Influence of arc interactions on heat and mass transfer during a two-arc hybrid welding

P91 steel is a typical steel used in the manufacture of boilers in ultra-supercritical power plants and heat exchangers in nuclear power plants. For the long-term serviced P91 steel pressurized structures, the main failure mode is the welded joint failure, especially the heat affected zone (HAZ) failure. Repair welding technique is an effective method for repairing such local defects. However, the thermal shock composed of high temperature and thermal stress in the repair welding process will pose a critical loading condition for the existing defects near the heat source which cannot be detected by conventional means. So, the evaluation of structural integrity for the welded joint in the thermal-mechanical coupling field is necessary. In this work, the crack propagation law in the HAZ for the P91 steel welded joint was investigated under repair welding thermal loads. The weld repair model of the P91 steel welded joint was established by ABAQUS. The transient temperature field and stress field in repair welding process were calculated by relevant user subroutines and sequential coupling simulation method. The residual stress was determined by the impact indentation strain method to verify the feasibility of the finite element (FE) model and simulation method. In order to obtain the crack propagation path, the elastoplastic fracture analysis of the welded joint with initial crack was performed based on the extended finite element method (XFEM). The influence of different welding linear energy on the crack propagation was analyzed. The results show that the cracks in the HAZ propagate perpendicular to the surface and tend to deflect to the welding seam under repair welding thermal loads. The crack propagation occurs in the early stage of cooling. Higher welding linear energy leads to larger HAZ and higher overall temperature. With the increase of welding linear energy, the length and critical distance of the crack propagation increase. Therefore, low welding linear energy can effectively inhibit the crack propagation in the HAZ. The above calculation and analysis provide a reference for the thermal shock damage analysis of repair welding process, which is of great significance to improving the safety and reliability of weld repaired components.

Elastoplastic Fracture Analysis of the P91 Steel Welded Joint under Repair Welding Thermal Shock Based on XFEM

A flux-cored wire for fusion welding butt joint of a titanium-steel composite board comprises the components in percentage by mass as follows: 80-81% of vanadium powder and 19-20% of chromium powder, and the sum of the mass percentageof the components is 100%. The invention further discloses a preparation method of the flux-cored wire. The preparation method comprises the steps as follows: the vanadium powder and the chromium powder are dry-mixed to obtain flux core powder, the flux core powder is placed on a charging machine of flux-cored wire production equipment, a copper belt is placed on a belt unwinding machine, ultrasonic cleaning is performed, then U-shaped groove rolling and powder adding operations are performed, the powder filling rate is controlled, sealing of the copper belt is performed through a forming machine, and a wire with the diameter of 3.8 mm is formed; then the flux-cored wire is obtained through six reducing treatment processes and a nine-stage reducing finish drawing treatment process sequentially. By means of the flux-cored wire, a titanium layer and a steel layer weld structure of the composite board can be effectively joined together, and the fusion welding butt joint of the titanium-steel composite board is realized; an obtained weld joint has excellent toughness; and the preparation process is simple, and mass production is facilitated.

Flux-cored wire for fusion welding butt joint of titanium-steel composite board and preparation method of flux-cored wire

Plastic limit load of Grade 91 steel pipe containing local wall thinning defect at high temperature

In this paper we devoted to evaluate the responses of a main steam pipe subjected to the steam flow by computational fluid dynamics and spectrum analysis. A fluid model was established to find the periodic fluid force excitation resulting from vortex shedding, the frequency characteristics of the exciting force was examined via Fast Fourier Transform. Based on the spectrum method, a structure model was built to extract the natural frequencies and the responses. The results conveyed that the resonance was unlikely to appear because the natural frequencies of the main steam pipe were one order of magnitude higher than the dominant frequencies of the fluid excitation. Moreover, the stress amplitude of the main steam pipe was observed to be 22.4 MPa, which was much lower than the stress limitation of fatigue and it was assured that no fatigue failure would arise during service life according to the ASME relevant standard. 

Flow induced vibration investigation of a main steam pipe suffering from high temperature steam flow

Failure analysis of a steam pipe weld used in power generation plant

The invention discloses a welding material and a welding method for welding a transition layer of a Ti-pipeline steel composite board. The welding material comprises a near-Ti-layer welding material and a near-steel-layer welding material, wherein the near-Ti-layer welding material comprises the components as follows: 52-58% of Ni, smaller than or equal to 0.04% of C, smaller than or equal to 0.007% of N, smaller than or equal to 0.035% of O, smaller than or equal to 0.001% of H and the balance of Ti; and the near-steel-layer welding material comprises the components as follows: 3.15-3.35% of Mn, 18-27% of Cr, 0.01-0.015% of Cu, 0.35-0.55% of Ti, 0.03-0.04% of Co, 1.8-2.0% of Nb, 0.2-0.6% of Ta, smaller than or equal to 0.02% of C, smaller than or equal to 0.025% of Si, smaller than or equal to 0.002% of P, smaller than or equal to 0.002% of S, smaller than or equal to 0.75% of Fe and the balance of Ni. According to the welding material and the welding method, the fusion welding butt joint of the Ti-pipeline steel composite board is realized, a welded joint has excellent obdurability, and the welding efficiency is high.

Welding material and welding method for welding transition layer of Ti-pipeline steel composite board

The invention provides a welding material for a butt fusion welding transition layer of a titanium-steel composite board and a preparation method of the welding material. The welding material comprises the components in percentage by weight as follows: 3.15%-3.35% of Mn, 18%-27% of Cr, 0.01%-0.015% of Cu, 0.35%-0.55% of Ti, 0.03%-0.04% of Co, 1.8%-2.0% of Nb, 0.2%-0.6% of Ta, smaller than or equal to 0.02% of C, smaller than or equal to 0.025% of Si, smaller than or equal to 0.002% of P, smaller than or equal to 0.75% of Fe and the balance of Ni, wherein the sum of the weight percentages of the components is 100%. The diameter of the welding material is small, weld microstructures of a titanium layer and a steel layer of the titanium-steel composite board can be effectively connected through manual TIG (tungsten inert gas) welding or MIG (metal inert gas) welding, butt fusion welding of the titanium-steel composite board is realized, and a welded joint has excellent strength and toughness; and the welding material is simple in preparation method, low in cost and suitable for batch production.

Welding material for butt fusion welding transition layer of titanium-steel composite board and preparation method of welding material

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Failure analysis of a steam pipe weld used in power generation plant

Welding material and welding method for welding transition layer of Ti-pipeline steel composite board

Welding material for butt fusion welding transition layer of titanium-steel composite board and preparation method of welding material