一.Acceptance and acceptance of raw materials

1、Raw materials shall meet the requirements of relevant standards or technical specifications.

2、The surface of raw materials should be free from oil pollution, excessive rust corrosion and obvious dent defects, low melting point metal pollution, etc.

3、Check the quality certificate, furnace number, batch number, specifications of raw materials, manufacturers and implementation standards.

4、The raw materials are mechanically de-rusted with wire brushes to meet the requirements of non-destructive testing.

5、Dimension testing of raw materials (length, width, thickness and unevenness of steel tubes).

6、After entering the factory, the steel pipe and steel plate should be re-examined by ultrasonic wave. Grade I is qualified.

7、Physical and chemical testing, chemical element analysis, mechanical properties and hardness testing of steel pipes and steel plates are carried out according to furnace batch number and specifications. The test results should meet the requirements of raw material standards.

8、After reexamination, the factory shall register the number according to the factory regulations.

二.Manufacturing Process

①Selection of raw material：elbow selection of appropriate steel plate or steel pipe, with template marking with oxyacetylene flame or sawing machine cutting, and raw materials furnace, batch number and pipe specifications, engineering name, number clearly marked.

②Rolling and welding the steel plate.

③The mandrel is loaded into the pusher by crane, the blank is further cleaned up, the inner wall is coated with graphite, and then mounted on the pusher (according to the length of the blank, more than one can be installed at a time). The mandrel is locked with a plug board, and the internal mould is preheated to the appropriate temperature for pushing (heating temperature and propulsion speed should be the best match).

④Adjust the intermediate frequency heating ring, heating the billet to the required temperature, and control the propulsion speed.

⑤Buckle bending. Correct the curvature radius of the formed elbow on the hydraulic press with suitable tool.

⑥To remove the end, according to the elbow specifications, use appropriate tools to align on the beveling machine, then fix the cutting gun, cut off the excess blank, and leave processing allowance for the car mouth.

⑦Shaping, clamping elbow with special tire and shaping port on press with brace.

4.Heat treatment: According to the heat treatment process, the elbow is put into the furnace for heat treatment.

5.Surface treatment: After heat treatment, the surface oxide scale of the pipe is removed by sandblasting machine.

6.After surface treatment, 100% radiographic inspection of elbow welds after surface treatment, and the second grade was qualified.

7.Mechanical properties testing: According to relevant standards, mechanical properties of elbows are tested to ensure that the mechanical properties of elbows meet the standards, and the testing items and sampling directions should meet the requirements of relevant standards.

8.End processing: mechanical end processing grooves according to design confirmation drawings. Within the range of 50mm from the end of the pipe, the excess height of the internal and external welds is grinded by an angle grinder.

9.Appearance detection

①There should be no cracks on the elbow and no hard spots on the surface.

②Welding repair is not allowed for any defect on elbow pipe body.

10.Dimension inspection: The company's relevant inspectors, according to the drawings and pipe fittings of the relevant standard requirements for dimensional inspection, and to meet their tolerance requirements.

11.Surface treatment: The inside and outside surfaces of elbows should be smooth, without any damage to strength and appearance defects, such as scars, scratches, heavy skins, etc. When defects are found, they should be repaired. The thinning of the repaired parts should be no less than 93.5% of the original wall thickness. The repaired parts should be smooth, and the defects should be cleared by dye or magnetic powder inspection.

12.Nondestructive testing of elbows

After the elbow heat treatment, the company holds the relevant qualification certificate personnel, according to the standard requirements of the elbow magnetic powder, ultrasound, test results reached the level I qualified.

13.Identification

Mark with a spray-brush or low-stress impression, and clearly mark the contents required by the standard on the outer wall in sequence.

14.Storage and transportation of elbows

Elbows should not contact any part of the carriage during transportation to avoid bumping.

Hebei Zhongran Pipefitting Co., Ltd.,:http://en.zrpiping.com/