KR20030026966A - Fe-ni or fe-ni-co or fe-ni-co-cu alloy strip with improved cuttability - Google Patents

Abstract

A strip made of an austenitic Fe-Ni alloy or a Fe-Ni-Co alloy or a Fe-Ni-Co-Cu alloy, wherein the chemical composition of the alloy is in weight percent: 30% ≤Ni≤70%; 0% ≦ Cu + 2 × Co ≦ 20%; 0% ≦ Mn + Cr ≦ 5%; 0% ≦ W + 2 × Mo ≦ 2%; 0% ≦ Ti + V + Nb + Al ≦ 1%; 0.0005% ≦ B ≦ 0.007% and the remainder are iron and impurities such as C, S, P, O, N; The chemical composition is Fe + Ni + Cu + Co ≥ 95%. The alloy has a cubic texture with a cubic texture index D _c ≧ 7. The present invention also provides a method for producing the strip and a method for producing a component by mechanical cutting.

Description

FE-NI or FFE-NI-CO or FFE-NI-CO alloy strips {FE-NI OR FE-NI-CO OR FE-NI-CO-CU ALLOY STRIP WITH IMPROVED CUTTABILITY}

The blanks from which the parts are cut are obtained from strips, which are generally isotropic or slightly textured, obtained by cold rolling and annealing. In the case of flat or nearly flat parts, ie parts with little plastic deformation of the blanks, the strip is often used in a work hardened state to have higher hardness and lower ductility than the strip obtained immediately after annealing. Such high hardness and low ductility are advantageous for mechanical cutting. On the other hand, where drawing is important, the strip is used in an annealed state to achieve high ductility and wide plastic deformation. In this case, the punching cutting operation sometimes proceeds after local work hardening intended to reduce the ductility of the metal along the cutting line. However, in the case of both slightly drawn parts and heavily drawn parts, the quality of the cut is often insufficient and a significant part of the cut part is discarded.

It is known to maintain very small amounts of residual elements such as carbon, sulfur, phosphorus or oxygen which may add small amounts of alloying elements such as molybdenum or niobium or form inclusions in order to improve the cutting quality. However, this means is not sufficient and it is believed that the mechanical cutting capacity of Fe-Ni or Fe-Ni-Co or Fe-Ni-Co-Cu alloys is very inferior to the mechanical cutting capacity of 305 stainless steel, for example.

The present invention relates to the production of parts made of alloys of the Fe-Ni or Fe-Ni-Co or Fe-Ni-Co-Cu type obtained by precision machine cutting of blanks which can be pre-drawn. will be. These parts are commonly used for miniature electrical or electronic components.

Electron gun components for color display cathode ray tubes or many small components, such as integrated circuit support frames or leadframes or micromotors, are made of an alloy of the Fe-Ni or Fe-Ni-Co type containing about 30% to 70% nickel. Drawable blanks are manufactured by precision machine cutting. For parts of this type, the quality of the cut is very important, in particular to prevent the presence of burrs.

1A is a schematic cross-sectional view of a strip punched by mechanical cutting, illustrating a cutting surface corresponding to poor machinability,

1B is a schematic cross-sectional view of a strip punched by mechanical cutting, illustrating a cutting surface corresponding to acceptable machinability,

1C is a schematic cross-sectional view of a strip punched by mechanical cutting, illustrating a cutting surface corresponding to good machinability.

The object of the present invention is in particular the machinability of Fe-Ni or Fe-Ni-Co or Fe-Ni-Co-Cu type alloys used in the formation of thin strips for manufacturing by precision mechanical cutting of parts used in electronic or electrical devices. The shortcomings are addressed by providing a means of improving cuttability.

The object of the present invention for this purpose is a strip made of an austenitic Fe-Ni alloy or a Fe-Ni-Co alloy or a Fe-Ni-Co-Cu alloy, the chemical composition of which is As%:

30% ≤Ni ≤70%

0% ≤Cu + 2 × Co ≤20%

0% ≤Mn + Cr ≤5%

0% ≤W + 2 × Mo ≤2%

0% ≤ Ti + V + Nb + Al ≤1%

0.0005% ≤B ≤0.007%

The remainder is iron and impurities such as C, S, P, O, N; The chemical composition is Fe + Ni + Cu + Co ≥ 95%. The alloy also has a cubic texture with a cubic texture index D _c ≧ 7.

