DE1458399A1 - Cold tooth nitriding steel - Google Patents

Description

Isliikawaäima-Iiariiiia Jvüzogjo Kabushiki Kaisha, lokyo

(Japan)

"Ealtzälier nitriding steel"

The invention relates to a cold tough nitriding steel.

As Gtälile for components that are preferably deep iiron atisgeset-nt oiiul, 'be Dislier Stälile t shared by silicon and Aliiminiixtn de so: are coded. Dio 2emperatu.r, "at which the notch impact strength decreases sharply, is considerably lower in such steels than in steels containing silicon alone clsDo: are ryaiert. The first-mentioned steels are therefore organic "at low temperatures it is tougher or more flexible than that lotstoron.

Ία siiir'i already known Siemens-Kartiii steels with nitrogen gels of 0.006 and 0.000, for the notch impact

New documents Art. > § ι ^. <. ., .. t s <az 3 d & / ßdtftmgsgvg. f. 4.9,

809901/0343

toughness values of up to 20.6 kgm / cm can be specified. Since these values have been clearly identified "at 2O ⁰ C, the steels quoted may njcht the task of lca.ltzähen steels accept.

When using deoxidizing agents such as silicon and aluminum to influence the so-called transition temperature, b at which the notched impact strength decreases noticeably, becomes. the effect mainly of aluminum oxide and aluminum nitride attributed to. The latter refines and evens out the Perrit grain. The invention, however, is the It is based on the knowledge that the influence on the so-called transition temperature in the v / es is borrowed from the proportion of the ge ·? · Falling out of aluminum nitride. :.: ._...? - ■

In the manufacture of aluminum nitride-grade steel, however, it is almost impossible to manufacture a steel containing only aluminum nitride, since some amount of metallic aluminum is inevitably present in solid solution. The invention is based on the further knowledge that it is impossible to obtain a fine-grained and therefore flexible steel at low temperatures if there is more than a certain proportion of metallic aluminum ir-i fixed hosting.

The task is to produce a nitriding steel with high

80990 1/0343

- 3 cold toughness to accomplish,

According to the invention, a steel is proposed for this purpose, which is characterized by a content of

0.04 * - 0.25 # carbon, 0.01 - 0.50 56 silicon

up to $ 1 manganese, less than $ 0.035 phosphorus, less

than 0.035 fo sulfur, Ä

0.014-0.044 fo nitrogen, with at least 0.011 $ 0.041 being aluminum nitride,

0.025-0.22 "acidic aluminum, with at least 0.004 - 0.141 / * as metallic aluminum in a pesticide solution exist,

and as heat iron with the inevitable impurities.

The extraordinarily high notched impact strength of the invention i Corresponding steel at low temperatures can be found in the description and illustration of exemplary embodiments below emerged.

The values given above assume a content of excreted Aluminum nitride from $ 0.05 - $ 0.12 from and are to be determined in the following way:

As the ratio of aluminum nitride to nitrogen contributes

43

2.926, it leads to a nitrogen equivalent of 0.01025 ) Ό "to 0.04101; ■.

Us l, but not the entire ann, i- ^m & efüge prev .nde: 'ie nitrogen in the nitride is converted?. 2s remains
rather at the 7ämebeha.ndlung, for the.later
information according to the invention follows, 0.0011-0.0030 nitrogen unbound as so-called free nitrogen.

If one chooses "the minimum content of free nitrogen as
the lowest limit and the ilaxinal content as the upper G-rense, the range is between 0.01135 /; and 0.04-1-1, "- '.

Neglecting the third and fourth digits after the liomma results in 0.012 .1 for the first limit of the nitrogen content and 0.044;? As the top limit. Of the proportion of -0.012; ' Nitrogen there is a rope of 0.001 / ungobuncen, ie at least: i3 0.011 ,, are as IJitrid gebu ^ cor .. aluminum nitride crh ^r: .l '' - HGii: nit only 0.0322;. '.

