ASTM A335 P91 Товстостінний трубопровід високого тиску Метод зварювання

A method for welding high-pressure thick-walled pipelines of domestic A335 P91 steel: область техніки – The present invention pertains to the field of welding technology, particularly relating to a method for welding high-pressure thick-walled pipelines of domestic A335 P91 steel.

We have Largest inventory of ASTM A335 P91 Alloy Steel Seamless Pipe

Alloy Steel Pipe A 335 P91:

Розмір : 1/2″ для 24 “IN OD & NB

Розклад: СЧ20, Сч30, Труба sch40.
тип : Зварні / виготовлений / Безшовні
Довжина : Single Random, Double Random & Cut Length.
кінець : Простый Кінець, Скошений кінець.

Матеріали :
Alloy Steel Pipe A335 P91 – AS Pipe A335 P91
ASTM A335, Гр. P5, P9, P11, P12, P21, P22 & P91

ASTM A335 P91 Chrome Pipe Composition Composition

Сорт	США	C≤	MN	Р≤	З≤	Si≤	Кл	МО
P1	K11522	0.10~0.20	0.30~0.80	0.025	0.025	0.10~0.50	-	0.44~0.65
P2	К11547	0.10~0.20	0.30~0.61	0.025	0.025	0.10~0.30	0.50~0.81	0.44~0.65
P5	K41545	0.15	0.30~0.60	0.025	0.025	0.50	4.00~6.00	0.44~0.65
P5b	K51545	0.15	0.30~0.60	0.025	0.025	1.00~2.00	4.00~6.00	0.44~0.65
P5c	K41245	0.12	0.30~0.60	0.025	0.025	0.50	4.00~6.00	0.44~0.65
P9	S50400	0.15	0.30~0.60	0.025	0.025	0.50~1.00	8.00~10.00	0.44~0.65
P11	К11597	0.05~0.15	0.30~0.61	0.025	0.025	0.50~1.00	1.00~1,50	0.44~0.65
P12	К11562	0.05~0.15	0.30~0.60	0.025	0.025	0.50	0.80~1.25	0.44~0.65
P15	K11578	0.05~0.15	0.30~0.60	0.025	0.025	1.15~1.65	-	0.44~0.65
P21	K31545	0.05~0.15	0.30~0.60	0.025	0.025	0.50	2.65~3.35	0.80~1.60
P22	К21590	0.05~0.15	0.30~0.60	0.025	0.025	0.50	1.90~2.60	0.87~1.13
P91	K91560	0.08~0.12	0.30~0.60	0.020	0.010	0.20~0.50	8.00~9.50	0.85~1.05
P92	K92460	0.07~0.13	0.30~0.60	0.020	0.010	0.50	8.50~9.50	0.30~0.60

A335 Gr P91 Pipes Composition Standard

Сі, %	Кл, %	C, %	МО, %	MN, %	P, %	N, %	S, %	V, %	Н, %	NB, %	Ал, %
0.2 для 0.5	8.0 для 9.5	0.08 для 0.12	0.85 для 1.05	0.3 для 0.6	0.02	0.03 для 0.07	0.01	0.18 для 0.25	0.4	0.06 для 0.10	0.04

ASTM A335 P91 Pipes Mechanical Strength Table

Elongational	Tensile Properties	НВ	Yield Properties
20	585	250	415

Equivalent Material Grade Of SA335 Gr P91 Pipes

США	ASTM	Equivalent Матеріал	АСМЭ
K91560	A335 P91	K90901, T91, 1.4903, X10CrMoVNb9-1	SA335 P 91

ASTM	АСМЭ	ВІН Г 3458	США	BS	DIN	ISO	ABS	NK	LRS
A335 P9	SA335 P9	STPA 26	S50400	3604 P1 629-470		2604 II TS38

Background: A335 P91 steel is a modified 9Cr-1Mo steel, primarily incorpo

A335P11 A335P91 A335P22 40cr 10CrMO910 35crmo 27SiMn Q345B 16Mn Welded Alloy Steel Pipe

rating alloy elements such as V and Nb into the original 9Cr-1Mo martensitic heat-resistant steel. This steel possesses excellent high-temperature oxidation resistance, high-temperature steam corrosion resistance, and creep resistance, effectively reducing structural weight and finding widespread application in large boiler units, pipeline systems, and the petrochemical industry. однак, due to the air-cooled martensitic nature of A335 P91 steel, it exhibits lower plasticity and poorer weldability, imposing high requirements on welding processes, impact toughness of welded joints, weld brittleness, post-weld heat treatment, and heat-affected zones of welds. Traditional A335 P91 steel welding generally employs manual gas tungsten arc welding (GTAW) for root pass and manual shielded metal arc welding (SMAW) for filling and capping, necessitating strict control of line energy, preheat temperature, and interpass temperature during the welding process. This method demands a high level of welding environment and welder skill, and manual welding efficiency is extremely low, consuming time and effort, severely restricting piping progress, affecting construction schedules, and particularly evident for large-diameter thick-walled pipelines.

