EP1201775B1 - Process of manufacturing cylindrical hollow bodies and the use thereof - Google Patents

Abstract

Production of cylindrical hollow bodies having a circular cross-section comprises forming a tube blank from a remelting ingot; molding to a tubular body by extrusion with a degree of deformation of at least 6 times; and optionally further processing. Preferred Features: The remelting ingot is made from a corrosion resistant martensitic steel containing (in wt.%) 12-29 Cr, 0.02-5.9 Mo, 0.05-0.8 C and 0.05-0.8 N; or 0.3-3.0 Mn, 12.1-28.0 Cr, 0.25-5.8 Mo, 0.01-3.0 Ni, 0.05-2.0 V, 0.15-0.7 C and 0.15-0.7 N.

Description

The invention relates to a process for the production of cylindrical hollow bodies of circular cross-section using solid martensitic chromium steels, in particular high mechanical stress rings, at least parts of the near-surface cylinder surface zones.
Furthermore, the invention comprises the use of extruded tubes of martensitic chromium steels.

Annular machine and tool components, such as e.g. Circular cutting blade, Rolling rings and the like, can withstand large mechanical stresses be exposed to the near-surface cylindrical surface zones. Each high Load capacity through surface pressure, high wear resistance, good toughness and high shear strength of the material are independent of direction in the Component required. For special fields of application is beside the mechanical one Material properties also a corrosion resistance of the material of great Meaning, which property profile synergetic by alloying Measures can be achieved.

Tubes as a starting material for cylindrical hollow bodies or rings, which on Cylindrical surfaces and / or at the adjacent edges in all directions are mechanically highly resilient, can be produced with different methods be the application of a particular manufacturing process of its Usability for the material, the required product properties and / or of whose profitability is dependent.

Highest material quality of high-alloyed rings or hollow bodies, created from Tubes, can be achieved when a cast or semi-finished block through Forging or rolling with a reduction of the cross section through a All-round hot deformation substantially perpendicular to the axis thereof deformed while being stretched in the longitudinal direction to a round bar, after which by boring out the center or drilling, in particular a deep hole drilling, a pipe rod is formed and separated from this the rings. In the Hot forming takes place an intensive kneading of the material or the alloy, so a material which is isotropic in terms of its properties can be produced. It is also possible, from a forging or rolling bar each individually, preferably by automated turning or drilling to work out hollow bodies, as well if necessary, consolidation-related center auction areas at most be ripped off. The thus prepared hollow body have a special Material quality, however, the production costs are high or the production consuming as well as the chip waste large.

It is known to use rolled tubes as a raw material for the manufacture of or outer rings of rolling bearings. DE-A-.19520833 discloses For example, a method in which essentially a continuous casting material from hypereutectoid Cr steel with high purity, fine carbide precipitates and high granularity is produced and that the insert length in the cast state and heated without heat treatment to forming temperature and a Pipe production plant, preferably supplied with a punch press, wherein during the hole process in the individual length to be reshaped a state of stress is built, the minimization of shear stress one has high negative mean voltage value. Both the state of tension when punching to prevent the tearing of the material including the Setting of a certain microstructure state, as from DE-C-19734563 has become known, are important for the quality of the rolling bearing rings.

For the production of seamless tubes as starting material for the production of Rolling bearing rings made of ordinary steels can also be used as a cross rolling mill trained hole apparatus may be provided, which at least one Tube rolling plant is arranged downstream.

The known pipe manufacturing methods usually have a high cost-effectiveness on, however, have the common disadvantage that these are for high-alloy Tool steels, e.g. for corrosion-resistant martensitic chromium steels, not can be used. Such steels have the corrosion resistance because of chromium contents of greater than 12 wt .-% and are optionally with Molybdenum alloyed. To be desired in a thermal annealing of the alloy To achieve mechanical properties of the material, must also high carbon concentrations can be provided.

High-alloy, heat-treatable steels are usually found at forging temperature Material properties, which exclude a punching and tube rolling. Especially when creating and expanding the hole of Feed through mandrels or similar tools form due to high Tensile and shear stresses in the material, so that a production of Tubes with a desired quality can not be done.

Here is the invention to remedy the situation and sets itself the goal of a method for To specify production of hollow bodies of the type mentioned, by means which with high economy a high product quality and Production security can be achieved.

Furthermore, it is an object of the invention, the use of an economic Manufacturing process for the production of hollow bodies made of corrosion-resistant show martensitic chromium steels.

