DE1950004B2 - Use of steel for components with high vibration resistance - Google Patents

Description

which is tempered by hardening temperatures between and 1050C and tempering to 550 to 650 ⁰ C to a tensile strength of over 160 kp / mm ² , as a material for the production of components with high fatigue strength, which in the gas flow or in the salt bath at the usual temperatures between 500 and 580 ° C have been nitrided.

2. Use of a steel according to claim 1, wherein the steel used 0.50 to 2.00% Contains silicon for the purpose of claim 1.

3. Use of a steel according to claim 1, consisting of

0.37 to 0.45 7 ₀ carbon, 0.70 to 1.00 7o silicon,

0.80 to 1.20 7o manganese,

1.20 to 1.60 7 ₀ chrome,

0.60 to 1.10% molybdenum,

0.35 to 0.50 7 ₀ vanadium,

Remainder iron and usual impurities,

for the purpose of claim 1.

4. Use of a steel according to claim 1 or 3, wherein the steel used contains 0.40 to 2.00% nickel, for the purpose according to claim 1.

5. Use of a steel according to one of claims 1 to 4, with the proviso that the Tempering combined with the nitriding process, d. H. at the same time, is carried out for the Purpose according to claim 1.

shear and economic importance. A high fatigue strength makes construction possible in the first place in lightweight construction and thus allows dimensions with the same load capacity and service life and to reduce the weight of the components and overall systems.

It is known that the fatigue strength of steels increases in tensile strength or yield strength increases. The use of high-strength steels for parts subject to alternating stress is now restricted by that the notch sensitivity increases with the tensile strength. This results in an increasing susceptibility against shape-related notches and surface damage, such as grooves, scratches, as well as against Decarburization (see Material Handbook Steel and Iron, 4th edition [1965], DIl, in particular Fig. 3).

The danger of surface notches is increased in the case of parts subject to bending and twisting increased by the fact that the load voltage is greatest on the surface. One has therefore been for a long time endeavored to reduce the notch sensitivity under vibration stress by suitable surface hardening to lower and to increase the fatigue strength. Such processes are case hardening, flame or Induction hardening and nitriding.

In addition to the older gas nitriding, nitriding in a salt bath has gained in importance in recent years.

The economical realization of the combination necessary for maximum vibration resistance a hardened, notch-insensitive, nitrided surface with a high tensile strength in the remaining cross-section failed so far because of the poor tempering resistance of known cheap steels and because of that high price of known temper-resistant steels.

With unalloyed and alloyed heat treatable steels according to DIN 17 200 as well as with the usual spring steels, after nitriding (or tempering) at temperatures of 500 to 580 ° C, there is a sharp drop in tensile strength in the core. The increase in fatigue strength compared to the non-nitrided state remains small, so that it is not possible to use it for highly stressed components. Numerous examples of the nitriding of steels with a tensile strength below 140 kp / mm ² are described in literature, e.g. B.

With the increasing use of lightweight construction in many areas of technology, its importance increases fatigue strength as the component property that determines the service life.

The object of the invention is, by combining the choice of a suitable economical steel, a tempering treatment ensuring high tensile strength and surface nitriding Use of a steel treated in this way as a material for the production of components with high fatigue strength, such as shafts, worms, axles or springs.

Fatigue failure, d. H. fractures caused by insufficient fatigue strength, present in the case of components especially the vehicle and machine house - the predominant cause of failure. The increase in Fatigue strength is therefore of great technical

B. Finnern, K. Vetter, H. J e s ρ e r, ZWF (1965), pp. 381 to 387 and 444 to 448:

"Fatigue strength and heat treatment of high-strength engineering steels";

H. B r a η d i s, DWE Technical Reports (1966, 1), pp. 7 to 10: "Nitriding behavior of cold work tool steel 45 CrMoV 6 7";

K. Walz, H. Reitmann, DRAHT (1968),

P. 624 to 630: "Influence of nitriding on fatigue strength".

On the other hand, studies are known in which steels with a tensile strength of over 160 kp / mm ^{2 were} nitrided:

4. K. Vetter, HTM (1965), pp 113-125: "development of the high strength structural steel with precious 57o chromium, molybdenum and 1.3 7 ₀ O, 57o vanadium";

5. W. W e s s 1 i η g, K. Vetter, Klepzig-Fachberichte (1968), pp. 677 to 683 and 744 to 752: "High-strength, martensit-hardenable nickel steels".

