DE1806224A1 - Aging austenitic steel - Google Patents

Description

The present invention relates to an austenitic age hardening steel having a '* 20 Vickers unit excessive roughness temperature hardness, good heat resistance, good wear resistance as well has good toughness both at room temperature and at elevated temperature.

The type of steel according to the invention is particularly suitable for use as a hot-work steel.

It has been found through research that a hot-work tool steel approx. 400 Vickers units Exceeding room temperature should have, so that a general deformation of the tool when using it is prevented. The previously used

909833/0783

ORIGINAL INSPECTED

■ ■ ■ ''I'TT! I ψ ¹ ''' Säf

Hot-work tool steels are of a martensitic type, and by hardening and tempering one has been able to achieve a sufficiently high roughness temperature. the However, the hardness of this type of steel showed a ratio- moderately rapid decline, exceeding about bOO ° C Temperatures, and for many purposes, e.g. Extrusion of copper, this temperature range is very important, and the hot hardness of those in question martensitic steels is therefore insufficient with poor wear resistance as a consequence.

It has therefore been suggested that in this context— ™

hanj; austenitic steel types to be used, as obtained in such austenitic steel types usually at temperatures above 650 C has a hardness that is higher than the hardness, have the above-mentioned inartensitisehe (ferritic) steel types.

However, such austenitic steel types have a hardness lower than 600 ° C. which is unsatisfactory when used in hot working tools. i

However, this unsatisfactory hardness at lower temperature in the austenitic steels can can be increased significantly by cold working.

However, such cold working has significant disadvantages, inasmuch as the hot working tool is made of a hard material must be, which of course means a disadvantage.

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Austeiiitischen steels show in the Hegel one very good toughness at room temperature, but this decreases with increasing temperature Toughness and typically a minimum toughness occurs around 600-700 ° C. Since this Temperature range is very important for many hot work steels, the said minimum toughness is a disadvantageous factor.

The present invention has proven possible to produce a steel in which all of the above-mentioned disadvantages are eliminated. The steel according to the invention is hardening and the result is that the tool can be manufactured from a material that has only been solution annealed and therefore has a relatively low hardness, which of course facilitates the manufacture of the tool. The steel according to the invention also has a room temperature hardness exceeding 400 Vickers units, good hot hardness, good wear resistance and abrasion resistance, and good toughness both at room temperature and at elevated temperature.

The hardening austenitic steel according to the present invention is characterized by that it contains the following components:

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Carbon 0.35 - 0.80 fa manganese h - 15 '»

Chromium 2 - 12 ^

Nickel 2 - 15 ^l ; a

Vanadium O, b - 1.0>

Molybdenum up to 3.0 ^c / o

Tungsten up to 5> 0 ¹ JO

The remainder is iron in addition to the usual impurities for this type of steel. The manganese and nickel contents are to be selected so that a stable austenite structure is obtained with certainty in the steel, and the molybdenum and tungsten contents so that 2x (the molybdenum content) + tungsten content exceed 2%.

The steel may suitably contain up to 0.6 fo niobium and up to 0.02% boron.

A suitable analysis interval is as follows;

Carbon 0.40 - Ο.όΟ%

Silica, max. 0.5 %

Manganese 8 - 12 %

Chrom 3 - 6 fa

Nickel 6 - 9 %

Vanadium 1.0 - 1.5 ^c } o

Molybdenum 0.8-1.8 "each

Tungsten 1.2 - 2.5%

Niobium 0.3 %

Boron 0-0.02 #.

