RU2566109C1 - Production of shell from structural complex-alloyed cold-shaping steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: performed are calibration, recrystallization annealing and preliminary machining of preset-size blanks of shells and rings. First strain hardening of shell blank is conducted at rotary drawing in several passes with intermediate recrystallization annealing while second one consists in quenching and tempering, rotary drawing and annealing to decrease the strain. Rotary drawing of conducted to get the shell bulged edges. Ring blanks are subjected to quenching, tempering and final machining to get the edges for ring welding of appropriate depth and length. After welding, produced welds are subjected to low-temperature tempering by HF currents.

EFFECT: high mechanical properties of welded shells, low residual inner strain, higher precision of geometrical sizes and strength of welds.

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Description

The invention relates to the processing of metals by pressure and welding, and in particular to the manufacture of shells, which are cylindrical thin-walled shells with thickened edges and cylindrical rings welded to them, intended for welded vessels operating under high pressure, for compressed air, liquefied and dissolved gases and used in various economic fields in the manufacture of fire extinguishers, oxygen and gas cylinders, compressed air cylinders, liners, receivers, etc.

The main requirements for pressurized enclosures are as follows: high structural and cyclic strength, geometric accuracy, surface finish, high quality welded joints, high manufacturing capacity and low weight.

A known method of manufacturing axisymmetric housings operating under pressure, RF patent No. 2295416, B21D 51/24, publ. 03/20/2007, bull. No. 8, which describes a method for the production of axisymmetric housings with end thickenings.

The method includes hardening, tempering, cold plastic deformation by rotational drawing in two passes, low-temperature annealing. Alloy steel is used, hardening and tempering are carried out, rotational drawing is carried out without intermediate annealing.

Also known is the “Method for sealing the neck of a cylinder”, patent RU 2002538 C1, B21D 51/24, by rotary machining by stepwise formation of the transitional and cylindrical portions of the neck at the heated end of the rotating tubular blank.

The main disadvantage of the above methods for the manufacture of bodies, shells and cylinders operating under pressure is the high complexity and cost of manufacturing, due to the shaping by pressure treatment of all-metal vessels that do not have welded joints.

The closest in technical essence and the achieved technical result is a method of manufacturing high-strength axisymmetric shells operating under high pressure (Novikov OM et al. "New technology for arc welding in protective gas of high-pressure cylinders", magazine "Professional welder" No. 1 , 2005, p. 14-15), adopted by the authors for the prototype, in which the machined part blanks are assembled using an assembly-welding fixture and the joints are welded with one-side mechanized electric arc welding with a melting tungsten electrode in two passes with filler wire in the second pass, with argon blowing from the inside from the root side of the seam, with alternating discrete (pulsating) supply of two protective gases - argon and helium to the zone of the continuously burning arc with simultaneous control of the arc voltage, then the final voltage is controlled machining, hardening heat treatment, control and testing of welds.

This method requires expensive helium, a complex system for regulating the supply of two protective gases and controlling their consumption, controlling the pulsation of separate flows of protective gases in the optimal frequency range. In addition, there is no strict system for fixing joints in welding. Welding is carried out on weight without lining.

The reasons that impede the achievement of the technical result indicated below when using the known method for manufacturing shells adopted by the authors as a prototype include the lack of the ability to provide high dimensional accuracy in alignment, as well as end and radial runout.

According to the applicants, the reason for the low accuracy in alignment, in the end and radial runout of the connected parts of the shells is the lack of solutions for fixing the edges to be welded during welding.

In addition, in this method, adopted by the authors for the prototype, there are no methods for the preparation and rotational processing of blanks of the shell and rings and their thermal strain hardening before welding.

The disadvantage of the prototype is also the hardening after welding of the cylinders, which leads to a change in geometric dimensions due to thermal influences.

Thus, the objective of this technical solution, adopted as a prototype, was to improve the quality of welded joints.

