WO2017153762A1

WO2017153762A1 - A steel, a welding consumable and a cast steel product

Info

Publication number: WO2017153762A1
Application number: PCT/GB2017/050636
Authority: WO
Inventors: Richard Stanley Goodwin; Bernard Rafe Ernest GOODWIN; Stephen Roberts; Steven Charles BIRKS
Original assignee: Goodwin Plc
Priority date: 2016-03-09
Filing date: 2017-03-09
Publication date: 2017-09-14
Also published as: GB2548175B; GB201615882D0; GB2548175A

Abstract

A steel including, in mass %: 0.09 to 0.14% carbon; 0.20 to 0.50% silicon; 1.4% or less manganese; 0.045% or less sulphur; 0.04% or less phosphorus; 0.23 to 0.5% nickel; 0.5% or less chromium; 0.3% or less copper; 0.2% or less molybdenum; 0.020% or less niobium; 0.03% or less vanadium; the balance being iron and incidental impurities, wherein, at least one of conditions (i)-(iii) is satisfied: (i) silicon between 0.20 and 0.45%, manganese plus nickel greater than or equal to 1.5%, carbon multiplied by niobium less than or equal to 0.0015%, and sulphur less than or equal to 0.007%; (ii) three of the quantities of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the fourth quantity of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur not falling within condition (i) falls within a respective condition (a)-(d): (a) niobium multiplied by carbon is less than or equal to 0.0022%; (b) manganese plus nickel is greater than or equal to 1.35%; (c) silicon is less than or equal to 0.50%; and (d) sulphur is less than or equal to 0.007%; or (iii) silicon is between 0.25 to 0.33% and two of the quantities of manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the third quantity of manganese plus nickel, carbon multiplied by niobium and sulphur not falling within condition (i) falls within a respective condition (e)-(g): (e) niobium multiplied by carbon is less than or equal to 0.0022%; (f) manganese plus nickel is greater than or equal to 1.35%; and (g) sulphur is less than or equal to 0.009%.

Description

A Steel, a Welding Consumable and a Cast Steel Product

The present invention relates to a steel, a welding consumable, and a cast steel product. In particular the invention relates to carbon-manganese steels such as those falling under the designation ASTM A352/A352M-06(2012) LCC and welding

consumables suited for welding such castings.

For many years companies have been making Low temperature impact resistant carbon steel under ASTM A352 LCC which is specified to have impact resistance at -46°C of 20 J Average and 16 Joules minimum. However, the majority of Oil & Gas companies require an Average of 27J with a minimum single value of 20 Joules at -46°C.

The ASTM standard does not specify that the impact test material should be taken from a representative cross section of test bar as compared to the casting section thickness, which often results in unrepresentative test bars (small cross-section) being used to accept material that would not pass the ASTM impact test requirement if a cross-section test bar that was representative of the casting cross-section was impact tested.

The Norsok standard requirements (Norsok M630 material data sheet MDS-C12) for LCC are more stringent in that they call for 27J Av / 20 J Minimum single value and that the impact test bars should be taken from test bars of representative section thickness as the casting.

Historically many foundries have suffered from inconsistent impact test results which in turn have led to re heat treatment of castings and even then sometimes castings still failing to obtain the impact test results specified and the castings end up being scrapped. The end result of this is that deliveries of impact tested C-Mn steel castings are often late.

Research and development work has resulted in a greater understanding of the mechanism required to produce LCC material with consistently good impact properties that also exceed the minimum specified impact criteria by 250 to 550% or more thereby providing a far greater safety margin to end users and the ability to provide consistently better deliveries especially in thick wall components.

This information is of significant value to developing countries embarking on making impact resistant steels as there is no guide within the ASTM standard and in fact the openness of the ASTM standard composition range encourages foundries to produce poor quality cast maternal.

