US3632455A

US3632455A - Ductile ultrahigh strength steel mainly consisting of quenched and tempered steel and a method of manufacturing the same

Info

Publication number: US3632455A
Application number: US829644A
Authority: US
Inventors: Hajime Nakamura
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1968-06-05
Filing date: 1969-06-02
Publication date: 1972-01-04
Anticipated expiration: 1989-01-04
Also published as: JPS5137905B1

Abstract

Ductile ultrahigh strength steel composed of multiple layers formed by combining quenched and tempered steel plates with nonferrous metal or nonferrous alloy plates whose modulus of elasticity is not higher than and whose percentage of elongation and rate of reduction of area are greater than those of the quenched and tempered steel and being characterized by extremely low diffusion of iron and carbon which are the principal components of the steel and the wetting phenomenon with the quenched and tempered steel, which steel product does not exhibit unstable fractures but retains suitable elongation and ductility and has a tensile strength of more than 180 kg./mm.2.

Description

United States Patent DUCTILE ULTRAHlGl-l STRENGTH STEEL MAINLY CONSISTING OF QUENCHED AND TEMPERED STEEL AND A METHOD OF MANUFACTURING THE SAME 4 Claims, 7 Drawing Figs.

u.s. c1 148/124, 29/196.3, 148/127, 29/l96.6, 148/34 Field 01 Search 148/127,

[56] References Cited UNITED STATES PATENTS 3,212,865 10/1965 Miller 29/ 1 96.3

Primary Examiner-Richard 0. Dean AttorneyNo1te and Nolte ABSTRACT: Ductile ultrahigh strength steel composed of multiple layers formed by combining quenched and tempered steel plates with nonferrous metal or nonferrous alloy plates whose modulus of elasticity is not higher than and whose percentage of elongation and rate of reduction of area are greater than those of the quenched and tempered steel and being characterized by extremely low difiusion of iron and carbon which are the principal components of the steel and the wetting phenomenon with the quenched and tempered steel, which steel product does not exhibit unstable fractures but retains suitable elongation and ductility and has a tensile strength of more than 180 kg./mm,.

PATENTEB JAH & B72

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SHEET 7 [IF 7 v ATTORNEYS DUCTILE ULTRAIIIGH STRENGTH STEEL MAINLY CONSISTING OF QUENCHED AND TEMPERED STEEL AND A METHOD OF MANUFACTURING THE SAME DETAILED EXPLANATION OF THE INVENTION The quenched and tempered steel in which the carbon which has been subjected to such heat treatments as quenching and tempering so as to obtain high strength plays a major role in quenching and tempering may fail to attain the expected maximum strength or may be broken under substantially lower stress than the maximum value of its strength when such quenched and tempered steel is subjected to tension, i.e., stretching or pulling action. This is a phenomenon referred to as unstable fracture which may occur in ultra-high-strength steel. Such phenomenon occurred in a sample tempered at a temperature lower than 300 C. Of high-carbon steel containing 0.85 percent of carbon as shown in FIG. 1 may also occur in other high-alloy steels. Because no ductility and percentage of elongation are shown, all such unstable fractures are brittle fractures. Therefore, although such steel has high tensile strength, it is not suitable for use as structural material for machinery and constructions because of the possibility of failure.

Such being the case, only very expensive high-alloy steel containing a large quantity of expensive elements is currently used as the structural material for which a tensile strength of approximately 180 kgjmm. is required.

It is an object of this invention to provide extremely inexpensive ultra-high-strength steel which does not show any unstable fracture as described above but retains suitable elongation and ductility and has a tensile strength of more than 180 kg./mm. and a method of manufacturing the said steel.

This invention relates to multilayer ultra-high-strength steel consisting of l) a nonferrous metal or nonferrous alloy as unstable fracture arresting material which has a modulus of elasticity (Youngs modulus) not higher than that of quenched and tempered steel and a greater percentage of elongation and reduction of area than that of quenched and tempered steel and which shows a minimum diffusion of iron and carbon which are the principal components of the steel and a wetting phenomenon against the quenched and tempered steel and of (2) quenched and tempered steel which may incur unstable fracture (the said quenched and tempered steel being carbon steel and alloy steel in which carbon plays a major part in the quenching and tempering processes). The ratio between the mean values of the thicknesses of the layers of the steel and the nonferrous metal or nonferrous alloy layers composing the said multilayer steel is 100 to 2.5-15, and the thickness of the single layer of the steel including the alloy layer formed during the processing with the unstable fracture arresting material and the quenched and tempered steel (hereinafter referred to simply as the thickness of the single layer of the steel) is l0.0l um. (I m.=0.001 mm.).

This invention also relates to a method of manufacturing ultra-high-strength steel having high ductility and consisting mainly of quenched and tempered steel comprising the steps of combining and pressing together a nonferrous metal or nonferrous alloy, as an unstable fracture arresting material, which has a modulus of elasticity not higher than that of the quenched and tempered steel and greater percentages of elongation and reduction of area than that of the quenched and tempered steel, and shows a minimum diffusion of iron and carbon which are the principal components of the steel and further a wetting phenomenon against the quenched and tempered steel, and such quenched and tempered steel as may incur unstable fracture in a ratio of thickness of 100 for the said steel to 2.5 to for said nonferrous metal or nonferrous alloy in a solid state after heating the materials to temperatures higher than their respective recrystallization temperatures, applying such combinations of the two materials one on top of the other to thereby form a multilayer steel, processing such multilayer steel so that the thickness of the single layer of steel thereby formed amounts to 10 to 0.01 pm. and finally quenching and tempering such multilayer steel.