In contrast to the prototype, the method proposed by the applicants for the manufacture of a shell from structural complex alloyed cold-formed steel, operating at high pressure, made in the form of a thin-walled shell with thickened edges and rings welded to them, includes obtaining dimensional blanks of the shell and rings by cutting pipes, their calibration, recrystallization annealing and preliminary machining, after which the shell blank is subjected to the first strain hardening by means of rotational grades for several transitions with intermediate recrystallization annealing with a degree of deformation increasing from the first transition to each subsequent one 1.1–4.5 times, and the second thermo-deformation hardening by quenching and tempering, rotational drawing with a degree of deformation (35 ÷ 55)% and annealing, which reduces stress, while at all transitions of the rotary hood use triangular profile rollers with rounded vertices with a radius equal to 0.20 ÷ 0.55 of the wall thickness of the workpiece, and perform a rotational hood to obtain thickened shell edges, the thickness of which is determined by the formula:

, где:

where:

S ₂ - wall thickness of the thickened edges of the shell, mm,

S ₃ - wall thickness of the shell, mm,

σ _b - tensile strength of the material of the shell, MPa,

σ _b ′ is the tensile strength of the material in the weld zone, MPa,

and the preforms of the rings after preliminary machining are subjected to hardening and tempering to reach the tensile strength of the material of the thickened edges of the shell and final machining to obtain edges for welding the rings, the thickness and length of which are equal to the thickness and length, respectively, of the edges for welding the shell, then trim the edges shells and rings and their alternate assembly and automatic welding on an expandable mandrel with a removable lining, while automatic welding is performed by a consumable electrode from izkolegirovannoy hromonikelmolibdenovoy wire in a mixture of 20% Ar and 80% CO ₂ in a single pass with a through-penetration welded edges, then welds are subjected to low-temperature tempering the induction by high-frequency currents produce X-ray inspection of welds obtained membrane, followed by tensile testing internal hydraulic pressure followed by checking the tightness of the welds with pneumatic pressure.

This is what allows us to conclude that there is a causal relationship between the totality of the essential features of the claimed technical solution and the achieved technical result.

These signs, distinctive from the prototype and to which the requested amount of legal protection applies, are sufficient in all cases.

The objective of the invention is to provide high mechanical strength, ductility and low level of residual stresses, geometric accuracy and manufacturability of the manufacture of shells, the strength of welded joints, reliability and cyclic strength with low weight and low complexity.

The new set of operations, as well as the presence of relations between them, allow, in particular, due to:

- execution of shell blanks and rings from structural complex alloyed cold-deformed steel to provide the possibility of obtaining welded shells with high mechanical properties (tensile strength and relative elongation) at a low level of internal residual stresses, high impact strength and cyclic strength during their thermal deformation hardening by quenching and tempering operations, rotational hoods and annealing, reducing stress;

- cutting pipes into measured blanks of the shell and rings, their calibration, recrystallization annealing and preliminary machining to increase the utilization of metal and prepare blanks of the shell and rings for subsequent processing;

- performing the first strain hardening of the shell blank by rotational drawing for several transitions with intermediate recrystallization annealing with a degree of deformation increasing from 1.1 to 1.5 times from the first transition to each subsequent one, to ensure high accuracy of geometric dimensions, since, according to experimental results works, with an increase in the degree of deformation from each previous to each subsequent transition, radial and axial loads increase, which allows the metal to be pressed in the foci of deformations Missions to the mandrel and to avoid the flow of metal in the radial direction and the phenomenon of “rolling”, that is, an increase in diametrical dimensions, values 1.1-1.5 times determined experimentally and are optimal for this class of alloy steels, with less than 1.1 times, the phenomenon of “rolling” occurs, which leads to corrugations and sunsets, and at more than 1.5 times the axial forces increase, which leads to drags and cracks in the deformation centers;

