A method of manufacturing a thin-walled cylindrical shell of maraging steel

 

The invention relates to mechanical engineering and can be used in the manufacture of thin-walled cylindrical shell with a wall thickness less than 0.2 mm After heat treatment of thick billet produce cutting its inner and outer surfaces with a minimum thickness variation. Then produce a rotational extrusion of the sheath a few preliminary operations and final. Rotary extrusion are for the minimum number of operations are valid for this material degree of deformation. When the thickness of the workpiece and the number of transactions rotary extrusion determine from these dependencies. Heat treatment membranes for stress relieving after preliminary operations rotary extrusion is produced in the free state, followed by carnerosana internal diameter. The result is the improvement of product quality at minimum cost. 1 C.p. f-crystals, 4 Il.

The invention relates to the field of engineering, and in particular to methods of manufacturing thin-walled cylindrical shell with a wall thickness of t<0,2 mm

The known method 2D/chr/916.gif">t0.01 mm with an inner diameter of125 mm made of Maraging steel (see technical report No. ETC 320-90-13 from 25.12.1998, JSC TITI, ,Tula). The method includes manufacturing a thick-walled workpiece, heat treatment, cutting the inner and outer surface of the thick-walled workpiece to the thickness t=8,25 mm, pre-operation rotary extrusion of the sheath to the wall thickness t1=2.8 mm and thickness variationt=0.1 mm, the subsequent cutting of the inner shell and the outer surface to the wall thickness t=1...1.2 mm with thicknesst0.01 mm and surface roughness of not coarser R 1,25, second and third operation rotary extrusion to the wall thickness t2=0,35 mm t3=0.12 mm with thicknesst0.01 mm, while after each operation rotary extrusion produce heat treatment coating on austenitic heat setting mandrel to relieve internal stresses and to provide a stable internal diameter.

The method has the following disadvantages.

1. Substantial consumption of materials and labor and after preliminary operations rotary extrusion. Cutting non-rigid shell of the Maraging steel in the hard tolerance variations in the inner diameter, thickness and thickness variation with small roughness is technically a very difficult task, because in the process of cutting vibrations occur, the elastic deformation of the metal, the rapid wear of the cutting tool and, as a consequence, the low quality of processing. While on the treated surfaces of the shell inevitably the presence of sharp peaks, scratches, burrs and other defects that are stress concentrators that can cause the failure envelope in the process of its further manufacture and during operation.

2. Considerable labor and energy costs during the heat treatment at the heat setting austenitic pots.

A known method of manufacturing a thin-walled cylindrical shell of Maraging steel (see the book Greditor M. A. Forming operation and a rotational extrusion. - M.: Mashinostroenie, 1971, S. 114-115) adopted for the prototype. The method includes manufacturing a thick-walled tube stock, its heat treatment, cutting the inner and outer surfaces of the tubular workpiece with a thickness of 0.05 mm, rotary extrusion about what about the wall thickness t~0.75 mm is produced with a degree of deformation of ~75%, to wall thickness in the range of 0.75-0.25 mm - with deformation rate of 40%, and a wall thickness less than 0.25 mm with deformation rate of 20-30%. After each operation, rotary extrusion to remove the internal stresses are heat-treated shell, after each heat treatment must be stable internal diameter of the shell under the subsequent operation of rotary extrusion.

From the recommendations of the heat treatment (annealing, normalizing, hardening) Maraging steel is known that the heat treatment of the membranes with an internal diameter of 100 mm is reduced from 0.1 to 0.5 mm from the source, so the heat treatment, as a rule, produce heat setting on the mandrels.

The disadvantages of the prototype is the following.

In the manufacture of thin-walled shells with wall thickness less than 0.2 mm thick blanks according to this method requires a large number of operations rotary extrusion and associated operations, heat treatment, turning, leaching, control, etc. that is associated with a significant expenditure of labour, material and energy costs, as well as with long manufacturing cycle shell, a large amount of technological cos the wall thickness t=0,13-0.02 mm of thick-walled tube stock wall thickness t~8.5 mm according to this method requires a minimum of seven operations rotary extrusion.

The invention solves the problem of producing high-quality thin-walled cylindrical shells of Maraging steel with a wall thickness of t<0.2 mm and thickness variationt0.01 mm of thick-walled tubular workpieces with minimal labor, material and energy costs.

The technical result obtained by carrying out the proposed method, is to ensure optimal number of operations rotary extrusion and associated operations, heat treatment, turning, washing, monitoring, etc. required to achieve the task.

This technical result is achieved in that in the method of manufacturing a thin-walled cylindrical shell of Maraging steel, including the manufacture of thick-walled pipe billet, heat treatment, cutting the inner and outer surfaces of the tubular workpiece, rotating the extrusion of the sheath a few preliminary and final operations and heat treatment for stress relieving after each operation rotary extrusion, it is new that the cutting of the inner and outer p what are the minimum number of operations are valid for this material degree of deformation, when this thickness and the number of transactions rotary extrusion is determined from the following relationships:

where tabout- the desired shell thickness;

tzag- accepted thickness processed by the cutting of billets;

1,2...n- received the degree of deformation of the membrane at the 1th, 2thand nthoperations;

tzagallowable thickness of the workpiece;

tabout- the desired thickness of the shell;

n - number of operations rotary extrusion;

1,5 - reduction ratio of the thickness variation of the sheath in one operation rotary extrusion.

