IE42201B1 - Welding and a steel suitable for use therein - Google Patents

Abstract

1532217 Steel alloy BRITISH STEEL CORP 12 Dec 1975 [12 Dec 1974] 53806/74 Addition to 1475072 Heading C7A A steel alloy, suitable for consumable welding rod or wire, contains C 0À15 max Mn 0À5-1À5 Si 0À03-0À10 MO less than 0À2 Al 0À05 max Ti 0À03-0À05 B 0À002-0À008 S 0À04 max P 0À04 max Fe Bal & impurities The manufacture of the wire may be by standard techniques, with the Al, Ti and B being added last. The rod or wire may be coated with up to 0À15 wt. per cent of copper, and is suitable in submerged arc or electro-slag welding. Preferably, a basic type of flux is used in welding to reduce oxidation and erosion and improve conductivity.

Description

This invention relates to welding, especially submerged arc welding and similar welding techniques, and to steel which is suitable for use as a consumable in welding processes.

British Patent Specification 1,475,072 5 is directed to a steel suitable for use as a welding consumable having low carbon and silicon contents and containing titanium,boron, and molybdenum as essential components. That steel has the following percentage composition : Carbon 0.15 maximum Manganese 0.5 - 1.5 Silicon 0.03 - 0.10 Molybdenum - 0.2 - 0.6 Aluminium' 0.05 maximum Titanium 0.03 - 0.05 Boron 0.002 - 0.008 Sulphur and Phosphorus: Each 0.04 maximum Iron and incidental impurities: balance We have now found that a steel suitable for use as a welding consumable cart be produced which does not require 20 molybdenum to be present at 0.2% or above but which is otherwise similar in composition.

According to the present invention there is provided a steel of the following percentage composition:Carbon : 0.15 maximum, preferably 0.10 maximum Manganese : 0.5-1.5 Silicon : 0.03-0.10 Molybdenum ; less than 0.2 4220] Aluminium: 0.05 max Titanium: 0.03-0.05 Boron: 0.002 - 0.008 Sulphur and Phosphorus: Each 0.04 max, preferably 0.03 max Iron and incidental impurities: balance Hie quantity of manganese present is chosen according to the desired strength of the final weld metal.

The aluminium is only present in consequence of its use as a deoxidant in the steelmaking process. It will normally be present in an amount of at least 0.02% for this reason. However, aluminium contents below 0.025% and more especially 0.02% and below, have been found to give the better weld properties.

The titanium content is very important as it produces additional weld pool deoxidation, promotes the formation of smaller globular inclusions and protects the boron present from the action of oxygen and nitrogen.

Some boron must be present uncombined. It is preferred that the uncombined, or free, boron should be present in an amount of at least 0.0002%. Ihe actual minimum amount of total boron required to be present in the steel will therefore depend on the amount which will be combined with oxygen and nitrogen, but it is considered that a minimum of 0.002% boron will usually result in sufficient free boron remaining in the steel. Low levels of oxygen and nitrogen in the steel are correspondingly desirable.

The type of steelmaking process chosen is not considered - 3 4220 1 to be important. It is preferred to make the steel lacking aluminium, titanium and boron, and to add these elements subsequently in that order. Ihe steel is killed, or deoxidised, principally with the aluminium, the titanium can remove a large part of any residual oxygen, and the boron is then finally added.

Ihe Invention additionally provides a welding consumable comprising a wire or rod formed of the steel of the invention, preferably provided with a thin coating of copper. The consumable in the form of wire or rod can be conveniently fed to the weld.site. Ihe copper coating improves electrical contact between the wire and the electrical power supply and also protects the wire against corrosion.

Ihe wire will preferably be of a diameter between 1 mm and 8 mm. The amount of copper coating on the wire is suitably up to 0.15% by weight of the wire, the practical upper limit being that amount which results in the quantity of copper being transferred to the weld metal having a detrimental effect on its properties.

The Invention further provides a method of welding, especially submerged arc welding or electroslag welding, wherein the consumable comprises the steel of the Invention or a wire or rod formed of such steel. The welding method Is otherwise conventional.

If the flux used is an acid flux there will be a tendency for the titanium and boron to oxidise and for silicon and manganese to transfer from the flux to the weld - 4 42201 pool. A basic £lux Is therefore preferred to reduce oxidation and silicon and manganese transfer.

In the following examples, Examples 1 and 2 Illustrate the Invention, while Example 3 relates to the use of a standard carbon-manganese weld wire and Is Included for comparison purposes only.

In all the examples a pair of plates to BS 4360 500 were joined by submerged arc welding with a commercially available basic flux containing the following components in the percentages specified - SlOjj 13·?, MnO, 0.1; 1*29; Al^, 19.6; CaO, 12.58; MgO, 29;0; T102, 0.5; K20, 0.76; Na20, 0.42; CaF2, 18.0; L102, 0.32; Zr203 , 1.58. The plate thickness was 1.5» (38.1 mm).

The analyses of the test plate used for all welds, of the weld wires used and of the weld metal produced arc shown in Table 1.

All welds were made with a D.C. arc and the consumable electrode polarity- was positive, although welds with a negative electrode are also possible.