The present invention provides a welding consumable including, in mass %: 0.05 to 0.14% carbon; 0.20 to 0.50% silicon; 1.4% or less manganese; 0.045%) or less sulphur; 0.04%) or less phosphorus; 0.23 to 0.5% nickel; 0.5% or less chromium; 0.3%> or less copper; 0.2% or less molybdenum; 0.020%) or less niobium; 0.03% or less vanadium; the balance being iron and incidental impurities, wherein, at least one of conditions (i)-(iii) is satisfied: (i) silicon between 0.20 and 0.45%, manganese plus nickel greater than or equal to 1.5%, carbon multiplied by niobium less than or equal to 0.0015%), and sulphur less than or equal to 0.007%>; (ii) three of the quantities of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the fourth quantity of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur not falling within condition (i) falls within a respective condition (a)-(d): (a) niobium multiplied by carbon is less than or equal to 0.0022%>; (b) manganese plus nickel is greater than or equal to 1.35%; (c) silicon is less than or equal to 0.50%; and (d) sulphur is less than or equal to 0.007%>; or (iii) silicon is between 0.25 to 0.33% and two of the quantities of manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the third quantity of manganese plus nickel, carbon multiplied by niobium and sulphur not falling within condition (i) falls within a respective condition (e)-(g): (e) niobium multiplied by carbon is less than or equal to 0.0022%>; (f) manganese plus nickel is greater than or equal to 1.35%; and (g) sulphur is less than or equal to 0.009%).

The present invention provides a steel including or consisting of, in mass percent, 0.09 to 0.14% carbon; 0.20 to 0.50% silicon; 1.4% or less manganese; 0.045% or less sulphur; 0.04% or less phosphorus; 0.23 to 0.5% nickel; 0.5% or less chromium; 0.3% or less copper; 0.2% or less molybdenum; 0.020%) or less niobium; 0.03% or less vanadium; the balance being iron and incidental impurities,

wherein, at least one of conditions (i)-(iii) is satisfied: silicon between 0.20 and 0.45%, manganese plus nickel greater than or equal to 1.5%, carbon multiplied by niobium less than or equal to 0.0015%), and sulphur less than or equal to 0.007%>; (ii) three of the quantities of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the fourth quantity of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur not falling within condition (i) falls within a respective condition (a)-(d):

(a) niobium multiplied by carbon is less than or equal to 0.0022%;

(b) manganese plus nickel is greater than or equal to 1.35%;

(c) silicon is less than or equal to 0.50%; and

(d) sulphur is less than or equal to 0.007%; or

(iii) silicon is between 0.25 to 0.33% and two of the quantities of manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the third quantity of manganese plus nickel, carbon multiplied by niobium, and sulphur not falling within condition (i) falls within a respective condition (e)-(g):

(e) niobium multiplied by carbon is less than or equal to 0.0022%;

(f) manganese plus nickel is greater than or equal to 1.35%; and

(g) sulphur is less than or equal to 0.009%).

If one or more of conditions (i)-(iii) is met and adequate levels of nickel are present, then high impact results of 95J average / 70J single minimum at -50°C can be achieved.

The adoption of the optimum specific chemistry of the present invention controls on Si, Mn + Ni, C x Nb and S of the present invention result in the following:

1) Impact properties in ASTM A352/A352M-06(2012) LCC that achieve up to 180J average / 150J single minimum at -46°C and that still achieve the other required mechanical properties as specified in the ASTM specification.

2) Impact properties at -60 Deg C in ASTM A352/A352M-06(2012) that

consistently achieve the Norsok M630 material data sheet MDS-C12 requirements of 27J Av / 20 J Minimum single value.

This level of mechanical performance and safety margin has historically never been achievable with representative thickness test bars on a consistent basis. The present invention further provides for the use of the steel or welding consumable in a liquid petroleum gas (LPG) facility.

The present invention will now be described by way of non-limiting example with reference to the following drawings.

Figure 1 is a table of the range of composition for ASTM A352/A352M-06(2012)

Figure 2 is a table of compositions and impact strengths at -50°C of examples of the invention and comparative examples; and

Figure 3 is a table of significant values for the examples of Figure 2 falling within claim 1 (i);

Figure 4 is a table of significant values for an example of Figure 2 falling within claim 1 (ii);

Figure 5 is a table of significant values for the examples of Figure 2 falling within claim 1 (iii); and

Figure 6 is a table of a composition and impact strengths at -46°C and ½T for a larger specimen thickness than in Table 2.

