DE2508007A1 - ROLLED LEADED STEEL BAR - Google Patents

Description

Dr.-1 ng. E. BERKENFELD · Dipl.-Ing. H. BERKENFELD, patent attorneys, Cologne Attachment file number

on the submission of January 13, 1975 VA / Named.Nm. INLAND STEEL COMPANY

and

S.A. ECiIEVARRIA

Rolled, leaded free-cutting steel bar

The invention relates to free-cutting steels, in particular leaded steel bars.

Steel rods can be machined with the form of steel or shape drills _e A cast steel is set on the outer surface of the steel rod and out perpendicular to the surface inwardly when the rod rotates, while a form drill attached to the middle of a steel bar and proceeds in the axial direction, as for the operation of a profile lathe is characteristic.

The cut machinability can be in cubic centimeters of the metal can be expressed, which are removed until the structural steel fails, or it can also be expressed as a dimensional increase reflecting tool wear that is inversely proportional to cut machinability. Both known leaded steel bars is the cut machinability of the steel bar in the one located immediately below the surface Area of the bar considerably lower than the cut machinability closer to the core or interior of the leaded steel bar. For example, the area immediately below the surface of a steel bar is at a depth of 1.58 to 4.74 mm in absolute distance from the surface of the steel rod with a diameter of 71.4 mm. This is about 5 to 15% of the depth up to the core of the rod. Because the diameter of the rod of 71.4 mm

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decreases, is the area immediately below the surface, in which the lower cut machinability occurs, closer, in absolute distance, to the surface of the bar; at For bars larger than 71.4 mm in diameter, the area immediately below the surface is further from the surface of the rod measured at an absolute distance.

In the area immediately below the surface of the known leaded steel bars are complex macro-inclusions, the composition of which is still to be specified. A macro inclusion is one that works at a magnification of 1 to 10 times is visible. A microinclusion is one that is visible at a magnification greater than 10X. At rolled Rods, the macro inclusions are stretched in the direction of rolling.

The term "complex macro-inclusions" refers to those inclusions which have oxides of manganese, silicon and iron with metallic lead distributed between these oxides. These complex macro inclusions have a ¥ f adverse influence on the machinability. These complex macro-inclusions are not the same as the lead macro-inclusions that also appear in the area immediately below the surface of known leaded steel bars? See, for example, US Pat. No. 3,671,224, which teaches how to avoid such lead macro inclusions, which are referred to as streaks or drops in this patent.

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The subject of the present invention is a leaded steel rod, in some of which the area immediately below the surface the rod has a relatively high cut machinability. The rod contains machinability enhancers Quantities of lead from 0.05 to 0.70% by weight, preferably larger Amounts as 0.15 to 0.5 wt%. The lead content is uniformly dispersed in the rod, and the lead content of the rod is in Micro-inclusions without a significant amount of lead-containing macro-inclusions.

The area of the rod just below the surface does not have a significant amount of complex macro-inclusions. In this specification, when it is said that there is no significant amount of complex macro-inclusions in the area immediately below the surface of the rod, it is intended to indicate a reduced amount of such macro-inclusions which is sufficiently small that (1) the cut machinability the immediately sub-surface area is greater than 50 % of the cut machinability of the interior of the rod, and preferably greater than 75 %; or (2) that the cut machinability of the immediately sub-surface area is about 90 % or more of the cut machinability of the rod as a whole , i.e. the area immediately below the surface plus the interior, or (3) both conditions apply. The above comparisons with regard to the machinability of cuts relate to the quantities of metal removed in cubic centimeters up to the failure of the tool; · Β in the percentages given above is the Sc

Cut machinability of the one immediately below the surface Area relatively high compared to known leaded steel bars. After editing, the surface has the rod is of better quality compared to that of known leaded steel rods.

Further characteristics and advantages of the invention emerge from the following detailed description in connection with the schematic Representations of the drawings.

Fig. 1 is a schematic diagram of a section of an apparatus for adding lead to steel in a ladle to produce a to manufacture leaded steel rod according to the invention;

Figure 2 is a section on line 2-2 of Figure 1; and

Fig. 3 is a diagram showing the machinability of 4. firstly a known leaded steel rod and secondly a leaded steel rod according to the invention, expressed in terms of dimensional gain.