- performing the second thermo-deformation hardening of the shell blanks by hardening and tempering operations, rotational drawing with a degree of deformation (35 ÷ 55)% and annealing, which reduces stress in relation to complex alloyed steels, to provide high mechanical properties: high tensile strength, ductility, high impact strength at a low level internal residual stresses, since the use of alloy steels of this class allows you to deform heat-strengthened workpieces, according to the results of experimental work the values of the degree of deformation (35 ÷ 55)% are optimal for this class of steels, when the degree of deformation is less than 35%, the final values of the tensile strength are reduced, and an increase in the degree of deformation of more than 55% leads to a decrease in ductility, impact strength, lower cyclic strength and a sharp increase internal residual stresses, and with a rotational hood - to reduce the service life of deforming rollers, mandrels and bearing assemblies;

- the use at all transitions of the rotational hood of rollers of a triangular profile with rounded vertices with a radius equal to 0.2 ÷ 0.55 of the wall thickness of the workpiece when processing shell blanks from complex alloyed steels, to ensure the possibility of plastic deformation of blanks from steel of this class, since the radius on the top of the rollers determines the area of the deformation zone and, therefore, the forces during rotational drawing are radial and axial, this range of the ratio of the radius and the initial wall thickness the workpiece is optimal from the point of view of stability of the forming process, when the ratio is more than 0.55, according to the results of experimental work, the metal pressure on the working surface of the roller increases, that is, the radial force increases due to an increase in the horizontal area of the deformation zone, which leads to rapid wear the working surface of the rollers and to the deterioration of the quality of the processed surface (to increase the height of the microroughness beyond the permissible limits), and when the ratio is less than 0.2, "tightening" occurs metal in the deformation zones and there is a “waviness” of the machining surface in the form of screw recesses that bring geometric dimensions beyond the limits of permissible deviations;

- perform rotational drawing of the shell blanks to obtain thickened edges with a thickness determined by the formula:

, где:

where:

S ₂ - wall thickness of the thickened edges of the shell, mm,

S ₃ - wall thickness of the shell, mm,

σ _b - tensile strength of the material of the shell, MPa,

σ _b ′ is the tensile strength of the material in the weld zone, MPa,

to ensure the mechanical properties of the heat affected zone of the welded joint at the level of the mechanical properties of the shell wall thickness, which determines the structural strength of the entire shell;

- hardening and tempering of the rings after preliminary machining to reach the tensile strength of the material of the thickened edges of the shell and final machining to obtain edges for welding rings whose thickness and length are equal to the thickness and length, respectively, of the edges for welding the shell, to ensure equal strength of the thickened edges of the shell rings in the weld zone;

- performing trimming of the edges of the shell and rings and their alternate assembly and automatic welding on an expandable mandrel with a removable lining, to ensure tight contact of the welded edges and their axial alignment with an error of not more than 10% of the thickness, and also to increase the manufacturability of assembly and welding operations;

- automatic welding with a consumable electrode of low-alloyed chromium-nickel-molybdenum wire in a mixture of 20% Ar and 80% CO ₂ in one pass with through-penetration of the welded edges to achieve a productivity increase of 2 ÷ 2.5 times with high strength and reliability of the welded joint;

- low-temperature tempering of welds by induction method with high-frequency currents to reduce the technological operation time compared to furnace heating, and also to maintain the level of mechanical properties of the metal;

- X-ray television control of the welds of the obtained shell quickly and reliably identify internal defects in the metal of the welds and heat-affected zones (lack of penetration, pores, cracks, slag inclusions, etc.);

- conducting strength tests with internal hydraulic pressure followed by checking the tightness of the welds with pneumatic pressure to ensure the tightness and structural strength of the welded joints and the entire shell.

Signs that distinguish the proposed technical solution from the prototype are not identified in other technical solutions and are not known from the prior art in the process of conducting patent research, which allows us to conclude that the invention meets the criterion of "novelty."

Studying the level of technology during the patent search for all types of information available in the countries of the former USSR and foreign countries, it was found that the proposed technical solution does not explicitly follow from the prior art, therefore, we can conclude that the criterion of "inventive step" ".

