting of LÍ2CO3 and LiF, preferably LiF. The metallic alloys of the at least one nitride former include an Al/Zr powder alloy and a Ca/Si/Ba powder alloy. The at least one rare earth metal is preferably selected from the group consisting of lanthanum and cerium.

[0013] In another aspect of the invention, a process is described to reduce the porosity of a weld bead which is made outside of the recommended contact-to-work distance using a flux-cored shielded T5 electrode, said weld made from the T5 electrode having a diffusible hydrogen as measured in mL/lOOg weld deposit of less than or equal to 4.0 comprising the step of: adding between 0.25 - 10 parts of at least one porosity reducing agent to the electrode composition comprising a lime-fluoride based slag, the at least one porosity reducing agent comprising at least one rare earth metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y.

[0014] In the process the flux-cored shielded electrode further includes a Li compound selected from the group consisting of LÍ2CO3 and LiF, preferably LiF. The at least one rare earth metal is preferably selected from the group consisting of cerium and lanthanum.

[0015] In yet a further aspect of the invention, a flux-cored shielded electrode is described having a diffusible hydrogen in a weld derived from the electrode of less than or equal to 4.0 mL/lOOg weld deposit, the electrode comprising at least one porosity reducing agent, the electrode forming a lime-fluoride based slag, and wherein the at least one porosity reducing agent includes: at least one rare earth metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y.

[0016] The Li compound is typically selected from the group consisting of LÍ2CO3 and LiF, preferably LiF while the at least one rare earth metal is selected from the group consisting of lanthanum and cerium.

[0017] These and other objects of this invention will be evident when viewed in light of the drawing, detailed description and appended claims.

Brief Description of the Drawing [0018] Fig. 1 is a graph of nitrogen taken from single pass welds using different electrodes in which the weld bead was drilled two inches from the end of the end weld bead, and wherein the welding conditions employed were CTWD = 2.5"; Wire Feed Speed ("WFS") = 300 ipm; Voltage = 36v; Travei Speed = 11.9ipm; Amperage = -450 amps; a CO2 gas flow rate of 35 CFH; and a wire diameter of 3/32".

Detailed Description of the Invention [0019] The best mode for carrying out the invention will now be described for the purposes of illustrating the best mode known to the applicant at the time of the filing of this patent application. The examples and figure are illustrative only and not meant to limit the invention, which is measured by the scope and spirit of the claims.

[0020] Unless the context clearly indicates otherwise: the word "and" indicates the conjunctive; the word "or" indicates the disjunctive; when the article is phrased in the disjunctive, followed by the words "or both" or "combinations thereof" both the conjunctive and disjunctive are intended.

[0021] Porosity in the molten weld puddle may be caused by many factors, at least one of which includes the presence of excessive nitrogen. One approach to reduce the nitrogen leveis is to combine the nitrogen in the molten State. This is done by the addition of at least one metallic nitride former, e.g., addition of metallic Ti, Zr, Ca, Ba and Al, and metallic alloys thereof or alloys which incorporate at least one of the identified metais or by the addition of at least one rare earth mineral, or both additions. The nitride formers combine with the available nitrogen in solution and float out into the slag. There may be some nitrides present in the solid solution after the welding is complete. By using the compositions of the present invention, the amount of weld metal nitrogen was capable of being reduced by 25-55% as compared with the standard Lincoln Electric Company UltraCore® 75C flux- cored electrode product. In the absence of Al in the electrode, it is possible to substitute lithium carbonate (LÍ2CO3) and lithium fluoride (LiF), although it is noted that LÍ2CO3 absorbs water and tends to increase weld metal hydrogen content, therefore, it is not preferred.

[0022] The addition of LiF appears to impact the bali transfer size in the welding arc, in some instances, making the bali more spherical and provide additional shielding to the arc plasma that may further result in lowering the porosity.

[0023] Lincoln Electric's UltraCore® 75C is a T5 welding electrode designed for high deposition in the flat and horizontal positions achieving H4 diffusible hydrogen leveis. It is typically used for welding with 100% CO2 as a shielding gas for premium arc performance and bead appearance. The flow rate is recommended between 40-55 CFH.

[0024] As used in this application, a T5 welding electrode will include a T5 flux-cored shielded electrode which meets H4 diffusible hydrogen leveis as illustrated in Table II. The electrode compositions which have a designation of T5, as used in this application, will be used with a CO2 shielding gas, although the electrodes may be used with a blend of CO2 and Ar to reduce spatter. It should be further noted that as used in this application, these electrodes have a lime-fluoride base slag (CaF2) .

[0025] Additionally, as used in this application, the lime-based slag or CaF2, which forms will preferably comprise approximately 80% of the slag system.