Leaded steel bars made by the method of the invention are rolled from ingots or continuously cast products, which in turn are cast from molten steel. ^

Such blocks and continuously cast products have the following sizes and physical shapes;

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Commercial size bars in their cast, uncut and unprocessed condition are approximately 17.75 by 17.75 by 203 cm or weigh 453 kg up to ingots of 11.325 t and more »Such bars are somewhat beveled and, as is well known, the thick end of the same can either go up or be directed downwards. A typical bar with the thick end facing up (lost head) is 71 times in size 86 by 213 cm or a weight of about 8.154 t. A typical downward thick end ingot is 72.5 by 72.5 by 222.5 cm or a weight of 11.325 t. The cross-sectional dimensions of the bars are usually at the top Measured at the end.

When the leaded steel is continuously cast into strands, a typical strand will be of a commercial size the narrow side has a size of 7.5 by 7.5 cm. Larger strands have sizes of 25 by 57.5 cm and more. These If necessary, strands are cut into lengths of up to 12 m.

The basic composition of steel, i.e. steel without lead, has practically all of the basic components that were previously Lead has been added to an extent that does not conflict with the description of the present invention. The basic composition Some typical types of carbon steel may be as follows;

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Element wt%

Carbon 0.03-1.03

Manganese 0.25 - 1.65 -

Sulfur 0.01-0.50

Phosphorus 0.005-0.20

Silicon 0.01-0.05

Nitrogen 0.03 max.

Iron essentially the rest

For other types of unalloyed carbon steels as well as for steel alloys, the basic composition can be in addition to the elements listed above, one or more of the following alloying elements on iron:

Element chrome

Nickel Molybdenum Vanadium Boron

titanium

Zircon niobium

aluminum Calcium Tellurium Silicon

Weight-96 • 1.70 0.01 - - 3.75 0.01 - - 0.50 0.01 - • 0.25 0 • 0.003 C. ■ 0.50 0 ■ 0.25 0 • 0.25 0 • 0.10 0.005 - • 0.02 0.001 - • 0.15 0 1.00 up to

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Typical examples of such basic compositions in the range of AISI 1200 steels include the following areas:

Element wt .- ^

Carbon 0.15 max «

Manganese 0.60-1.15

Phosphorus 0.04-0.12

Sulfur 0.08-0.35

Iron essentially remainder

Lead is added to these basic compositions in an amount that the final lead content is greater than 0.05 wt .-? a and typically is up to 0.7% by weight; the lead content is preferably in a range from more than 0.15 to 0.50 wt.

Before the steel is poured into a block or strand form, lead is added to the steel in the following manner with reference to FIGS. 1 and 2 of FIG Drawings added in the manner indicated.

Molten steel of the desired composition and having a temperature in the range from 1593 to 1710 ° C is known from a known one Steel making furnace is drained into a ladle 10 with most of the slag remaining in the furnace. The ladle is closed with a lid 11 to isolate the inside of the ladle from the outside atmosphere. Just a very thin layer of slag 12 at this time covers the molten steel bath 13 in the ladle.

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The ladle bottom 14 has a removable stopper rod 26 closed outlet 25 and a pair of porous, spaced apart plugs 15 and 16, through v / elche as in * ertes Gas argon is introduced into the bath. The rising argon gas bubbles 17 stir the molten steel, and where the argon bubbles break through the surface of the bath at 18 and 19, the slag layer 12 is pushed aside and part of the exposed molten steel bath 13 above. After introducing the argon into the steel bath for 15 to 60 seconds is lead through a through an opening 21 in the Gießpfannendekkel 11 line 20 on top of the bath at one of the Slag-covered point 18 of the bath introduced, however, at a point 22 which is not immediately above the plug 15, 16 lies. The stirring with argon is continued during the lead feed, which takes about 2 to 3 minutes, and gradually after adding the lead, stirring with argon is also continued for 2 to 3 minutes.