Totaln 0 c _kA_ 1 .0035 .0117 cn o .035 .035 .031 t-i <0 UZ o [*- CM CM o> · m vO tn m m cn 1 o o O O o o © o o o o o · · • • • . tn CM r- co m I O‘ t-t t—1 t-i o o o O © © o \Z \/ in m vO 00 CO o o. O i—1 o z O o o O o o 1 * ν' tn tn 00 co o o o t—i CQ I o o «-1 •t-i o © 00 o o •ri 2: .- · * tai L η vO in m m I ό r*i t-i t—I o o o o © © CM tn n n CM CM t-i t—i t-i S O © o o o • o © \O co vO vO r^- vO CM o co o o o r-i CO o © o o © o O • • * m * [·> o o Γ-. ft t—i o o r-i I—i t—i o o o o . © O O • - » • • « • *. CO iO CO CM o o Q o O 00 cn Ov © 2 • • • • • - r_l «-i •H tn \O r·'. CM cn CO CO CO CO O CM t—I . t-i r*1 CM - · · * • * iA CM CO vO m Ό t-i m 00 Γ-- r* o t-i O t—t o O © o * • * * Cfl Q> r—1 CM CU a r-i . CO t-i CM CM co (0 Φ r-i Φ 0) Φ Φ r-i r-i t-i t—1 Hcm I—I < ft Q« a e CU sjy cu ε Ίϊ «9 £ & a «a S3 & Φ t— 4J (1) 03 ct5 M u ω ft 5 s 4J X) Ό « i-H t-i ω JD vO I 43201 Example 1 A weld was made with a heat Imput of 72 Kj/in. (2.8Kj/mm) The weld was tested for notch toughness (Charpy V-notch method) and tensile properties in the as-welded condition and in the stress-relieved condition.

Example 2 A weld was made with a high heat input of 164 KJ/in (6.42 KJ/tnm). A two-sided fully commercial welding procedure was used and mechanical tests were carried out on samples extracted from both sides of the welded joint, in the as-welded condition.

Example 3 A weld was made for comparision in an identical manner as in Example 1 with the same heat input of 72KJ/in (2.8 KJ/mm) using the conventional weld wire. Impact properties and tensile properties were measured in the as-welded and in the stressrelieved conditions. 320 1 The measured tensile properties of the welds are shown In Table 2.

TABLE 2 0.27. Proof Stress N/mrn^ Ultimate Tensile Stress N/mni Elongation X Seduction of Area X Example 1 As welded 488 543 28 70 Stress, relieved 383 463 31 76 Example 2 Side 1 (as welded) 478 558 24 69 Side 2 (as welded) 443 541 26 69 Example 3 As welded 445 488 28 72 Stress relieved 414 506 32 77 The Impact properties of the welds, measured In Joules, are shown in Table 3. 4230 J TABLE 3 Impact Test Temperature -65°C -60°C -40°C -20°C 0°C L5°C 20°C Example 1 As welded 88 - 219 230 234 - 229 Stress relieved - - 88 96 215 - - Example 2 Side 1 (as welded) - 42 90 129 L58 - Side 2 (as welded) - 50 141 144 L55 - Example 3 As welded - 18 38 44 60 - 100 Stress relieved - 20 41 60 80 - 135 The accompanying drawings are graphs comparing the impact performance of the welds in the as-welded and stress relieved conditions. Figure 1 compares the welds of Examples 1 and 3 in the as-welded condition. Figure 2 compares the same two welds in the stress-relieved condition. Figure 3 compares the welds of Examples 1 and 2 in the as-welded condition, illustrating the effect of the higher heat input In Example 2. It can be seen from the graphs that the impact properties at lower temperatures achieved with the wire according to the invention are much superior to those given by the standard carbon-manganese wire. '

Claims (12)

1. CLAIMS:1. Steel having the following percentage composition: ίο Carbon Manganese: Silicon:· Molybdenum Aluminium: Titanium: Boron: Sulphur: Phosphorus: 0.15 maximum 0.5 - 1.5 0.03 - 0.10 less than 0. 2. 0.05 maximum 0.03 - 0.05 0.002 - 0.008 0.04 maximum 0.04 maximum Iron and incidental impurities: Balance.

.2. Steel as claimed in claim 1 in which the carbon content is not more than 0.10%

3. Steel as claimed in claim 1 or claim 2 in which the aluminium content is not more than 0.025%.

4. Steel as claimed in claim 1 or claim 2 in which the aluminium content is not more than 0.020%.

5. Steel as claimed in any one of the preceding claims 20 in which the sulphur and phosphorus contents are each not more than 0.03%. b. Steel as claimed in any one of the preceding claims in which uncombined boron is present in an amount of at least 0.0002%. - 10 42201

6. 7. A welding consumable comprising a wire Formed of a steel, as claimed in any one of the preceding claims. K. Λ welding consumable as claimed in claim 7 provided with a thin coating of copper up to about 0.15% by weight of the wire,

7. 9. A method of welding steel wherein the welding consumable comprises a steel as claimed in any one of claims 1 to 6.

8. 10. A method of submerged arc welding wherein a consumable electrode comprising a steel as claimed in any one of claims 1 to 6 is melted under a basic flux.

9. 11. A method of welding with a consumable electrode comprising a steel as claimed in any one of claims 1 to 6 wherein the formed weld is subsequently subjected to stress relieving.

10. 12. Steel, as claimed in claim 1 substantially as hereinbefore described with reference to the examples.

11. 13· A welding consumable as claimed in claim 6 substantially as hereinbefore described with reference to the examples·

12. 14. A method of welding steel as claimed in claim 9 substantially as hereinbefore described with reference to the examples.