Super high strength gas protection welding wire containing V and manufacturing method therefor

Abstract

Provided is a superhigh strength gas shielded welding wire containing V, the mass percentage contents of the chemical elements thereof being: 0.08-0.12% of C, 0.65-0.80% of Si, 1.80-1.95% of Mn, 0<Cu0.25%, 0.20-0.40% of Cr, 0.2-0.6% of Mo, 1.30-1.80% of Ni, 0.08-0.20% of Ti, 0.01-0.05% of V, 0.0070-0.0130% of N, and the balance of Fe and other inevitable impurities. Also provided is a method for manufacturing the welding wire. A weld metal obtained after welding with said welding wire has a higher strength and toughness, and also has a good crack resistance, weldability and plasticity.

Claims

1. A superhigh strength gas shielded welding wire containing V, characterized in that a mass percentage contents of chemical elements of the superhigh strength gas shielded welding wire are: 0.08-0.12% of C, 0.65-0.80% of Si, 1.80-1.95% of Mn, 0<Cu 0.25%, 0.20-0.40% of Cr, 0.2-0.6% of Mo, 1.30-1.80% of Ni, 0.08-0.20% of Ti, 0.01-0.05% of V, 0.0070-0.0130% of N, and a balance of Fe and other inevitable impurities, wherein the superhigh strength gas shielded welding wire containing V is characterized by further satisfying 0.20%Cr+Cu0.42%, and wherein the superhigh strength gas shielded welding wire containing V has a tensile strength R.sub.m of 909-1022 MPa.

2. The superhigh strength gas shielded welding wire containing V of claim 1, characterized by further satisfying 0.46%Cr+V+Mo0.88%.

3. The superhigh strength gas shielded welding wire containing V of claim 1, characterized by further satisfying 0.10%V+Ti0.22%.

4. The superhigh strength gas shielded welding wire containing V of claim 1, characterized in that an interpass temperature is controlled between 100 C. and 165 C., a welding heat input is 8-13 kJ/cm, and a weld surface structure of a deposited metal obtained from said superhigh strength gas shielded welding wire containing V is bainite.

5. The superhigh strength gas shielded welding wire containing V of claim 4, characterized in that the weld surface structure of said obtained deposited metal further comprises irregular ferrite in a volume fraction of 2-5%.

6. The superhigh strength gas shielded welding wire containing V of claim 1, characterized in that an interpass temperature is controlled between 100 C. and 165 C., a welding heat input is 8-13 kJ/cm, and structures of weld interpass heat affected zones of a deposited metal obtained from said superhigh strength gas shielded welding wire containing V are all lower bainite.

7. The superhigh strength gas shielded welding wire containing V of claim 1, characterized in that an interpass temperature is controlled between 100 C. and 165 C., a welding heat input is 8-13 kJ/cm, and a deposited metal obtained from said superhigh strength gas shielded welding wire containing V has precipitates, the precipitates being Ti(C,N) and V(C,N).

8. A method for manufacturing the superhigh strength gas shielded welding wire containing V of claim 1, characterized by comprising steps of smelting, refining, casting, hot rolling, slow cooling, spinning into wire rods, pickling, rough drawing, heat treatment, fine drawing and copper plating, wherein a heat treatment temperature in said heat treatment step is 680-720 C.

9. The superhigh strength gas shielded welding wire containing V of claim 1, characterized in that a deposited metal obtained from said superhigh strength gas shielded welding wire containing V has a tensile strength R.sub.m of 880-1060 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a microstructure photograph of a weld surface of a deposited metal obtained from a welding wire in Example 1.

(2) FIG. 2 is a microstructure photograph of a weld surface of a deposited metal obtained from a welding wire in Example 2.

(3) FIG. 3 is a metallographic image of the structure of a weld interpass heat affected zone of a deposited metal obtained from a welding wire in Example 3.

(4) FIG. 4 is a metallographic image of the structure of a weld interpass heat affected zone of a deposited metal obtained from a welding wire in Example 4.

(5) FIG. 5 is a metallograph of a weld surface structure of a typical deposited metal.

(6) FIG. 6(a) is a 1000-fold scanning electron micrograph of a weld surface of a typical deposited metal.