The argon during stirring and during the addition the lead accumulating in the top of the ladle, for example argon and lead vapors, are discharged through a discharge line 23, which connects to the opening 24 in the pouring ladle cover 11.

To remove the gases that collect in the head of the ladle, known exhaust gas fans (not shown) can be used. The discharge of the gases can be adjusted so that there is a greater pressure within the covered ladle than atmospheric pressure. Above the bath, inside

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half of the ladle during the lead addition and afterwards maintain an atmosphere that is less oxidizing than the atmosphere outside the ladle.

Sufficient lead is added to achieve the desired final lead content. «Rare earths are not added to the steel, and the atmosphere in the ladle during the addition of the lead is less oxidizing than the atmosphere ■ & outside the ladle, since such a condition is less favorable for the formation of lead oxide than when the atmosphere inside the ladle is the same as the outside atmosphere »

After adding the lead and after further stirring with argon gas, As described above, the introduction of argon is interrupted, the lid 11 is removed from the pan 10 and the Surface of the bath covered with expanded vermiculite or a similar material to suppress smoking; dtB © l · lead-containing molten steel is made in known block forms (Chill molds), either with the thick end up or down, or poured into the funnel of a known continuous caster, to achieve a continuous cast steel. The temperature of the steel during casting is around 1,566 ° C or higher.

The porous plugs are removed about 5 to 10 seconds before insertion The argon is blown through with oxygen and about 30 to 60 seconds after the slag has been emptied, which follows the »pouring.

Another method of leading steel is in the open

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Legungsschrift ρ 23 23503.2 described, to which reference is hereby made will.

After casting to molds or continuously cast products, which is done in a known manner, the solidified leaded steel becomes a full bar rolled out in a known manner.

The result is a leaded steel bar in the rolled state, which has a relatively high cut machinability in the area immediately below the surface without one considerable amount of complex macro-inclusions in the area immediately below the surface or in its interior.

In steel rods, the lead is mainly present in micro-inclusions, which are distributed relatively evenly over the entire length and cross-section of the rod. The lead in the micro-inclusions consists essentially of elemental lead. If both tellurium and lead are added to the steel to improve its machinability, the lead can combine with the tellurium to form lead telluride. However, the lead can also not be connected to other inclusions or to inclusions such as manganese sulphide. No lead is actually present as lead oxide, lead oxide since no meters containing inclusions can be detected in a microscopic examination of the lead. This condition occurs even in the absence of aluminum in the amounts usually present when aluminum is added to calm the steel or to refine the grain size, for example in amounts of 0.015 to 0.065% by weight

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Attempts have been made to investigate the machinability of the invention Compare leaded steel bars with known leaded steel bars. The known Leaded steel rods are manufactured by the process in which the lead is added to the steel in the mold. Representative attempts - apart from failures - are further described below.

In Table I are the compositions of a number of known ones leaded steel bars (Examples 44542-549) and leaded steel bars according to the invention (Examples 44554-556 and 44558-559). The test results obtained with these rods are given in Tables II and III.

C. TABEL I. Weight % S. Pb example 0.09 P. 0.34 0.25 number 0.08 Mn 0.08 0.29 0.21 44542 0.08 1.11 0.07 0.26 0.20 44543 0.06 1.06 0.06 0.28 0.21 44544 0.07 1.05 0.08 0.30 0.23 44545 0.06 1.03 0.07 0.29 0.22 44546 0.06 1.07 0.06 0.30 0.22 44547 0.08 1.04 0.07 0.30 0.21 44548 0.09 0.82 0.08 0.33 0.40 44549 0.09 0.82 0.08 0.30 0.39 44554 0.07 0.96 0.08 0.29 0.65 44555 0.06 0.94 0.08 0.33 0.38 44556 0.06 0.97 0.08 0.33 0.38 44558 0.86 0.07 44559 0.85

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-12- 25080D7

Table II compares the cut machinability to that immediately Sub-surface area with cutting machinability inside, both from known leaded Steel rods (examples 44542-549) and of leaded steel rods according to the invention (examples 44554-559),

