DD154614A1 - PROCESS FOR PRODUCING SPRING WIRE - Google Patents

Abstract

The invention relates to a method for the production of spring wire, wherein the wire rod by targeted Abkuehlung from the rolling heat such strength and plasticity relations obtains that he gets without subsequent patenting only by one to three cold strands the required utility value properties. Economic goal of the invention is the saving of stages of patenting and cold drawing with constant use value characteristics. The technical task of the invention for this purpose is to quench unalloyed or low-alloyed wire rod with more than 0.40% C from the rolling heat or after separate heating and subsequent coiling into coils in such a way that as a result of a targeted heterogeneous structure of the structure Cross section of the wire strength and plasticity relations are improved so far that can be manufactured without patenting with only one to three trains ready to use spring wire up to 16 mm diameter.

Description

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Inventor : PA 130

Pr.-Ing. Hans-Hermann Rönnecke Dr.-Ing. Heinz Klaas Dipl.-Ing. Hans Steininger. Dipl.-Ing. Galina Schulz

Representative : IPC: C 21 D 9/52

Ernst-Karl Tollbrecht

YEB steel and rolling mill

"Wilhelm Florin".

VEB quality and stainless steel combination.

- Office for Property Rights -

1422 Hennigsdorf

Veltener street

Title of the invention

Method for producing spring wire

Field of application of the invention

The invention relates to a method for producing spring wire, wherein a wire rod of unalloyed or low-alloy steel with a carbon content of more than 0.40 % from the heat in one or more cooling stages is cooled at its surface to a temperature below M. The wire rod treated in this way should be usable without further heat treatment as a starting material for spring wire in a variety of forms in mechanical engineering.

Characteristic of the known technical solutions The conventional methods for producing spring wire are based on a v / arm-rolled wire with more than 0.4% C, which undergoes cold deformation of up to 60 % in several drawing stages, depending on the desired strength class. Since these, for reasons of strength necessary high cold deformation requires a fine-grained Perlitgefüge, is usually the

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Drawing process a separate heat treatment -patierenvorgeschaltet.

To rationalize this three-stage process hot rolling patenting multi-stage cold drawing a number of methods have become known. Either the process step of patenting is advanced into the rolling process -d. H. Patenting from the Wälzhitze- or are produced by the rolling process · by a homogeneous martensitic compensation from the rolling heat such structure and strength relations that both the patenting and the solidification stages, d. do the pulling, be saved. In the latter case, low cold drawing or cold grinding only serves to improve the surface properties and the dimensional tolerances (DDR patent 13 723, 142 455 and 143 630). However, this method of martensitic tempering from the rolling heat over the entire cross-section is limited to wire diameter up to 10 mm 0 for reasons of limited through-hardenability.

The tempering heat treatment methods, which aim at advancing the patenting of pearlitic structures, can be roughly divided into two groups. In the first of these groups fall the methods in which the wire rod is pre-cooled in several stages in a water cooling section, wherein the martensite point is not exceeded at any point of this wire. Thereafter, the individual turns of wire are fanned out non-concentrically prior to coil formation and thus further cooled on air (US Pat. No. 2,926,628 and Belgian Pat. No. 2,815,090). The application of these methods is also limited to wire rod diameter up to about 10 mm.

With the aim of extending the scope of the patent from the rolling heat to about 20 mm 0, a second group of methods has been developed, wherein a multi-stage cooling of the wire rod is made such

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that it is quenched in the range of maximum pearlite conversion rate prior to the coiler operation in multiple stages. In the first stage, martensite is formed by intensive isolation until just above the Ac ^ point in the boundary layer, which again completely converts to austenite before continuing the further cooling. In the second cooling stage, the cooling intensity is either staggered so that over the cross section a homogeneous finely striated Perlitgefüge is achieved by not falling below the Ac., - Point or by falling below the Acv point in cross section an inhomogeneous structure of self-tempered martensite in the edge zone and dichtstreifigem Perlite is achieved in the core zone (DDR patent 137 729, Belgian Patent 2,804,306, BKD-OS 26 20 449). Optionally, these processes are separately annealed again.

All of these methods of patenting from rolling heat aim to save patenting by incorporating them into the rolling process as a separate operation. Therefore, they only aim at an initial strength of the conventionally patented wire and thus require the same cold deformations as are required by the conventional patenting method,

Savings of drawing stages are achieved according to the stated prior art only at full martensitic compensation from the rolling heat. However, these methods are limited to diameters up to about 10 mm.

Aim of the invention

The aim of the invention is to develop a process for the production of spring wire up to 16 mm 0, which makes it possible to save the process step -Patentieren- »and reduce the number of cold passes significantly.

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Explanation of the essence of the invention

The invention has for its object to soften by single or multi-stage quenching preferably from the rolling heat and the utilization of the Anlaß.wirkung the core heat in the coil such targeted improvements in the strength and plasticity relations of the wire rod that subsequently without patenting in one to three trains the strength levels patented cold drawn spring wires can be achieved. ' .... , ..... According to the invention, this object is achieved in that the wire rod is then coiled into coils and further cooled in air to room temperature, such that an annealed martensitic surface layer and in the core a transformation structure is formed and that the wire rod in 1-3 stages with a TJmformgrad of 10 - 20 % is cold drawn. According to this method, the wire rod can be cooled both from the rolling heat and after a separate heating and cold-worked.

embodiment

The treatment according to the invention was carried out on the wire rod 12 mm 0 of the steel brand 55 SiIvIn 7, wherein the wire after rolling from the rolling heat in several stages was quenched to a balancing temperature in front of the reel of 600 to 700 C. After self-annealing in the coil, the following strength and plasticity values are established in comparison with conventionally rolled wire of the same quality:

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treatment

Thermally strengthened wire rod

Tensile strength Constriction MPa %

cooled to 690 ⁰ C compensation 970

temperature

cooled to 625 C compensation 975

temperature

48

conventional cooling

860

After dragging, the following characteristics are achieved:

Number d. Compensating wire tension indenting temperature Diameter strength lacing

1 690 ⁰ C 11 mm 1210 IIPA 44 , 2 % 2 690 ⁰ C 10 mm 1240 MPa 41 , 4 % 3 625 ⁰ C 9 mm 1400 MPa 44 , 5 %

For. Spring wires of these strengths, there is a wide range of applications in vehicle and machine construction.

Claims (3)

-e- 2254 0 1 Invention claim 1. A method for producing spring wire, wherein a wire rod of unalloyed or low-alloy steel with a carbon content of more than 0.40 % from the heat in one or more cooling stages is cooled at its surface to a temperature below M_, characterized that the wire rod is then coiled into coils and further cooled in air to a low temperature, such that an annealed martensitic surface layer and in the core a transformation structure is formed and that the wire rod in 1-3 stages with a degree of deformation of 10-20 % is cold drawn · 2 «method according to item 1, characterized in that the wire rod is cooled from the rolling heat and cold formed. 3. The method according to item 1, characterized in that the wire rod is cooled after a separate heating and cold-formed.