guofang

How to Form the Production Technology of Spiral Steel Pipe

Gfzg2019 — Wed, 17 Jul 2019 04:03:48 +0000

Spiral steel pipe is a kind of spiral steel pipe, which is made of strip coil as raw material and is often extruded at high temperature. It is welded by automatic double-wire submerged arc welding process.

(1) Raw materials are strip coil, welding wire and flux. Strict physical and chemical tests are required before investment.

(2) Submerged arc welding with single or double wires is used for butt joint of strip head and tail, and automatic submerged arc welding is used for repair welding after coiling into steel pipe.

(3) Before forming, the strip is leveled, trimmed and planed, and the surface is cleaned, conveyed and bent.

(4) Using electric contact pressure gauge to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth conveying of strip steel.

(5) Externally or internally controlled roll forming.

(6) Weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, offset and weld gap are strictly controlled.

(7) Both internal welding and external welding are performed by single-wire or double-wire submerged arc welding with Lincoln Welding Machine, USA, so as to obtain stable welding specifications. (8) The welds after welding are inspected by on-line continuous ultrasonic automatic damage instrument, which ensures 100% non-destructive detection coverage of spiral welds. If there are defects, alarm automatically and spray marking, production workers can adjust the process parameters at any time to eliminate defects in time. (9) Air plasma cutting machine is used 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 of welds, chemical composition, dissolution status, surface quality of steel pipes and non-destructive testing to ensure that the pipe-making process is qualified before being put into production. (11) Where there is a continuous acoustic flaw detection mark on the weld seam, after manual ultrasonic and X-ray inspection, if there is a defect, after repair, the defect is subjected to non-destructive inspection again until it is confirmed that the defect has been eliminated.

(12) The tube where the butt weld of strip steel and the T-joint intersect with the spiral weld are all inspected by X-ray television or photography. (13) After hydrostatic test, the pressure of each steel pipe is sealed radially. The test pressure and time are strictly controlled by the micro-computer detection device of steel pipe hydraulic pressure. The test parameters are printed and recorded automatically.

(14) The end of the pipe is machined so that the verticality, groove angle and blunt edge of the end face can be accurately controlled.

Advantages and Strength of Stainless Steel Elbows

Gfzg2019 — Wed, 17 Jul 2019 04:02:38 +0000

Stainless steel elbows do not cause corrosion, pitting, rust or wear. Stainless steel is still one of the most powerful building metal materials. Because stainless steel has good corrosion resistance, it can make structural parts permanent to maintain the integrity of Engineering design. Stamping elbow of stainless steel containing chromium is also a combination of mechanical strength and high extensibility. It is easy to process and manufacture parts and meets the needs of architects and structural designers. All metals react with oxygen in the atmosphere to form oxide films on the surface. Unfortunately, iron oxide formed on common carbon steel is oxidized successively, which enlarges the corrosion and eventually forms holes. Carbon steel can be electroplated with paint or oxidation-resistant metals (e.g., zinc, nickel and chromium), but as is known, this protection is only a thin film. In addition, the front end of the push head is usually large outside diameter, which needs to be shaped through the shaping die. The whole die is actually a press, with a set of dies, two semi-circular arcs, one upper and one lower. After shaping, the outer diameter of the finished product meets the size requirements. The wall thickness is controlled since then. The wall thickness tolerances of elbows and pipes are the same, both of which are (+12.5%). In addition to chromium, the commonly used alloying elements are nickel, molybdenum, titanium, niobium, copper, nitrogen, etc. to meet the requirements of various uses for the structure and function of stainless steel stamping elbows.

Calculation Method of National Standard Tee-Tong Suitable for Engineering Application

Gfzg2019 — Wed, 17 Jul 2019 03:55:40 +0000

In view of the importance of the national standard tee in the safety assessment of pressure pipelines with defects due to its complex structure, many structural parameters and limit load research, the difficulty of establishing analytical solutions of stress and limit load of tee with local thinning defects and the limitation of theoretical derivation can not well simulate the mechanical model and boundary conditions. In this paper, the method of finite element analysis is used to obtain the formula of plastic limit load on the basis of accumulating a large number of plastic limit load data of tees with different geometric parameters, so as to explore the calculation method suitable for engineering application. In view of the existing problems, the following research contents are determined on the basis of previous research results:

(1) Finite element method is used to analyze and calculate the ultimate load of flawless welded tees under internal pressure, and the influence of geometric parameters of national standard seamless tees on the plastic ultimate internal pressure is studied, so as to simplify the influence factors of plastic ultimate internal pressure, and on the basis of a large number of finite element calculations, the plastic covering area is established. Limit internal pressure database.

(2) Based on the established database of plastic limit internal pressure of defect-free welded carbon steel tee, the engineering estimation formula of plastic limit internal pressure of defect-free tee is fitted, which is suitable for engineering application and has high precision.

(3) The plastic limit internal pressure of welded tees with local thinning defects under internal pressure is studied by numerical analysis and calculation.

Pressure Opening Technology for Large Caliber Head

Gfzg2019 — Mon, 15 Apr 2019 02:58:52 +0000

In addition, the sealing performance of the splint valve and the head is difficult to meet when the medium is continuously transported under pressure. At the same time, the perforation chip and the life of the barrel knife will affect the performance and efficiency of the head.

In order to improve the working efficiency of large-caliber long-distance pipeline open-end, finite element simulation analysis of hanging head for open-end and design and laboratory test of double-stage hanging head were carried out, which improved the performance of open-end.