(7) FIG. 6(b) is a 3000-fold scanning electron micrograph of the weld surface of the typical deposited metal.

(8) FIG. 7(a) is a 6000-fold transmission electron micrograph of a weld surface of a typical deposited metal.

(9) FIG. 7(b) is an 8000-fold transmission electron photograph of a weld surface of a typical deposited metal.

(10) FIG. 7(c) is a 15000-fold transmission electron micrograph of the weld surface of the typical deposited metal.

(11) FIG. 7(d) is a 50000-fold transmission electron micrograph of the weld surface of the typical deposited metal.

(12) FIG. 8(a) is a 1000-fold scanning electron micrograph of a weld surface of a typical deposited metal.

(13) FIG. 8(b) is a scanning electron micrograph and energy spectrum test point positions of a weld surface of a typical deposited metal.

(14) FIG. 8(c) is the energy spectrum test result of test point 1 (Spectrum 1) on the weld surface of the typical deposited metal.

(15) FIG. 8(d) is the energy spectrum test result of test point 2 (Spectrum 2) on the weld surface of the typical deposited metal.

DETAILED DESCRIPTION OF EMBODIMENTS

(16) The superhigh strength gas shielded welding wire containing V of the present invention and the manufacturing method therefor are further explained and described below in conjunction with the accompanying drawings and specific examples; however, the explanations and description do not constitute an inappropriate limitation to the technical solution of the present invention.

(17) Table 1 shows the mass percentages of the chemical components of the welding wires in Examples 1-5 of the present invention.

(18) TABLE-US-00001 TABLE 1 (wt. %, the balance being Fe and other inevitable impurities in addition to elements P, S, Al, O and H) No. C Si Mn Cu Cr Mo Ni Ti V N 1 0.085 0.78 1.90 0.06 0.36 0.49 1.66 0.16 0.02 0.008 2 0.105 0.70 1.85 0.13 0.28 0.42 1.38 0.11 0.04 0.011 3 0.093 0.75 1.85 0.16 0.23 0.60 1.52 0.15 0.01 0.010 4 0.08 0.80 1.95 0.10 0.40 0.20 1.80 0.20 0.01 0.013 5 0.12 0.65 1.80 0.19 0.20 0.31 1.30 0.08 0.05 0.007

(19) The welding wires in Examples 1-5 of the present invention are manufactured by the following steps: smelting, refining, casting, hot rolling, slow cooling, spinning into wire rods, pickling, rough drawing, heat treatment, fine drawing and copper plating. These steps are basically common steps in the welding wire manufacturing field, and therefore no more detailed description is provided with regard to these manufacturing steps in this technical solution. The difference merely lies in that the heat treatment step is different from the prior art, which is closely related to the implementation effect of the present invention. In this technical solution, the heat treatment temperature is 680-720 C., and the cooling process is slow cooling, with a cooling time of 5 hours.

(20) Table 2 lists the heat treatment temperatures in the method for manufacturing the welding wires of Examples 1-5 of the present invention.

(21) TABLE-US-00002 TABLE 2 No. Exam- Exam- Example 1 Example 2 ple 3 Example 4 ple 5 Heat treatment 700 C. 680 C. 710 C. 690 C. 720 C. temperature ( C.)

(22) A low-alloy high-strength steel plate having a thickness of 20 mm is welded with the welding wires in Examples 1-5 without preheating, with the groove type being 45 single-sided V type and the gap being 12 mm, wherein an 80% Ar+20% CO.sub.2 shielding gas is used in Examples 1-3, an 80% Ar+15% CO.sub.2+5% O.sub.2 shielding gas and a 95% Ar+5% O.sub.2 shielding gas are used in Examples 4 and 5, the interpass temperature is controlled between 100 C. and 165 C., the welding heat input is controlled at 8-13 kJ/cm, and multi-layer and multi-pass welding is carried out on the base metal, ensuring the welds to be fully penetrated. After welding, the weld metals are subjected to an all-element spectral analysis, a longitudinal tensile test and a Charpy V-notch impact test of a full sample size, with the parameters being shown in Table 3 in detail.

(23) Table 3 lists the mechanical property parameters of the weld metals obtained after gas shielded welding with the welding wires in Examples 1-5 of the present invention.

