Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement

Abstract

A Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement, includes the following chemical components in percentage by mass: 0.04-0.1% of C, 0.4-1.5% of Mn, 7.5-12.5% of Ni, ≤0.5% of Si, 17.0-19.0% of Cr, ≤0.4% of Mo, 2.5-3.5% of Cu, 0.3-0.6% of Nb, 0.05-0.12% of N, ≤0.01% of S, ≤0.02% of P and the balance of Fe and other inevitable impurity elements. The welding wire can be used for welding of Super304H steel used in ultra super critical thermal power stations, has a weld being in a double-phase structure of austenite and a small amount of ferrite (volume fraction is 3-12%), and has good hot cracking resistance capability.

Claims

1. A Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement, consisting of following chemical components in percentage by mass: 0.04-0.1% of C, 0.83-1.0% of Mn, 9.34-12.5% of Ni, ≤50.5% of Si, 17.0-19.0% of Cr, 0.05-0.2% of Mo, 2.5-3.5% of Cu, 0.3-0.6% of Nb, 0.05-0.12% of N, ≤0.01% of S, 0.014-0.02% of P and the balance of Fe and other inevitable impurity elements; wherein the Super304H steel welding wire forms a double-phase structure of austenite and ferrite: volume fraction of the ferrite in the double-phase structure is 3-12%.

2. The Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement according to claim 1, wherein C: 0.06-0.08%.

3. The Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement according to any one of claim 1, wherein a welding method used in application of the welding wire in Super304H steel welding is argon tungsten-arc welding.

4. The Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement according to claim 3, wherein when the diameter of the welding wire is 1.0 mm, the welding current is 140-200 A, the arc voltage is 9-11V the wire feed speed is 85-350 mm/min, the protective gas flow is 16-20 L/min, and the interlayer temperature is controlled below 100° C.

5. The Super304H steel welding wire capable of resisting high-temperature creep and aging embrittlement according to claim 3, wherein when the diameter of the welding wire is 2.4 mm, the welding current is 80-110 A, the arc voltage is 9-14 V, the welding speed is 50-100 nim/min, the protective gas flow is 8-10 L/min, and the interlayer temperature is controlled below 100° C.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is comparison of calculation results of weld structures of a welding wire of the disclosure and a YT-304H welding wire.

(2) FIG. 2 is a thermodynamic calculation result of the influence of Mn and Mo contents on a a phase of a Super304H weld.

(3) FIG. 3 is comparison of microstructures of welds of a welding wire (1 #) of the disclosure, a comparison example welding wire (4 #) and a YT-304H welding wire (5 #).

(4) FIG. 4 is comparison of endurance strengths of joints of a welding wire example (1 #) of the disclosure, a comparison example welding wire (4 #) and a YT-304H welding wire (5 #).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) Next, the technical solution of the disclosure will be further and specifically described through embodiments and in combination with drawings. According to the composition range of the disclosure, a welding wire having a diameter of 2.4 mm is prepared according to a general welding wire preparation process flow: vacuum furnace smelting.fwdarw.forging.fwdarw.wire rod.fwdarw.solution treatment.fwdarw.multiple drawing treatment and hydrogen recession.fwdarw.bright treatment.fwdarw.cutting packaging. The Super304H small caliber tube with the specification of Φ45 mm×9.2 mm is selected to prepare the welded joint by using the GTAW method. The welding process is that current is 90-110 A, voltage is 11-13V, interlayer temperature is ≤100° C., gas flow is 9-10 L/min, and welding speed is 60-100 mm/min. Table 1 lists typical chemical components of three groups of examples of the welding wires of the disclosure and two comparison example welding wires, wherein 1 #-3 # are the welding wires of the disclosure for trial production; 4 # is a comparison example welding wire for trial production, in which wire the C content is obviously reduced, about 0.9% of Mo is added, and other element components are similar to those of 1 #-3 #. Table 1 is used to explain the influence of formation of excessive ferrite in the weld on the high temperature service performance.5 # is a typical component of a YT-304Hwelding wire.