3 4

However, due to their high levels of molybdenum, tungsten, vanadium, titanium and zirconium, these steels are

Alloy content of 5% chromium (e.g. steel X 41 for the purpose of improving the nitridability of high

Have CrMoV 5 1) or even 18% nickel, 8% cobalt and aluminum content of up to 2 ° / ₀ Al

5% molybdenum (e.g. the martensite-hardenable steel can be sufficient. In practice, such steels are with

X 2 NiCoMo 18 8 5) very expensive and only used in special cases 5 with an Al content of around 1%. Nice

economically. the chemical composition of these steels

The aim of the invention is not based on the steel composition according to the invention

laying of a selected steel composition. From a remuneration treatment, a gas or

Use of a tempering and nitriding treatment salt bath nitriding, tensile strength values over 160 kp /

to enable which the achievement of high ^{fatigue strength io mm 2} and higher fatigue strength is not

Vibration resistance with simultaneous tensile strength of spoken.

Ensure at least 160kp / mm ^a . In the Steel and Iron Materials Handbook (1965),

This aim of the invention is achieved by the Chap. H 13, on page H 13-2 is the steel 34 CrAlMo 5

Use of a steel, consisting of named, whose Al content 0.80 to 1.1% is mandatory

0.35 to 0.50% carbon, ^{l5 is This} nitriding steel is hardened by

0 20 to 2 00 ° / silicon temperatures in the range 900 to 950 C, and its

050 to 16O ^0/0 manganese abuse resistance is 80 to 100 kgf / mm ² fixed

070 to 200 ° / ° chrome '. However, strengths of more than 160 kp / mm ² are

0 ', 40 bi>l', 60% molybdenum ^{well above the} stated strength range and requires

0 25 to 100 ° / Vanadium '20 are methods of treatment determined according to the invention.

θ 'bis 0J030-V0 Phospho'r, ^{The German} patent application R 13 30 relates to

η hk η mn 0 / Q _n Wp (Vi components of the

0 to? Πη ° / N'rlfpi Vehicle and engine construction made of steel with 0.50

0 bs 2 00 "° Wotfram ^{bi &} ° ^'65"> <> ^C; ° ^{80 to 1} ^ ⁰ ° / ^{"Mn; 1} ^ ^{0 to 2' 50} ° ^{/ o Cr:}

0 to 1 00 ⁰ I titanium ²⁵ ° ' ^{2 to} ^ ⁰⁰ ° / o ^Si : ° ^to °' ²⁵ ° / o ^V ' ^{remainder iron} ' ^{those without}

Remainder iron and usual impurities, insert treatment (carburizing) on a strength

be remunerated by at least 150 kp / mm ² , and

the hardening of temperatures between 970 with the use of low tempering temperatures

and 1050 ^c C as well as tempering to 550 to 650 ⁰ C on doors. Apart from that the steels are another

a tensile strength of over 16Ο kp / mm ^{2 is} tempered, 30 carbon range are to be added, the

as a material for the production of components with high quality specification different, and according to the invention

Fatigue strength, which is lacking in the gas flow or in the indispensable nitriding treatment, the contrary

Salt bath at the usual temperatures between holding completely, not using any

500 and 580 ° C have been nitrided. Mission treatment is considered a significant privilege.