(24) TABLE-US-00003 TABLE 3 Charpy V-notch Charpy V-notch Yield Tensile impact energy at impact energy at strength strength 20 C. (KV2, J) 40 C. (KV2, J) R.sub.el R.sub.m Elongation Mean Mean Example C.sub.eq P.sub.cm (MPa) (MPa) A (%) value value 1 0.683 0.286 865 966 19 84 105 78 89 63 53 51 56 2 0.653 0.290 810 909 18 108 90 87 95 62 65 85 71 3 0.671 0.288 950 1020 21 125 114 97 112 93 98 51 81 4 0.647 0.269 919 953 18 114 156 97 122 93 98 49 80 5 0.619 0.289 941 1022 21 87 97 91 92 57 42 58 52

(25) As can be seen from Table 3, for the weld metals obtained by gas shielded welding with the welding wires in the above-described Examples 1-5, the yield strengths (R.sub.el) are all 810 MPa, the tensile strengths (R.sub.m) are all 909 MPa, the elongations A are all 18%, and the mean values of Charpy V-notch impact energy at 20 C. are all 89 J and the mean values of Charpy V-notch impact energy at 40 C. are all 52 J; furthermore, the carbon equivalents C.sub.eq of the weld metals are all less than 0.7, and the welding cold crack indexes P.sub.cm are all less than 0.3%, which indicates that the welding wire of the present invention has a higher strength, a greater impact toughness, a better plasticity and a better crack resistance, with the mechanical properties being all capable of matching superhigh strength steels having a grade of 90 kg or higher, and is a gas shielded welding material applicable to the manufacturing fields of engineering machinery, hydropower engineering, oceanographic engineering, commercial vehicles, etc.

(26) It can be seen by analysis that the addition of titanium in the welding wire can allow carbon nitride compounds of titanium to be precipitated at a higher temperature and prevent austenite grains from growing, and plays a role of grain refining. With the decrease in temperature, vanadium precipitates on the periphery of carbon nitride compounds of titanium to form (Ti,V)(C,N) compounds. At a lower temperature, fine carbon nitride compounds of vanadium continue to precipitate inside the matrix and have a precipitation strengthening effect.

(27) In addition, FIG. 1 shows the microstructure of a weld surface of a deposited metal obtained by welding with the welding wire in Example 1. As shown in FIG. 1, the microstructure of the weld surface of the deposited metal is completely bainite.

(28) FIG. 2 shows the microstructure of a weld surface of a deposited metal obtained by welding with the welding wire in Example 2. As shown in FIG. 2, the microstructure of the weld surface of the deposited metal is mainly bainite, and further comprises irregular ferrite in a volume fraction of 2-5%.

(29) FIG. 3 shows the structure of the weld interpass heat affected zone of the deposited metal obtained by welding with the welding wire in Example 3. As shown in FIG. 3, the structure of the weld interpass heat affected zone of the deposited metal is completely lower bainite.

(30) FIG. 4 shows the structure of the weld interpass heat affected zone of the deposited metal obtained by welding with the welding wire in Example 4. As shown in FIG. 4, the structure of the weld interpass heat affected zone of the deposited metal is completely lower bainite.

(31) FIGS. 5 and 6 provide the metallograph and the SEM photograph of a typical surface weld, and it can be seen that the structure thereof is composed of bainite+lath martensite+a small amount of quasi-polygonal ferrite, with the ferrite lath being finer. FIG. 7 is a TEM photograph of a surface weld, and the structure thereof being mainly composed of martensite. FIG. 8(a) is an SEM photograph of a weld metal, and it can be observed that there are dispersedly distributed fine precipitates. FIGS. 8(b), (c) and (d) provide the analysis results of the precipitate components using EDS, and it can be seen that titanium is contained therein. Since the precipitates of vanadium are too fine, it is difficult to determine the composition thereof by means of detection.

(32) It should be noted that those listed above are merely specific examples of the present invention, and it is obvious that the present invention is not limited to the above examples, and may have many similar variations thereof. All the variants that can be directly derived from or associated with the contents disclosed in the present invention by a person skilled in the art should fall within the scope of protection of the present invention.