DD298214A5 - METHOD FOR PRODUCING CIRCULAR BIMETALLIC CAVITY BZW. FULL PROFILE - Google Patents

Abstract

The invention relates to a rolling process for producing a mechanical bond of high strength for circular bimetallic hollow and solid sections by cold or hot forming. In addition to the choice of the ratios of the initial dimensions, the invention also includes the specific calibration-technical application of continuous rolling with and without a running internal tool {hot rolling; Cold rolling, continuous; Internal tool; Single drive; Material connection; Calibration}

Description

For this 1 page drawings

Field of application of the invention

The invention relates to the technical field of producing circular or similar bimetallic hollow or solid profiles, wherein the layers have different physical and / or chemical properties and consist of seamless or longitudinally welded hollow profiles or the inner body is a solid profile.

Characteristic of the known technical solutions

S. K. Lohe and D.H. Sansom describe in Tube International 4 (1985) 2, pp. 103-105, Kaltziehverfahren for producing bimetallic hollow body. Starting tubes of the desired material pairing are made with the same initial length, pushed over one another and then joined together by pulling. However, the degree of deformation is limited. In addition, pulling is always associated with material loss through the drawbar.

In DD-PS 245136 solid lubricants are proposed to achieve a hydrodynamic friction. It will achieve a total decrease of up to 85%. But at least three Umformzuge and a Anlegezug are necessary, making this procedure is very laborious.

For applying metallic coatings to strand material or wire, a number of technologies are known, e.g.

Electroplating or dipping in molten metal.

DD-PS159611 proposes to combine this job with an immediately following compaction in an extrusion or drawing die. However, the procedure is complicated and expensive. It is also applicable only to relatively low melting metals and does not guarantee good adhesion of the coating material. It also brings strand material with metal band and lets follow a pulling, being worked with or without Verschweißeffekt. However, this procedure is very expensive

and expensive. It is not suitable for soft coating metals.

Object of the invention

The aim of the invention is a cost-effective production of bimetallic hollow or solid profiles, with high productivity, a low Materialabft! and to ensure a good quality of the coating.

Explanation of the essence of the invention

The invention has for its object to provide circular metallic hollow or solid profiles so with a metallic coating; that bimetallic hollow or solid profiles of layers of different physical and / or chemical properties with good mechanical bond and tight fit arise.

According to the invention the object is achieved in that a circular hollow section of good formable material and a Hohloder solid profile are prepared separately from a material with higher strength. Thereafter, the first-mentioned hollow profile is positioned on the second hollow profile or the Voilprofil. It follows the rolling of the outer Hohlpi ofils on the inner body in a known continuous rolling mill warm, at medium temperatures or cold. The heating of the inner or outer profile takes place in dependence on the necessary flow properties of the material or the desired strength of the composite. The initial length of the outer hollow section is smaller by a factor λ than the initial length of the inner profile. The degree of stretching λ is limited, inter alia, by the increase in strength associated with the deformation of the outer body to be rolled, ie X, _u i. must be determined beforehand. From this and from the permissible length of rollable body (technological size of the rolling mill), the initial length I _{0 of} the outer profile is determined. The inner surface of the outer hollow profile and / or the outer surface of the inner profile are provided with a defined roughness before nesting. The outer hollow profile is positioned on the inner profile that, taking into account the flow of material in the applied rolling process at the end of the rolling process, the inner profile is completely covered. During rolling, the inner profile serves as an internal tool (ie it is not deformed). The rolling process is completed when the outer hollow profile has reached the initial length of the inner profile, that is stretched by λ. The yield strength of the outer layer is then close to the deformation resistance of the inner profile. The decrease in the outer profile per stitch, experiences a limitation by the rolling force occurring, which can lead to an elastic deformation of the inner profile, especially in hollow sections. The acceptance distribution over the stitch sequence is interpreted as falling.

The rolling process is terminated with one or two passes with little decrease in the outer layer. In this case, there is still a plastic deformation of the outer layer but only elastic deformation of the inner profile. Due to the elastic springback of the inner profile, a shrinkage effect occurs between the outer layer and the inner profile, whereby a better adhesion is effected.

The rolling process is carried out without technological Kühi- / Schmiermittol. If necessary, the rolling mill is cooled by a gaseous medium. In a particular embodiment, the interface between the outer hollow profile and inner profile with a dry, completely self-consuming in the rolling process lubricant is provided. When manufacturing bimetallic hollow profiles is in the inner profile in addition an internal tool when the d / s ratio of the inner profile is greater than 5. A mandrel bar as an internal tool is also used when the plastic deformability of the outer and inner profiles are approximately equal.

If necessary, further rolling out of both profiles on the roll bar, after the outer hollow profile has reached the length of the inner profile. As a result, the bond between the two layers is further improved.

embodiment The invention will be explained in more detail in the following example. The corresponding pictures show 1: a slipped onto an inner tube positioned outer tube in section, Fig. 2: the rolling process by a schematically illustrated »mehrgerüstiges continuous rolling mill.