The present invention relates to a steel with a composition which falls within ASTM A352/A352M-06(2012) and which has a tighter composition to increase low temperature impact resistance particularly in thick sections and at high depths, whilst maintaining the other physical requirements of ASTM A352/A352M-06(2012) such as yield, UTS and elongation.

The reasons for restricting the chemical composition of the steel of the present invention compared to ASTM A352/A352M-06(2012) will now be described. An explanation of the effect of additions which are not varied from the ASTM standard is omitted.

All percentages are weight percent unless otherwise indicated. The term

"consisting of is used herein to indicate that 100% of the composition is being referred to and the presence of additional components is excluded so that the percentages add up to 100%.

In the present invention, compared to A352/A352M-06(2012) the silicon content is relatively limited, the magnitude of the multiple of carbon and niobium is relatively limited, the sum of the amount of nickel and manganese is relatively high and the amount of sulphur is relatively limited. It has been found that a combination of low silicon content, low multiple of carbon and niobium, high sum of nickel and manganese and low sulphur content results in high impact properties at -50°C.

The following relationships have been found to achieve high impact toughness at - 50°C. It has been found that high impact toughness at -50°C also tends to lead to high impact toughness at -60°C.

BASE TARGET RANGE

(Parameters): Silicon is between 0.20% and 0.45%, manganese plus nickel is greater than or equal to 1.5%, and carbon multiplied by niobium is less than or equal to 0.0015%; Sulphur less than or equal to 0.007% and Nickel is between 0.23 and 0.50%.

IDEAL RANGE:

Si (0.20% to 0.25%), Mn + Ni (1.60 to 1.9%), C x Nb ( less than or equal to 0.0006), S (equal to or less than 0.005%) and Ni between 0.45 and 0.50%.

Wherein, at least one of conditions (1) to (3) below is satisfied:

(1) If all four parameters meet the base target range, then impact results of 951 average / 701 single minimum at -50°C can be achieved.

If three parameters meet the base target range, then the fourth parameter must meet one of the following parameters to achieve impact results of 951 average/ 701 single minimum at - 50°C :

(Nb x C) < 0.0022

(Mn + Ni) > 1.35

Si < 0.50%

S <0.007%

If Si is 0.25% to 0.33%, (i.e. much closer to the ideal range), and two other parameters meet the base target range, then the fourth parameter must meet one of the following parameters to achieve impact results of 951 average / 701 single minimum at -50°C:

(Nb x C) < 0.0022

(Mn + Ni) > 1.35

S < 0.009% The inventive steel has a composition falling within ASTM A352/A352M- 06(2012) as set out in Figure 1. The following is an explanation of preferable limits for certain elements.

Carbon (C)

Carbon is effective for strengthening the steel. An amount of carbon of 0.09% or more is required to achieve the required tensile strength. However, the amount of carbon is preferably limited to 0.14%> to achieve the required C x Nb level. Thereby the carbon amount is limited to 0.14%. In an embodiment, carbon is limited to 0.12% or less in order to keep the value of C x Nb low. For a welding consumable, is desirable to have an even lower carbon content. So a carbon range of 0.05%> to 0.14%, more desirably 0.06% to 0.14% or 0.05% to 0.12% or 0.06% to 0.12% is desirable for a welding consumable.

Silicon (Si)

Silicon is present as a deoxidizer. Silicon may be present up to 0.50%. A minimum amount of silicon of 0.20% or more is needed to ensure deoxidation. However, the presence of silicon can lead to a reduction in low temperature impact strength.

Therefore, preferably the amount of silicon is limited to 0.40% or less, more preferably to 0.30%) or less and most preferably to 0.25% or less. It is difficult to achieve silicon levels of below 0.20%) in practice in the foundry.