In each of the experiments reported in Table II, a round bar that was 71.4 mm in diameter was used; the rod was machined about 1.58mm to 59.85mm to make it to train. The radial advance of the tool on each rod was 3.18 mm to allow for the machinability of the immediately below the surface area to be checked (column X). After completion of the tests with a radial advance of 3.18 mm, the rod trimmed to 63.5mm to remove the portion immediately below the surface and the radial advance continued down the length of the bar from the point where the radial feed was 3.18 mm, set to 12.7 mm for the machinability to test the inside of the rod (column Y), the speed of rotation of the rod was set so that with the 12.7 mm feed the surface velocity was the same as on that one previous 3.18 mm feed; the peripheral speed of the 69.8 mm rod was 95 m per minute, while the peripheral speed the 63.5 mm rod was 104 mm per minute.

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TABEL (Y) 12.7 mm
(1/2 inch)
on the same
chen rod
after the Ent
removal of the
outer 6.35
mm (1/4 inch) II (Y) - (X)
λ πη ¥ (χ)
100 %
(Y) ■ ζ
Removed metal in cnr to
to break the tool for 117.99 (χ) 32 % at
game
No. (X) 3.18 mm
M / 8 inch)
tadia & r lurscZntb
to 69.8 mm
(2 3/4 inches)
pole 122.90 213 % 23 % 44542 37.69 103.24 341 % 44543 27.86 185.17 294 % Λ Λ Ο '
ι ι γο 44544 26.22 219.59 842 % 19 % 44545 19.66 209.75 436 % 15 % 44546 40.97 227.78 574 % 40 % 44547 31.14 239.25 148 % 47 % 44548 91.77 186.81 115 % 63 % 44549 111.43 214.67 58 % 44554 117.99 214.67 39 % 62 % 44555 154.04 281.86 61 % 77% 44556 132.73 339.21 28 % 55% 44558 219.59 81 % 44559 186.81

It is the changes in the life of the tool in cubic centimeters that have been removed to the point of failure of the tool, between a rod on which an attempt with a tool (division a) on the outer 3.18 mm of a 69.8 mm diameter rod and another Tool (column b) on the outer 12.7 mm of the same

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Pole. Test (b) of Table III shows the machinability, when cutting through both the immediately below the The surface lying part as well as the inside of the rod was carried out in comparison sum test (Y) of Table II, which made a section through shows the inside of the bar after the portion immediately below the surface has been removed.

Example no.

44542 44543 44544 44545 44546 44547 44548 44549

TABLE III

Removed metal in cnr 'to failure of the tool if the machining was done on

(a) the outside 3.18 mm

.a)

100 %

37.69 27.86 26.22 19.66

40.97

31.14

91.77

111.43

(b) the outside
g ends 12.7 mm (b) 51 % 73.74 53 % 52.44 57 % 45.88 27 % 73.74 51 % 80.30 42 % 73.74 66 % 139.29 79 % 145.84 108 % 109.79 104 % 147.48 96% 137 »6a 123 % 178.62 90 90 208.11

44554 44555 44556 44558 44559

117.99 154.04 132.73 219.59 186.81

By Figo 3, the machinability, expressed in the dimensional increase of the part subject to the cutting machining, namely (A) of

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known steel bars and (B) steel bars according to the invention. The increase in size is an indication of the tool wear, which is inversely proportional to the machinability. The extent however, the increase in size is not equal to the wear and tear of the tool; due to the given mechanical factors is for one given piece output, the dimensional increase is greater than the wear and tear. In general, a larger increase in size ..- than 0.254 mm is uneconomical.

The leaded steel bars A and B on which the tests in FIG. 3 were based were cold-rolled 25 »4 mm round bars of the following Composition:

Element wt%

Carbon 0.06-0.15

Manganese 0.85-1.15

Phosphorus 0.04-0.09

Sulfur 0.26-0.35

Lead 0.20-0.30

Iron essentially remainder

It can be seen from Table II that a leaded steel bar according to the present invention has a cut machinability in the immediately subsurface range of from 3/4 to 77 % of the cut machinability of the interior of the bar compared to 11 to 47 % of a known leaded steel bar.

