A welding wire coil, welding wire and welding process suitable for pipeline steel in hydrogen environment

Abstract

The application discloses a welding wire coil for pipeline steel used in hydrogen environment, which contains Fe and inevitable impurity elements, and also contains the following chemical elements with mass percentage as follows: C: 0.04-0.08%, Mn: 0.8-1.2%, Si: 0.6-0.9%, Cr: 0.1-0.2%, Cu: 0.1-0.2%, Nb: 0.05-0.07%. The application also discloses a welding wire for pipeline steel used in hydrogen environment, which is prepared by using the welding wire coil. The welding wire for pipeline steel used in hydrogen environment has excellent strength and toughness, and has good hydrogen embrittlement resistance.

Description

Technical Field

[0001] This invention relates to a welding wire rod, welding wire, and welding process, and more particularly to a welding wire rod, welding wire, and welding process for pipeline steel. Background Technology

[0002] With the rapid development of hydrogen energy, X52 pipelines are being used in hydrogen transportation. Existing patent literature already relates to this field, for example:

[0003] Chinese patent document CN101128273A, published on February 20, 2008, entitled "High-strength welded steel pipe with excellent resistance to hydrogen embrittlement cracking of weld metal and its manufacturing method", discloses a high-strength welded steel pipe with excellent resistance to hydrogen embrittlement cracking of weld metal and its manufacturing method. The key to the manufacturing method of the welded steel pipe, which involves seam welding from the inner and outer surfaces and then expanding or shrinking the pipe, is to control the hydrogen concentration in the weld metal at room temperature below 0.2cc / 100g, thereby achieving excellent resistance to hydrogen embrittlement of the weld joint.

[0004] Chinese patent document CN1833046A, published on September 13, 2006, entitled "Steel for Hydrogen Environment, Structural Mechanical Components and Manufacturing Method Thereof", discloses a steel for hydrogen environment, a structural mechanical component and manufacturing method thereof. It uses steel containing 0.3 to 30% Cr as the base material and sets an oxide film with a thickness of more than 100 nm on the surface of the base material, thereby possessing excellent resistance to hydrogen embrittlement.

[0005] Chinese patent document CN1796588A, published on July 5, 2006, entitled "Ultra-high strength thin steel sheet with excellent resistance to hydrogen embrittlement and machinability," discloses an ultra-high strength thin steel sheet with excellent resistance to hydrogen embrittlement and machinability. The sheet, by mass%, satisfies the following: C: 0.25–0.60%, Si: 1.0–3.0%, Mn: 1.0–3.5%, P: less than 0.15%, S: less than 0.02%, Al: less than 1.5% (excluding 0%), with the remainder consisting of iron and unavoidable impurities. The microstructure after tensile processing with a processing rate of 3% satisfies the following: the area ratio of the entire microstructure is: retained austenite ≥ 1%, bainite, ferrite, and martensite totaling ≥ 80%; ferrite and pearlite totaling ≤ 9% (including 0%), and the average axial length (long axis / short axis) of the retained austenite grains is ≥ 5, with a tensile strength of ≥ 1180 MPa. Summary of the Invention

[0006] One of the objectives of this invention is to provide a welding wire rod for pipeline steel suitable for hydrogen environments. The welded joints obtained by the welding wire prepared from this rod not only have high tensile strength and ductility at room temperature, but also have excellent resistance to hydrogen embrittlement.

[0007] To achieve the above objectives, the present invention provides a pipeline steel welding wire rod suitable for hydrogen environments, which contains Fe and unavoidable impurity elements, and further contains the following chemical elements in the following mass percentages:

[0008] C: 0.04 to 0.08%, Mn: 0.8 to 1.2%, Si: 0.6 to 0.9%, Cr: 0.1 to 0.2%, Cu: 0.1 to 0.2%, Nb: 0.05 to 0.07%.

[0009] Furthermore, in the pipeline steel welding wire rod described in this invention, the mass percentage content of each chemical element is as follows:

[0010] C: 0.04–0.08%, Mn: 0.8–1.2%, Si: 0.6–0.9%, Cr: 0.1–0.2%, Cu: 0.1–0.2%, Nb: 0.05–0.07%, with the balance being Fe and unavoidable impurities.