The known steels 14 CrMoV 6 9 (material 35 The German Auslegeschrift 1 199 006 deals

No. 1.7735) and 45 CrMoV 6 7 (material No. 1.7737) with the use of steels with the machining

have in the state of the art only at contents of sulfur and / or which promote comparability

low strengths found application. Lead for nitrided gears. A steel assembly

These steels are particularly suitable for a setting according to the present application is not

Silicon content from 0.50 to 2.00%. There are preferably 40. As a heat treatment for the unalloyed

To use steels that are made from steels is a normalizing or a quenching and tempering under

0.37-0.45% carbon, using a quenching temperature of 80O = C

0 70 to 1 00 ° / silicon provided and tempering at nitriding temperatures

080 to 12O ⁰ / manganese ^or above. With these measures are components

1 * 20 to 1 * 60 ° / ° Chromium '45 is unattainable ^{according to the invention.}

0 ', 60 to 1', 10% molybdenum, ^A "the two examples below are intended to show

0 35 to 0 50 ° / vanadium, which increase the fatigue strength

Remainder iron and usual impurities, ^{with the new} components is possible.

example 1
exist. 5 °

The steels mentioned can also contain nickel. A melt (No. 2296) of the invention

in the range of 0.40 to 2.00%. Such contents increase steel with the composition 0.42% C; 0.80% Si;

the through-hardening of these cross-sections and 1.02% Mn; 0.024% P; 0.017% S; 1.54% Cr; 0.65%

improve toughness. Mo and 0.39% V became 30 mm bars

The tempering following hardening can be rolled out given a given diameter. Samples reached after

if in the nitriding bath take place at the same time as nitriding. a tempering treatment of 30 '1000 ° C / oil + 2h

The combination according to the invention of a suitable 600 ° C./air has a tensile strength of 165 kp / mm ² . the

Narrow steel selection, certain heat-treatable treatment cycle fatigue strength was notched on

treatment and nitration in a gas flow or salt bath with samples («& = 2.0) for a limit load cycle of 10 ⁸

the result of high fatigue strength at a 60 determined. It was ± 34 kp / mm ² and could through

Tensile strength of over 160 kp / mm ² has not yet been bath nitriding for 2 h at 570 ° C to ± 65 kp / mm ²

strived for and realized. That is also not going to be increased.

the case in the documents dealt with below, which The corresponding fatigue strength values for a

The following were considered: »usual« tempered steel 42 CrMo 4, tempered on

The German patent specification 547 965 relates to the 65 120 kp / mm ² tensile strength, were included for comparison

Use of steel alloys with a ± 27 or ± 49 kp / mm ² .

Carbon content up to 0.7% and a total content by applying the inventive concept — choice

from 1 to 8% of chromium, manganese, silicon, nickel, suitable tempering-resistant steel, tempering

to over 160 kp / in ² as well as bath nitriding - an improvement in the fatigue strength of the nitrided samples by 32.6% could be achieved.
Example 2

Another melt (No. 23 115) with the composition 0.49% C; 1.56% Si; 1.12% Mn; 0.018% P; 0.014% S; 1.27% Cr; 0.96% Mo and 0.53% V was similarly ™ ™ * f
treated. After tempering 30 1000 C / "J + J 600 ° C / air, the tensile strength was 188 kp / mm ² and the fatigue strength ± 35 kp / mm * After chemical bath nitriding, the fatigue strength reached ± 71 kP / mm ² an increase of 45% for the nitrided steel which is tempered only to 120 kp / mm ^2.

Claims (1)

Patent claims: 1. Use of a steel consisting of 0.35 to 0.50% carbon, 0.20 to 2.00 7 ₀ silicon, 0.50 to 1.60 7 ₀ manganese, 0.70 to 2.00 7o chrome, 0.40 to 1.60 7o molybdenum, 0.25 to 1.00 7o vanadium, 0 to 0.030 7 ₀ phosphorus, 0 to 0.0307 ₀ sulfur, 0 to 2.007 ₀ nickel, 0 to 2, OO7o tungsten, 0 to 1.00% titanium, Remainder iron and usual impurities,