Тому, the rational selection of welding parameters and processes for A335 P91 steel and the development of welding process conditions suitable for production hold significant practical and economic value.

Invention Content: To address the shortcomings of existing technology, the technical problem to be solved by the present invention is to provide a method for welding high-pressure thick-walled pipelines of domestic A335 P91 steel, aiming to improve welding efficiency and weld якість, reduce construction costs and labor intensity, and improve the working environment.

To achieve the above objectives, the present invention employs the following technical solutions:

A method for welding high-pressure thick-walled pipelines of domestic A335 P91 steel, comprising the following steps in sequence:

(1) Pre-weld bevel processing: Process the welding area of the pipeline to be welded into a double V-shaped bevel, perform dye penetrant inspection on the bevel surface to ensure no surface cracks, and clean the bevel and the surface rust, масло, and oxides within a 20mm area on both sides of the bevel;

Continuing with the welding method for domestically produced A335 P91 high-pressure thick-walled steel pipes:

4. Post-weld heat treatment: Після зварювання, seal both ends of the pipe and use electric heating to heat the area on both sides of the weld, at least 3 times the width of the weld and no less than 25mm. Heat the area to a temperature range of 750-770°C and hold it for 2.5-4 hours, depending on the pipe thickness.

Please note that the temperature in this method is monitored using an infrared thermometer. This welding method for A335 P91 high-pressure thick-walled steel pipes has the following advantages:

1. The use of multi-layer, multi-pass welding reduces the cross-sectional area of each weld layer, improving the toughness of the welded joint and avoiding the narrowing of the heat-affected zone in thick welds, as well as the softening of the weld joint during long-term operation at high temperatures.

2. Manual gas tungsten arc welding (GTAW) for root welding has a slower welding speed, and sealing both ends of the pipe helps control the interlayer temperature. Automatic submerged arc welding (Бачив) for filling and covering layers has a faster welding speed and higher current, releasing heat more quickly. At least one end of the pipe should be unsealed, and continuous welding can be performed without the need for interlayer temperature control.

3. Using small-diameter welding wires (no more than 2.5mm) and low-hydrogen flux for welding can reduce the linear energy during the welding process, improve the welding deposition rate, refine the base material grains, and reduce the possibility of defects such as porosity and cracks in the weld.

4. In windy environments, the protection effect of automatic submerged arc welding is better than other arc welding processes.

5. Compared to traditional manual welding methods, this method effectively shortens the heat treatment and welding cycle, improves weld якість and welding efficiency, reduces labor intensity, and saves construction costs.

 

Implementation example 1: Using domestic A335P91 pipeline DN350 as the base material, the following welding method is adopted:

(1) The welding area of the pipe to be welded is processed into a double V-shaped groove as shown in Figure 1, with a blunt edge height of 1mm, a bottom angle of 60±5° in the direction of the pipe length, a height of 15mm, and an upper angle of 78-82° in the direction of the pipe length. The groove surface is colored inspected to ensure that there are no surface cracks on the groove. The surface rust, oil stains, oxides, д. within 20mm on both sides of the groove are cleaned;

(2) The two sections of the welded pipe are assembled, ensuring that the end face gap of the butt joint is 3-6mm, the height is even, and the misalignment is not greater than 1mm;

(3) Manual argon arc welding GTAW is used for the bottom welding. Before welding, the end ports of the pipe to be welded are blocked, and the inner wall or back of the weld is filled with argon gas for protection. The steel pipe to be welded is preheated, and the temperature of the groove is monitored in real-time using an infrared thermometer. When the temperature reaches 160℃, welding begins, using ER90S-B9 welding wire with a diameter of to weld three layers. The process parameters are selected as follows: DC positive connection of the power supply, welding current of 118A, arc voltage of 14V, and welding speed of 3-10cm/min. Attention should be paid to the following points during manual argon arc welding GTAW: A) The surface of the workpiece to be welded should not be ignited by the arc, tested for current, or temporarily welded to support or clamp;b) The manual argon arc welding starts from the lowest point of the pipe to be welded, and is symmetrically welded by two people, with the welding joints staggered between 100-150mm; C) During manual argon arc welding, the preheating temperature on both sides of the groove should be monitored in real-time, and the preheating temperature should be strictly controlled between 150℃ and 200℃; D) During manual argon arc welding, wind protection measures should be taken, and the wind speed in the welding environment should not exceed 2m/s. There should be no draft in the pipe to be welded, and moisture, rain, and snow protection measures should be taken;