Preferably, the boron content is between 0.0007% and 0.004%, individually or in combination, the index D _c is greater than 10, the carbon content is 0.05% or less, the sulfur content is 0.01% or less, more preferably 0.007% or less Oxygen content is less than 0.005%.

The invention also

Producing a strip made of an alloy having a chemical composition as defined above by cold rolling at a strain of at least 80%;

Performing a fine-grain recrystallization annealing operation on the strip; And

Optionally, a complementary cold rolling operation with a strain of 40% or less

It relates to a method for manufacturing a strip made of Fe-Ni or Fe-Ni-Co or Fe-Ni-Co-Cu alloy.

Finally, the present invention is a method of manufacturing a part by mechanical cutting or mechanical cutting and drawing, which takes a blank from a strip according to the invention and at least one mechanical cutting operation and optionally at least one drawing operation for the blank. And at least one drawing operation can be performed before or after the at least one mechanical cutting operation. The component is, for example, an electron gun having a life span through which electrons pass. The component can also be a leadframe with a connection lead. The component can also be a magnetic core of a micromotor or transformer. This list of applications is not limited.

The invention is now described in more detail with reference to the accompanying drawings and illustrated by way of example.

The strip according to the invention is a thin cold rolled strip made of an alloy of the type Fe-Ni or Fe-Ni-Co or Fe-Ni-Co-Cu, which is known per se in its most common form (thickness generally less than 1.5 mm) ). In this type of alloy, cobalt, which is nickel or a substitute for nickel, allows for the control of properties such as coefficient of thermal expansion or magnetic permeability. Nickel content is 30% to 70%; The copper and cobalt content is in amounts of up to 20% Cu + 2Co total, with these two elements being optional. The remainder are essentially impurities such as carbon, sulfur, phosphorus, oxygen and nitrogen, complementary alloying elements such as manganese, chromium, tungsten, molybdenum, titanium, vanadium, niobium and aluminum, and iron. However, the contents of iron, nickel, copper, and cobalt should satisfy Fe + Ni + Co + Cu ≧ 95%. The content of the alloying element should satisfy Mn + Cr <5%, W + 2Mo ≦ 2%, and Ti + V + Nb + Al ≦ 1%. It may be desirable to contain small amounts of certain impurities, such as carbon, sulfur and oxygen, which can form inclusions because they have a beneficial effect on machinability. However, the carbon content should preferably be kept below 0.05%, the sulfur content should be kept below 0.01%, more preferably below 0.007% and the oxygen content preferably below 0.005%.

The alloy also contains a cubic texture index D _c containing from 0.0005% to 0.007% of boron, preferably from 0.0007% to 0.004% of boron and greater than 7, preferably greater than 10. (001) <100> has a cube structure. This is because the inventors have found that the addition of boron, together with the surprisingly high cube structure, substantially improves the mechanical cutting capacity of Fe-Ni or Fe-Ni-Co or Fe-Ni-Co-Cu type alloys. .

The cube structure index D _c is along the 45 ° line in the rolling direction at the point located 54 ° 44 'from the center of the figure on the (111) polar figure on the one hand and the sample of the strip to be characterized on the other hand. The ratio of the measured maximum refractive X-ray intensity, I _cubic / I _isotropic .

The degree of texture of the strip can also be evaluated by a simple but roughly drawing test measuring the drawing ear. This method can only be used to evaluate the characteristics of a sufficiently ductile metal. To use this method, for example, a disk of 60 mm in diameter can be drawn to form a cup with an average of 33 mm in diameter and 19 mm in height, on average. The height difference between the highest point and the lowest point of the upper edge is then measured. If this height difference is less than 0.3 mm, the strip is isotropic or there is little tissue, and if this difference is greater than 1.5 mm, the strip has a very pronounced texture.