[0026] As used in this application, the term "approximately" is within 10% of the stated value, except where noted.

[0027] Lincoln Electric UltraCore® 75C welding electrodes are typically sold in the following wire diameters listed in both inches and in parentheses, mm: 1/16" (1.6), 5/64" (2.0) and 3/32" (2.4). The mechanical properties as required per AWS A5.20/A5.20M (2005) are illustrated in Table II below.

Table II

[0028] The deposition composition as required per AWS A5.20/A5.20M (2005) is illustrated in Table III.

Table III

[0029] Typical operating procedures for the flat and horizontal welding position are as follows in Table IV.

Table IV

[0030] A comparative set of examples were made (see Table V) and a subset tested to illustrate decreased porosity as illustrated in Fig. 1.

Table V

[0031] In the above table, (S) represents a standard T5 welding electrode as sold by the Lincoln Electric Company and at least examples (1) through (4) exhibit reduced porosity. Examples (7) through (13) are anticipated to also exhibit reduced porosity. Examples (5) and (6) performed no better than a standard T5 flux cored shielded welding electrode. As illustrated in Fig. 1, when welding out of the recommended specifications illustrated in Table IV, the porosity was unacceptable.

[0032] In Fig. 1, samples 1-4 performed better than the standard T5 electrode (S) as well better than comparative test compositions 5-6, the compositions of which are found in Table IV, the best composition to date showing a 52% reduction in nitrogen in the weld metal as compared to the standard T5 electrode (S) . Samples 7-13 are anticipated to perform better than the standard electrode (S).

The inclusion of metallic nitride formers, e.g., the addition of at least one metallic Ti, Zr, Ca, Ba and Al, including metallic alloys thereof or alloys which incorporate at least one of the identified metais, into the standard composition UltraCore® 75C flux-cored electrode resulted in a reduced porosity attributable at least in part to nitrogen by between approximately 25-55% as compared with the standard UltraCore® 75C flux-cored electrode product. It is noted that UltraCore® 75C flux-cored electrodes do not pass the porosity test illustrated in the legend to Table VI. In the absence of Al in the electrode, it is possible to substitute lithium carbonate (LÍ2CO3) and lithium fluoride (LiF). A further set of experimental results are illustrated in Table VI.

Table VI (nominal percent fill is 25.5%) * WFS (ipm) = 300; CTWD (in) =2 H; Voltage = 36; Travei speed (ipm) = 11.9; current = 450 (approx.); gas flow rate (cfh) = 35 [0033] A further set of experiments are characterized in Table VII, illustrating the inclusion of rare earth metais, including rare earth silicides and oxides.

[0034] Table VII

Table VII (nominal percent fill is 25.5%) * WFS (ipm) = 300; CTWD (in) = 2 H; Voltage = 36; Travei speed (ipm) = 11.9; current = 450 (approx.); gas flow rate (cfh) = 35 (1> As used in this application, Rare Earth Silicide will have the approximate composition as illustrated in Table VIII .

[0035] Table VIII

[0036] In one specific analysis of Rare Earth Silicides, the following composition was experimentally determined as illustrated in Table IX.

[0037] Table IX

[0038] It is believed that the inclusion of at least one rare earth silicide and/or at least one rare earth oxide, preferably combinations thereof, improves the characteristics of the final weld product as illustrated in Table VII.

[0039] The best mode for carrying out the invention has been described for purposes of illustrating the best mode known to the applicant at the time. The examples are illustrative only and not meant to limit the invention, as measured by the scope and merit of the claims. The invention has been described with reference to preferred and alternate embodiments. Obviously, modifications and alterations will occur to others upon the reading and understanding of the specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

REIVINDICAÇÕES

Claims

1. PROCESSO PARA REDUZIR A POROSIDADE DE UM CORDÃO DE SOLDA USANDO UM ELETRODO T5 BLINDADO FLUXADO, a referida solda feita a partir do elétrodo T5 tendo um hidrogênio difusivel como medido em mL/100 g de depósito de solda de menos do que ou igual a 4,0, caracterizado por compreender o passo de: adição de entre 0,25 - 10 partes de pelo menos um agente de redução da porosidade à composição de elétrodos compreendendo uma escória à base de fluoreto de cal, selecionado do grupo consistindo em (a) pelo menos um formador de nitreto metálico selecionado do grupo consistindo em Ti, Zr, Ca, Ba e Al, incluindo suas ligas metálicas ou ligas que incorporam pelo menos um dos metais identificados, e adicionalmente em que quando nenhum Al está presente no pelo menos um formador de nitreto metálico, um composto de Li está substituído; ou (b) pelo menos um metal de terra rara selecionado do grupo consistindo em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc e Y; incluindo combinações de (a) e (b).