[0011] Compared with existing equal-strength welding wires, the pipeline steel welding wire rods of this invention have significant differences in element and composition control.

[0012] In this invention, a micro-Nb alloy system is employed, with small amounts of Nb and Cu elements added while strictly controlling the content of S and P elements. Due to the different metallurgical principles used, the alloy element ratios and their functions differ in this invention. The elements and their ratios used in this invention not only achieve conventional performance indicators but also exhibit superior resistance to hydrogen embrittlement. The design principles of each chemical element are as follows:

[0013] C: In the pipeline steel welding wire rod described in this invention, a certain amount of carbon (C) is essential to achieve the required strength grade. Simultaneously, the carbon is fixed in stable Cr, Ti, and Nb-containing carbides, which is beneficial for hydrogen resistance. However, when the mass percentage of carbon is too high, it will severely damage the toughness of the deposited metal. Therefore, in the pipeline steel welding wire rod described in this invention, the mass percentage of carbon is controlled between 0.04% and 0.08%.

[0014] Mn: In the welding wire rod for pipeline steel described in this invention, Mn is an important element for the strength and toughness of the deposited metal, and also plays a role in desulfurization and deoxidation during the molten pool process. Therefore, in order to ensure suitable strength, the mass percentage of Mn in the welding wire rod for pipeline steel described in this invention is controlled between 0.8% and 1.2%.

[0015] Si: In the pipeline steel welding wire rod described in this invention, an appropriate amount of Si can, on the one hand, help improve the fluidity of the weld pool during the weld pool stage, and on the other hand, help Si combine with oxygen to form inclusions that float to the surface, thereby reducing the oxygen content in the weld pool and playing a deoxidizing role. Si can also work in conjunction with Mn to refine the weld microstructure and improve toughness. Therefore, in the pipeline steel welding wire rod described in this invention, the mass percentage of Mn is controlled between 0.6% and 0.9%.

[0016] Cr: In the pipeline steel welding wire rod described in this invention, a certain amount of Cr element can be added to ensure that the weld metal has certain corrosion resistance and to control the proportion of ferrite structure. However, if the Cr element content is too high or too low, a good balance of strength and toughness cannot be achieved. Therefore, in the pipeline steel welding wire rod described in this invention, the mass percentage content of Cr element is controlled between 0.1% and 0.2%.

[0017] Cu: In the pipeline steel welding wire rod described in this invention, an appropriate amount of Cu can improve the corrosion resistance of the material without affecting the welding performance. Therefore, in the pipeline steel welding wire rod described in this invention, the mass percentage of Cu is controlled between 0.1% and 0.2%.

[0018] Nb: In the pipeline steel welding wire rod described in this invention, an appropriate amount of Nb can, on the one hand, strengthen and toughen the weld structure through grain refinement and dispersion strengthening; on the other hand, Nb can combine with carbon in the steel to form stable carbides, which act as intragranular hydrogen traps to capture hydrogen and enhance resistance to hydrogen embrittlement. Therefore, in the pipeline steel welding wire rod described in this invention, the mass percentage of Nb is controlled between 0.05% and 0.07%.

[0019] Furthermore, in the pipeline steel welding wire rod described in this invention, the mass percentage content of unavoidable impurity elements satisfies at least one of the following: P≤0.005%, S≤0.005%.

[0020] In this invention, unavoidable impurity elements are phosphorus (P) and sulfur (S), which can cause welding defects such as hot cracking. Therefore, in the pipeline steel welding wire rod described in this invention, in order to obtain a weld with high strength, the mass percentage of phosphorus is controlled to P ≤ 0.005%, and the mass percentage of sulfur is controlled to S ≤ 0.005%.

[0021] Furthermore, in the pipeline steel welding wire rod described in this invention, the grain boundaries of the microstructure of its deposited metal are proeutectoid ferrite, and the interior is dense and uniform lath ferrite.

[0022] Furthermore, in the pipeline steel welding wire rod described in this invention, the properties of its deposited metal satisfy the following: hydrogen diffusion coefficient <1.2×10⁻⁶. -6 cm 2 / s, and the surface adsorbed hydrogen concentration C0 < 12 μmol / cm 3 .