13. The specified range for aluminum calculated: .

.., ....,. "OP 901/0543 8AB0WQJNAL

lower limit Upper limit Total nitrogen 0.012 # 0.044 fo IT in AlIT 0.011 0.041 AlIT 0.0322 0.120 Al in AlN 0.0212 0.079 Metallic Al
(Claim) 0.003 0.15

Acid soluble Al 0.0242

0.229

! laughing rounding the limits of 0.025 ^c were obtained for acid soluble aluminum 'p to 0.22? o. The metallic aluminum in the fuel solution is then in the range of 0.004 - 0.141 / ί. ■

At this point it should be pointed out that under "acid-soluble aluminum" the sum of "Aliiniiiiium, that of nitrogen in the form of aluminum nitride "bonded" is understood to mean "aluminum which is left as metallic aluminum in IT solid solution" will.

!. ■ line advantageous embodiment of an inventive '■ nitriding steel is characterized in that it also contains aiii or more of the following elements:

as I ^ liickal, Chrc :: i, IlolyV.dsLtj .., YanacLiun, ICupfer

a i / o343

OWGiNAL

and less than Ό.10 fo boron.

As a method of treating a steel according to the invention, it is proposed that the steel be ^{heated to 300-1050 degrees Celsius, that is to say the 1} Jeaiperaturspänne in which the greatest precipitation of aluminum nitride takes place, and then cooled in air, oil or tea will.

The steel is expediently tempered between 150 and 750 ° 0.

The drawings and photos are intended to explain the 2air explanation of the Invention according to en nitride steel with high cold toughness to serve.

3 ¹ Ig. 1 shows the dependence of Charpian notch values on the test temperature for various carbon steels with an excess amount of precipitated aluminum chloride and aluminum in solid form

2 this dependence are at vcrcc '.ied isgierten, eber.fclls VLn ± 2i: r .->.' /: Δ ^ ^ ΙΛο .η ausgeschiedenein VluEiinir ^".λ: ': .xiC \. .C A3, uminiuni in festsr Losuiir; ■: ·. · ■: '€ .rl "'.: R ". again;

■ - ■ - ■ —C --- -

BA © ORKäiNAl

Pig. 3 shows the relationship between the amount metallic Aluminum in solid solution and the ferrite grain size;

Fig. 4 shows the relationship between the conditions of the heat treatment and the ferrite grain size "at different, steels containing less than 0.15? ole of metallic aluminum in solid solution;

Fig. 5 gives the influence of the amount of metallic aluminum

in fixed solution to the number of 1 mm present Ferrite grains again;

]? ig. 6 shows the relationship between the amount deposited Aluminum nitrides and the ferrite grain size with different, different amounts of metallic Types of steel containing aluminum in solid solution. '

Photos 1 to 4 explained below are micrographs of steels and show the ferrite grain size. Photo and 2 are made of a carbon steel which contains 0.09 λ »carbon, 0.091 $ precipitated aluminum nitride and 0.0024 yj metallic aluminum and which has been air-cooled after heating to 930 ° for one hour. Photo 5 and Photo 4 are micrographs of the same 1-3n steel type with the percentage given above

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Composition, which after one hour of heating
Cooled 930 ° by being pocketed in oil, but then
again heated to 650 ° for 1 1/2 hours and only then
has been air-cooled. The Eotos 5 to 8
are micrographs of low-alloy, different
Henge.li in steels containing precipitated aluminum nitride and metallic aluminum in solid solution, "which
Provide information about the austenite grain size present in these steels, l'oto 9 and 10 are electron micrographs of what was deposited in carbon steel
Aluminum nitride. On the electroiienmikoskopischeii
Potos 11 and 12 can be seen the aluminum nitride ai deposited in low-alloy steel.

Table 1 provides information on the chemical composition of some of the carbon steels examined.

Sabelle 1 Chemical composition versc; r ^: .edener
Carbon steels

Ges. G-SE.

Example C Si l-Zo. ITi Or Gu Al: .T _O

haiidelsübl.

Steel 0.13 0.13 0.79 0.043 0.0f4 0.13 0.02 0.00 "

03 0.09 0.31 0.58 0.0 C0 0.064 0.1 D 0.104 ^, - Z;

ill 0.22 0.45 0, G2 0.030 0.045 0.22 0.1 ";",?;?.