2. PROCESSO, de acordo com a reivindicação 1, caracterizado pelo composto de Li ser selecionado do grupo consistindo em LÍ2CO3 e LiF.

3. PROCESSO, de acordo com a reivindicação 2, caracterizado pelo composto de Li ser LiF. 0 processo de acordo com a reivindicação 1, caracterizado pelas ligas metálicas de pelo menos um formador de nitreto metálico compreenderem uma liga em pó de Al/Zr e uma liga em pó de Ca/Si/Ba.

4. PROCESSO, de acordo com a reivindicação 1, caracterizado por pelo menos um metal de terra rara ser selecionado do grupo consistindo em cério e lantânio.

5. PROCESSO, de acordo com a reivindicação 1, caracterizado pelo elétrodo T5 blindado fluxado compreender:

6. ELÉTRODO T5 BLINDADO FLUXADO, tendo um hidrogênio difusivel em uma solda derivada do elétrodo de menos do que ou igual a 4,0 mL/100 g de depósito de solda, caracterizado pelo elétrodo compreender pelo menos um agente de redução da porosidade, formando o elétrodo uma escória à base de fluoreto de cal, o pelo menos um agente de redução da porosidade selecionado do grupo consistindo em (a) pelo menos um formador de nitreto metálico selecionado do grupo consistindo em Ti, Zr, Ca, Ba e Al, incluindo suas ligas metálicas ou ligas que incorporam pelo menos um dos metais identificados, e adicionalmente em que quando nenhum Al está presente no pelo menos um formador de nítreto metálico, um composto de Li está substituído; ou (b) pelo menos um metal de terra rara selecionado do grupo consistindo em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc e Y, incluindo combinações de (a) e (b).

7. ELETRODO BLINDADO FLUXADO, de acordo com a reivindicação 6, caracterizado pelo composto de Li ser selecionado do grupo consistindo em LI2CO3 e LiF.

8. ELETRODO BLINDADO FLUXADO, de acordo com a reivindicação 7, caracterizado pelo composto de Li ser LiF.

9. ELETRODO BLINDADO FLUXADO, de acordo com a reivindicação 7, caracterizado pelas ligas metálicas de pelo menos um formador de nitreto metálico compreenderem uma liga em pó de Al/Zr e uma liga em pó de Ca/Si/Ba.

10. ELETRODO BLINDADO FLUXADO, de acordo com a reivindicação 7, caracterizado por pelo menos um metal de terra rara ser selecionado do grupo consistindo em lantânio e cério.

11. PROCESSO PARA REDUZIR A POROSIDADE DE UM CORDÃO DE SOLDA USANDO UM ELETRODO T5 BLINDADO FLUXADO, a referida solda feita a partir do elétrodo T5 tendo um hidrogênio difusível como medido em mL/100 g de depósito de solda de menos do que ou igual a 4,0, caracterizado por compreender o passo de: adição de entre 0,25 - 10 partes de pelo menos um agente de redução da porosidade à composição de elétrodos compreendendo uma escória à base de fluoreto de cal, compreendendo o pelo menos um agente de redução da porosidade pelo menos um metal de terra rara selecionado do grupo consistindo em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc e Y;

12. PROCESSO, de acordo com a reivindicação 11, caracterizado pelo elétrodo blindado fluxado compreender adicionalmente: um composto de Li selecionado do grupo consistindo em LI2CO3 e LiF.

13. PROCESSO, de acordo com a reivindicação 12, caracterizado pelo composto de Li ser LiF.

14. PROCESSO, de acordo com a reivindicação 13, caracterizado por pelo menos um metal de terra rara ser selecionado do grupo consistindo em cério e lantânio.

15. ELÉTRODO BLINDADO FLUXADO, tendo um hidrogênio difusivel em uma solda derivada do elétrodo de menos do que ou igual a 4,0 mL/100 g de depósito de solda, caracterizado pelo elétrodo compreender pelo menos um agente de redução da porosidade, formando o elétrodo uma escória à base de fluoreto de cal, e em que o pelo menos um agente de redução da porosidade compreende: pelo menos um metal terra rara selecionado do grupo consistindo em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc e Y.

16. ELÉTRODO BLINDADO FLUXADO, de acordo com a reivindicação 15, caracterizado por compreender adicionalmente: um composto de Li é selecionado do grupo consistindo em LI2CO3 e LiF.

17. ELÉTRODO BLINDADO FLUXADO, de acordo com a reivindicação 16, caracterizado pelo composto de Li ser LiF.

18. ELETRODO BLINDADO FLUXADO, de acordo com a reivindicação 17 caracterizado por pelo menos um metal de terra rara ser selecionado do grupo consistindo em lantânio e cérío.