Disclosure of Invention
The technical problems solved by the invention are as follows: the gas shielded welding wire for the all-position automatic welding of the pipeline steel is provided, and the reasonable component ranges of C, Mn, Si, Ni, Mo, Ti and Ce elements are determined, so that when X80-grade pipeline steel is welded, weld metal has high strength, high low-temperature impact toughness, excellent welding process performance and good adaptability, the surfaces of the weld joints at different positions are smooth and uniform, and the appearance of the weld joint is attractive. The method is suitable for all-position welding of X80 grade pipeline steel, and is particularly suitable for girth welding of X80 grade pipeline steel.
The technical solution of the invention is as follows: a gas shielded welding wire for all-position automatic welding of pipeline steel comprises the following components in percentage by weight: 0.08 to 0.1 percent of C, 0.7 to 1.0 percent of Si, 1.6 to 2.5 percent of Mn, less than 0.010 percent of P, less than 0.005 percent of S, 0.5 to 1.0 percent of Ni, 0.2 to 0.4 percent of Mo, 0.04 to 0.1 percent of Ti, 0.1 to 0.4 percent of Ce0.1 to 0.4 percent of Fe and the balance of Fe. Wherein,
c is a main element for adjusting the strength of the weld metal, a certain content of C in the welding wire must be ensured, but the excessively high C element promotes the formation of high-carbon martensite, thereby influencing the crack resistance and impact toughness of the weld metal. Controlling the carbon element in a proper range is the basis for improving welding manufacturability and weld joint strengthening and toughening, and in a certain addition range of the C element, along with the increase of the C content, the arc stability is improved, the molten drop transition characteristic is improved, and the welding wire technological performance is improved, so that the C content in the welding wire is controlled within the range of 0.08-0.1%.
Mn is a welding wire strengthening element and a deoxidizing element, and oxides formed in the deoxidizing process can improve the strength and low-temperature impact toughness of weld metal and improve welding manufacturability. Mn is an austenite stabilizing element, the content of acicular ferrite in weld metal is obviously increased along with the increase of the content of Mn, the content of proeutectoid ferrite is reduced, the number of side plate bar ferrite is obviously reduced, and the acicular ferrite is refined, so that the content of Mn in the welding wire is controlled to be 1.6-2.5%.
Si is a deoxidizing element, the welding process performance is improved, the welding seam deposited metal strength is improved, when the Si content is low, the deoxidizing is insufficient, the oxygen content of the welding seam is too high, and the low-temperature impact toughness of the welding seam is affected; when a proper amount of Si element is added into the welding wire, the welding manufacturability of the welding wire can be improved, and the strength of welding seam metal can be improved; however, excessive Si element can harden the weld metal, reduce the low-temperature toughness of the weld metal, increase welding spatter and reduce the welding wire processing performance. The toughness of the deposited metal depends largely on the contents of Si and Mn, and the toughness may be lowered by too much or too little contents of Si and Mn. Therefore, the content of Mn and Si is in a proper range, which is beneficial to reducing the generation of non-metallic inclusions and improving the toughness, and the content of Si in the welding wire is controlled between 0.7 and 1.0 percent.
Ni is an element for improving the strength and low-temperature impact toughness of a welding line, the Ni can refine the structure to promote the formation of acicular ferrite, and plays an important role in strengthening the welding line metal, the influence of the Ni on the impact toughness in the welding line metal and the content of Mn have an interaction effect, and when the two elements are positioned in the optimal matching range, the corresponding welding line metal has excellent toughness matching, so that the addition of the Ni in the welding wire is determined to be 0.5-1.0% according to the addition of the Mn.
Mo can lower the phase transition temperature, inhibit the generation of proeutectoid ferrite, promote the transformation of acicular ferrite, increase the proportion of acicular ferrite and improve the precipitation strengthening effect of nitrides. Mo is in the range of 0.2-0.4% and is favorable for improving the obdurability, can change the gamma-alpha transformation characteristic, narrow the gamma-alpha transformation temperature range, reduce the amount of proeutectoid ferrite and obtain fine acicular ferrite.
Ti is an element for refining grains, and the addition of a proper amount of Ti has the effects of increasing the stability of an electric arc, improving the welding manufacturability and the welding seam structure of the welding wire and improving the low-temperature toughness of the material. Ti is added as a microalloy element at the same time, and the Ti and N in the parent metal form TiN particles during welding, so that not only can grains be refined, but also the formation of pro-eutectoid ferrite can be reduced, and the content of acicular ferrite is increased, therefore, the content of Ti is 0.04-0.1%.
The addition of a proper amount of rare earth element Ce can improve the size and the form of inclusions such as sulfide and the like in a welding seam, reduce the number of inclusions such as columnar crystals and reticular dendritic crystals and the like, purify the welding seam structure, refine crystal grains, improve the impact toughness of the welding seam and improve the welding process performance of the welding wire. The content of the rare earth element Ce in the welding wire components is 0.1-0.4.
S and P are harmful impurity elements, the impact toughness and the stress corrosion resistance of the weld metal are reduced, the content of the S and the P is strictly controlled to ensure that S, P in the weld metal is at a lower level, and the S is controlled to be less than 0.005 and the P is controlled to be less than 0.010 in the invention S, P.