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As pointed out above, the stable austenite structure is enhanced by the addition of manganese and Micke! ensured. Aging tests at 700 C and 2.5 hours are made with a material made from approximately 0 _t h fo silica, 4.5 % chromium, 1.0 fo vanadium, 1.5 fo molybdenum, 1.5 fo tungsten and a carbon content of 0.3 and iron alloy consisting of 0.8% and varying amounts of manganese and nickel. In the 0.8 fö carbon-containing steel type was found diaß this both without the addition of manganese and nickel as well as with the addition of 2 h or ^c / a manganese strong magnetic properties was obtained. A corresponding alloy, but with k fo manganese and 1 fo nickel or 4 fo manganese and 2% nickel, still has weak magnetic properties, while additions of 6 % manganese and 2 fo nickel, 6 fo manganese and 4 fo nickel, 8 fo manganese and 4 ^C , 0 nickel and 10 % manganese and 6 ^c / o nickel all gave amagnetic steels. An alloy containing 0.8% carbon, 3.9 % manganese and 2.3 % nickel gave an X-ray ferrite content (martensite content) of about 10 %.

0.3% carbon-containing steel alloys, it was found that they were all strongly magnetic with a content of k & manganese and 0.5% of nickel, manganese and 4 fo 2 $ »nickel, manganese and 6 f o 2 f o nickel. The corresponding alloy with 8 fo manganese and 2 fo nickel was magnetic, and that with 8 fo manganese and k fo nickel was weakly magnetic, while an addition of 10 fo manganese

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and b ^ nickel made an amagnetic steel. A ^{steel alloy containing 0.3 p} / o carbon, 7.3 % manganese and k _t 7% nickel resulted in a ferrite content (martensite content) of approx. 10% according to the X-ray picture.

From the above experiments it can be seen that, in the case of steel types according to the invention with 0.8 ^c p carbon, contents below h ', "manganese and 2 % nickel and with 0.3 ^c k carbon below 7 # manganese and below 5 /'" Nickel do not result in a stable austenite structure.

The hardening, which is decisive for the hardness, is essentially brought about by the addition of vanadium, and the excretion of vanadium carbides is likely to be of great importance here. These vanadium carbides, and in particular those that are not dissolved in the solution heat treatment, also have a particularly advantageous effect on the wear resistance of the alloy. Investigations have shown that the vanadium content should be at least 0.6 Jo , ^{but not exceed 1.6 c} / o , as this reduces the deformability at high temperatures. I.

The addition of chroa is beneficial for hardening and also has a beneficial effect on resistance to oxidation.

Molybdenum and tungsten are also cheap Effect on hardening and also obviously improve the wear resistance of the alloy,

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It has therefore proven necessary to add molybdenum and tungsten in the amounts specified above in the alloy bring in.

The addition of niobium has a very beneficial effect on the grain size and probably also on the minimum toughness at 500 - 700 ° C. However, excessively high niobium contents showed that they reduce hardening and contents above 0.6 ^c / o should not occur. A niobium content of 0.2 % appears to be the most beneficial in the steel of the present invention.

Finally, as regards boron, the addition of this alloy counteracts the formation of the toughness minimum at 500-700 ° C. and is particularly beneficial in terms of constriction. However, the boron content should not exceed approx. 0.02% , since this results in a deteriorated deformability at high temperature. In the type of steel according to the invention, a boron content of about 0.01 % has proven to be the most favorable.

ψ The invention will now be described with reference to some in

the steel alloys contained in the attached tables are described in more detail. Table 1 shows the composition of 15 different steel alloys used in Have been examined in connection with the present invention, and Table 2 gives the hardness at Room temperature for these steel alloys

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departed high heat treatments. Table 3 gives the hardness at elevated temperature and table ^l i various strength properties for some of the steel alloys examined. Table 5 contains the grain size for some of the steels examined.

As can be seen from Table 1, steels 1, 2 and 3 fall outside the prescribed analysis limits, and in accordance with Table 2 they also give a much lower hardness at room temperature

than the other steels and therefore do not meet the *

demands made.

When comparing steels 3, 4 and 5 in Table 2

one can clearly see the effect of the change in the vanadium-

see content, and notice the very strong effect of this alloy component during hardening.