Nickel (Ni)

Nickel improves tensile strength and hardenability. Experiments have shown that increased nickel content improves impact resistance. Nickel is present at least 0.23% but experience of the inventors shows a level of at least 0.25% is desirable and in particular a minimum amount of nickel of 0.30% provides good impact strength, though increasing nickel to 0.35% is preferred. A more preferred minimum amount of nickel of 0.4% or more leads to higher impact resistance. However, best results are achieved at levels of nickel of 0.43% and above or even 0.45% and above. Nickel is limited to 0.5% or less by ASTM A352/A352M-06(2012)

Manganese (Mn)

In combination with nickel it has been found that an increased manganese content tends to improve impact resistance. Therefore, manganese is present at a preferred minimum of 1.15%. Nickel plus manganese is desirably at least 1.60%. Increasing nickel plus manganese even further mitigates for other elements not being in the optimal range or further increases impact strength. Therefore a level of nickel plus manganese of 1.65% or more or even 1.70% or higher is preferred. It is anticipated that a level of 1.80%) or more nickel plus manganese will give the very best impact performance. ASTM A352/A352M- 06(2012) limits nickel plus manganese to 1.9%.

Molybdenum (Mo)

An increased level of Mo of 0.08%> or above is desirable for hardenability and resistance to TE (temper embrittlement). Preferably Mo of >0.10% is desirable, and more preferably 0.12% to 0.20%.

Niobium (Nb)

Niobium is not referenced in the ASTM A352/A352M-06(2012). However, niobium, which is found in steel scrap and other raw materials used for melting, in trace amounts is detrimental to impact properties. The presence of niobium in amounts of greater than 0.015%> can lead to a reduction in the impact strength of the steel. Therefore, the amount of niobium is limited to 0.015%, more preferably niobium is limited to 0.012% or less or even to 0.010%> or less for best performance. A level of 0.015%> or less niobium is very low compared to most steels of this type manufactured, which normally have a level of at least 0.02% up to 0.03%> or more, though the precise level is often not controlled or reported because of niobium's prevalence at these concentrations. The ASTM specifications do not place any limitation on the level of niobium. In order to achieve a low niobium concentration, very low residual melt base such as Armco iron is required. As Nb is an active slag ingredient, special process controls and sequencing is required to eliminate the risk of cross contamination from previous heats.

Sulphur (S)

Sulphur may be present in steel under the ASTM A352/A352M-06(2012) standard up to 0.045%). Reducing sulphur to 0.015%> is seen as beneficial for low temperature impact resistance and so this is preferable. Limiting sulphur content even further say to 0.005%) or less is preferable.

If the sulphur is 0.005%> or less then the impacts will be at the higher end and if the sulphur is 0.006 to 0.01%> then the impacts will be at the lower end of the 100 to 180J average at -50°C.

Incidental Impurities Incidental impurities may be present, preferably each only up to a maximum of: titanium 0.020%, zirconium 0.020%, cobalt 0.10%, tungsten 0.010%, tin 0.03%, antimony 0.025% and arsenic 0.025%. Aluminium preferably should not exceed 0.05%. ASTM A352/A352M-06(2012) also sets individual limits for nickel, chromium, molybdenum, copper, vanadium (as "Specified Residual Elements") and requires the total to be less than 1.00% by mass. The lower the level of vanadium the better and limiting to below 0.02% is preferred as vanadium is detrimental to low temperature properties. Titanium is often used for deoxidation purposes. However, it is detrimental to low temperature impact properties and is therefore preferably limited to 0.015% or less.

Examples

Steels having the chemical composition shown in Figure 2 were prepared. Castings of 50 mm thickness were prepared. These castings were heat treated to the ASTM

A352/A352M-06(2012) specification. Charpy Impact tests were carried out using 10mm x 10mm x 55mm specimens to ASTM E23 Standard "Test methods for Notched Bar Impact Testing of Metallic Materials" revision 2012-C, at -50°C at half thickness and the results are given in figure 2.

