Monday, October 20, 2014

The superiority of spiral pipe in uses

According to the nature of doing HDPE plastic spiral coil, with a light texture, high strength, good toughness, easy to lay, water resistance, low cost, corrosion resistance, etc., its performance and economic benefits far exceed the reinforced concrete pipe and general specifications iron pipe, engineering pipe replacement products. In metallurgy, petrochemical and other industries exchanger design, there are various forms of heat, but the presence of a conventional heat exchanger ineffective, difficult to clean, fouling resistance and large more drawbacks, can not meet production of customer needs. According to the spiral knot spiral hose heat exchanger to do its good effect of heat transfer, easy to clean, low fouling resistance, compact structure and so on.

Plastic spiral steel pipe (also called hollow wall winding plastic tube) is a wall structure is very reasonable plastic tube. The overall use spiral structure. In for urban drainage projects, improve drainage capacity facility (or narrow diameter) and engineering service life, easy construction, shorten the construction period, when the water table is high, the depth of excavation and restoration of large or require high road, the project cost significantly reduced. Spiral has many superior heat transfer characteristics and structural features straight tube. Heat transfer coefficient is higher than the straight tubes, more heat transfer area can be obtained in the same space, the longer the pipe is arranged to reduce the seam to improve the safety. So spiral heat exchangers and steam generators in the field of power engineering, chemical, aerospace, and nuclear energy has been widely applied.

Large plastic spiral steel pipe is formed with a "T" shaped ribs with a sheet of polyvinyl chloride (UPVC) mixing the carbon black or high density polyethylene (HDPE) using a hot press method. Then on the volume of the machine roll cut into spiral. By quickly locking mechanical connection, the application of an adhesive or melted PVC reinforced molded plastic spiral. It has a large diameter, high corrosion resistance, good anti-leakage effects, quick construction and other characteristics.

Friday, October 17, 2014

Galvanized surface pretreatment

In order to get a good layer of zinc, steel surface must be very clean, rust, iron oxide, and this will reduce the adhesion properties of the coating, prevent binding of iron and zinc. Therefore, before plating steel surface preparation must be carried out. The process includes a general degreasing, washing, pickling, and then washing with water. Also included in the dry storage of galvanized, painted solvent.

The purpose is to remove grease clarinet skim the surface, dirt, steel pickling plant so as not to affect the results, degreasing can be achieved by burning or caustic, often caustic. Alkaline cleaning solution is an aqueous solution containing about 10-12% NaOH, the temperature is 70-80 ℃. Cleaning time is 8-10 minutes.

The purpose is to remove pickling steel surface oxide skin, the acid is generally used sulfuric acid and hydrochloric acid, sulfuric acid pickling effect depends on the temperature, the effect of hydrochloric acid depends on the concentration of H ions. The pickling solution is an aqueous solution of sulfuric acid containing 10-15% sulfuric acid at a temperature of 60-80 ℃, hydrochloric acid pickling solution containing 10-15% aqueous hydrochloric acid, at a temperature below 40 ℃, the pickling time is usually 30 minutes. The advantage of hydrochloric acid is that it can operate at room temperature, removing the oxide scale capability, less erosion of the base metal by absorption of the hydrogen gas and small in the possibility of contamination of the residue of carbon black, ferric oxide generated acid matter, dark angle, easy to remove, no effect on zinc from galvanized perspective, hydrochloric acid is more appropriate. However, the low sulfuric acid prices, easy regeneration, therefore, countries choose pickling solution under different circumstances, the United States and more with sulfuric acid, hydrochloric acid and West Germany, multi-purpose. Adding an appropriate amount of inhibitor in the acid, the acid can etch the surface of the pure steel decreases, so that the contact is reduced with hydrogen in the steel pipe. In addition, also reduce acid consumption and mist generated, the amount inhibitor is typically 0.1-0.5%. Usual amount inhibitor is generally 0.1-0.5%, commonly used inhibitor of water such as plastic.

