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Local heat treatment method of thick-wall P92 pipeline in field condition

Through a combination of experiments and finite element analysis, the local heat treatment formula and process of P92 steel pipes were formulated, which solved the problem of uncertain heating width and insulation width under on-site working conditions, achieved stress relief and temperature difference control at the welded joints, and ensured Safe operation of pipelines.

Active Publication Date: 2012-07-25
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, it is found that there are cracks in the welded joints of P92 service pipelines that have undergone partial heat treatment, which is related to the inappropriate local heat treatment process

Method used

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  • Local heat treatment method of thick-wall P92 pipeline in field condition
  • Local heat treatment method of thick-wall P92 pipeline in field condition
  • Local heat treatment method of thick-wall P92 pipeline in field condition

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] First, the P92 main steam pipe with ID538 (inner diameter) × 94.5 (wall thickness) mm is used for welding according to the P92 steel welding process, and a monitoring thermocouple is installed on the inner wall of the pipe before welding.

[0026] Calculate the width of the heating zone HB=1230mm, the width of the heat preservation zone GCB=1950mm, customize the heater and insulation cotton specifications (ie length) according to the calculation data, and choose the WDK-6360 flexible ceramic resistance heater.

[0027] The X-ray method is used to test the residual stress at different distances from the center of the weld. Considering the distribution characteristics of the welding residual stress of the pipe joint, the interval between the test points in the weld area is 3mm (3 points close to the heat-affected zone), and the heat-affected The distance between the three test points in the area is 1.5mm, the distance between the first three points of the base metal is 3mm...

Embodiment 2

[0037] The P92 main steam pipe with ID538×91mm is used for welding according to the P92 steel welding process, and a monitoring thermocouple is installed on the inner wall of the pipe before welding.

[0038] Calculate the width of the heating zone HB=1167mm, the width of the heat preservation zone GCB=1859mm, customize the specifications of the heater and insulation cotton according to the calculation data.

[0039] Local heat treatment of the steel pipe: when the P92 pipe is naturally and slowly cooled (that is, cooled at room temperature in the air) to 150°C, install a corresponding heating device, heat preservation device, and arrange a thermocouple outside the P92 pipe according to the calculation results. When the temperature drops to 100 ℃, turn on the electricity to heat, keep the temperature at 100℃ for 2 hours; heat at 150℃ / h to 300℃, after the temperature reaches 300℃, raise the temperature to 765℃ at 80℃ / h, and keep the temperature for 8 hours. Control the cooling ...

Embodiment 3

[0047] The P92 main steam pipe with ID550×80mm is used for welding according to the P92 steel welding process, and a monitoring thermocouple is installed on the inner wall of the pipe before welding.

[0048] Calculate the width of the heating zone HB=944mm, the width of the heat preservation zone GCB=1548mm, and customize the specifications of the heater and heat preservation cotton according to the calculated data.

[0049] Local heat treatment of the steel pipe: when the P92 pipe is naturally and slowly cooled to 130°C, install the corresponding heating device, heat preservation device and thermocouple outside the P92 pipe according to the calculation results. It is kept at a constant temperature of 90°C for 2 hours; heated at 150°C / h to 300°C, and when the temperature reaches 300°C, it is heated at 80°C / h to 765°C, and the holding time is 8 hours. Control the cooling rate from 100°C / h to 300°C, turn off the power, cool slowly to room temperature, and remove the heater.

...

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Abstract

The invention discloses a local heat treatment process of a thick-wall P92 pipeline in field condition. The method comprises the following steps: calculating by adopting the experiment and the data simulation according to the internal diameter and the wall thickness to obtain the corresponding heating width and the corresponding heat-preserving width; locally heating the pipeline by using a flexible ceramic resistance heater; energizing the pipeline when the temperature reaches 80-100 DEG C, heating, and keeping the temperature constant for 2h; heating the pipeline to 300 DEG C at the speed of 150 DEG C per hour; heating the pipeline to 765 DEG C at the speed of 80 DEG C per hour when the temperature reaches 300 DEG C, and preserving the heat for at least 4h at the rate of 5min for the wall thickness of every 1mm; decreasing the temperature of the pipeline to 300 DEG C at the speed of 100 DEG C per hour; deenergizing the pipeline; and cooling the pipeline slowly to room temperature. Due to the adoption of the technical scheme, the temperature difference (less than 25 DEG C) between the inner wall and the outer wall of the P92 pipeline can be reduced effectively during the heat treatment at constant temperature after welding, the residual stress at the welded joints of the pipeline subjected to heat treatment can be reduced effectively, and the use performance of the material can be guaranteed.

Description

technical field [0001] The invention relates to a local heat treatment process for high-grade heat-resistant steel, in particular to a local heat treatment process for large thick-walled P92 long pipelines under on-site working conditions. Background technique [0002] At present, the power industry is facing unprecedented challenges. To speed up the pace of power development, we are faced with the need to speed up the adjustment of the power structure. The most realistic and feasible way is to speed up the construction of ultra-supercritical units. Thermal power generation with ultra-supercritical pressure parameters is a new technology that effectively utilizes energy. By increasing the pressure and temperature of its steam to a certain extent, the thermal efficiency of the unit can be improved. To ensure the stable operation of the unit at higher temperature and pressure, steel with higher high-temperature strength must be used, otherwise the wall thickness of the compo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D9/08
CPCC21D2221/00C21D9/08B23K2203/04C21D1/30C21D9/50B23K31/027C21D1/34B23K2201/10C21D9/14B23K2201/06B23K2101/06B23K2101/10B23K2103/04C21D1/40H05B3/141H05B3/34Y02B30/00
Inventor 徐连勇苗艺韩永典荆洪阳
Owner TIANJIN UNIV
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