Low-alloy high-strength and high-toughness submerged-arc welding electrode

The invention relates to a welding material, in particular to a Mn low silicon micro-alloy submergedarc welding wire, is mainly used for submerged-arc welding, is especially suitable for large-scale steel bridges, the welding of the structure.

The bridge, a ship, a large-scale structure such as large pressure container, relatively thick steel plate, joint forms, large weld bead, the environmental temperature is low, the welding joint requires higher impact toughness and crack resistance, the welding material the very high requirements.

Over the past ten years, the International Ti, B micro-alloying wire. Ti, B the mechanism of action of the: solution in austenite grain boundary precipitation B, the grain boundary can reduce, inhibit the precipitation of the pro-eutectoid ferrite. The weld seam and oxide TiN of cementite of a ferrite core, to promote the formation of the ferrite, the toughness of the weld metal. These welding wire with: 1992 years 2 by steel research Institute of metallurgical industry of such applications, "low carbon micro-alloyed submerged-arc welding wire", Patent application number 92105621.4 and 1982 years 1 month of the British Patent application GB   2090615 " the micro molybdenum or does not have the molybdenum welding material". These welding wire adopts C-Mn-Mo-Ti-B, C-Mn-Mo-Cr-Ti-B, series alloy such as C-Mn-Cr-Ti-B, are in different extent satisfying the using requirements joint performance, but they have the disadvantages that: toughness are still low, particularly in the high input energy welding, or post-weld heat treatment under the condition of eye candidate, marked decline in low-temperature toughness. If the weld seam is C-Mn-Ti-B the welding wire 2, together, the weld metal -40   V-shaped impact for merit approximately[...] 80J, and when the weld seams are 4 when together, is lowered to 29J. Although welding seam welding C-Mn-(Mo)-Cr-Ti-B improved performance after heat treatment, but it is still difficult to the toughness of the steel material and the advanced phase matching, it is difficult to meet welding requirements the actual structure. These welding wire used for the welding energy 20KJ the left and right a welding of sheet metal, plate thickness ≥ 35 mm welding not see application, and welding wire in Mn, Mo, the content of alloy elements such as Cr to, in general, relatively high, it is difficult to simultaneously maintain good weld strength and toughness, elements of the alloy and the cost of the welding wire is also greatly improved.

The purpose of this invention is to provide a kind of suitable for large line energy welding, the welding performance of the submerged arc welding wire; the wire to the welding groove angle of a thick steel plate and welding the adaptability of a relatively strong energy, without preheating before welding, to need no heat treatment after welding, the welding technique of good performance; suitable for bridge, ship, pressure container, making the welding of large-scale structure.

The invention, in order to achieve the above-mentioned goal, offer a kind of alloy high-strength high-toughness submerged-arc welding wire, which is characterized in that the chemical composition of the welding wire containing C according to the weight (%)   0.06-0.12, Mn   1.20-1.80, Si0 . 02-0.06, Ni   0.20-0.50, Ti   0.10-0.16, B   0.006-0.010, the rest are Fe and unavoidable S, P, also need to strictly control the welding wire, content. Welding wire S can not be avoided, the content of P is S≤ 0.01 (weight %)requirement, P  [...] 0.015, ≤ 0.005.

Chemical composition of the welding wire of the invention possesses the following is a description of the design principle of:

C content of less than 0.06%, , welding wire strength is relatively low, the proportion of ferrite in the weld metal is relatively high, is not conducive to the formation of the acicular ferrite, more than 1.2% strength of the weld metal will be too high, pearlite ratio is increased, a large amount of acicular ferrite is also not conducive to forming.

Weld Si containing Si should be in the amount of 0.4% the following, in the flux and the base metal contains a relatively high Si, Si phenomenon in the course of welding is relatively serious, should therefore be the content of Si in the control wire, the control content of 0.02-0.06% the most suitable.

Mn is an effective element to strengthen the weld, weld metal in the Mn content is less than 1.0%, the, weld strength on the low side, in the Mn content is higher than 1.6% time, low-temperature toughness of the weld metal is obviously reduced. In favour of the weld seam Mn deoxydize, hot crack preventing the formation of iron sulfides. In the content of Mn to control the welding seam, the content of Mn should be in the welding wire in 1.20-1.80% between.

Ni can improve the toughness of the weld metal, in particular the low-temperature impact toughness of the weld metal, reducing the brittle transition temperature. Mn and Ni at the same time can be in a quite large in the content range of favorable for improving the toughness of the weld metal. However, because it belongs to a valuable element is are advised to doga, the Ni content in the welding wire 0.20-0.50% between.

Ti added weld metal organization can be thinned. N Ti and with extremely high affinity, with Ti TiN N the mass formed by the binding, as a crystal nucleus, to form fine acicular ferrite a large amount. The content of the weld metal in the Ti 0.01-0.04% between, because the Ti excessive coefficient is low, the content of Ti should be in the welding wire 0.10-0.16%.

B B solid solution of the austenite grain boundary segregation, reducing grain boundary energy, control the precipitation of the pro-eutectoid ferrite. B also be postponed austenite-ferrite phase transition temperature, to promote the formation of the acicular ferrite within the crystal grains. The increase in the number of acicular ferrite, low-temperature toughness of the weld metal will be obviously improved. The content of the welding seam B in general in 0.001-0.004%, since the excessive coefficient is low, the welding wire B content of 0.006-0.01%.

S, P element to a low-temperature toughness of the weld metal with the function, should be reduced as much as possible. S ≤ 0.01 for welding wire, P  [...] 0.015 (weight %).

N smelts dries builds up in the course of the welding wire, can be avoided not N in the molten steel to enter the welding wire, the metal of the welding seam has a greater impact on the low-temperature toughness, however, when the Ti processing when welding the welding seam as alloy elements, the element becomes necessary N, welding wire N should be in the content of less than 0.005%.

To summarize: C appropriately reduced, the content of Mn, Si content is controlled, reducing S, P, proper addition of Ni, Ti, is B Mn-Ni-Ti-B series. The weld strength appropriate, refinement austenitic, ferritic organization, the organization of reducing embrittlement (such as non-metal inclusions) and solution N, the quantity of the acicular ferrite eventual increase, improve low-temperature toughness of the weld metal.

The welding wire of the invention possesses Mn-Ni-Ti-B series alloy used, stable the smelting process of welding wire is easy to realize, the lower cost of the welding wire.

Welding wire of the present invention has the following remarkable effects:

1. By this invention the weld metal of the welding wire to weld with good comprehensive performance, with higher tensile strength and low-temperature impact toughness and excellent anti-crack performance.

2. Welding wire of the present invention is particularly suitable for high-energy welding, even if the energy reaches 44KJ/cm, weld -40 the impact work [...] remains very high, reaching 111J, is far higher than the other wire impact work. The welding energy and the welding groove type adaptability, without preheating before welding, to need no heat treatment after welding, to the process conditions of actual production. The ideal is the large-scale structure of welding of the welding material.

3. Welding wire of the present invention can be used for single-layer or multi-layer, single-sided or multi-plane multiple technological requirements and welding of various thickness.

4. Welding wire of the present invention simple component design, the Mn alloy element, does not have high content of Ni, welding wire low cost, stable the smelting process, is easy to produce, is easy to be popularized.

Welding wire of the present invention is suitable for the bridge, the oil pipeline, such as large pressure container the welding of the structure.