Research on Bundling Mode of X80 Pipeline Steel Coil

Abstract : Through investigation and analysis, it is found that the main reason for the breakage of the X 80 pipeline steel coil bundle is the springback of the tail and head of the steel coil. This paper proposes a mechanical and mathematical model of the tail leading the free end of the pressure, and uses the finite element software Ansyswotkbench to verify the model through simulation experiments , which provides a theoretical basis for the research and development of the bundled method of X 80 and other pipeline steel coils .
Key words : X80 pipeline steel ; steel coil tail ; bundling ; strap fracture ; springback

require large-diameter, high-pressure, corrosion-resistant oil and gas pipelines due to long transportation distances . Increasing the pipeline steel grade can reduce the pipeline construction cost. In recent years, the steel grades of steel used in natural gas pipeline engineering around the world are getting higher and higher . The thickness of the strip is getting thicker and thicker , and both X70 and X80 have been put into use in batches. At present, the X -series pipeline steel rolled by the domestic hot-rolling production line is delivered in the form of steel coils . Due to the high strength and high elasticity of the X -series pipeline steel, especially thicker varieties, it is required that the steel coils be packaged and bundled with a large binding force. , bundling is very difficult. For various reasons , Strap breaks occur frequently , lead to loose coils , It will cause scratches and contusions on the surface of the steel plate, or even the scrapping of the entire steel coil, which will also pose a threat to the safety of the operators.

The bundling quality of steel coil directly affects the quality of steel coil. This paper mainly conducts theoretical analysis, calculation and simulation experiments on the main factors that cause the fracture of X80 steel coil strapping . Combined with the calculation and analysis of the advantages and disadvantages of the current bundling method , The research idea of the bundling method of high-strength steel coils is put forward.
Analysis of the Causes of Strap Breakage

22 On-site investigation
After investigation, the factors that may cause the straps to break are analyzed.

1. strapping. Generally, standard black lacquer straps are used , with a thickness of 0.9 mm and a width of 31.75 mm . Steel coils are bundled with 6 to 8 straps in the circumferential direction and 2 to 4 straps in the radial direction .
2. lock. At present, the maximum locking force of the locking type pneumatic tying heads ( including imported products ) commonly used in our country is about 6 000 ~ 8 000 N , and the maximum locking force of the fully automatic tying heads used abroad is 17000 ~ 20000 N. Under the condition that the tensile strength of the strap is the same, the size of the strapping force is determined by the strapping head. The locking force of the pneumatic strapping head is inherently small, and it is also affected by factors such as air source pressure and worker operation. Therefore, the locking force of the strapping straps for manual packaging is insufficient, and the strapping of steel coil packaging is not tight.
3. steel coil. Because the tail head leaves the rolling mill during coiling , the coiling tension cannot be established , and the X70 and 80 steel grade strips have high strength and large thickness, so the pressure roller on the coiler cannot press the tail head against the steel coil. For example, X80 steel coil with a thickness of 20 mm has a head at the end

①The tape head springs up , and the end of the tape head is in direct contact with the strap , causing the strap to be cut , as shown in Figure 2 .
② When the bundled steel coils are hoisted into the warehouse , the coils are stacked close to each other . The self-weight of the steel coils makes the tail bounce off , and the lead is pressed against . The head springs back and the strap is pulled, causing the strap to break.
③ After the steel coil is in the hands of the user, it is uncoiled and opened again . The bounced part of the tail of the steel coil is not easy to roll on the ground roller . If the steel coil rolls in the opposite direction, it will only cause the steel coil to deviate .

The bounce is serious , and the maximum bounce distance ( referring to the distance between the end of the belt head and the entire diameter of the steel coil to the scrapping direction of the steel coil ) is about 70 mm . See Table 1 for the bounce distances of coils of other steel grades .

(4) Others. ① There is a large gap between the head and the steel coil at the end of the spring-off steel coil . When the driving clamp falls inaccurately , it will be knocked on the strap to break the strap ; at the same time, the strap at the gap of the lead is easy to hang on other steel coils And was pulled off. ② During the long-distance transportation, the hoisting of the steel coil knocks down the clamp , causing the clamp to slide , and the sliding clamp makes the tail of the steel coil more elastic, causing the strap to break. The long-distance transport of the steel coil is subject to vibration , which causes the lock at the joint of the strap (the lock is the weak point of the strap) to break easily.
, the main reasons for the breakage of the steel coil straps of X70 , X80 and other series of pipeline steel coils are obtained.
3 Calculation of the pressure force of the steel coil head
In order to effectively eliminate the impact of the springback of the steel coil head on the bundling, the mechanical theory calculation is carried out on the pressure of the tail head.
31 Mechanics and Mathematical Models
In order to simplify the theoretical analysis and calculation and simplify the actual stress situation, the following assumptions are made for the model: ① Neglect all friction forces; ② One end of the steel coil head is a fixed end; The roll is a rigid cylindrical surface; ⑤The external load F is a concentrated load and acts on the free end of the head.

F = R ; when F > Fo , a part of the tape head is in contact with the cylindrical surface, and AC section is in contact with the cylindrical surface, AC = x then
1 J 「 F( Lx ) =] EI
PR EI ' FR

After the AC section is in contact with the belt head , point C moves to point C , point B moves to point Bi , and point G cannot move down due to the restriction of the rigid cylinder ; But point Bi can continue to move down to point B 2 due to the elastic deformation of the CiBi section lead , so the displacement wb of point B at the free end of the lead consists of three parts.

Calculation example and result analysis :

project	value
Steel coil and strip steel grade	X 80
Bandwidth b/inm	i 800
Belt thickness t/inm	20
Belt length 1 / mm	360
Coil radius R / mm	900
Elastic modulus E heart Pa	210
Yield limit J/MPa	680
Strength limit % MPa	800

 in conclusion

1. for the breakage of the X70 and X80 pipeline steel coil straps is the springback of the tail of the steel coil.
2. A mechanical model and a mathematical model of the pressure of the tail of the steel coil with the head are proposed.
3. The finite element software simulation experiment shows that the selected mechanical and mathematical models are reasonable and can meet the precision requirements.

for the research and development of the X80 pipeline steel coil bundling method, and provides a certain reference value for improving its bundling quality and efficiency and reducing its bundling cost.

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