Gas Cylinder Manufacturing (2) -Gas cylinder typical process

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(2) typical process

1.blanking
Volume of 40 liters of gas cylinders (m), the raw material for 4219 seamless steel pipe, the feeding length is about 5 - 7m, cutting long about 1450, as with oxygen acetylene cutting material usually by a fixed distance multi torch cutting device and by using a mechanical shearing device cut pipe, see chart below.

Tool steel blade contact with the rotating steel pipe, the blade gradually under pressure, and gradually cut down the steel pipe. Cutting feed nozzle quality is less than the material and mechanical, material to clear the tube of molten slag. The billet material for domestic oxygen acetylene or oxygen - Liquefied petroleum gas flame cutting, multi band or foreign cutting circular sawing machine. Oxygen and liquefied petroleum gas cutting can be used as follows: oxygen pressure is about 1.18MPa (12ksf / cm2G), liquefied petroleum gas pressure is about 592Pa (cm2G / 0.6kSf), cutting line speed, about min / 120mm. Bottle bottle weight about 57kg, taking into account the loss in the process of, such as burning, incision and, under the weight of material to 1.1 times the bottle weight, about 62kg, for 200X200 square steel billet, blanking length approximately is 220mm. In order to reduce the deviation of the wall thickness of the blank, the cutting surface of the billet is provided, and the cutting surface should be smooth and smooth,"Shooting" should be used as cutting grinding wheel, grinding and cutting slope should be gentle, finished, should not be quenched, such as water etc.. Cutting equipment, can be stepless speed regulation, semi automatic gas cutting machine, such as welding and cutting machinery factory in Hangzhou, the types of CC3, 100 semi automatic gas cutting machine. In order to improve the accuracy of cutting surface, supersonic nozzle is usually adopted, which has the advantage of cutting speed and good roughness. Compared with common cutting nozzle, cutting speed can be increased by 1 ~ 3 times. The main principle is that hyperbaric oxygen pore shape is similar to the form of Laval nozzle, supersonic flow reaches at the exit. Hyperbaric oxygen flow boundary neat, wind incision length, narrow. The structure of the fast cutting mouth is shown in Figure, as shown in brass.

Disc saw as shown below:

The roller billet transport, with a fixed length in the table, according to the length of fixed length. When the billets shall be cut, motionless in the table, start the circular saw, and saw before and after moving on the slipway, cutting. Mltacut disc saw performance:
(1) the saw material specification 25 ~ 330mm;
(2) cutting length tolerance 0.25mm;
(3) cutting vertical 0.05mm;
(4) sawing material carbon steel, alloy steel, the hardness of HR is less than or equal to 45;
(5) saw blade speed n =62 rpm, n =10 rpm;
(6) the maximum length of the saw is Lmax=914mm;
(7) the diameter of the saw blade is D = 762 ~ 1016mm.

2. billet heating
The heating specification of the billet is determined by the critical temperature and process requirements. 40Mn2 critical temperature data are as follows

Symbol	Explain	Temperature
AC1	When steel is heated, the temperature of austenite begins to form.	713
AC3	Hypoeutectoid heating, all ferrite were transformed into austenite temperature	766
Ar1	After high temperature austenite of steel, the austenite is decomposed into ferrite and pearlite.	627
Ar3	Hypoeutectoid steel, high temperature austenite, cooling, ferrite start temperature analysis	704

40Mn2 critical temperature data table

Specification for tensile temperature of 40Mn2 steel

For this purpose, the billet is heated to 1200 ~ 1180, and the temperature difference between the upper and lower temperature is required, and the surface and center temperature are close, so as to reduce the wall thickness difference caused by the temperature difference. Heating equipment is usually used in a continuous heating furnace or an annular heating furnace, with heavy oil or coke oven gas or liquefied petroleum gas as fuel. The structure of the ring heating furnace is shown in the following diagram:

The heating furnace is supported by 12 supporting rollers, the side walls and the roof still, only by rotating the piston pushing the hearth bottom. A stroke of piston, bottom rotate 4. The bottom rotating, reciprocating cycle, rotation about 2.5h. The bottom seal. The main technical performance of the circular heating furnace is as follows:

