The spiral pipe in Guangxi is a spiral seam steel pipe with steel coiled plate as raw material, which is often extruded and formed by welding with automatic double-wire submerged arc welding process.

Production Process

(1) The raw materials are strip coil, welding wire and flux. Before input, it must undergo strict physical and chemical tests.

(2) The head and tail of the steel strip are connected by single-wire or double-wire submerged arc welding, and automatic submerged arc repair welding is used after being rolled into a steel pipe.

(3) Before forming, the strip steel is leveled, trimmed, planed, surface cleaned and transported, and pre-bent.

(4) The electric contact pressure gauge is used to control the pressure of the oil cylinder on both sides of the conveyor to ensure the smooth transportation of the steel strip.

(5) Using external control or internal control roll forming.

(6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the weld gap are all strictly controlled.

(7) Both internal and external welding use American Lincoln electric welding machine for single-wire or double-wire submerged arc welding, so as to obtain stable welding quality.

(8) All welded seams are inspected by online continuous ultrasonic automatic flaw detector to ensure 100% non-destructive testing coverage of spiral welds. If there are defects, it will automatically alarm and spray marks, and the production workers will adjust the process parameters at any time according to this, and eliminate the defects in time.

(9) Use air plasma cutting machine to cut the steel pipe into single pieces.

(10) After cutting into a single steel pipe, each batch of steel pipes must undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion state, surface quality of the steel pipe and non-destructive inspection to ensure that the pipe making process is qualified Only then can it be officially put into production.

(11) The parts with continuous sonic flaw detection marks on the welding seam are reviewed by manual ultrasound and X-ray. If there are any defects, after repair, they are subjected to non-destructive inspection again until it is confirmed that the defects have been eliminated.

(12) Tubes with butt-welded welds of steel strips and D-type joints intersecting with spiral welds are all inspected by X-ray TV or filming.

(13) Each steel tube undergoes a hydrostatic pressure test, and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe hydraulic microcomputer detection device. Test parameters are automatically printed and recorded.

(14) The mechanical processing of the pipe end enables the verticality of the end face, the bevel angle and the blunt edge to be accurately controlled.

Weld processing

The spiral steel pipe feeds the strip steel into the welded pipe unit. After being rolled by multiple rollers, the strip steel is gradually rolled up to form a round tube blank with an open gap. Adjust the reduction of the squeeze roller to control the weld gap to 1 ~ 3mm, and make the two ends of the welding port flush.

1. If the gap is too large, the proximity effect will be reduced, the eddy current will be insufficient, and the welding joint between the crystals will be poor, resulting in unfused or cracked.

2. If the gap is too small, the proximity effect will increase, and the welding heat will be too large, resulting in burnt welds; or the welds will form deep pits after extrusion and rolling, which will affect the quality of the weld surface.

After heating the two edges of the tube blank to the welding temperature, under the squeeze of the squeeze roller, the common metal grains penetrate and crystallize to form a strong weld. If the squeezing force of the spiral steel pipe is too small, the number of common crystals formed is small, the strength of the weld metal decreases, and cracks will occur after the force is applied; if the squeezing force is too large, the molten metal will be pushed out of the weld, Not only reduces the strength of the weld, but also generates a lot of internal and external burrs, and even causes defects such as welding overlap.

Process characteristics

The main technological characteristics of spiral steel pipe:

a. During the forming process, the steel plate deforms uniformly, the residual stress is small, and the surface is not scratched. The processed spiral steel pipe has greater flexibility in the range of diameters and wall thickness dimensions, especially in the production of high-steel grade thick-walled pipes, especially small and medium-diameter thick-walled pipes, which have unparalleled advantages in other processes and can satisfy users. More requirements in terms of spiral steel tube specifications.

b. Using advanced double-sided submerged arc welding process, welding can be achieved in the best position, it is not easy to appear defects such as wrong edges, welding deviation and under-welding, and it is easy to control the welding quality.

c. Carry out 100% quality inspection on the steel pipe, so that the entire process of steel pipe production is under effective detection and monitoring, which effectively guarantees the product quality.

d. All the equipment of the entire production line has the function of networking with the computer data collection system, realizing the real-time data transmission, and the technical parameters in the production process are controlled by the central control room.