The effect of molybdenum and tungsten goes out

a comparison in Table 2 between the steels I ₁

k and 2, 6 and here you can see that these components also have a very beneficial effect on the

Have hardening. '

The effect of the addition of niobium on hardening

results from steels 6-9. The niobium content in steel 9 is higher than the permissible upper limit and it appears to result in a reduction in hardness.

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For examinations in the practical. Operation with ER inventive Stähien has been found that a stamping die for spraying a ^c f of 0.12 »carbon, 0.35 ^c / o silica, 0.03 / β copper, 0.21, o iron, 0.26 ^c io manganese, 15.1 ^C ; O chromium, 1.18 ^c , o titanium, 4.71 f «aluminum, 20.1> cobalt, 4.93 '<> molybdenum, 0.009 ^c , -> boron and the rest Nickel existing alloy could be used for I30 spray processes as the mean of six different spray series. When during the years I966 - 67 tests carried out with two often used in this context martensitic alloys containing 0.3B% carbon, 0.3 / o silica, 2.8 ° / o chromium, 2.8% molybdenum, 2.8 # cobalt, 0.5 io vanadium and 0.4% carbon, 0.3% silica, 2.8 io chromium, 1.5 1 '' molybdenum, 5.0% tungsten, 2.2 ^C, O cobalt, 1 % vanadium, the corresponding mean values were only 80 injection processes per embossing mold.

In the case of injection processes with embossing molds made of the aforementioned martensitic steels, there are scratches in the sprayed workpieces have already been observed after about 10 sprayings, while with sprayings with embossing molds made of steel according to the present invention, the corresponding scratches only after about 100 sprayings began to perform. This clearly shows the superiority in wear resistance in the latter called steel. Cracks in the actual embossing forms, which led to their being rejected, were found in many

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ίο

Observed opportunities in martensitic steels, but not in a single case with steels according to the present invention.

The steel according to the invention therefore has practical Operational tests have shown that it has a much higher resistance to wear and tear, than earlier types of steel normally used in this context.

Tables 2, 3 and k clearly show that

that a steel according to the present invention according to the %

Solution annealing at approximately H50 ° C and curing at 70o C ⁰ k2Ü a Vickers units receives exceeding room temperature hardness and also good strength at high temperature, satisfactory toughness and good wear resistance. In addition, a fcarn hardness of at least 240 Vicker units at 700 ° C was achieved. The above good combination could not previously be used with the previously used martensitic hot-work steels or non-cold-worked austenitic,

Varmwork steels can be achieved.

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Tabel

Composition of investigated steel alloys

3?

c j Si Percentage of Mn Cr Ni Mo j V / V ^j j - B. Steel no. , 42 y , 46 11.5 4.9 9.0 j
i . !
i , 92: Nb j - , 48 y , 48 10.1 4.4 8.0 i 1.55; !
1 - , 011 1 .46: .44 10.5 4.8 3.5 1.41 I. 1.9 I. - , 009 2 , 44 , ^ 0 9.0 4.5 8.1 1.4-5, 1.6 1.05 , 17th ., 010 3 , 46 , 41 9.8 4.5 8.0 1.44 y 1.5 1.56 , 44 , 012 j 4th , 47 , 47 9.8 4.5 7.9 1.24 1.4 1.42 , 68 , οίο I 5 , 49 , 56 8.9 4.6 8.2 1.52 1.9 1.22 , 007 I. β , 45 , 42 9.6 4.5 7.9 1.41 1.5 1.51 I.
I _
Ϊ , 015 7th , 49 , 59 8.9 4.6 8.2 1.55 1.9 1.20 i "* , 009 8th , 45 , 40 9.6 4.5 8.5 , 80 2.4 1.12 , 011 9 , 45 , 41 9.0 10.0 8.6 , 82 2.3 . 1.02 _l
, 004 10 , 46 , 40 8.4 10.0 8.4 , 81 . M. 1.04 - , 015 11th , 63 , 44 9.6 4.2 8.5 , 77 ! 3.8 , 99 , 010 12th , 42 , 40 11.0 5.0 8.5 1.50 ! i, s 1.01 - 13th , 42 »St 10.6
.. _ .. 5.2 8.5 1.51 j 1.7 1.05 , 015 14th 15th

ro ι

CO O (T)