The goal is achieved in a generic method in that in a remelting block is created at a first manufacturing stage and from this one Rohrluppe made and in a second stage finished this at Hot deformation temperature by extrusion with a degree of deformation of deformed at least 6 times to a tube and this if necessary is further processed, according to which in a third stage manufacturing from the tube hollow body be removed and after finishing this same one be subjected to thermal tempering treatment.

A remelt block can largely without segregation with respect to the Block length and over the cross section are created. Further, this block free from coarse and its quality reducing non-metallic process-related Inclusions and centric discontinuities and has a high Hot workability in all zones, effectively using large vertical components the solidification direction characterizes the crystallization. According to the invention made from such a block by means of division into insert lengths of tube billets, despite the high quality of the block center, the introduction of the axial bore in this is preferably done by cutting drilling. The outer diameter of the Pipe dies can be replaced by a corresponding production of the block or by Forging and machining of the same must be created. In further Sequence of the method according to the invention is a tube blank Forming temperature brought and by extrusion to a seamless tube formed. Technically seen in extruding a pressing of the Material through an annular gap. Surprisingly, this also occurs in the essential high-alloy heat-treatable steels no cracking or a Riefenformung with the risk of Rißinitiation on. Furthermore, at a Pressing a material through an annular gap in all areas of the Cross-section of the tube thus formed an axis-parallel line structure in Material causes, what in the opinion of the experts, for example, from it manufactured rolling bearing rings, which are predominantly radially stressed, prematurely Wear of the work surfaces leads. Opposite this opinion are at Investigations rather improved service lives of heavily loaded bearings been found. Unexpectedly it was also found that after extrusion the pipes largely problem-free and error-free to those with others Dimensions can be processed without, when using a appropriate technology, defects such as cracks in the near-surface Cylinder surface zones occur.

After removal from the tube and finishing of the hollow body These are subjected to a thermal treatment. It was found that a tendency to material distortion, resulting in increased rework by grinding is reduced.

The advantages achieved by the method according to the invention are as above technically set out, in particular, that with this corrosion-resistant, cylindrical hollow body with a circular cross-section, in particular Circular knife and rolling bearing rings and the like parts, from martensitic Chrome steels with unexpectedly improved performance characteristics highest can be produced economically.

12   bis 29 Chrom (Cr)

0,02   bis 5,9 Molybdän (Mo)

0,05   bis 0,8 Kohlenstoff (C)

0,05   bis 0,8 Stickstoff (N) Rest Eisen (Fe) und übliche Verunreinigungen mit der Maßgabe legiert ist, daß der Summenwert ( C+N)

0,1   bis 1,4 Kohlenstoff plus Stickstoff beträgt.

Durch den Stickstoffgehalt wird eine feine Mikrostruktur im geglühten Werkstoff erreicht, wodurch ein verbessertes Warmumformvermögen desselben vorliegt. Weiters unterdrückt der Gehalt an Kohlenstoff und Stickstoff in den angegebenen Grenzen im Stahl eine beim Strangpressen sich bildende zeilige Struktur, was weitgehend vollkommene Isotropie der mechanischen Materialeigenschaften im Preßling bewirkt.The advantages of the invention are particularly pronounced when the remelt is formed from a corrosion-resistant, martensitic steel, in wt .-% with

12 to 29 chromium (Cr)

0.02 to 5.9 molybdenum (Mo)

0.05 to 0.8 carbon (C)

0.05 to 0.8 nitrogen (N) remainder iron (Fe) and common impurities are alloyed with the proviso that the sum value (C + N)

0.1 to 1.4 carbon plus nitrogen.

By the nitrogen content, a fine microstructure is achieved in the annealed material, whereby there is an improved hot workability of the same. Furthermore, the content of carbon and nitrogen within the specified limits in the steel suppresses a zeolige structure forming during extrusion, which causes largely perfect isotropy of the mechanical material properties in the compact.

0,3   bis 3,0 Mangan (Mn)

12,   128,0 Chrom (Cr )

0,25   bis 5,8 Molybdän (Mo)

0,01   3.0 Nickel (Ni)

0,05   bis 2,0 Vanadin (V)

0,15   bis 0,7 Kohlenstoff (C)

0,15   0,7 Stickstoff (N)

Rest Eisen (Fe) und übliche Verunreinigungen
mit der Maßgabe legiert ist, daß der Summenwert (C+N) 0,31 bis 1,1 Kohlenstoff plus Stickstoff (C+N) beträgt, werden besondert hohe Zähigkeitswerte des gehärteten und angelassenen Werkstoffs des Hohlkörpers erreicht. If, as can be provided in a favorable manner, the remelt block is formed from a steel which is in wt.%

0.3 to 3.0 manganese (Mn)

12, 128.0 chromium (Cr)

0.25 to 5.8 molybdenum (Mo)

0.01 3.0 Nickel (Ni)

0.05 to 2.0 vanadium (V)

0.15 to 0.7 carbon (C)

0.15 0.7 nitrogen (N)

Remaining iron (Fe) and usual impurities
is alloyed with the proviso that the sum value (C + N) is 0.31 to 1.1 carbon plus nitrogen (C + N), particularly high toughness values of the cured and annealed material of the hollow body are achieved.