In order to obtain a strip of alloy having a distinct cube structure, the desired thickness obtained by melting, casting and hot rolling the alloy in a manner known per se by cold rolling at a cross sectional shrinkage of at least 80%, more preferably at least 90% A hot strip of thickness is obtained which enables a cold strip with The thickness of the hot rolled strip is for example 5 mm. Cold rolling should be done without intermediate annealing, but can be done following the annealing step. This is especially the case when it is necessary to make several stages of continuous cold rolling passes due to the thickness of the hot strip and the thickness planned for the cold strip. Following the final cold rolling pass (section shrinkage of 80% or more), for example, recrystallization annealing usually done in a tunnel furnace under a protective atmosphere consisting of a mixture of calcination and nitrogen with dew points below -40 ° C. Step proceeds. An oven temperature of about 1000 ° C. should be sufficient to obtain fine-grain recrystallization, but not too high to prevent secondary grain crystallization of undesirable coarse grains. The duration of the annealing stage is typically about 1 minute. Those skilled in the art will know how to tailor the annealing conditions precisely to obtain fine grain recrystallization while avoiding secondary recrystallization on an individual case basis.

Optionally, in order to increase the hardness of the strip, recrystallization annealing may be followed by complementary cold rolling with a cross sectional shrinkage of 50% or less or more preferably 30% or less so as not to excessively degrade the initial cube structure. If the cross-sectional shrinkage of the complementary cold rolling is less than 10%, a cold strip with a pronounced cubical structure softened or slightly work-hardened is obtained. If the cross-sectional shrinkage of the complementary cold rolling is greater than 10%, a work hardened cold strip with a pronounced cubic structure is obtained.

Given the thickness of the hot strip, the cold rolled strip obtained generally has a thickness of less than 0.5 mm.

In order to produce the parts according to the invention from strips with a cube tissue index of at least 7, or more preferably at least 10, even more preferably at least 15, the blanks are cut by mechanical cutting in a known manner. The blank may be part that has been finished and then flattened, or may be a preform. The preform may be molded by drawing and then cut again by mechanical cutting. Cutting at this time may be a drill operation, for example. A local work hardening step can be made prior to this cutting operation.

If the part is highly deformed by drawing or bending or local thickness reduction, i.e. at 20% or more strain, the strip is softened or slightly work hardened, ie without complementary cold rolling or with a complementary shrinkage of less than 10 Used for cold rolling. This is the case, for example, for certain electron gun components for color display cathode ray tubes.

The quality of the cut is assessed by the cutting surface comprising a sheared region and a torn region. The boundary between these two areas should be regular and located approximately in the middle thickness. There should also be no burrs at all.

Three cutting surfaces are illustrated in FIGS. 1A, 1B and 1C. These surfaces are observed around the holes 1a, 1b, 1c drilled in the strips 2a, 2b, 2c by punching. Only half of each hole is shown after cutting the strip into a plane through the axis of the life preserver. The walls 3a, 3b, 3c of each of the holes have shear regions 4a, 4b, 4c and rupture regions 5a, 5b, 5c.

1a is opposed to a strip of alloy with poor machinability. Shear region 3a covers most of the thickness and ends with a substantial bur 6a near the bottom.

Figure 1b corresponds to a strip of alloy with barely acceptable machinability. Shear region 3b is approximately half the thickness and ends with several burrs 6b near the bottom.

1C corresponds to a strip of alloy with good machinability. Shear region 3c is approximately half the thickness and there is no burr.

These figures are presented for illustration only. Those skilled in the art will know in each case how to evaluate the quality of the cut according to more precise criteria than can be inferred directly from these figures.

Apart from the observation of these cutting surfaces, the cutting quality can also be evaluated by the geometric quality of the parts obtained. If the cutting is to drill a circular hole, the evaluation of the cutting foam quality is to consider how close to the circle the hole is.

In general, the observations necessary for evaluating the quality of a cutting part are made at magnifications from 10 to 50.

For comparison with the examples, a hot rolled strip was prepared of FeNi14 alloy material having a thickness of 4.5 mm and a chemical composition represented by weight% as shown in Table 1 below.

TABLE 1

division Ni Mn Si C S P Al B N O Fe PV408 40.8 0.45 0.07 0.005 <0.0005 0.003 <0.005 <0.0005 0.002 0.0025 Remainder PV588 41.1 0.40 0.10 0.004 <0.0005 0.004 <0.005 0.0038 0.002 0.0025 Remainder PW075 40.6 0.43 0.12 0.009 0.0032 0.003 <0.005 0.0018 0.002 0.0035 Remainder

Alloys PV588 and PW075 have a composition according to the invention and alloy PV408 is presented for comparison.