PO

Table 2

Vickers hardness (HV 50) at room temperature for those specified in Table 1
Steels after various heat treatments

steel no. Solution heat treatment
1150 C, lh,
water Harden
700 C, 5 h Solution heat treatment 4o8 II50 C, 1 h water Harden
700 ° C, 12 h as 1 I. 170 285 ! Harden
j 700 ° C, 6 205 Hi 5S7 2 198 ί 556 445 ί
i 412 co
O 5! 208. i 455 i
I. (O 4! 202 454 t
1
I. 458 OO
co 5 215 454 454 ί 445 6th 212 h> \ 6 I 450 4 ^ 15 O 7th 250 455 447 OO 8th 214 452 ! ms 420 ^ω 9 ! 560 418 10 j 221 451 I 596 466 11th 229 I w ; 411 12th 251 ·. j 459 15th 259 459 4Co 14th I85 524 455 453 15th 178 555 454 1123 Harden
700 C, 24 h 5S5 4O6 240 44o 455 450 425 457 456 442 461 4'Il 457

OO O CD ΓΟ

Al

Table 3

Violcer hardness (HV 30 at 20 ° C and HV 5 at the elevated temperatures) for some of the steels specified in Table 1 (heat treatment: solution heat treatment 11.50 ° C,

1 h water and hardening 700 C, 12 h)

hardness after Victors at the following ». Temper 650 ° C 700 ° C!
1 Steel no. 20 ° C 500 ° C ' oC0 ° C j
I. 236 271! 4th 43Γ; 306 291 ^255:: 5 443 328 j 300 j 273 j 259 j 6th 443 296 j 295! 257 j 244 8th 420 233 j 273 j 279!
232 j 25 ^
252 j
I. 10
13) 466 317
316 j 293!
OO.9! Table 4

Festigkoitsct ^ onschaiten at £ 00C for some of the in Table 1 indicated st \ ". Ilo

Stretch limit Breaks * * -ι 1 rf j * - Doh tion 24, iruns Steel Mr. 0.2 kgf / mm . * 3! Ep / ' ^l 0 ^c ' 58.6 65, 0 6th , 0 ^! 37, 5 1 67.5 73, 9 8th , 0 -! 26, ο 2 26.7 5 - "> # O 32 36, 7th 3 81.5 Sf), 2 , 3 ^: 45, 2 4th 82.3 37, 9 5 «2 13, 0 6th 79.0 35, 4th 5 , I. 27, 3 8th 71.3 35, , 0; 5 14th 73.9 36, 6th 4th i 9 ¹⁵ I.

All provisions are gen. Zan executed in SIS 11 23 11 (i960.Oo.30, Issue 1) provisions specified.

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Tabel Grit for some of the chairs listed in Table 1

: tahl Mr,

1 4 5 7 p

6.5 3.5

5.5

6.5 p

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-15-BAD ORfGfNAL

Claims (1)

1 * Ausliärteader by the following Le ^ ie "3 * Eohlsnstoff 0.35 « Manganese 4 ig iur ε ^ι ί: t : ■ Ι: - · ⁷ λ ·. 9 O e 8 3 3 / O 7 δ S BAD ORlOfNAL - 0.40 0.60 1806224 carbon Max. "0.5 Silica 8th - 12 * manganese 3 - 6 % chrome 6th - 9 % nickel 1.0 - 1.5 % Vanadium 0.8 - 1.8 molybdenum 1.2 - 2.5 % ■ tungsten 0 - 0.3 % niobium 0 0.02 % boron % k. Method for producing steel according to one of the preceding claims, characterized in that the steel is subjected to hardening after the solution heat treatment. 5. The method according to claim 4, characterized in that that the solution heat treatment at oa. 1150 ° C and hardening at approx. 700 ° C. 909833/0783