The invention is illustrated by drawings, where in FIG. 1 shows the process of rotational drawing of a shell blank for several transitions with rollers 3, 4 and 5 with a radius at the vertices R (mm), F (mm / min) - feed rollers, n (min ^-1 ) - rotation speed of the mandrel and the workpiece; in FIG. 2 shows the assembly and welding of a shell 1 with a ring 2 on an expandable mandrel with a removable lining 7, a collet 8, a rod 9, and a copper insert 10; in FIG. 3 type I - welded joint of the shell 1 with the ring 2, lining 7 and copper insert 10; in FIG. 4 is a general view of the shell with the shell 1 and the rings 2 welded to it.

Example.

Pipes from structural complex-alloyed cold-deformed steel 22KH3GN2M1FA ⌀180 × 20 mm are cut on pipe cutting machines to measuring blanks of the shell and rings, respectively 500 mm and 200 mm in length, and subjected to calibration on hydraulic presses, recrystallization annealing in shaft furnaces and mechanical (turning). Thus, the blanks of the shell and rings are prepared for further processing.

The shell blanks are first subjected to the first strain hardening by a rotary hood for two transitions with intermediate recrystallization annealing on a pressure-rolling machine: at the first transition with a degree of deformation

, где: S₀ (мм) - исходная толщина стенки, S₀=12 мм, S₁ (мм) - толщина стенки после первого перехода, S₁=8 мм, на втором переходе со степенью деформации

where: S ₀ (mm) is the initial wall thickness, S ₀ = 12 mm, S ₁ (mm) is the wall thickness after the first transition, S ₁ = 8 mm, at the second transition with a degree of deformation

where S ₂ (mm) is the wall thickness after the second transition, S ₂ = 5 mm

Intermediate annealing is performed in shaft furnaces at a recrystallization temperature of 575 ÷ 600 ° C.

The degree of deformation of the shell blank at the second transition ε ₂ % exceeds the degree of deformation at the first transition ε ₁ % 1.126 times.

[ε₂=(1,1÷1,5)ε₁ по формуле изобретения].

[ε ₂ = (1.1 ÷ 1.5) ε ₁ according to the claims].

и отжига, уменьшающего напряжения при температуре (400÷450)°C;

[ε₃=(1,1÷1,5)ε₂ и ε₃=(35÷55)% по формуле изобретения].Then, the second thermodeformational hardening of the shell blanks is performed in the form of hardening operations at a temperature of (900 ÷ 920) ° C and tempering at a temperature of (520 ÷ 540) ° C in shaft furnaces, a rotational hood of the third transition (Fig. 1) with a degree of deformation ε ₃ = fifty%

and annealing, which reduces stress at a temperature of (400 ÷ 450) ° C;

[ε ₃ = (1.1 ÷ 1.5) ε ₂ and ε ₃ = (35 ÷ 55)% according to the claims].

The result is a shell with dimensions: wall thickness S ₃ = 2.5 mm, the thickness of the thickened edges S ₂ = 5 mm and the length of the thickened edges b ₁ = 55 mm

, т.е

, 5≥2,83, что соответствует формуле изобретения.The thickness of the thickened edges of the shell corresponds to the formula

i.e.

, 5≥2.83, which corresponds to the claims.

When rotating the hood at all three transitions, use rollers with a radius at the apex R = (3 ÷ 6) mm, R = (0.25 ÷ 0.5) S ₀ = (0.25 ÷ 0.5) · 12 = (3 ÷ 6) mm, which corresponds to the claims.

Thus, the shell blanks are prepared for further processing.

,

- предел прочности материала после второго перехода ротационной вытяжки обечайки, на котором формируются утолщенные кромки (фиг. 1).The blanks of rings 2 (Fig. 4 and Fig. 5) after preliminary mechanical (turning) processing are subjected to hardening and tempering to the ultimate strength of the material of the thickened edges of the shell

,

- the tensile strength of the material after the second transition of the rotational hood of the shell, on which thickened edges are formed (Fig. 1).