(6) TABLE-US-00001 TABLE 1 Components of welding wires in examples and comparison examples (wt %) Number C Si Mn P S Cr Ni Cu Mo N Nb Fe 1# 0.08 0.20 0.91 0.014 0.005 18.47 9.53 2.83 0.05 0.08 0.42 balance 2# 0.07 0.23 0.85 0.008 0.005 18.42 9.40 2.91 0.08 0.08 0.41 balance 3# 0.08 0.21 0.94 0.008 0.006 18.52 9.34 2.96 0.06 0.09 0.43 balance 4# 0.01 0.26 0.83 0.007 0.004 18.33 9.30 2.93 0.84 0.09 0.40 balance 5# 0.11 0.19 3.29 0.006 0.004 18.70 16.04 2.94 0.87 0.21 0.67 balance

(7) The test results of room-temperature mechanical properties of the welded joints of the welding wires of the disclosure are listed in Table 2. It can be seen from Table 2 that the room-temperature tensile strength of the joint of the welding wire of the disclosure meets a requirement that the room-temperature tensile strength of the joint of the Super304H steel is not less than 590 MPa, stipulated by ASME SA213-2010 and GB5310-2008, and the joint has good plasticity.

(8) TABLE-US-00002 TABLE 2 Test results of room-temperature mechanical properties of joints of examples and comparison examples Number R.sub.m (MPa) Bending 1# 610 Bend to 180° no crack 2# 610 Bend to 180° no crack 3# 610 Bend to 180° no crack 4# 610 Bend to 180° no crack 5# 625 Bend to 180° no crack

(9) The impact test results of the weld of the welding wire of the disclosure after high temperature aging are listed in Table 3. It can be seen from the Table 3 that the room-temperature impact energy of the welding wire of the disclosure after long-term aging exceeds 41 J, which is 1.8 times of that of the YT-304H welding wire. Due to excessive ferrite content, the impact energy of the weld of the 4 # welding wire after aging is significantly lower than that of the 1 # weld, which is close to that of YT-304H weld (5 #), indicating that the high ferrite content leads to obvious aging embrittlement occurring in the weld.

(10) TABLE-US-00003 TABLE 3 Room-temperature impact energy KV.sub.2 (J) of weld in examples and comparison examples after 650° C. aging Time Number 500 h 1000 h 3000 h 5000 h 1# 77 65 56 44 4# 49 41 28 23 5# 41 37 25 24 Note: 1) the size of the sample is 7.5 mm × 10 mm × 55 mm, and data in Table 3 are numerical values converted to values of the standard sample (10 mm × 10 mm × 55 mm); 2) the notch is in the center of weld of welded joint.

(11) The creep fracture strength test results of the welded joints of the welding wires of the disclosure are listed in Table 4. From an endurance curve shown in Table 4 and FIG. 4, it can be seen that under the condition of low stress creep, the fracture service life of 1 # welding wire joint is significantly higher than that of a YT-304H welding (5 #) wire joint, and its advantages are more and more obvious with the decrease of test stress. According to the endurance curve, the creep rupture strength of the welding wire joint at 650° C./10.sup.4 h is extrapolated as 176 MPa, which is equivalent to the average value of the endurance strength (175 Mpa) of the Super304H steel. This shows that the 1 # welding wire joint has better high-temperature creep resistance under service conditions. The creep rupture strength of the 4 # welding wire joint is slightly better than that of the YT-304H welding wire joint, but significantly lower than that of the 1 # welding wire joint, which indicates that the excessive ferrite in the weld has a great adverse effect on the creep performance of the joint.

(12) TABLE-US-00004 TABLE 4 Endurance fracture time (h) of the joints of welding wires in examples and comparison examples under different stresses at 650° C. Number Stress 1# 4# 5# 280 MPa 5.6 34.8 — 260 MPa 60.3 51.9  60.8 240 MPa 110.1 108.8  145.8 220 MPa 181.9 206.9  277.8 210 MPa 1098.2 — — 200 MPa 1339.1 849.9  544.2 190 MPa 3112 — — 180 MPa 5654.7 1871.6 1268.7 170 MPa — 2841.2 — 160 MPa — 5037 3344.4 150 MPa — — 5363.6 140 MPa — — 10142.4 

(13) In conclusion, compared with the existing Super304H steel homogeneous welding wire, the welding wire of the disclosure obviously improves the high-temperature creep resistance of the joint and the aging embrittlement resistance of the weld on the premise of ensuring the room temperature mechanical properties of the joint. The weld of the welding wire has a double-phase structure of austenite+a small amount of ferrite, and also has better hot cracking resistance capability. Compared with the nickel-based welding wire, this welding wire has the advantages of good process performance and low cost.

(14) The protection scope of the disclosure is not limited to the above examples. Obviously, those skilled in the art can make various changes and deformations to the disclosure without departing from the scope and spirit of the disclosure. If these changes and deformations belong to the scope of the claims and equivalent technologies of the disclosure, the intention of the disclosure is also included within these changes and deformations.