Seamless steel tube for pipeline engineering welding techniques

Steel pipe transported to the site, firstly according to equipment and fittings position pipes, and in the field will be specific length of each pipe of measurement is good, mark the specific size and arrangement of the position, so that when the interface condemnation, the use of lower crane tube, down tube process be used in nylon lifting sling to pipe insulation protection.

Dual control heating pipes, under normal circumstances can reduce 25% of project cost (using FRP do protective layer) and 10% (high-density polyethylene made ​​protective layer) around. Pipe shall have a cross weld anywhere. When tack welding, weld all electrode positioning number (or grade) should be formally welding the same, but some fine electrode diameter optional. Positioning the welding current is selected from the weld becomes larger than the time of welding, is usually 10% -15% larger, in order to ensure penetration. For pipe welding, the weld should be smooth, uniform width, root penetration, no obvious defects and undercut bump phenomenon, should be above the pipe welds to strengthen the surface area of ​​about 2 mm, welding the groove edge 2-3 mm. When the pipe and flange welding, pipe flanges should be inserted thirds, flange and pipe should be perpendicular to the axis of the two coincide.

a, horizontal pipe slope of not less than 0.3%.
b, should be checked before welding welding environment, welding installation equipment, welding materials, and dry cleaning, must comply with the specifications and requirements of welding operations.
c, welding pieces of double-sided welding, weld root should be cleaned and checked back, after cleaning up the defect before welding seam on the back. The provisions of gouging welds should be visually inspected after gouging before welding.
d, the wall of the pipe must fight more than 4mm groove before welding, bevel surface may not have dissection, cracks, damage processing, burrs and flame cutting slag and other defects. After coating should knock welding clean, weld should be rendered uniform scaly, without pores, slag, cracks, welding tumor and other phenomena, biting flesh length should be within specifications.

Thursday, October 16, 2014

The purpose of precision seamless steel tube heat treatment

Precision seamless steel tube as a product must have a certain performance to meet the needs of using conditions.There are two ways to improve the performance of the steel, it is adjusting the chemical composition of steel, which uses alloying method;The other is the combination of heat treatment and heat treatment and plastic deformation.In the field of modern industrial technology, heat treatment in the aspect of improving the performance of the steel is still dominant.

There are many types of precision seamless steel pipe, and formulate the corresponding standards, the use of steel seeds range, sometimes users according to their own conditions attached to increase demand.In the standard, as one of the terms of delivery performance indicators must meet specified requirements.The performance of precision seamless steel tube mainly refers to the mechanical properties, physical properties, performance and process capability, etc.And the heat treatment by heat, heat preservation and cooling to obtain certain steel microstructure and properties of the corresponding, in order to meet the product standard and the user's requirements.

Precision seamless steel tube heat treatment embodied in the following aspects: the purpose of homogenization for precision seamless steel tube group By heat treatment can eliminate the original precision seamless steel tube production of uneven performance of organization, to achieve the required uniform organization and physical properties;To eliminate the defects in production Such as cold drawn precision seamless steel tube processing production after hardening of 1.3 1.6 times higher strength, elongation rate was reduced by 30% - 35%, corresponding to cold working can pull off, so you need to intermediate annealing to eliminate internal stress;When hot rolled seamless precision seamless steel tube in the residual stress is bigger, affect the corrosion resistance, the fight against performance also need to eliminate the residual stress in heat treatment.

Spiral steel pipe heating process

In spiral steel pipe production process, the main processing was conducted under the thermal state, so the heating operation is very important to determine product quality process.

Heating operation lies in: the temperature of billet uniformly heated to suitable for processing due to punch a great influence on the quality, that is to say, the temperature of the perforation process is one of the important conditions affect the quality, so often to the perforation process of billet temperature control.Improper heating will be inside the tube billet surface or outer surface crack, folding and eccentric waste products.Blank hole temperature varies according to different materials.But mostly at about 1200 ℃, carbon and other alloying elements is large temperature is somewhat low.Heating operation the second key is to minimize the number of scale: especially in hot extrusion elbow, from the tool life and surface quality of extruded tube, more strict.Such as hot stove, according to their functions, divided into two kinds of furnace and furnace again;The former is used to heat the blank from room temperature to the processing temperature;The latter will be used in the processing process, then heated to the necessary processing temperature.There are many kinds of heating furnace, but the main use of annular furnace.This kind of furnace has annular furnace bottom, it can turn slowly, the diameter of the blank from the entrance along the bottom direction loading, turning a can be used at the exit of the heating and soaking to the specified temperature of a stove.Spiral steel pipe production process more slowly, but the factory use the spiral steel pipes are all conform to the specifications of the products.