As can be seen from figure 2 all of the examples have a composition falling within A352/A352M-06(2012) (figure 1). However, only examples which satisfy one of conditions (i)-(iii) (figures 3 to 5) achieve higher average impact strength.

Figure 6 shows a composition in the most preferred range, namely 0.20 to 0.25%

Si, 1.6 to 1.9% Mn + Ni, C x Nb < 0.0006, S < 0.005%, 0.45 to 0.50% Ni, 0.12 to 0.20% Mo, 0.09 to 0.12% C and Nb < 0.010%. The results show that at -46°C for 200mm test blocks impact strengths at ½T of 126,70,160 were achieved with an average of 119 J easily achieving the minimum required by ASTM A352 LCC at -46°C which has not been possible for such thick test pieces previously.

In the present invention an average impact strength at ½ T is preferably at least 60J, more preferably at least 100 J average and a minimum single of 45 J, more preferably at least 80 J or more as measured by ASTM E23, 2012-C at -46°C (and up to 100 mm thickness).

Claims

1. A steel including, in mass %: 0.09 to 0.14% carbon; 0.20 to 0.50% silicon; 1.4% or less manganese; 0.045%> or less sulphur; 0.04% or less phosphorus; 0.23 to 0.5% nickel; 0.5%) or less chromium; 0.3%> or less copper; 0.

2% or less molybdenum; 0.020%) or less niobium; 0.03%> or less vanadium; the balance being iron and incidental impurities,

wherein, at least one of conditions (i)-(iii) is satisfied: silicon between 0.20 and 0.45%, manganese plus nickel greater than or equal to 1.5%, carbon multiplied by niobium less than or equal to 0.0015%), and sulphur less than or equal to 0.007%>;

three of the quantities of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the fourth quantity of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur not falling within condition (i) falls within a respective condition (a)-(d):

(a) niobium multiplied by carbon is less than or equal to 0.0022%>;

(b) manganese plus nickel is greater than or equal to 1.35%;

(c) silicon is less than or equal to 0.50%; and

(d) sulphur is less than or equal to 0.007%>; or

silicon is between 0.25 to 0.33% and two of the quantities of manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the third quantity of manganese plus nickel, carbon multiplied by niobium and sulphur not falling within condition (i) falls within a respective condition (e)-(g):

(e) niobium multiplied by carbon is less than or equal to 0.0022%>;

(f) manganese plus nickel is greater than or equal to 1.35%; and

(g) sulphur is less than or equal to 0.009%).

The steel of claim 1, including 0.12% or less carbon.

3. The steel of claim 1 or 2, 0.25% or more nickel, preferably 0.30% or more nickel, more preferably 0.35% or more nickel, even more preferably 0.4% or more nickel, even more preferably 0.43% or more nickel and most preferably 0.45% or more nickel.

4. The steel of claim 1, 2 or 3, including 1.15% or more manganese.

5. The steel of any of claims 1-4, including 0.015%) or less niobium, preferably 0.012% or less niobium and more preferably 0.010% or less niobium.

6. The steel of any of claims 1-5, including 0.40% or less silicon, preferably 0.30%> or less and more preferably 0.25% or less.

7. The steel of any of claims 1-6, including 0.006%) or less sulphur, preferably 0.005%) or less sulphur.

8. The steel of any of claims 1-7, including manganese plus nickel between 1.6 and

I .9%, preferably between 1.65 and 1.9%, more preferably between 1.7 and 1.9% and most preferably between 1.8 and 1.9%.

9. The steel of any of claims 1-8, including carbon multiplied by niobium less than or equal to 0.0006%.

10. The steel of any of claims 1-9, including 0.08% or more molybdenum, preferably 0.10% or more molybdenum, more preferably 0.12% or more molybdenum.

I I . The steel of any of claims 1-10, wherein the steel is a steel in accordance with A352/A352M-06(2012).

12. The steel of any of claims 11-11, wherein an average impact strength at ½T is 60J Average or more, preferably 100 J Average or more and a minimum single 45 J or more, preferably 80J or more as measured by ASTM E23, 2012-C at -46°C.