For producing a bimetallic hollow profile is on an inner tube part 2, which was cut to the required length Ii, an outer tube part 1 with a defined length 1 a and defined outer diameter da, taking into account the amount χ positioned. The outer diameter and the insert length of the outer tube part are calculated taking into account the inner tube length and the possible Gesamtumformgrades considering the outer tube material. The positioning is dependent on the Gleitpaarungseigenschaften both materials as well as the adjustable kinematic movements between the individual rolling stands 3 on the set roller speeds η 1 to η 4, taking into account the caliber shape used. The entire rolling process runs at a certain rolling speed vwab, which is set as a function of the heating conditions, resulting from the deformation and frictional heat, via the base speeds. During the rolling process, the deferred outer tube 1 is reduced to the inner tube part 2 in the continuous passage both in diameter and in the wall thickness by the driven at different peripheral speed roller sets and at the same time taken along in the rolling direction proportionally.

The caliber rolls of the rolling stands enclose a substantially flat-round caliber such that the outer tube guided over the inner tube is partially stretched on the two opposite sides of the circumference in the rolling plane. Depending on the wrap angle of the rolling mill systems used, the rolling levels are determined.

The embodiment relates to the production of eir.es copper-steel composite pipe of dimension 20 χ 3.0 mm. For this purpose, a copper tube measuring 24 χ 2.0mm is made. It is annealed and pickled and then divided into operational length. A steel tube made of St35b-2, work hardened and pickled, dimension 18 x 2.0 mm serves as inner tube. In it sits a mandrel with a diameter of 14mm. The length of the mandrel bar is 7000m, the length of the steel tube 6000mm and the

-3- 293

Initial length of the copper tube 2600 mm. It is a uniform extension of the copper pipe on the steel pipe in and

contrary to rolling direction presupposed. This results in a central position of the copper pipe on the steel pipe as

Starting position. There is a continuous rolling out of the copper pipe on the steel pipe in a cold state in FIG

Duo rolling mills arranged directly behind one another with degrees of elongation of initially λ = 1.20 to 1.15 and at last \ = 1.03 per framework. The rolling stands are equipped with calibrated rollers whose caliber form is a round calibration with a

Flank angle of 45 to 30 ° depending on falling individual degrees of stretch. It is rising with a move of 1 to 5%

rolled.

Oval calibres with ovalities of 1.05 to 1.08 can also be used to roll out the copper tube. To produce composite tubes measuring 18 x 2.0 mm, the above tubes are detached from the mandrel bar and split. Thereafter, after the heat treatment, they are pushed individually onto a mandrel bar of 13.8 mm and into further

6frames rolled out with a total stretch of λ - 1.6. To improve the wall thickness tolerance are 2 additional

Rolling mills can be used below 45 ° rolling level without additionally calculated wall removal. In the second example, a rod of steel brand St 44-2 with a diameter of 29 mm with a 0.5 mm thick Alum'niumschicht be plated. For this purpose, an aluminum tube tJor dimension 34 x 1.5mm with a length of 1820 mm

positioned a bar steel with 030mm and the passage length 6800mm analogous to the first example. There is a continuous rolling of the aluminum tube on the bar steel at average temperatures around 350-550 ⁰ C in 10 immediately after one another arranged 3-roll stands with falling single strands of 1.25 to 1.02. The rolling stands are provided with calibrated rolls whose caliber shape is a round calibration with a flank angle of -0 to 15 ° depending on the falling single stretch degree.

The tensile conditions between the rolling stands are in accordance with the first example speed eini estellt. The heating of the bar steel is carried out here continuously during the rolling process between the second and third Roll stand after completion of the rolling process of the aluminum tube inductive. The thus produced plated composite has

due to the stretching of the bar steel a maximum total length of 7000mm.

Claims (6)

1. A process for the preparation of circular bimetallic hollow and solid sections with an outer well-formed special layer and an inner full or Hchlprofil with carrying function, with separately prepared and prepared starting profiles of selected materials are connected by deformation, characterized by the application of production-specific surface roughness of the inner profile and / or the outer profile, the application of a lubricant consumed during the rolling process to the internal profile, the positioning of the outer profile, which is shorter by the factor λ, on the inner profile as a function of the ratio lead / backflow of the respective rolling process, the rolling out of the outer profile with a certain degree of extension λ on and over the inner profile, wherein the inner profile is only elastically deformed and the rolling takes place without technological coolant and lubricant, - The inclusion of a conscious speed increase from stitch to stitch in multi-stand rolling mills for the fine control of the outer layer of the bimetallic composite. 2. The method according to claim 1, characterized by the application of a stationary or moving gaseous medium for technological cooling. 3. The method according to claim 1, characterized by the preferably use of a continuous rolling mill with 2- or 3-roller assembly, wherein at a diameter / wall ratio of the inner profile § 5 with additional internal tool whose diameter is equal to the inner diameter of the inner profile, is worked. 4. The method according to claim 1 and 3, characterized by the use of an oval calibration with an ovality of 1.0 to 1.10, preferably 1.02 to 1.08, or a circular calibration with a flank angle of 0 to 35 degrees, preferably from 15 to 30 degrees when rolling without an internal tool. 5. The method of claim 1 and 3, characterized by the application of an oval calibration with an ovality of 1.05 to 1.08 or a round calibration with a flank angle of 20 to 50 degrees when rolling with an internal tool. 6. The method of claim 1, 3, 4 and 5, characterized by rolling in four consecutive stitches with the same wall decrease, by rolling especially in rolling stands in duo design, always in another roll plane, preferably at 45 degrees.