DE2317290A1 - USE OF HIGH STRENGTH STEELS FOR THE MANUFACTURING OF IMPACT, IMPACT AND CONTINUOUSLY USED PARTS - Google Patents

Description

PATENT ADVERTISER DR. EANS-GUNTHSR EGGERT ₁ DIPLOMA CHEMIST

5 COLOGNE 51, OBERLÄNDER UFER 90

Cologne, 3O.3.1973 Ax / 6 6

ügine Aciers, Io Rue du General Foy, Paris / France

Use of high-strength steels for production parts subject to impact, impact and permanent stress

The invention relates to new uses of high strength steels.

In British patent 1 085 466 steels the following composition by weight described:

C 0.08 to 0, ^ 0 #

Si 0.02 to 0.60 #
Mn 0.5 Ms 2.5 %

Np <O, O45 # in the form of nitrides of Al, Nb,

Ti or Zr

Nb <0> 20 #

Ti <0.12 #

Zr <0.20 #

at least one of the elements Ni (0.10 to Vf) , Cr (0.10 to Yf) ₃ Mo (0.05 to Vf), Cu (0.05 to Vf), V (0.005 to 0.30 $), B ($ 0.0005 to $ 0.01) Pe and impurities: remainder

These steels are cheap, weldable and tough, and have high strength. They'll be great for making We use components for ships, metal structures, bridges and pressure vessels.

Structural and structural steels are used in other patents which have similar analyzes and also contain nitrogen, but have so far been used by

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no one noticed the special properties which the presence of nitrogen gives steel.

It has been found that this influence of nitrogen opened up new uses for this type of steel

The invention relates to the use of steels of the composition by weight

C- $ 0.25-0.50

Si $ 0.20 - $ 0.50

Mn $ 0.20-3

Total content of Cr and possibly Mo, V, W, Ti,

Zr, lib, Ta and B $ 0.3-10 /

optionally Ni to $ 5.

N ₂ 0.015 $ up to the solubility limit of this element under the smelting and casting conditions at the solidification temperature of the steel

Fe and impurities: remainder

for the production of tempered parts, the large ones Are to be exposed to continuous loads as well as strong impacts at the same time, e.g. rolls of rolling mills and Parts of aircraft chassis,

In aircraft undercarriages, it is advantageous _s when the Ni content is more than $ 1 and the total content of Cr and other elements of compensation substantially between 0.3 and 5 $ "

In the case of rolls of rolling mills, a Ni content of 0 to $ 2 and a content of Cr and other compensation elements from $ 5 to $ 10 preferred.

So far, the residual nitrogen has been used for these uses as a noxious impurity, and its content has been increased in particular by performing a degassing under vacuum during smelting at the lowest possible

3098-3 / 0862

Value held on the order of $ 0.010.

It has now surprisingly been found that the presence of nitrogen in these steels in the above mentioned quantities, their fatigue strength and fatigue strength greatly improved without their in the tempered Condition usual impact resistance to deteriorate. In this state, these steels have a strength that exceeds l40 hbar when subjected to tensile stress. you have one fine-grained structure of 6/8 according to ASTM, but this grain fineness alone is not capable of the one used according to the invention Justify improvement of fatigue strength and fatigue strength.

The solubility limit of nitrogen in these steels at normal pressure is about $ 0.030 at the solidification temperature. It can be done by using special procedures during smelting and casting, for example by working under nitrogen pressure, can be increased. the Improvement due to nitrogen is illustrated by the following example.

Starting from the same starting materials, three steel castings (a), (B) and (C) produced with the following weight composition:

C. 0.38% Si $ 0.40 Mn. $ 0.37 Ni $ 3.75 Size $ 1.52 Mon $ 0.31 Al $ 0.025 S. o, oo8 $ P. $ 0.012 Fe rest

The block (A) was made with ordinary ferrochrome. It contained $ 0.007 N ₂ . Blocks (B) and (C)

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- * r 7-317290 H.

were produced with the addition of a mixture of ordinary ferrochrome and nitrided ferrochrome with Ζ> Λ% Np. They had the following final nitrogen content:

(B) 0.0i7 # N ₂

(C) ■ 0.026 $ N ₂

The nitrogen content of the block (C) was very close to the maximum solubility in this steel.

From these three blocks, which differed only in the nitrogen content, bars were forged 15 mm in diameter for the manufacture of test specimens, which were subjected to heat treatment consisting of austenite at 850 ⁰ C, air cooling and then to -196 ⁰ C. and. Tempering at 200 ^° C. existed. Their tensile strength was now 180 hbar.

The test specimens were subjected to the rotary bending test under a load of 75 hbar on a Moore testing machine. which ran at 10,000 rpm. The figure shows the percentages of specimens of each cast that Withstood 100 million revolutions without breaking. The figure shows that 100 million revolutions only from $ 8 of the specimen of the block (A) were reached while this proportion was $ 55 for casting (B) and for Casting (C) reached $ 85.

It was also found that the beneficial influence of nitrogen does not depend on how it is introduced into the metal, i.e. it does not depend on whether the nitrogen is introduced via a nitrided ferro-alloy or by the fact that the liquid metal is introduced under nitrogen pressure is held.

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Claims (4)

7,317,290 claims 1) Use of steels of the composition by weight G $ 0.25 to $ 0.50
Si $ 0.20 to $ 0.50
Mn $ 0.20 to $ 3
Cr $ 0.3 to $ 10 Np $ 0.015 up to the solubility limit of this Elements under the smelting and casting conditions at the solidification temperature of steel Pe and impurities rest for the production of tempered parts, the violent Are subjected to impact and shock loads and high permanent loads. 2) Use of steels according to claim 1, characterized in that that at least part of the chromium is replaced by at least one of the elements Mo, V, W, Ti, Nb, Zr, Ta and B is replaced «, 3) Use of steels according to claims 1 and 2 with 5 to 10 $ Cr and not more than 2 $ Ni for the production of rolls for rolling mills « 4) Use of steels according to claim 1 and 2, which contain 0.3 to 5 $ Cr and 1 to 5 $ Ni, for the production of parts for aircraft chassis, 309843/0862 Blank page