To both set for a setting of high nitrogen levels in the steel up to 0.8 wt .-% and purity with respect to other non-metallic inclusions therein, it is advantageous if the remelting as product elevated jolt D E S lektro- chlacke- U melt block (DESU block) is created.

High security against occurrence of internal cracks in the pipe wall is achieved if the billet by machining a central hole made from a solid starting material. In the plant are at Upset of the tube blank and during pressing each in the radial direction Compressive stresses built, which prevents cracking during deformation.

It may be favorable for adapting to desired dimensions of the hollow bodies, if in the second stage of manufacture a further deformation of the extruded Tube is performed. This makes it possible to required To comply exactly with the cross-sectional dimensions of the tube and therefore low Abspanverluste and the like processing times in a hollow body production to reach.

The further object of the invention is achieved by using pipes, which made of solid raw material of corrosion-resistant, martensitic Chrome steels by forming by extrusion one of a Remelting block created tube blank are manufactured, for the production of Hollow bodies with a circular cross-section with high mechanical stress at least parts of the near-surface cylindrical surface zones, in particular for Ball bearing rings and ring bodies of axle drives and ball screws.

Hollow bodies made by the above technology are not only unexpectedly high Material quality but it is also an extremely large economy achieved this generation, because the centric bore already in the tubular Starting material is present and both the processing time and chip chipping low are. It was quite surprising that pipes made of corrosion-resistant, martensitic chromium steels are produced by extrusion such that from this a highly economical production of hollow bodies, which is a special one Quality must be possible, is possible.

12   bis 24 Chrom (Cr)

0,02   bis 5,9 Molybdän (Mo)

0,05   bis 0,8 Kohlenstoff (C)

0,05   bis 0,8 Stickstoff (N)

0,1   bis 1,4 Kohlenstoff plus Stickstoff (C+N) gegebenenfalls

0,3   bis 3,0 Mangan (Mn)

0,01   bis 3,0 Nickel (Ni)

0,05   bis 2,0 Vanadin (V)

Rest Eisen (Fe) und übliche Verunreinigungen
gebildet ist, können im Vergleich mit der Herstellung gemäß dem Stand der Technik ein besonders hohes Materialausbringen und wesentlich geringere Bearbeitungsaufwendungen erreicht werden.If, as provided for by the invention, the corrosion-resistant, martensitic steel of an alloy containing in wt .-%

12 to 24 chromium (Cr)

0.02 to 5.9 molybdenum (Mo)

0.05 to 0.8 carbon (C)

0.05 to 0.8 nitrogen (N)

0.1 to 1.4 carbon plus nitrogen (C + N) optionally

0.3 to 3.0 manganese (Mn)

0.01 to 3.0 nickel (Ni)

0.05 to 2.0 vanadium (V)

Remaining iron (Fe) and usual impurities
is formed, in comparison with the preparation according to the prior art, a particularly high material output and significantly lower processing costs can be achieved.

Although lower chip waste is given, it can be production and be suitable for the area of the inner bore to be favorable when the pipes pass through Extruding a tube blank, which created a by machining Bore, are produced at hot forming temperature.

The economic production of the hollow body can be further increased, if the tubes by a further or subsequent shaping treatment dimensioned and / or calibrated. This makes it possible, only small Abspanungen, gegebnenefalls by grinding on the cylindrical surfaces to provide. Surprisingly, it was also found that the work zone created with it apparently by an immediate engagement effect of the deformation tools a has particularly high quality.

In the following the invention will be explained in more detail with reference to only one comparative embodiment.
A jolt D E S lektro- chlacke- U mschmelzblock with concentrations shown in Table 1 of the alloying elements has been created. Furthermore, Table 1 also shows the alloy contents of a comparative steel. C Si Mn Cr Mo N C + N DESU material 0.32 0.6 0.3 15.0 1.0 0.4 0.72 DIN material no. 1.4125 1.05 0.4 0.4 17.0 0.5 ---- ----

Of a DESU material and the comparison steel were round rods with manufactured a diameter of 200 mm and a length of 2 m and as Feedstock rated 100%.