A41 0.27 0.3 7 0.4 "0.030 0.033 0.30 1.1 ^ 0.011

LZA 0.1G C, 42 0.3'J 0.030 0, ⁿ -; 2 ⁿ , 'C ",' - '. / ^A , C";; ·

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Table 1 (continued)

Met. Acid- ... _n Example All H (Al) Free H Al soluble Al ^A1 2 ^U 3

• 0.0014 0.005 0.0055 - - - rolled

CS. 0.091 0.0311 0.0019 0.024 0.084 0.037 930 ° C / H

All 0.091 0.0311 0.0019 0.096 0.156 0.017 "

A41 0.029 0.0099 0.0011 1.073 1.092 0.032 »

A51 0.023 0.0079 0.0011. 2.657 2.672 0.026 »

The values of the "IT (Al)" and "Free IT" overwritten Columns of Table 1 are based on calculations from the previously specified values of the corresponding components.

Fig. 1 shows the transition temperature curve of the carbon steels listed in the table; the Charpy kerbsehig values Depending on the transition temperature, the curves of steels A 41 and A 51 run as a result their excess content of metallic aluminum is lower than those of the commercially available steel containing less aluminum, while the curves of steel C 8, which as a result of the ITitridgeiialteo less metallic aluminum in solid Contains solution, high up and that of the heat-treated steel 03 even leads no σ "ι higher. The curve A 11 lies despite matching aluminum nitride content lower than those of 03, \ tfeil A 11 more metallic aluminum in solid solution contains. The result shown in Fig. 1 is major attributed to the ferrite grain size. liie from the

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809901/0343

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the following can be seen, is the transition temperature the higher the larger the particle size.

The lig. 3 and 4 show the relationship between the]? Erritkorngröße and the G-ehalt of metallic Altimiiaium in solid solution for carbon steel with 0.04 Ms 0.25 ^c p carbon. l'Ieim one has finer grain sizes than 2.2 mn. srfc wants to aim, "is the limit" with respect to the solved

Aluminum 0.1 ^c p for a steel that is heated to 930 ° for one hour and then cooled in the air; The limit, however, is 0.35 Jj for a steel that is heated to 930 ° for 1 hour, counted in oil, heated again to 650 ° for 1.5 hours and then cooled in the air. Although a connection between the 3-erite grain size and the carbon content itself can be seen, because when the carbon is extracted, the amount of gaseous nitrogen that is soluble in metal ground and the length of a, n aluminum nitride are reduced and the dissolved metallic aluminum is reduced: .ri; v / ird, seigen the 3? ig. 3 and 4 nevertheless 3ezieIuinge: .T. : .i ^T .-; isclien all the above mentioned l? £ i: gates.

The transfer of the in JPig · 5 and 4 tlar ^ elo ^ tci::.; Or ;: ^r .3r:, ". Ii; ja in a log-log-Jhala in -Ibbildun ^; f ei ' _o .'. 'ijt 3: *.:.: e Ii: - ~ κ :: z

shows the Jjezlol: ^^ ': j \ t'.so "- \ 3i :. den \ .ur: jo, jcli: \ edc: iev.

ΒΑ © 809 9 0 1/0343

Aluminum nitride and the 3 erite grain size for different types of steel containing different amounts of metallic aluminum in solid solution. In the case of a low content of aluminum in solid solution, the limit value of the amount of precipitated aluminum nitride, which is now required for a perite grain size below 2.17, is greater than 0.035 ° if the steel has cooled down in the air after being heated to 930 ° for one hour and more than $ 0.0075, | when the steel has been cooled in oil after heating it to 930 ° for one hour and then heating it to 650 ° for 1 1/2 hours in the air. With a high content of metallic aluminum in solid solution, the limit value of the amount of precipitated aluminum nitride, which is required for a ferrite grain size below 2.17 mm, is greater than 0.51 % if the steel is in the air after heating to 930 ° for one hour cooled and greater than 0.0575 ° if the steel has been cooled in oil after heating to 930 ° for one hour and then air-cooled after heating to 650 ° for 1 1/2 hours.