The invention has the advantages and beneficial effects that:
1. the invention contains lower C element, higher Mn and Ni, proper amount of Si and Mo elements, and enlarges the transformation area of the acicular ferrite by adding Ti element, increases the acicular ferrite in the prior austenite crystal, thereby stably obtaining a large amount of acicular ferrite in the welding line. The comprehensive action of each element and rare earth elements enables the welding seam to achieve higher strength, good low-temperature impact toughness and good welding process performance.
2. The deposited metal of the invention has the following mechanical properties: the tensile strength (Rm) is more than or equal to 715MPa, the yield strength (Rel) is more than or equal to 625MPa, the elongation (A) is more than or equal to 22 percent, and the impact energy is more than or equal to 140J (-30 ℃).
3. The invention has good adaptability. The welding device is suitable for all-position welding of X80 grade pipeline steel, and is particularly suitable for semi-automatic welding and all-position automatic welding of X80 grade pipeline steel girth weld gas shield welding. The invention is applied to the pipeline circular weld automatic welding machine produced by the middle petroleum pipeline bureau to carry out the circular weld all-position welding test, the welding process performance is excellent, the electric arc stability, the all-position operation performance and the weld forming are good, the appearance of the circular weld is good, the shooting is qualified, and the mechanical property meets the welding technical specification of Q/SY-GJX0110 west two-line pipeline engineering lines.
4. The invention can replace the imported welding wire, can obviously save the construction cost of long-distance oil and gas conveying pipelines and generate great economic benefit.
The specific implementation mode is as follows:
the method adopts desulfurized molten iron, controls the sulfur content of the molten iron entering the furnace, selects raw materials with low S, P content, adopts converter steelmaking and top-bottom combined converting processes, controls C, S, P at the smelting end point at a lower level, adopts external refining processes such as an LF furnace and the like after deoxidation alloying, smelts molten steel with components meeting requirements, fully protects and casts the molten steel into continuous casting billets through a variety casting machine, and the continuous casting billets are rolled into wire rods with phi 4mm through a high-speed twistless rolling machine. The wire rod is made into finished welding wires with the diameter of 1.0mm, the diameter of 0.9mm or other specifications through shelling, acid cleaning, wire drawing and copper plating.
The first embodiment of the invention:
1. the welding wire comprises the following chemical components in percentage by weight (the balance being Fe):
2. the welding process comprises the following steps: the welding protective gas is argon-rich mixed gas of 80% Ar and 20% CO2. The welding current is 270A, the welding voltage is 29V, the welding speed is 30cm/min, and the gas flow is 20L/min. And (3) welding the deposited metal into six layers, wherein each layer has 8-10 welding lines, the welding line energy of backing welding is 16KJ/cm, the welding line energy of filling welding is 13.5KJ/cm, and the interlayer temperature is kept at about 150 ℃.
The experimental welding wire has good process performance, stable welding electric arc, small splashing, suitability for all-position welding, beautiful welding bead forming, no welding defects of air holes, slag inclusion, incomplete fusion and the like of a welding seam.
3. Mechanical property of welding wire deposited metal test: the deposited metal welding test is carried out according to the GB/T8110-2008 'carbon steel and low alloy steel welding wire for gas shielded arc welding'. Tensile, impact and metallographic specimens were prepared from the deposited metal according to standard requirements.
The mechanical properties of the deposited metal are as follows: the tensile strength (Rm) is 725MPa, the yield strength (Rel) is 660MPa, the elongation (a) is 23.4%, and the average impact energy is 149J (-30 ℃).
The second embodiment of the invention:
1. the welding wire comprises the following chemical components in percentage by weight (the balance being Fe):
composition (I) |
C |
Mn |
Si |
S |
P |
Mo |
Ni |
Ce |
Ti |
Content (wt.) |
0.9 |
1.88 |
0.92 |
0.0036 |
0.0075 |
0.28 |
0.82 |
0.26 |
0.085 |
2. The welding process comprises the following steps: the welding protective gas is argon-rich mixed gas of 80% Ar and 20% CO2. The welding current is 270A, the welding voltage is 29V, the welding speed is 30cm/min, the gas flow is 20L/min, six layers of deposited metal are welded, 8-10 layers of deposited metal are welded, the welding line energy of backing welding is 16KJ/cm, and the welding line energy of filling welding is 13.5KJ/cm, and the interlayer temperature is kept at about 150 ℃.
The experimental welding wire has good process performance, stable welding electric arc, small splashing, suitability for all-position welding, beautiful welding bead forming, no welding defects of air holes, slag inclusion, incomplete fusion and the like of a welding seam.
3. Mechanical property of welding wire deposited metal test: the deposited metal welding test is carried out according to the GB/T8110-2008 'carbon steel and low alloy steel welding wire for gas shielded arc welding'. Tensile, impact and metallographic specimens were prepared from the deposited metal according to standard requirements.
The mechanical properties of the deposited metal are as follows: tensile strength (Rm) 715MPa, yield strength (Rel) 625MPa, elongation (a) 22.4%, and average impact energy 140J (-30 ℃).
The invention has good process performance, stable welding electric arc, small splashing, no air hole, beautiful welding bead forming, is suitable for all-position welding and can be widely used for the field welding of the X80 pipeline steel girth weld.
The above-mentioned embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and therefore, all equivalent changes made by the contents of the claims of the present invention should be included in the claims of the present invention.