DE1178881B - Deforming steels in a drawing or pressing die - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C21d

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German class: 18 c -7/14

L 17667 VI a / 18 c
January 12, 1954
October 1, 1964

The invention relates to a method for deforming steels in a drawing or pressing die, which results in steels with improved mechanical properties. Thereby steels with improved Properties obtained that are otherwise only found in alloy steels or more expensive heat-treated steels have so that they can be replaced by the cheaper non-austenitic steels.

It is known to produce steels in a continuous process above room temperature but below deform the lower transformation temperature. It was also the prevailing view that the plastic deformation at elevated temperatures either the tensile strength or the processability of the material decreases. It was also known that excretory processes were an important one, but still exert unexplained influence in the deformation, causing the steel in unintentional and uncontrollable Way harder and more brittle as well as less deformable. A deformation of steels at elevated temperature, therefore, in those steels which had the appearance of precipitation hardening do not expect any significant success. Surprisingly, however, it has now been found that in the plastic deformation at elevated temperatures of steels, their tensile strength at this processing is increased, the processability of the material is not only maintained but it is even possible to further improve the workability.

Of particular importance is the fact that in the process according to the invention, the deformation stage is carried out at elevated temperature with the hot-rolled steel, without special, otherwise usual process and annealing operations must be carried out in between.

According to the invention the method for the continuous plastic deformation of hot-rolled Steels by guiding them in bar form through a drawing or pressing die at room temperature elevated temperatures but below the lower transformation temperature applied to steels, which a) have a pearlite structure in a matrix of free ferrite and b) during processing result in deformation hardening at elevated temperature in the area between 200 and 300 ° C as well as hardening by some kind of precipitation, the deformation in the drawing or pressing die between 200 and 300 ° C is carried out.

Drawing at the specified elevated temperature provides numerous unexpected benefits in terms of the reduced drawing load that he-deforming steels in a drawing or
Press die

Applicant:

Lassalle Steel Company, Hammond, Ind.

(V. St. A.)

Representative:

Dr.-Ing. H. Ruschke, patent attorney,

Berlin 33, Auguste-Viktoria-Str. 65

Named as inventor:

Elliot S. Nachtman,

Eldon B. Moore, Park Forest, JIl. (V. St. A.)

increased drawing speed and / or the possibility of more pronounced deformations of the steel, achieved. Mechanical properties that have not previously existed are also created in the steel, such as high tensile strength, high proportionality limits, hardness and the like. Of particular importance is the improved machinability. The machining parameters are generally determined by comparison of the metal against a standard metal (in this case standard metal B 1112). To do this, the metals are placed on a lathe and with a non-powered tool cut. The constant pressure exerted on the lathe tool results in dependencies of the machinability of the metal to be examined, changes in the feed rate, see above that the feed rate is taken as a comparison value for the machinability of the steel can be. The surface roughness of the metal is determined using a profilometer.

The invention is based on the discovery that the achievement of improved properties, in particular of improved machinability from the composition of the steel and the state in which it is the components of which are located during the drawing operation.

It is of course difficult to precisely determine the relationship between processability, composition, drawing temperature and to show deformation. It resulted

409 689/225

however, that some grades of non-austenitic steels contain more than 0.1% but not less than Containing 0.5% carbon, the machinability of the steel is increased when it is at high temperatures be drawn within the range of 200 to 300 ° C. Given such steel compositions very important improvements in the machining parameters for low-sulfur steels a carbon content between 0.1 and 0.25% when drawn at these temperatures.

In other tests it was also found that in non-austenitic steels, the free ferrite contain and result in deformation hardening when processed at the specified temperature and harden through any type of precipitation, the unexpected improvements in their properties when drawn at these temperatures. For steels that have little or no free ferrite in their Structure, the machinability seems to be essentially unaffected by the drawing temperature. On the other hand, non-austenitic steels containing substantial amounts of free ferrite show that as Influence of the drawing process is hardened, a marked improvement in machinability by precise control of the drawing temperature, d. H. at temperatures between 200 and 300 ° C for non-austenitic ones Steels that have a carbon content of preferably between 0.10 and 0.20%.

By processing the non-austenitic steels at elevated temperatures in the range of It is not 200 ° C to below the lower transformation temperature for the steel composition only possible, previously unachievable strengths, proportionality limits and other improvements the mechanical and physical properties to be achieved, but it arises through the choice the temperature a very substantial improvement in machinability. The improvements in strength and the proportionality limits may or may not be obtained at the expense of elongation which is determined by the treatment temperature. By treatment at elevated temperatures in the manner described it is also possible to reduce residual stresses to low values, as they were previously available through the usual methods of drawing steel, but which relaxation followed. In this way it is possible through the present metallurgical process Deliver many of the benefits that previously required many steps in a single step.

While the improvements in machinability depend on the composition of the steel, the size of the caliber decrease and other properties, such as the surface roughness, not to be so dependent, although they are generally increased by treating the steel at Temperatures are largely improved.