(1) furnace size diameter 8410mm, high 2420mm;
(2) the bottom area of 272m2;
(3) maximum productivity H / 4500kg;
(4) the maximum loading capacity of 90 pieces per furnace; (5) the highest temperature of 1350 DEG ;
(6) fuel coke oven gas;
(7) low calorific value of fuel m3 / 16.7MJ;
(8) H / 715m3 maximum fuel consumption;
(9) gas pressure 0.029MPa;
(10) 7511 of the high pressure nozzle of the gas nozzle model.
Annular furnace is divided into three zones: preheat temperature 1050 - 1150, heating zone temperature 1260 ~ 1300 DEG C, uniform temperature zone temperature of 1300 ~ 1350 DEG C, total heating time of 2.5 ~ 3H, most should not more than 4 hours. In order to heat evenly, the distance between the two blocks should not be less than lOOmm. The temperature by the thermocouple, electronic potentiometer and automatic recorder, measured by optical pyrometer temperature. Steel billet in and out of the heating furnace, respectively, with the feeding manipulator. And the feeding machine hand to achieve, by the heating of the material from the furnace out of the material from the furnace, placed on the feeding car, on the way through high pressure water to remove the oxide skin, the car to the vertical hydraulic pressure machine for extrusion. In order to improve the quality of heating, Anshan high pressure vessel factory to introduce the United States gas cylinder production line, the use of electric heating, the billet heating the use of power frequency. Induction heating furnace as shown below:

The technical performance of the furnace:

(1) production capacity of 4358 ~ 8626kg / h;
(2) the highest temperature 1320;
(3) the voltage value is 440 - 850V;
(4) cooling water pressure from 0.2 to 0.48MPa;
(5) cooling water min / 1495L;
(6) air pressure 0.39 - 0.59MPa;
(7) total heating time is 37 ~ 48min;
(8) baked temperature 1320+10.
The furnace with thermocouple, electronic potential difference meter of temperature adjustment and control and monitoring with optical pyrometer and infrared temperature measurement meter.

3 extrusion
Extrusion and extension is the E type production of seamless gas cylinder of the most important two processes, after heating the billet material, the first in the vertical hydraulic press on the anti extrusion, after the anti extrusion cup shaped parts see the left, at this time the cup shaped pieces of temperature, generally at 1000 degrees Celsius, with the car quickly into horizontal pressure machine for thin stretch, pull out of the bottle blank see right.

Mold is squeezed and stretched the main process equipment, anti-extrusion die as shown in the following figure standing on a hydraulic press. Punch the outside diameter φ215mm, material 5CrMnMo, surface hardness after quenching HRc40 ~ 42; lower die diameter φ260mm, material ZG45, surface hardness after quenching HRc50 ~ 55; order to facilitate the return feed from the mold, the lower mold large hole under small, about 1% of the slope. After the anti-extrusion die installed in a vertical hydraulic press, adjusting the gap around, so the relative gap between the two positions is not more than 0.5mm, then preheat the mold to a temperature of not less than 200 ℃, after pressing a few cup after the mold temperature, the mold would need internal cooling water, maintaining the temperature at about 250-300 ℃.

Former anti-extrusion billets heated surface oxide has been using high-pressure water rinse, and the punch and the die surfaces are coated with a lubricant (graphite plus oil) as a stripper convenience, the gob also added a teaspoon of crushed coral, this time with a vertical hydraulic press activity crossbeam punch quickly depressed, so that the blank to complete the anti-extrusion process. Each manufacturer of vertical hydraulic press to squeeze pressure were about 1000 ~ 2 000t.