[0023] Furthermore, in the pipeline steel welding wire rod described in this invention, the properties of its deposited metal also meet the following requirements: tensile strength ≥ 540 MPa, elongation ≥ 27%, and impact toughness value at 0℃ ≥ 120 J.

[0024] Another object of the present invention is to provide a welding wire for pipeline steel suitable for hydrogen environments, which not only has excellent strength and toughness, but also has good resistance to hydrogen embrittlement.

[0025] To achieve the above objectives, the present invention provides a pipeline steel welding wire suitable for hydrogen environments, which is made from the above-mentioned pipeline steel welding wire rod.

[0026] Furthermore, in the welding process of the pipeline steel welding wire described in this invention, the welding heat input is controlled to be 5-11 kJ / cm.

[0027] Furthermore, in the welding process of the pipeline steel welding wire described in this invention, no preheating is performed before welding, and / or no heat treatment is performed after welding.

[0028] Furthermore, in the welding process of the pipeline steel welding wire described in this invention, gas metal arc welding is adopted, and the welding current is controlled at 210-260A, the welding voltage at 22-28V, and the welding speed at 40-75cm / min.

[0029] The welding wire rod, welding wire, and welding process for pipeline steel suitable for hydrogen environments described in this invention have the following advantages and beneficial effects:

[0030] The welded joints prepared from welding wire rods for pipeline steel suitable for hydrogen environments, as described in this invention, not only have high tensile strength and ductility at room temperature, but also excellent resistance to hydrogen embrittlement.

[0031] The welding wire for pipeline steel suitable for hydrogen environments described in this invention can be widely used in the welding of pipeline steel, especially in the welding of X52 pipeline pipes.

[0032] The pipeline steel welding wire process for hydrogen environments described in this invention does not require preheating before welding and does not require heat treatment after welding, which can ensure that the weld will not crack. Attached Figure Description

[0033] Figure 1 The microstructure of the tube body after welding with the welding wire of Embodiment 1 of the present invention is shown.

[0034] Figure 2 The image shows the microstructure of the heat-affected zone after welding an X52 pipe body using the welding wire of Embodiment 1 of the present invention.

[0035] Figure 3 The image shows the microstructure of the weld seam after welding using the welding wire of Embodiment 1 of the present invention. Detailed Implementation

[0036] The following will further explain and illustrate the welding wire rod, welding wire, and welding process for pipeline steel suitable for hydrogen environments, as described in this invention, with reference to specific accompanying drawings and embodiments. However, this explanation and illustration do not constitute an undue limitation on the technical solution of this invention.

[0037] Examples 1-5

[0038] Table 1 lists the mass percentage of each chemical element in the welding wire rods of Examples 1-5.

[0039] Table 1.

[0040] serial number C Mn Si Cr Cu Nb P S Example 1 0.07 1.2 0.9 0.11 0.2 0.06 0.005 0.003 Example 2 0.08 0.8 0.6 0.11 0.10 0.05 0.005 0.005 Example 3 0.05 1.2 0.8 0.2 0.15 0.05 0.004 0.004 Example 4 0.04 0.8 0.6 0.10 0.12 0.07 0.005 0.003 Example 5 0.05 1.0 0.6 0.15 0.13 0.07 0.004 0.004

[0041] The welding wire rods in Examples 1-5 can all be prepared using the following steps:

[0042] The steel ingot is heated to 1200-1250℃ in a vacuum heating furnace and held for 1.5-3 hours. After being cooled in the furnace to 1050-1100℃, it is taken out and forged into a Ф55mm square billet or round billet. It is then heated to 700-800℃ and drawn into a Ф5.5~6.5mm wire rod. Finally, the wire rod is drawn into a Ф1.2mm welding wire.

[0043] The welding wires obtained in Examples 1-5 were used to perform GMAW (Gas Metal Arc Welding) welding on X52 (outer diameter 457 mm, wall thickness 20.6 mm), and the mechanical properties of the deposited metal were tested. The test results are listed in Table 2. Among them:

[0044] Mechanical property testing: GB / T 25774-2010 Inspection of Welding Materials Part 1: Preparation and testing methods of mechanical properties test specimens of steel, nickel and nickel alloy weld metals.