Stacking principle requirements

1. The principle requirement of spiral steel tube stacking is to palletize according to varieties and specifications under the premise of stable palletizing and ensuring safety. Different materials should be palletized separately to prevent muddy and mutual erosion;

2. It is forbidden to store items that have a corrosive effect on the steel around the spiral steel pipe stacking station;

3. The bottom of the spiral steel pipe stack should be high, strong and flat to prevent the material from being damp or deformed;

4. The same kind of materials are stacked separately according to the storage order;

5. Spiral steel pipes stacked in the open air must have wooden pads or stones underneath, the stacking surface is slightly inclined to facilitate drainage, and pay attention to the placement of the materials straight to prevent bending deformation;

6. The height of spiral steel pipe stacking, manual work should not exceed 1.2m, mechanical work should not exceed 1.5m, and stack width should not exceed 2.5m;

7. There should be a certain channel between the stacks, the inspection channel is generally 0.5m, and the access channel depends on the size of the material and the transport machinery, generally 1.5 ~ 2.0m;

8. Angles and channel steels should be stacked in the open air, that is, with the mouth facing down, the I-beam should be placed upright, and the I-slot surface of the steel should not be facing upwards, so as to avoid water rust

9. The bottom of the stack is high. If the warehouse is a sunny concrete floor, the height should be 0.1m; if it is mud, the height should be 0.2 ~ 0.5m. If it is an open field, the height of the cement floor is 0.3-0.5m, and the height of the sand surface is 0.5-0.7m.

Spiral steel pipes shall be tested for mechanical properties, flattening and flaring before they leave the factory, and shall meet the requirements specified in the standard. The quality inspection methods of straight seam steel pipes are as follows:

1.Jdging from the surface, that is, visual inspection. The appearance inspection of welded joints is a simple and widely used inspection method, which is an important content of finished product inspection, mainly to find defects and dimensional deviations on the surface of the weld. Generally, it is inspected by naked eyes, with the help of tools such as standard templates, gauges and magnifying glass. If there is a defect on the surface of the weld, there may be a defect inside the weld.

2. Inspection of physical methods: The physical inspection method is a method of measuring or inspecting using some physical phenomena. The inspection of internal defects of materials or workpieces is generally performed by non-destructive testing. Non-destructive testing includes ultrasonic testing, radiographic testing, penetration testing, magnetic testing, etc.

3. Strength inspection of pressure vessel: In addition to the tightness test, the pressure vessel must also undergo a strength test. There are two kinds of water pressure test and air pressure test. They can check the tightness of the welds of containers and pipes that work under pressure. The air pressure test is more sensitive and faster than the water pressure test. At the same time, the product after the test does not need to be drained. It is especially suitable for products with difficult drainage. But the risk of the test is greater than the hydrostatic test. During the test, the corresponding safety technical measures must be observed to prevent accidents during the test.

4. Tightness test: Welding containers storing liquids or gases, the non-density defects of the welds, such as penetrating cracks, pores, slag inclusions, under-welded and loose tissues, etc., can be found by the compactness test. Denseness testing methods include: kerosene test, water load test, water flush test, etc.

5. Hydrostatic test Each steel tube should be hydrostatically tested without leakage. The test pressure is calculated by pressing the test P = 2ST / D where the S—hydrostatic pressure test stress Mpa and the hydrostatic test stress are determined accordingly. The steel strip standard specifies 60% of the minimum yield (235Mpa for Q235). Pressure stabilization time: D <508 test pressure retention time is not less than 5 seconds; D≥508 test pressure retention time is not less than 10 seconds X-ray or ultrasonic inspection. The spiral welds of steel for flammable general fluid transportation should be 100% SX-ray or ultrasonic inspection, and the spiral welds of steel pipes for general fluid transportation of water, sewage, air, heating steam, etc. should be X-ray or Ultrasonic inspection spot check (20%).

According to the quality inspection results of spiral steel pipes, spiral steel pipes are generally divided into three categories: qualified products, repaired products and scrap products. Qualified products refer to spiral steel pipes whose appearance quality and intrinsic quality meet relevant standards or technical conditions for delivery and acceptance; reworked products refer to appearance quality and intrinsic quality that do not fully meet the standards and acceptance criteria, but are allowed to be repaired, and the standards and acceptance conditions can be reached after repair. Spiral steel pipe; scrap refers to spiral steel pipe whose appearance quality and internal quality are unqualified, which are not allowed to be repaired or still fail to meet the standard and acceptance conditions after repair.

Waste products are divided into internal waste and external waste. Internal waste refers to the waste spiral steel pipe found in the foundry or foundry; external waste refers to the waste found after the delivery of the spiral steel pipe, usually revealed during mechanical processing, heat treatment or use, and the economic loss caused by it is far Greater than domestic waste. In order to reduce external waste, it is best to sample and heat-treat spiral steel pipes for mass production before the factory for experimental heat treatment and rough machining. If possible, find potential spiral steel pipe defects in the spiral steel pipe factory, so as to take necessary remedial instructions as soon as possible.