(4) Automatic submerged arc welding SAW is used for filling and covering. Before automatic submerged arc welding filling and covering, at least one end of the pipe to be welded is unblocked, and the welding area is preheated. When the temperature reaches 200℃, continuous welding begins, using EB9 welding wire with a diameter of and MARATHON543 welding flux for multi-layer and multi-pass filling and covering welding. The SAW welding parameters are selected as follows: DC reverse connection of the power supply, welding current of 280A, arc voltage of 28V, and welding speed of 25-45cm/min.

 

Attention should be paid to the following points during automatic submerged arc welding SAW:

A) The welding wire should be kept clean and dry, and the welding flux should be stored in a dry place to prevent moisture absorption;

b) The welding wire should be fed smoothly and evenly, and the welding flux should be added in time to ensure the welding якість;

C) The welding speed should be stable, and the welding gun should be kept perpendicular to the pipe axis to ensure the consistency of the weld bead;

D) The welding slag should be removed in time after each layer of welding is completed, and the surface of the weld should be cleaned with a wire brush or grinding wheel to ensure the quality of the next layer of welding;

Е) The welding process should be monitored in real-time, and the welding parameters should be adjusted in time according to the actual situation to ensure the welding quality. After the welding is completed, the weld surface should be inspected visually and by non-destructive testing to ensure that there are no defects such as cracks, pores, шлакові включення, and incomplete penetration. Нарешті, the welded joint should be heat-treated according to the process requirements to eliminate welding stress and improve the mechanical properties of the welded joint.

Implementation example 2: Using imported A335P91 pipeline DN500 as the base material, the following welding method is adopted:

(1) The welding area of the pipe to be welded is processed into a double V-shaped groove as shown in Figure 1, with a blunt edge height of 1.5mm, a bottom angle of 60±5° in the direction of the pipe length, a height of 20mm, and an upper angle of 78-82° in the direction of the pipe length. The groove surface is colored inspected to ensure that there are no surface cracks on the groove. The surface rust, oil stains, oxides, д. within 20mm on both sides of the groove are cleaned;

(2) The two sections of the welded pipe are assembled, ensuring that the end face gap of the butt joint is 4-8mm, the height is even, and the misalignment is not greater than 1.5mm;

(3) Automatic submerged arc welding SAW is used for bottom welding. Before welding, the end ports of the pipe to be welded are blocked, and the inner wall or back of the weld is filled with argon gas for protection. The steel pipe to be welded is preheated, and the temperature of the groove is monitored in real-time using an infrared thermometer. When the temperature reaches 200℃, welding begins, using EB9 welding wire with a diameter of and MARATHON543 welding flux for multi-layer and multi-pass filling and covering welding. The SAW welding parameters are selected as follows: DC reverse connection of the power supply, welding current of 350A, arc voltage of 32V, and welding speed of 25-45cm/min. Attention should be paid to the following points during automatic submerged arc welding SAW: A) The welding wire should be kept clean and dry, and the welding flux should be stored in a dry place to prevent moisture absorption; b) The welding wire should be fed smoothly and evenly, and the welding flux should be added in time to ensure the welding quality; C) The welding speed should be stable, and the welding gun should be kept perpendicular to the pipe axis to ensure the consistency of the weld bead; D) The welding slag should be removed in time after each layer of welding is completed, and the surface of the weld should be cleaned with a wire brush or grinding wheel to ensure the quality of the next layer of welding; Е) The welding process should be monitored in real-time, and the welding parameters should be adjusted in time according to the actual situation to ensure the welding quality.

(4) Automatic submerged arc welding SAW is used for filling and covering. Before automatic submerged arc welding filling and covering, at least one end of the pipe to be welded is unblocked, and the welding area is preheated. When the temperature reaches 250℃, continuous welding begins, using EB9 welding wire with a diameter of and MARATHON543 welding flux for multi-layer and multi-pass filling and covering welding. The SAW welding parameters are selected as follows: DC reverse connection of the power supply, welding current of 450A, arc voltage of 36V, and welding speed of 25-45cm/min. After the welding is completed, the weld surface should be inspected visually and by non-destructive testing to ensure that there are no defects such as cracks, pores, шлакові включення, and incomplete penetration. Нарешті, the welded joint should be heat-treated according to the process requirements to eliminate welding stress and improve the mechanical properties of the welded joint.