[0045] Table 2 lists the mechanical properties of the weld metal deposited by the welding wires of Examples 1-5 of the present invention.

[0046] Table 2.

[0047]

[0048] Note: In Table 2 above, the test results for yield strength, tensile strength, elongation and reduction of area are in two columns, which are the test results of two samples under the corresponding embodiment. The test results for 0℃ impact toughness are in three columns, which are the test results of two samples under the corresponding embodiment.

[0049] As can be seen from Table 2 above, the tensile strength of the welding wires in Examples 1-5 is ≥540MPa, the elongation is ≥27%, and the impact toughness at 0℃ is ≥120J, thus exhibiting high tensile strength and ductility.

[0050] Metallographic preparation was performed on the welded pipe body, the heat-affected zone, and the weld. After etching with 4% HNO3 alcohol, the microstructure was observed using a metallographic microscope.

[0051] Figure 1 The microstructure of the tube body after welding with the welding wire of Embodiment 1 of the present invention is shown.

[0052] like Figure 1 As shown, the microstructure of the X52 tube body in Embodiment 1 of the present invention mainly includes polygonal ferrite and pearlite.

[0053] Figure 2 The image shows the microstructure of the heat-affected zone after welding an X52 pipe body using the welding wire of Embodiment 1 of the present invention.

[0054] like Figure 2 As shown, the Mao islands in the welding heat-affected zone of Embodiment 1 of the present invention are mostly distributed inside the ferrite matrix, and the ferrite grains are relatively uniformly distributed.

[0055] Figure 3 The image shows the microstructure of the weld seam after welding using the welding wire of Embodiment 1 of the present invention.

[0056] like Figure 3 As shown, the weld microstructure of Embodiment 1 of the present invention consists of proeutectoid ferrite at the grain boundaries and dense, uniform lath ferrite within the grains.

[0057] The welding wires prepared in Examples 1-5 were used again to perform gas metal arc welding on X52 (outer diameter 457mm, wall thickness 20.6mm), and the specific welding process parameters are shown in Table 3.

[0058] Table 3 lists the welding process parameters for Examples 1-5 of the present invention.

[0059] Table 3.

[0060]

[0061] It should be noted that in this invention, preheating is not required before welding, and heat treatment is not required after welding.

[0062] Hydrogen permeation tests were conducted on the welded joints obtained based on the welding wires of Examples 1-5. After the hydrogen permeation tests, the apparent hydrogen diffusion coefficient D and the steady-state current density I were calculated. ≦ The surface adsorbed hydrogen concentration C0 was measured, and the results are recorded in Table 4. Among them:

[0063] Hydrogen permeation test: Three ping-pong paddle-shaped samples with a diameter of 35 mm were used as working electrodes. Before the experiment, the samples were progressively sanded and mechanically polished with sandpaper, cleaned with alcohol and deionized water, and nickel was plated on the anode side of the samples. The nickel plating solution was Watts bath (250 g / L NiSO4·7H2O + 45 g / L NiCl2·6H2O + 40 g / L H3BO4), and the nickel plating current was 10 mA / cm. 2 The time is 2 minutes. The purpose of nickel plating is to prevent the sample from being corroded by the anolyte solution and to promote the ionization of hydrogen at the hydrogen release end (preventing atomic hydrogen from recombinating into molecular hydrogen and promoting H to become H). + In the experiment, the area of ​​the hydrogen-permeable sample exposed to the solution was 3.14 cm². 2 .

[0064] Connect the hydrogen release electrolysis cell to the terminals and inject sufficient 0.1 mol / L NaOH solution into the cell. Use a Gamry electrochemical workstation to measure the open-circuit potential of the sample for 3600 s. Then, polarize the sample surface at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, and record the curve of the anolyte current changing over time using the electrochemical workstation. Once the background current drops below 200 nA, inject a 0.1 mol / L NaOH hydrogen-charging solution into the cathodic electrolysis cell and immediately apply a constant cathodic hydrogen-charging current (current density × area exposed in the solution). Record the time when the cathodic current is first applied. After the current stabilizes, continue testing for a period of time, then end the experiment. Obtain the hydrogen permeation curve and calculate the apparent hydrogen diffusion coefficient D and steady-state current density I based on the curve.∞ The surface adsorbed hydrogen concentration C0. A larger D indicates faster hydrogen diffusion and easier access to defect sites, and a higher steady-state current density I. ∞ The larger the surface, the more hydrogen passes through the sample in a stable state. The larger the C0, the higher the concentration of hydrogen adsorbed on the surface, and the higher the risk of hydrogen embrittlement.