Heat treatment membranes for stress relieving after each operation rotary extrusion is produced in the free state, followed by the normalization of the internal diameter to ensure its stability.

Cutting the inner and outer surface of the thick-walled tube stock with close tolerance on thickness variation according to the formula (2) easy d is Ino to reduce the original thickness machined billet to a predetermined thickness and thickness variation of the shell.

Carrying out heat treatment in the free state with the introduction of operation carnerosana membrane after heat treatment prior to the next operation rotary extrusion allows you to provide a small surface roughness and high precision internal diameter, necessary for carrying out qualitative operations rotary extrusion, with reduced labor, material and energy costs and the manufacturing cycle of the shell.

In addition, upon receipt by any reason of any preliminary operations rotary extrusion shell more than the allowable thickness variationtiits possible repair by machining the outer surface of the shell is pressed into her mandrel-mandrel ensuring acceptable thickness variation.

Technical solutions with the features distinguishing the claimed solution to the prototype, is not known and obvious manner from the prior art is not necessary. It can be considered that the claimed solution is new and involves an inventive step.

The invention is illustrated by sketches, where Fig.1 shows a thick-walled tubular workpiece after machining the inner and outer on top of the after trimming the ends, heat treatment (hardening) and carnerosana inner diameter; Fig.4 shows the shell after trimming the ends, heat treatment (quenching) and turning (repair) outer diameter that is pressed therein a mandrel-mandrel.

An example implementation of the method in the manufacture of thin-walled shell of Maraging steel CS with an inner diameter of125,6+0,1, wall thickness t=0.120.01 mm and thickness variationt0,01 mm

The maximum degree of deformation in a single operation rotary extrusion of a cylindrical shell75%.

The acceptable level of deformation for 5...15% less than the limits and is=64...71%.

Accept the degree of deformation at all operationsi=65%.

Used equipment - raskatnoe mill St40-22CNC.

For known dependencies defined allowable thickness for steel billet 4C35, which can be processed on machine

,

where tn=10 mm maximum wall thickness of the workpiece under a rotational extrusion of the passport is machine St40-22CNC;

Dmax=400 mm - maximum diameter of the shell, which can be processed on the machine;

Dp=260 mm - diameter pressure roller;

D=125,6 mm - inner diameter of the shell.

After mathematical calculations will receive tzag.max=8,9 mm

Accept wood thicknesses tzag=8 mm

From the dependence (I) tabout=tzag(1-)nat an equal strain on all transactions rotary extrusion and after substitution of all the data we find n=4, i.e., a rotational extrusion of the shell thickness tabout=0.12 mm of thick-walled workpieces with a thickness of tzag=8 mm is feasible at least 4 operations.

From the dependence (2)tzagtabout1,5nfind the tolerance on the thickness of the workpiece, i.e.tzag0,05 mm

Accept tighter tolerancetzag=0.03 mm, because this is easily achievable when cutting thick-walled cylindrical workpiece.

Made of thick-walled workpiece sequentially subjected to rotary extrusion to the wall thickness and R is mt20,015 mm

t3=0.35mmt30,01 mm

t4=0.12 mmt40,01 mm

After 1, 2 and 3thoperation rotary extrusion cut ends, washed and produce quenching in a free state, and after quenching darnerud shell up to a diameter of 0.1...0.2 mm larger than the diameter of the shell, obtained in the previous operation rotary extrusion.

After carnerosana inner diameter is formed into the axial end face and produce a subsequent operation rotary extrusion.

After the fourth rotary extrusion to the wall thickness t=0.120.01 mm with thicknesst0.01 mm trimmed the ends, wash the shell and produce a hardening austenitic heat setting mandrel.

If after the second operation rotary extrusion thickness shellt>0.015 mm, then the membrane repair after quenching by pressing wrapped mandrel-mandrel and turning of the shell on the mandrel-mandrel outer surface to the wall thickness t2Claims

1. A method of manufacturing a thin-walled cylindrical shell of Maraging steel, including the manufacture of thick-walled pipe billet, heat treatment, cutting the inner and outer surfaces of the tubular workpiece, rotating the extrusion of the sheath a few preliminary and final operations and heat treatment for stress relieving after each operation rotary extrusion, characterized in that the cutting of the inner and outer surfaces of billets produced with a minimum thickness, and rotary extrusion carried out for the minimum number of operations are valid for this material degree of deformation, the thickness and the number of transactions rotary extrusion is determined from the following relationships:

tabout=tzag(1-1)(1-2)...(1-n),

tzagtabout1,5n,

where tabout- the desired shell thickness;

tzagthe thickness of the processed pipe cutting zag - Rinata the degree of deformation of the membrane at the 1th, 2thand nthoperations;

tzagallowable thickness of the workpiece;

tabout- the desired thickness of the shell;

N - number of operations rotary extrusion;

1,5 - reduction ratio of the thickness variation of the sheath in one operation rotary extrusion.

2. The method according to p. 1, characterized in that the heat treatment membranes for stress relieving after preliminary operations rotary extrusion is produced in the free state, followed by carnerosana internal diameter.

 

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