13. A cast product or a welding consumable formed of a steel according to any of claims 1-13.

14. A welding consumable including, in mass %: 0.05 to 0.14% carbon; 0.20 to 0.50%> silicon; 1.4% or less manganese; 0.045%) or less sulphur; 0.04% or less phosphorus; 0.23 to

0.5%) nickel; 0.5% or less chromium; 0.3%> or less copper; 0.2% or less molybdenum; 0.020%) or less niobium; 0.03% or less vanadium; the balance being iron and incidental impurities,

wherein, at least one of conditions (i)-(iii) is satisfied:

(i) silicon between 0.20 and 0.45%, manganese plus nickel greater than or equal to 1.5%, carbon multiplied by niobium less than or equal to 0.0015%), and sulphur less than or equal to 0.007%>;

(ii) three of the quantities of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the fourth quantity of silicon, manganese plus nickel, carbon multiplied by niobium, and sulphur not falling within condition (i) falls within a respective condition (a)-(d):

(a) niobium multiplied by carbon is less than or equal to 0.0022%>; (b) manganese plus nickel is greater than or equal to 1.35%;

(c) silicon is less than or equal to 0.50%; and

(d) sulphur is less than or equal to 0.007%>; or

(iii) silicon is between 0.25 to 0.33% and two of the quantities of manganese plus nickel, carbon multiplied by niobium, and sulphur fall within the conditions of (i) and the third quantity of manganese plus nickel, carbon multiplied by niobium and sulphur not falling within condition (i) falls within a respective condition (e)-(g):

(e) niobium multiplied by carbon is less than or equal to 0.0022%>;

(f) manganese plus nickel is greater than or equal to 1.35%; and (g) sulphur is less than or equal to 0.009%).

15. The welding consumable of claim 14, including 0.12% or less carbon.

16. The welding consumable of claim 14 or 15, including 0.06% or more carbon.

17. The welding consumable of claim 14, 15 or 16, including 0.25% or more nickel, preferably 0.30% or more nickel, more preferably 0.35% or more nickel, even more preferably 0.4% or more nickel, even more preferably 0.43% or more nickel and most preferably 0.45% or more nickel.

18. The welding consumable of claim 14, 15, 16 or 17, including 1.15% or more manganese.

19. The welding consumable of any of claims 14-18, including 0.015%) or less niobium, preferably 0.012% or less niobium and more preferably 0.010% or less niobium.

20. The welding consumable of any of claims 14-19, including 0.40% or less silicon, preferably 0.30% or less and more preferably 0.25% or less.

21. The welding consumable of any of claims 14-20, including 0.006%) or less sulphur, preferably 0.005%) or less sulphur.

22. The welding consumable of any of claims 14-21, including manganese plus nickel between 1.6 and 1.9%, preferably between 1.65 and 1.9%, more preferably between 1.7 and 1.9% and most preferably between 1.8 and 1.9%.

23. The welding consumable of any of claims 14-22, including carbon multiplied by niobium less than or equal to 0.0006%).

24. The welding consumable of any of claims 14-23, including 0.08% or more molybdenum, preferably 0.10% or more molybdenum, more preferably 0.12% or more molybdenum.

25. The welding consumable of any of claims 14-24, wherein the steel is a steel in accordance with A352/A352M-06(2012).

26. The welding consumable of any of claims 14-27, wherein an average impact strength at ½T is 60J Average or more, preferably 100J Average or more and a minimum single 45J or more, preferably 80J or more as measured by ASTM E23, 2012-C at -46°C.

27. A welding consumable according to any of claims 14-26, wherein the welding consumable is a filler weld metal or a welding electrode.

28. A cast product substantially as hereinbefore described with reference to and/or illustrated in the accompanying drawings.

29. A welding consumable substantially as hereinbefore described with reference to and/or as illustrated in the accompanying drawings.

30. A steel substantially as hereinbefore described with reference to and/or as illustrated in the accompanying drawings.