The DESU round bar was divided into four parts by normal sawing, on each of which drilling a hole with a diameter of 46 mm  took place. The extruding of the tube blank occurred after heating Forging temperature to tubes with an outside diameter of 69 mm  and an inside diameter of 45 mm , with 25.5 m usable pipe material was created with near-net-shape cross-section for the hollow body production.

The comparison steel bar (DIN material no. 1.4125) became one in the rolling mill Round rod with a diameter of 70 mm  rolled, from which 15 m usable round material resulted, which by deep hole drilling with a bore was machined with a diameter of 45 mm .

The spreading of the round rod material on pipe pre-stock for the Hollow body production was in the process according to the invention at about 87%, however such was in a production of a solid rod and a boring of 51%.

The material investigations of the nitrogen-containing martensitic steel gem. Table 1 gave a fine isotropic anneal texture with particular suitability for an extrusion, however, were in the comparison material gem. Table 1 in annealed state eutectic carbides present which the hot workability the steel and in particular ultimately in tempered state the Use characteristics of the part adversely affected.

Claims (10)

1. A method for the manufacture of cylindrical hollow bodies of circular cross-section using solid starting material composed of corrosion-resistant martensitic chromium steels, in particular of rings with high mechanical loading at least of parts of the cylindrical surface zones near the surface, in which method a remelting block is prepared and a tubular ingot produced therefrom in a first manufacturing step, which tubular ingot is, in a second manufacturing step, deformed at a hot-forming temperature by extrusion with a degree of deformation of at least six times to form a tubular body which is optionally processed further, after which in a third manufacturing step hollow bodies are taken off the tube and, after finish-machining, are subjected to a heat treatment.
2. A method according to Claim 1, in which the remelting block is formed from a corrosion-resistant martensitic steel alloyed with

   12 to 29 wt.% chromium (Cr);

   0.02 to 5.9 wt.% molybdenum (Mo);

   0.05 to 0.8 wt.% carbon (C);

   0.05 to 0.8 wt.% nitrogen (N);

   remainder iron (Fe) and the usual impurities,
   wherein the sum (C+N) has a value of 0.1 to 1.4 carbon plus nitrogen (C+N).
3. A method according to Claim 1, in which the remelting block is formed from a steel alloyed with

   0.3 to 3.0 wt.% manganese (Mn);

   12.1 to 28.0 wt.% chromium (Cr);

   0.25 to 5.8 wt.% molybdenum (Mo);

   0.01 to 3.0 wt.% nickel (Ni);

   0.05 to 2.0 wt.% vanadium (V);

   0.15 to 0.7 wt.% carbon (C);

   0.15 to 0.7 wt.% nitrogen (N);

   remainder iron (Fe) and the usual impurities,
   wherein the sum (C+N) has a value of 0.31 to 1.1 carbon plus nitrogen (C+N).
4. A method according to any one of Claims 1 to 3, in which the remelting block is prepared as an electroslag remelting under high pressure block (ESRP block).
5. A method according to any one of Claims 1 to 4, in which the tubular ingot is produced by machining out a central bore from a solid starting material.
6. A method according to any one of Claims 1 to 5, in which further deformation of the tube is carried out in the second manufacturing step.
7. Use of tubes produced from a solid starting material composed of corrosion-resistant martensitic chromium steels by extrusion-forming of a tubular ingot prepared from a remelting block for manufacturing heat-treated hollow bodies of circular cross-section with high mechanical loading at least of parts of the cylindrical surface zones near the surface, specifically roller-bearing components, annular bodies of axial drives and sphere spindles.
8. Use of hollow bodies according to Claim 7, characterised in that the corrosion-resistant martensitic steel is formed from an alloy containing

   12 to 24 wt.% chromium (Cr);

   0.02 to 5.9 wt.% molybdenum (Mo);

   0.05 to 0.8 wt.% carbon (C);

   0.05 to 0.8 wt.% nitrogen (N);

   0.1 to 1.4 wt.% carbon plus nitrogen (C+N);

   optionally

   0.3 to 3.0 wt.% manganese (Mn);

   0.01 to 3.0 wt.% nickel (Ni);

   0.05 to 2.0 wt.% vanadium (V);

   remainder iron (Fe) and the usual impurities.
9. Use of hollow bodies according to Claim 7 or 8, characterised in that these tubes are produced by extrusion, at hot-forming temperature, of a tubular ingot having a machined bore.
10. Use of hollow bodies according to Claim 7 to 9, characterised in that these tubes are dimensioned and/or calibrated by a further or subsequent shaping treatment.