GB2548175A

GB2548175A - A steel, a welding consumable and a cast steel product

Info

Publication number: GB2548175A
Application number: GB1615882.6A
Authority: GB
Inventors: Stanley Goodwin Richard; Rafe Ernest Goodwin Bernard; Roberts Stephen; Charles Birks Steven
Original assignee: Goodwin PLC
Current assignee: Goodwin PLC
Priority date: 2016-03-09
Filing date: 2016-09-19
Publication date: 2017-09-13
Anticipated expiration: 2036-09-19
Also published as: WO2017153762A1; GB2548175B; GB201615882D0

Abstract

A steel which comprises (by mass): 0.09-0.14 % carbon or 0.05-0.14 % carbon when forming a welding consumable, 0.20-0.50 % silicon, 1.4 % or less manganese, 0-0.009 % sulphur, 0-0.04 % phosphorus, 0-0.5 % nickel, 0-0.5 % chromium, 0-0.3 % copper, 0-0.2 % molybdenum, 0-0.020 % niobium and 0-0.03 % vanadium with the balance being iron and incidental impurities, wherein one of the following conditions is satisfied: (i) Silicon is between 0.20 and 0.45 %, manganese plus nickel at least 1.5 %, carbon multiplied by niobium 0-0.0015 % and 0-0.007 % sulphur. (ii) Three of the requirements set in (i) are met and the other satisfies the following: 0.20-0.50 % silicon, manganese plus nickel at least 1.35 %, carbon multiplied by niobium 0-0.0022 % and 0-0.007% sulphur. (iii) Silicon is between 0.25 and 0.33 %, two of three other requirements set in (i) are met and the other satisfies the following: manganese plus nickel at least 1.35 %, carbon multiplied by niobium 0-0.0022 % and 0-0.009% sulphur. The steel has a narrower composition range than ASTM A352/A352M-06(2012) LCC to increase low temperature impact resistance.

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; 0.5% or less 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; 0.5% or less 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%.

If one or more of conditions (i)-(iii) is met, then high impact results of 95 J 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 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); and

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

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%; and Sulphur less than or equal to 0.007%. IDEAL RANGE:

Si (0.20% to 0.25%), Mn + Ni (1.6 to 1.9%), C xNb (less than or equal to 0.0006) and S (equal to or less than 0.005%).

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 95J average / 70J single minimum at -50°C can be achieved. (2) If three parameters meet the base target range, then the fourth parameter must meet one of the following parameters to achieve impact results of 95J average/ 70J single minimum at -50°C : i) (Nb X C) < 0.0022 ii) (Mn + Ni) > 1.35 iii) Si < 0.50% iv) S <0.007% (3) 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 95J average / 70J single minimum at -50°C: i) (Nb X C) < 0.0022 ii) (Mn + Ni) > 1.35 iii) 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. A 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. 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%.

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 by the formation of carbides and/or intermetallic phases. 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.

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 Impnrities

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 then 1.00% by mass.

Examples

Steels having the chemical composition shown in Figure 2 were prepared. These castings were heat treated to the ASTM A352/A352M-06(2012) specification. Charpy Impact tests were carried out using lOmm x 10mm x 55mm specimens to ASTM E23 Standard “Test methods for Notched Bar Impact Testing of Metallic Materials” revision 20I2-C, at -50°C 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(20I2) (figure I). However, only examples which satisfy one of conditions (i)-(iii) (figures 3 to 5) achieve higher average impact strength.

In the present invention an average impact strength at '/2 T is preferably at least lOOJ average and a minimum single of 80 J or more as measured by ASTM E23, 20I2-C at -46°C.

Claims

1. 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; 0.5% or less 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%.

2. The welding consumable of claim 1, including 0.12% or less carbon.

3. The welding consumable of claim 1 or 2, including 0.06% or more carbon.

4. The welding consumable of claim 1, 2 or 3, including 0.4% or more nickel, preferably 0.43% or more.

5. The welding consumable of claim 1, 2, 3 or 4, including 1.15% or more manganese.

6. The welding consumable of any of claims 1-5, including 0.015% or less niobium, preferably 0.012% or less niobium and more preferably 0.010% or less niobium.

7. The welding consumable of any of claims 1-6, including 0.40% or less silicon, preferably 0.30% or less and more preferably 0.25% or less.

8. The welding consumable of any of claims 1-7, including 0.006% or less sulphur, preferably 0.005% or less sulphur.

9. The welding consumable of any of claims 1-8, including manganese plus nickel between 1.6 and 1.9%.

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

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

12. The welding consumable of any of the preceding claims, wherein an average impact strength at V2T is lOOJ Ave or more and a minimum single 80J or more as measured by ASTM E23, 2012-C at -46°C.

13. A welding consumable according to any one of the preceding claims, wherein the welding consumable is a filler weld metal or a welding electrode.

14. 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; 0.5% or less 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, carhon multiplied by niobium and sulphur not falling within condition (i) falls within a respective condition (e)-(g): niobium multiplied by carbon is less than or equal to 0.0022%; manganese plus nickel is greater than or equal to 1.35%; and sulphur is less than or equal to 0.009%.

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

16. The steel of claim 14 or 15, including 0.4% or more nickel, preferably 0.43% or more.

17. The steel of claim 14, 15 or 16, including 1.15% or more manganese.

18. The steel of any of claims 14-17, including 0.015% or less niobium, preferably 0.012% or less niobium and more preferably 0.010% or less niobium.

19. The steel of any of claims 14-18, including 0.40% or less silicon, preferably 0.30% or less and more preferably 0.25% or less.

20. The steel of any of claims 14-19, including 0.006% or less sulphur, preferably 0.005% or less sulphur.

21. The steel of any of claims 14-20, including manganese plus nickel between 1.6 and 1.9%.

22. The steel of any of claims 14-21, including carbon multiplied by niobium less than or equal to 0.0006%.

23. The steel of any of claims 14-22, wherein the steel is a steel in accordance with A352/A352M-06(2012).

24. The steel of any of claims 14-23, wherein an average impact strength at V2T is lOOJ Ave or more and a minimum single 80J or more as measured by ASTM E23, 2012-C at -46°C.

25. A cast product or a welding consumable formed of a steel according to any of claims 14-24.

26. A welding consumable according to claim 25, wherein the welding consumable is a filler weld metal or a welding electrode.

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

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

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