[0065] Table 4 lists the apparent hydrogen diffusion coefficient D and steady-state current density I of Examples 1-5 of the present invention. ≦ and surface adsorbed hydrogen concentration C 0。

[0066] Table 4.

[0067] serial number <![CDATA[Hydrogen diffusion coefficient D(10 -6 cm 2 / s)]]> <![CDATA[Steady-state current density I ∞ (μA / cm 2 )]]> <![CDATA[Surface adsorbed hydrogen concentration C0 (μmol / cm 3 )]]> Example 1 1.15 15.29 11.02 Example 2 0.81 10.19 10.43 Example 3 1.12 14.01 10.37 Example 4 1.01 7.01 5.75 Example 5 1.18 10.51 8.79

[0068] As can be seen from Table 4 above, the hydrogen diffusion coefficients of Examples 1-5 are all less than 1.2 × 10⁻⁶. -6 cm 2 / s, and the surface adsorbed hydrogen concentration C0 is less than 12 μmol / cm. 3 Therefore, it can be seen that the hydrogen diffusion coefficient of the welding wires in Examples 1-5 is lower than that of ordinary welded joints, and the surface adsorbed hydrogen concentration is also lower. This indicates that the welding technology provided by the present invention has better hydrogen resistance, can reduce the diffusion and accumulation of hydrogen inside the welded joint, and reduce hydrogen adsorption on the surface, thereby effectively reducing the risk of hydrogen embrittlement.

[0069] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0070] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A pipeline steel welding wire rod suitable for hydrogen environments, containing Fe and unavoidable impurity elements, characterized in that, It also contains the following chemical elements in the following percentages by mass: C: 0.04 to 0.08%, Mn: 0.8 to 1.2%, Si: 0.6 to 0.9%, Cr: 0.1 to 0.2%, Cu: 0.1 to 0.2%, Nb: 0.05 to 0.07%.

2. The pipeline steel welding wire rod as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: C: 0.04–0.08%, Mn: 0.8–1.2%, Si: 0.6–0.9%, Cr: 0.1–0.2%, Cu: 0.1–0.2%, Nb: 0.05–0.07%, with the balance being Fe and unavoidable impurities.

3. The pipeline steel welding wire rod as described in claim 1 or 2, characterized in that, The unavoidable impurity element mass percentage content must meet at least one of the following conditions: P ≤ 0.005%, S≤0.005％。 4. The pipeline steel welding wire rod as described in claim 1 or 2, characterized in that, The microstructure of the deposited metal consists of proeutectoid ferrite at the grain boundaries and dense, uniform lath ferrite within the grains.

5. The pipeline steel welding wire rod as described in claim 1 or 2, characterized in that, Its deposited metal properties meet the following requirement: hydrogen diffusion coefficient <1.2×10⁻⁶. -6 cm 2 / s, and the surface adsorbed hydrogen concentration C0 < 12 μmol / cm 3 .

6. The pipeline steel welding wire rod as described in claim 5, characterized in that, Its fused metal properties also meet the following requirements: tensile strength ≥540MPa, elongation ≥27%, and impact toughness at 0℃ ≥120J.

7. A welding wire for pipeline steel suitable for hydrogen environments, characterized in that, It is made from the wire rod for pipeline steel as described in any one of claims 1-6.

8. The welding process for pipeline steel welding wire as described in claim 7, characterized in that, The welding heat input is controlled at 5–11 kJ / cm.

9. The welding process as described in claim 8, characterized in that, No preheating is performed before welding, and / or no heat treatment is performed after welding.

10. The welding process as described in claim 8, characterized in that, Gas metal arc welding is used, with the welding current controlled at 210–260A, the welding voltage at 22–28V, and the welding speed at 40–75cm / min.

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