Then perform the final machining of the workpieces of the rings 2 to obtain the edges for welding with a thickness and length equal to the thickness S ₂ = 5 mm and the length of the edges b ₁ = 55 mm for welding the shell 1.

After that, the trimming of the edges of the shell and rings for welding is performed for a length b ₂ = 40 mm (Fig. 2).

Then perform alternate assembly and welding of the joints of the shell 1 and rings 2 on the expandable mandrel with a removable lining 7 and a copper insert 10 (Fig. 2, Fig. 3 and Fig. 4).

The mandrel is made in the form of a expanding collet 8, on the outer surface of which a removable lining 7 with a copper insert 10 and an annular groove for forming a melt is installed. In the inner surface of the collet 8, having a conical surface, includes a rod 9 with a conical outer surface.

To assemble the welded joint of the ring 2 and the shell 1, the thrust 9 is moved to the left, while the thrust with a conical surface converts the axial displacement into radial, as a result of which the split lining with a copper insert is pressed against the inner surface of the welded edges to be joined.

Automatic welding is carried out with a consumable electrode of low-alloyed chromium-nickel-molybdenum wire in a mixture of 20% Ar and 80% CO ₂ in one pass with through penetration of the welded edges.

Then, the welds of the welded shell are subjected to low-temperature tempering at a temperature of 400 ° C by the induction method with high-frequency currents in a special induction installation.

After low-temperature tempering, an X-ray television inspection of the shell welds is performed to identify internal defects in the weld metal and the weld zone.

Strength tests are carried out by internal hydraulic pressure at a hydraulic test installation.

In conclusion, they check the tightness of the welds of the shell with pneumatic pressure at a pneumatic test installation.

The method allows to provide high mechanical properties of welded shells (tensile strength, elongation, toughness) at a low level of residual internal stresses, high accuracy of geometric dimensions, strength of welded joints, processability of welding, operational reliability and high cyclic strength with a high metal utilization rate and low labor input.

Laboratory tests were carried out and a pilot batch of welded shells was manufactured.

Claims (1)

A method of manufacturing a shell from structural complex alloyed cold-deformable steel operating at high pressure, made in the form of a thin-walled shell with thickened edges and rings welded to them, including obtaining dimensional blanks of the shell and rings by cutting pipes, their calibration, recrystallization annealing and preliminary machining, after whereby the shell blank is subjected to the first strain hardening by rotational drawing in several transitions with an intermediate p crystallization annealing with a degree of deformation increasing from the first transition to each subsequent one 1.1–1.5 times, and the second thermodeformation hardening by quenching and tempering, rotational drawing with a degree of deformation (35–55)% and annealing, which reduces stress, at this, at all transitions of the rotational hood use triangular profile rollers with rounded vertices with a radius equal to 0.20 ÷ 0.55 of the wall thickness of the workpiece, and perform a rotational hood to obtain thickened edges of the shell, the thickness of which is determined by the formula:

where
S ₂ - wall thickness of the thickened edges of the shell, mm,
S ₃ - wall thickness of the shell, mm,
σ _b - tensile strength of the material of the shell, MPa,
σ _b ′ is the tensile strength of the material in the weld zone, MPa,
and the preforms of the rings after preliminary machining are subjected to hardening and tempering to reach the tensile strength of the material of the thickened edges of the shell and final machining to obtain edges for welding the rings, the thickness and length of which are equal to the thickness and length, respectively, of the edges for welding the shell, then trim the edges shells and rings and their alternate assembly and automatic welding on an expandable mandrel with a removable lining, while automatic welding is performed by a consumable electrode from izkolegirovannoy hromonikelmolibdenovoy wire in a mixture of 20% Ar and 80% CO ₂ in a single pass with a through-penetration welded edges, then welds are subjected to low-temperature tempering the induction by high-frequency currents produce X-ray inspection of welds obtained membrane, followed by tensile testing internal hydraulic pressure followed by checking the tightness of the welds with pneumatic pressure.

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