From Table III it can be seen that one was leaded in accordance with the invention

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Steel bar (Examples 44554-559) has a machinability of the area immediately below the surface (test a) 90 to 123 % of the cut machinability4 of the bar as a whole (part immediately below the surface and the inside) (test b), while a known one leaded steel rod (examples 44542-549) has a machinability of the part immediately below the surface (test a) 27 to 79 % of the machinability of the rod as a whole (test b) »

From Fig. 3 it can be seen that the dimensional increase in a cutting machining with a piece output of 5OOO it is a third of a known leaded steel bar amounts to (0.076 mm as opposed to 0.228 mm).

As already stated, the machinability of cuts is according to the invention Steels are superior to known steels for all lead contents. But also the ability to work with a drilling tool a leaded steel rod according to the invention is with at least comparable to that of a known leaded steel rod,

Leaded steel rods generally have a lead content up to 0.35 wt -.%, At higher lead content, for example 0.40 to 0.50 wt .-%, has a steel rod according to the invention is improved in machinability by both a forming tool and by a Drilling tool «

A leaded according to the invention. After machining, the steel rod

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tion has a better surface quality than a known one leaded steel rod.

With regard to mechanical properties, such as flow resistance, tensile strength and ductility (elongation at break), the leaded steel rods according to the invention are comparable to known leaded steel rods.

Tests were carried out to determine how many parts are produced per work shift if, instead of a known steel rod with a higher than usual content of lead (0.15 to 0.35 Gevr .-% lead), a steel rod according to the invention with an increased lead content (0.40 to 0.50 wt. %) Is used. Otherwise, the composition of the steel rod was in the range as given above for rods A and B in FIG. The results obtained were as follows:

When producing cranked iron rings from a 52.4 mm cold-drawn round piece using an undercut tool, a 10 percent increase in production was achieved. For example, an undercut tool cuts grooves on the inside surface of an axially drilled hole.

When producing a gas control flange from a 25 mm cold-drawn round piece using a cutting tool, a 30 percent increase in production achieved. ♦

In the manufacture of hose couplings from - and 50.8 mm

hexagonal bars for which both cutting and drilling machine tools were used, the production increase achieved was 1 %,

When manufacturing hose couplings from 23? 2 mm cold drawn Hexagonal pieces using cutting and drilling machines achieved a 17 percent increase in performance,

In the production of - and bushings from 22 mm cold drawn round pieces by means of cutting and boring tool suction machines, whereby an undercut tool was decisive ^ wards ^ ins achieved an increase in production of 16 to 23 % .

P ε. t e η ι £ η s ό r- ü c h e:

Claims (6)

Dr.-lng. E. BERKENFELD · Dipl.-Ing. H. BERKENFELD, patent attorneys, Cologne Attachment file number for entry · dated January 13, 1975 VA / Named. Ann ,. INLAND STEEL COMPANY and S.A. ECHEVARRIA PATENT CLAIMS 1. Rolled free-cutting steel bar, characterized in that it has evenly dispersed micro-inclusions of lead, the lead being present in machinability increasing amounts but not a significant amount of complex macro inclusions in contains the area immediately below the surface; and further characterized in that the immediately below the The area lying on the surface has a relatively high cutting machinability through structural steel and this machinability through the amount of metal removed up to the failure of the tool is expressed " 2. Steel rod according to claim 1, characterized in that the Lead content is in the range from 0.05 to 0.70% by weight. 3. Steel rod according to claim 1, characterized in that the lead content is greater than 0.15 to 0.50 G _e w .- #. 4. Steel bar according to claim 1, characterized in that the machinability of the cut of the part lying immediately below the surface is greater than 50 % of the machinability of the cut of the inside of the bar. 5. Steel rod according to claim 1, characterized in that the cutting machinability of the lie- 60.9910 / 0550 genden'Teiles of the rod is greater than 75 % of the cutting machinability of the interior of the rod. 6. Steel rod according to claim 1, characterized in that the
The part immediately below the surface has a cut machinability that is greater than 90 % of the cut machinability. ability of the whole rod.