From I? Ig. 3 to 6, taking into account the Experiments during the heat treatment applied cooling effect can be seen that a fine-grained steel can be obtained when the amount of deposited AIu-

0.03 to 0.12 ^c / o and the ilege metallic

- 12 -809 * 01 / 0343- ßA® OWGJNA

ί - 12 -

Aluminum in solid solution is 0.003 "to 0.15 f '·.

The knowledge gained on carbon steels were confirmed by tests with low-alloy steels with high tensile strength. The le / belle 2 shows the chemically Composition of some low-alloy steels with high tensile strength. ". ·

Table Z Chemical composition of the various non-clad steels

Attacked G Si Hn Hi Cr Iio Gu Y B

80 0.10 ö, '\ 5 0.82 0.85 0.4 ?. 0.40 0.21 0.061 0.003

82 0.10 0.26 0.85 0.83 0.53 0.44 0.33 0.075 0.0004

85 0.11 0.18 0.84 0.86 0.51 0.49 0.31 0.082 0.0002

table 2 (ülocation)

Example total of three

Al U ₂ AlU E (Al) IT I-lGt. ..M

^J 80 0.039 0.004 0.004 00014 0.0026 O, "53.82 0.033 0.016 0.014 00043 0.0112 0.0222 j 85 0.17 0.029 0.078 00266 0.0024 O, '. O37

j ^ ie fourth of the with "1Γ (Λ1)" BC "Vr ^ '. Gi ⁱ '" uborschricuorie :! opalts from [Jr / oslle 2 are ε.ν.α the previous ·. · a ^^ o-jjo "^: -.-.-: ^1. ■ / erten f'.lr ciitsprechoncle llo ~ ujo ~ - .. ? ::: 'ucn

? ig. 2 ^ ei (; '' j c'.r.rpvsc. "

acid soluble
JJ. 0 I ₂ O ₃ 0.0579 ■ 0 , 002 0.031 ·: 0 , 00 " 0.15-3 , 025

809901/0343

Curves representing the transition temperature such low-alloy steels with high tensile strength. Compared to aluminum nitride, it is quite a bit metallic Sample containing aluminum in solid solution Mr. 30, which is a lot of aluminum nitride and a lot of metallic Sample Ir containing aluminum in solid solution. 35 and the sample ITr. 32, the composition of which ranged from that of 30 and 35, have different values for deep! Eetfjschlagzäliigkeit. Especially ITr. 85 has excellent toughness despite its high tensile strength. So Ma: a recognizes that low-alloyed ones Steels with high tensile strength and the carbon steels listed above are similar in their behavior.

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809901/0343

table 5 liechan. Jüigensehaften of carbon steel

Mr. Tisdlng.d. Durclm.d. length d. Stretching iiugfe- L ¹ in breakage yield i>

'iVannebeii. under. liei-piece limits stigfc. Stretching tight. Ugly

Iiandelsübl.
stole

OO

11

Q. ¹ J.

R.A.M

mm

kg / naa kg / mm '

10 0 40 32.2 47.0 35 , 2 67.0 A. 60 , 4 , I! * Z Λ Α
- * τ j, "r 47.5 36 , 3 66.2 Il . 76 , 2 ■> 10 0 40 35.7 44.5 37 , 5 70.8 A. 77 , 3 I. Il It . 33.7 45.2 40 , 0 76.0 Il 79 , 0 10 0, 40 41.9 54.1 35 , 0 63.0_ A. 71 , 5. It ti 34 f p 54.2 33 , 3 64.2 Il 77 10 ■ 0 ;O 34.5 53.4 31 , 25 57.5 A. 61 , 7 I! II 42.1 56.7 , 0 57.6 Il 61 , 0 10 0 40 42.3 29 , 5 49.6 A. 72 , 3 II II 50.5 29 , 5 51.9 II 72 , 3 •
■ 'J30 ° υ - 1 - 1 H. air cooled • J .: 930 ° 0 - Oil cools and