Cold strips were prepared by a method comprising the following steps from these hot strips according to six different manufacturing schemes labeled A, B, C, D, E and F: a primary cold rolling pass with a strain of DEF1, Recrystallization annealing step into tunnel, and secondary cold rolling pass with strain DEF2. The primary deformation is optionally followed by a preliminary deformation of the hot rolled strip, followed by a recrystallization annealing step to adjust the thickness to the desired value.

The strain rate in each scheme, the hardness Hv and elongation at the resulting break A% (same in all three alloys) are shown in Table 2.

TABLE 2

Scheme A B C D E F DEF1 68% 50% 88% 91% 96% 96% DEF2 60% 23% 23% 20% 20% 445 Hv 230 205 205 205 205 220 A% One% 5% 5% 5% 5% 2%

In each of the above schemes, the cube structure index D _c obtained for each alloy is shown in Table 3.

TABLE 3

A B C D E F PV408 D _c = 1 D _c = 1 nd nd D _c = 25 nd PV588 D _c = 1 D _c = 1 nd D _c = 10 D _c = 25 D _c = 7 PW075 D _c = 1 D _c = 1 D _c = 10 D _c = 25 D _c = 45 D _c = 12

To obtain a cube tissue index D _c greater than 10, the results indicate that the strain DEF1 should be high and preferably at least 80% and the strain DEF2 should not be too high.

Cold rolled strips made of PV588 alloys obtained using schemes D, E and F and cold rolled strips made of PV588 alloys obtained using schemes C, D, E and F correspond to the invention. Others are presented for comparison.

Leadframes were made by mechanical cutting from strips of 0.25 mm thickness corresponding to the three alloys and production scheme D. In accordance with the present invention boron containing PV588 and PW075 alloys provided 100% good parts. On the other hand, PV408 alloys produced significant burrs to provide poor parts.

Three strips of 0.4 mm thickness were prepared from PW075 alloy (containing boron according to the invention) using schemes A, B and C, respectively, from which a batch of flat parts having a circular hole of 0.5 mm diameter formed by punching The batch was cut.

In batches corresponding to Scheme A (comparative), only 24% of the parts were good, and in batches corresponding to scheme B (comparative) only 53% of the parts were good. In contrast, in the batch corresponding to scheme C (invention) 100% of the parts were good.

Claims (10)

A strip made of an austenitic Fe-Ni alloy or Fe-Ni-Co alloy or Fe-Ni-Co-Cu alloy, wherein the chemical composition of the alloy is 30% ≤Ni ≤70% 0% ≤Cu + 2 × Co ≤20% 0% ≤Mn + Cr ≤5% 0% ≤W + 2 × Mo ≤2% 0% ≤ Ti + V + Nb + Al ≤1% 0.0005% ≤B ≤0.007% Same as The rest are impurities such as iron and C, S, P, O, N; The chemical composition is Fe + Ni + Cu + Co ≥ 95%, The alloy has a cubic texture with a cubic texture index D _c ≥ 7 strip. The method of claim 1, And wherein B is 0.007% ≦ B ≦ 0.004%. The method according to claim 1 or 2, And wherein D _c is D _c > 10. The method according to any one of claims 1 to 3, A strip, characterized in that the carbon content of the alloy is 0.05% or less. The method according to any one of claims 1 to 4, And a sulfur content of the alloy is 0.01% or less. The method of claim 5, And wherein the sulfur content of the alloy is less than 0.007%. The method according to any one of claims 1 to 6, Strip characterized in that the oxygen content is less than 0.005%. Producing a strip made of an alloy having a chemical composition as defined in claims 1 to 7 by cold rolling at a strain of at least 80%; Performing a fine-grain recrystallization annealing operation on the strip; And Optionally, a complementary cold rolling operation with a strain of 40% or less Method for producing a strip of any one of claims 1 to 7, characterized in that it comprises a. A method of manufacturing a part by mechanical cutting or mechanical cutting and drawing, Taking a blank from the strip of claim 1; And Performing at least one mechanical cutting operation and optionally at least one drawing operation on said blank; Including, The at least one drawing operation may be performed before or after the at least one mechanical cutting operation. Part manufacturing method. The method of claim 9, The component is an electron-gun component having a hole through which an electron passes, a lead frame having a connecting lead, or a magnetic core of a micromotor or a transformer. .