4. Pulling

The cup-shaped member stretched preform about 1.5m, the hot deformation process and anti-extrusion process is different, this pulling is stretched thin, pulling mold shown below horizontal hydraulic machine, die bar outer diameter φ206mm, slightly tapered to facilitate the release, the material is 3Cr2W8 or 5CrMnMo, best heat treated for long life. When pulling through five die ring, until a predetermined outer diameter and wall thickness, diameter die five laps were about φ242, φ234, φ228, φ223 and φ220.5 (which five die ring size refers to the outside pulling 219 diameter cylinders, such as cylinders punch other specifications, the need to change the mold ring size), mold rings made of 40 gauge steel, die part after welding and high temperature wear resistant surfacing cobalt-based electrode. The role of top and bottom mold is a concave top to the bottom of the preform bottom, the separation distance of five die ring has certain requirements. The inner diameter of the mold is determined based on deformation coefficient, mold ring spacing distance is determined, at the same time to meet the mold when pulling laps while working no more than two of requirements, therefore, the main requirements for horizontal hydraulic press is not pressure, but stroke length (about 6m). Since the stroke length, naturally increases the horizontal hydraulic machine design and process operations in some of the difficulties of factors. Horizontal hydraulic pulling machine mold have preheating temperature not lower than 150 ℃, after pulling a few, the ejector pin Once the temperature rises need ejector pin internal water cooling, maintaining the temperature at about 250 ~ 300 ℃. Before pulling need to sprinkle a teaspoon of graphite powder in the cup after extrusion, and apply lubricant to die in five circles. At this horizontal hydraulic press activity crossbeam with ejector pin to move quickly to the top of the cup-shaped member over five.

 

Where: Fo-- before pulling, that is, after the biggest anti-extrusion cup mold cross-sectional area;
After finally pulling F--, cylinders preform minimum cross-sectional area;
μ-- elongation.
When using single-mode, allows a maximum elongation of 1.4, in the use of the mold, the total elongation of the maximum allowable 1.7, while three or more mold ring while pulling difficult to balance and harmony, it should not be used, in addition In design mode ring size, should as far as possible elongation of the first to die larger; and finally - to die elongation smaller, which prevent the pull-off and improve the surface quality of the preform are good.

Similarly obtained: μ2 = 1.39, μ3 = 1.29, μ4 = 1.28, μ5 = 1.24. If found by elongation of each runner mold ring confrontation of misallocation should readjust the inner diameter of each circle runner mold. Horizontal hydraulic machine when pulling, pulling force P (kg) by the following formula were checking.

Where: Fo-- pull the cross-sectional area of the stretch before, cm2; the cross-sectional area after pulling F--, cm2; a-- pulling on Corner stretch ring mold, usually a = 15. f-- friction coefficient, taking 0.4σb-- in pulling temperature tensile strength, kgf / cm2. For general medium carbon steel, μb value can be 5,55kgf / cm2 at 1 100 ℃, at 1 000 ℃ advisable 825kgf / cm2, through a second molding ring, extending the maximum force, it can be molded on the second lap accounting that P = 134 × In1.39 × 825 [1 + 0.4 (ctgl5. + tgl5.)] = 95 000kg = 95 ton (considering the value of the mold should be doubled by households) in 1981 after China's use of E-type production of seamless gas cylinders manufacturers, have felt the fixed mold ring were pulling, friction large, requires a horizontal hydraulic press with a large-tonnage, particularly due to pulling the metal deformation 'is by and die ring surface complete heat friction, resulting in low life ring mold, bottle after pulling surface scratches can be serious, especially in vertical scratches effect on the strength of a large bottle, a lack of competitiveness in the international market. For this reason, the manufacturers use the scroll mode reference to foreign circles pulling bottles of advanced technology, design of the rolling pulling new process has the characteristics of each plant, so-called "having the characteristics of the plant" means the plant were taken into account in the design the actual situation of the plant, such as the use of existing horizontal hydraulic press (stroke unchanged), and some plants even do not change the diameter of the mold base. To this end, the plant is the deformation of the metal are still carried out using a fixed mold ring rolling mold ring mainly to solve the stent ring and scratches caused by rolling in addition to sizing problems. Scroll die overall structure as shown below:

The late 1980s, our country each cylinder manufacturer, to improve product quality, the international market, the introduction of foreign advanced technology transformation, so that replacement products. The first is the transformation of the press stand and lying press, mainly to solve the problem of large deviations wall. Large vertical press tonnage at most about 2000 tons, this press rigidity is good; second is to Dun thick, then squeeze, so the blank and die concentric, in addition, the guide sleeve is installed in the mold, the upper and lower mold on the positive, extrusion punch, one for a change, then punch cooling, two punches used interchangeably, thus reducing the partial wall preforms, general wall impartial than 1mm; bench press on rolling mold ring so that the cylinder surface is smooth, the other punch is a punch for a change, then cooling, a few punches are used interchangeably, so on the one hand to ensure the cylinder size, on the other hand to extend the service life of the punch.

( Editor: Peter )