The following examples serve to further illustrate the invention.

example 1

In a series of tests, hot-rolled Bessemer screw steel, a freely machinable one Variety of the non-austenitic type with pearlite structure in a matrix of free ferrite, with various Temperatures pulled 19% reduction in area on 15.88 mm round stock to achieve. The composition of the steel is as follows:

0.08% carbon, 0.75% manganese,

0.12% phosphorus, 0.27% sulfur, 0.01% silicon. 0.015% nitrogen.

Example 2

In another series of tests, hot-rolled Siemens-Martin steel with a medium carbon content was used and sufficient machinability of the non-austenitic type with pearlite structure in one Base mass of free ferrite drawn at temperatures corresponding to those in Example 1 to achieve a similar reduction on 15.88 mm round stock. The composition of this steel is the following:

0.48% carbon, 1.50% manganese,
0.03% phosphorus, 0.27% sulfur, 0.30% silicon,

0.005% nitrogen.

Example 3

In a third series of tests, hot-rolled Siemens-Martin steel with a low sulfur content was used and relatively poor machinability of the non-austenitic type under the conditions of Examples 1 and 2 drawn to give a similar reduction in 15.88 mm round stock achieve. The composition of this steel is as follows:

0.17% carbon, 0.75% manganese,
0.03% phosphorus, 0.04% sulfur, 0.08% silicon,
0.005% nitrogen.

procedure

Rods or bars of any of the above compositions were made without any prior heating sent through the drawing die, with the usual lubricants on their surfaces found. Other bars of each composition were heated to different temperatures and then sent through the same die with the same type of lubricant on its surface, to achieve a 19% reduction in cross-section. The drawn poles could of course move cool to room conditions and were then examined for machinability. The following table shows the results obtained:

Claims (2)

Table I Comparison of the machinability of different steels drawn at different temperatures Temperature of the drawn steel Machinability, (based on standard steel B 1112 steel des = 100%) steel of example 2 steel of (0C) example 190 Steel according to Example 1, which is characterized by a carbon content of less than 0.1% and a relatively high phosphorus and sulfur content and probably contains very little free ferrite, shows a high machinability, which is not due to the use of the temperature treatment. In contrast, the Siemens-Martin steel according to Example 3, with its low phosphorus and sulfur content and a carbon content of 0.17%, is dependent on the temperature treatment in order to produce marked improvements in machinability; for example, the machining values are practically unchanged at temperatures between 23.9 and 200 ° C, but at temperatures between 200 and 300 ° C there is a marked increase to around 62. This is of course a very important factor with regard to the use of such a steel. In the case of the steel according to Example 2, which has a medium carbon content and a high sulfur content, but only has a small proportion of free ferrite, there is a slight improvement in the Machinability at temperatures between 200 and 300 ° C. When heated to significantly higher temperatures for drawing, the machinability of the steels of Examples 2 and 3 is considerably impaired. The improvement in the physical and mechanical properties that are achieved in steels of the type described when they are heated within the temperature range of 200 to 300 ° C for optimal improvement of the machinability is illustrated by the following table. Table II Physical and mechanical properties of steels giving 19% reduction in area at various temperatures Example steel 2293 ° C Example 32930C23.9 ° C10 40023.9 ° C71709600101006170711090007 39061305700422020.6443039,234,47,048,28,09.00 , 3610,00,230,3850,80,2725,440,631178,720924192174619053Patent claims: Tensile strength (kg / cm2) Yield or yield point (kg / cm2) Proportionality limit (kg / cm2) Cross-section reduction (%) Elongation to 50.8 mm (° / o) Rejection value surface roughness (cm-8) Brinell hardness Machinability figure It turns out that besides the considerable improvement in the machinability figure, the steel of the non-austenitic type at the temperature used according to the invention also shows considerable improvements in tensile strength, yield point and proportionality limit. Associated with these improvements are improvements in hardness and surface roughness. The present process thus represents a simple and economical process which has significant advantages. The method used to heat the steel to the desired temperature is insignificant, and it is sufficient that the steel can be heated by conventional means, for example in a gas-heated furnace or by electrical induction heating or in a liquid bath, which may also contain agents prepare the surface of the steel for drawing. 1. Application of the process for continuous plastic deformation of hot-rolled Steels by guiding them in bar form through a drawing or pressing die at room temperature elevated temperatures, but below the lower transformation temperature, on steels that a) have a pearlite structure in a matrix of free ferrite and the b) deformation hardening during processing at elevated temperatures in the area between 200 and 300 ° C result as well as harden by some kind of precipitation, whereby the deformation in the drawing or pressing die is carried out between 200 and 300 ° C is. 7 8 2. Application according to claim 1 to steels with Bullens, "Steel and its Heat Treatment", 1948, a low carbon content of about 0.1 Vol. 1, p. 234; up to 0.2%. Goer ens, "Metallographie", 1948, p. 397, para. 3 and 4; Publications considered: 5 F. Rap atz, "Die Edelstahle", 4th edition, 1951, French Patent No. 767 081; P. 100; U.S. Patent No. 2,320,040; "Metals Handbook", 1948, p. 261. 409 689/225 9.64 © Bundesdruckerei Berlin