Carbon steel pipe cap

The circular (ring) carbon steel pipe cap stress and meridional stress at various points on the shell (axial) are changing, the vertex equals the hoop stress and axial stress, and stress on the equator.Carbon steel pipe cap under uniform internal pressure, axial stress of constant for the tensile stress (positive), an by a maximum point toward the equator gradually decreased to the minimum; hoop stress at the head transition zone will begin to appear compressive stress, continue to increase, if the length of axis ratio head transition zone on the edge of the compressive stress value will increase rapidly, the head is shallow, the higher the compressive stress values on the edge of the head, so will head length ratio limit within 2.6 is more reasonable.

Carbon steel pipe cap on QiuGuanXing head design, should pay attention to the cylinder connected to the pipe cap thickness should be not less than the thickness of the head, or should be set up to strengthen the period of transition between head and cylinder connections.Cylinder should strengthen the thickness of the section and the top thick, length should not be less than, the purpose is the cutting edgestress.

Tuesday, October 14, 2014

Carbon steel seamless steel tube concrete classification

Carbon steel seamless steel pipe concrete classification and application
1, general carbon seamless pipe
General carbon content 0.25% or less steel is low carbon steel, mild steel annealing organization for ferrite and a small amount of pearlite, its low strength and hardness, plasticity and toughness is good, easy to drawing, stamping, extrusion, forging and welding, including 20 cr steel used more widely.The steel has the certain strength, after the steel quenching tempering at low temperature has good comprehensive mechanical properties, good low temperature impact toughness, temper brittleness is not obvious.
USES: in the machinery manufacturing is suitable for making welding structure, and by forging, hot stamping and machining parts are not affected by high stress, corrosion in the steam turbine and boiler manufacturing for more than medium work of pipes, flanges, header, and various kinds of fasteners;Applies to the manufacture of automobiles, tractors and general machinery manufacturing small and medium-sized carburizing and carbonitriding parts, such as car hand brake shoe, passive gear lever fork shaft, transmission speed, transmission and tractor on the camshaft, hanging balancer shaft, balancer, inner and outer bushing, etc.;In medium and heavy machinery industry, such as forging or suppression of rod, shackle, leverage, sleeve, fixture, etc.
 
2, low carbon steel seamless steel tube
The carbon content of mild steel carburizing: in more than 0.15% of low carbon steel after carburizing and quenching and low temperature tempering treatment, surface requirement for high hardness, good wear resistance shaft, shaft sleeve, sprocket, and some parts, such as plastic mold.Low carbon steel after carburizing and quenching and low temperature tempering treatment for surface for high carbon martensite, the core of low carbon martensite organization, so as to ensure that the surface has high hardness, high wear resistance and core has good strength and toughness.Hand for the production brake shoe, fork lever shaft, transmission speed, transmission driven gear and the tractor on the camshaft, hanging balancer shaft, balancer, inner and outer sleeve, sleeve, fixture, etc.


3, medium carbon steel seamless steel tube
Medium carbon steel, carbon is 0.25% ~ 0.25% of the carbon steel, 30, 35, 40, 45, 50, 55 brand belongs to the medium carbon steel, because of the content of pearlite in the steel, before its strength and hardness is improved, the hardness after quenching can increase significantly.Among them, with the most typical of 45 steel.45 steel is the carbon quenched and tempered high strength steel, has a certain plasticity and toughness, good cutting performance, the quenched and tempered treatment can obtain good comprehensive mechanical properties, low hardenability.Used in the manufacture of high strength requirement, the toughness of medium parts.Usually in conditioning or using normalized condition.In order to make the steel has the necessary toughness and eliminate the residual stress, should be after the steel quenching tempering sorbite.