1.5 3td. - air-cooled

CJl QO CO CD

C.
"2-

table 4 Median. Properties of low-alloy
Steels

Conditional Durclia.d. length d. Stretch tension

ο 85 Q.3. 10 jS 40 91.7 93.6 19.3 67.5 B 98.0 co

<ß η η η "91.7 93.6 18.5 67.5" 98.0

ο ι

* ■ *** vji

⁰ H _ Λ Ρ. + Λ _ rH CoTHi ^- HI + n-nrl I

92.5 28.5 46.4 78.3 36.8 79.8 77.7 36.8 79.3 93.6 19.3 67.5 93.6 18.5 67.5

ο>! Dead: QI: 93O ^W Ö - 1 hour -, oil-cooled and

650 ° 0 - 1.5 hours - air-cooled

yield

80 Q.T. 14 0 50 85.0 92.5 28.5 46.4 A 91.9 82 Q.T. 10 0 40 77.7 78.3 36.8 79.8 A 99.2 "" "" 76.7 77.7 36.8 79.3 A 98.7

osen QO CO CO CD

The ferrite grain size can be smaller than 1 - 4 according to the ferrite grain size designation than in rolled or be forged condition when the carbon and low alloy steels of the invention starting at a temperature above the transformation temperature of the steel, hardened or hardened with tempering. A noticeable deposition of aluminum nitride takes place here. If the steels are cooled in oil or water instead of in air, a much finer ferrite grain size can be achieved as 1 to 1.5 according to the ferrite grain size designation and a shift in the transition temperature according to lower values can be achieved.

From photos 1 to 4 it can be seen that the ferrite grain size was refined to 1 to 1.5 according to the ferrite grain size designation. From the electron microscopic Recordings of photos 9 to 12 shows the nature of the deposited aluminum nitride in different carbon and low-alloy steels.

Photos 9 and 10 are made of carbon steels, photos 11 and 12 of low-alloy steels. Photo 9 $ ■ is made of steel containing 0.091 pounds of deposited aluminum nitride. I place square or rectangular black structures. A]

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809901/0343

ORIGINAL

nitride crystals. That of. made of sample A4I photo 10 shows that the deposits of very little aluminum nitride and other non-metallic inclusions. This shows from sample 85 gemadibe loto 11 square or rectangular aluminum nitride while the round structures have other, non-metallic inclusions, mainly deposited carbide. Ioto 12 of sample 80 shows only a few aluminum nitride particles. By distributing the aluminum nitride in large quantities and In a very even form, the grain size becomes even finer and more uniform, which in turn reduces the low-temperature properties of the above-mentioned steels containing aluminum nitride with a certain, a certain level not exceeding. increasing amount of metallic aluminum in solid solution can be significantly improved. - <

Shall contain the ₄ cold-resistant nitriding steel according to the invention, which is 0.03 to 0.12 $ deposited aluminum nitride and only $ 0.15 0,003ULs metallic aluminum in .fester solution possesses a remarkable high toughness, "at low Eempera-? Doors. This steel is not only excellent as a structural material for components used at lower than normal outside temperatures, but is also very useful in many other areas.

- Claims: - 18-

809901/0343

Claims (4)

Patent claims: 1. Cold-tough nitriding steel, marked by a content of $ 0.04-0.25 carbon, $ 0.01-0.50 silicon Ms to $ 1 manganese, less than $ 0.035 phosphorus, less than $ 0.035 sulfur, 0.014 - 0.044 $ nitrogen, wooei at least 0.011 $ 0.041 present as aluminum nitride, 0.025-0.22 $ acid-soluble aluminum, where "at least 0.004 - Oj, 14t $ as metallic aluminum in Pesticide solution are present, and as the "remainder iron with the inevitable impurities. 2. Mtrier steel according to claim 1, characterized in that that one or more of the following elements are also included: less than $ 1 nickel, chromium, molybdenum, vanadium, copper, and less than $ 0.10 boron. 3. Process for treating a steel according to an or , _iU3 8 09901/0343 "Both of the preceding claims, characterized in that the steel is heated to 800" to 1050 ⁰ C, i.e. the temperature range in which the greatest precipitation of aluminum nitride takes place, and then cooled in air, oil or water ". 4. "The method according to claim 3, characterized
is left on. shows that the S ^- WiI is between 150 and 750 ⁰ O 809 90 1/0 3 43