This invention will be further described below by some preferred embodiments:

The quenched and tempered steels which are liable to unstable fracture although high strength can be obtained by such heat treatment as quenching and tempering include carbon steel and low-alloy steels consisting of such carbon steel containing in addition of nickel, chromium, molybdenum, vanadium, tungsten, cobalt or other alloy elements. In the following embodiments of this invention, we used high-carbon steel containing 0.85 percent of carbon for the quenched and tempered steel as a typical example of such steels and pure nickel, pure copper, monel metal as a typical example of nickel-copper alloys, and their alloys for the unstable fracture arresting material. The results of the tests conducted on such materials will be described below. The samples used for the test of mechanical properties in the following examples are a plate having a width at its parallel portion of 4 mm. a gauge length of 20 mm. and a thickness of 2 mm.

FIG. 1 is a graph showing the relationship between the tempering temperature, tensile strength and percentage of elongation with respect to high-carbon steel containing 0.85 percent of carbon as it is tempered at the various temperatures after quenching, said high-carbon steel being an object of this invention and well-known relatively inexpensive quenched and tempered steel having high strength.

FIG. 2 is a graph showing the relationship between the thickness of the resulting single layer of steel (including the alloy layer), tensile strength and percentage of elongation of the multilayer steel according to this invention as it is tempered at various temperatures the said multilayer steel consisting of high-carbon steel plates containing 0.85 percent of car bon and of nickel plates as unstable fracture arresting material each of which is placed on top of each of the said high-carbon plates and pressed together at the ratio of parts of the high-carbon plates and 20 parts of the nickel plates.

FIG. 3 shows the results of the tensile test of the multilayer steel according to the present invention consisting of the steel plates and nickel plates laid on top of each other and pressed together in the same manner as described in FIG. 2 but at the ratio of 100 of the steel plates to 10 of the nickel plates.

FIGS. 4 and 5 are graphs showing the results of the similar tensile test of the multilayer steel according to the present invention consisting of the steel plates and the pure nickel plates combined and pressed together but this time at the ratio of 100 of the steel plates to 5.0 and 2.5 respectively of the nickel plates.

FIG. 6 indicates the results of the tensile test similar to those described in FIGS. 2 to 5 carried out on the multilayer steel of this invention which is in this case composed of 100 parts of the steel plate and 10 parts of the pure copper plate as an unstable fracture arresting material.

FIG. 7 shows the results of the tensile test of the multilayer steel according to the present invention which in this case consists of 100 parts of steel plates and 10 parts of monel metal plates as an unstable fracture arresting material which is a typical example of the copper-nickel alloys.

As indicated in FIG. 1, all the samples of the carbon steel with 0.85 percent carbon contents which were tempered at 300 C. or a lower temperature showed brittleness and incurred unstable fracture. The sample which was tempered within such temperature range as to cause no unstable fracture and had a maximum strength of 180 kg./mm. showed a percentage of elongation lower than 5 percent. On the other hand, the samples of the steel processed and treated according to this invention showed high ductility and ultrahigh strength as is clear in the following examples.

EXAMPLE I.

In example 1, nickel was employed as the unstable fracture arresting material. Nickel plates were combined with carbon steel plates in the ratios in the mean value of plate thickness of 100 of the steel plate to 2.5, 5, l0 and 20 respectively of the nickel plate. Such materials were heated at temperatures higher than their respective recrystallization temperatures then combined in a solid state and pressed together thereby forming multilayers. The multilayer samples thus formed were then rolled so that the thickness of the single layer of the steel could be in the range of 100 to 0.00] am. The multilayer steel samples were then quenched at 800 C. and tempered at 100 C. or higher temperatures. FIG. 2 shows the relationship between the thickness of the single layer of the steel, the tensile strength and percentage of elongation with respect to the samples of the multilayer steel consisting of carbon steel plates and nickel plates combined and pressed together in a manner described above at the ratio of 100 to 20 as they were tempered at 200 C., 250 C. and 300 C. respectively. All the samples which were tempered at temperatures lower than 150 C. showed unstable fracture and therefore were not included in the FIGURE. As is clear from the FIGURE, the sample with the thickness of the single steel layer of 100 pm. which was tempered at 250 C. showed a maximum tensile strength of 200 kgjmm. but incurred unstable fracture.

The sample having a thickness of the single layer of the steel of pm. which was tempered at 250 C. showed a maximum tensile strength of 190 kg./mm. and exhibited ductile fractures. The one tempered at 200 C. showed ductile fracture and a tensile strength of approximately 200 kgJmmF. All the samples having a thickness of the single layer of the steel of 1 pm. or less showed ductile fracture and the tensile strength is seen in the neighborhood of 150 kg./mm. regardless of the tempering temperatures and the thickness of the single layer of the steel. The sample with the thickness of the single layer of the steel of 100 pm. which was tempered at 300 C. showed ductile fracture at a maximum tensile strength of 178 kg.lmm. and the elongation percentage of approximately 6.5 percent. The sample with the thickness of the single layer of the steel of 10 am. showed ductile fracture at a tensile strength of 160 kg./mm. and elongation percentage of 9.5 percent.

FIG. 3 shows the results of the similar test carried out on samples composed of carbon steel plates and nickel plates at the ratio of 100 to 10. All the samples tempered at 100 C. showed unstable fracture and brittle fracture with the tensile strengths unstably varying between 150 and 235 kg./mm. and elongation percentages being almost zero. The sample tempered at 150 C. showed increased tensile strength as the thickness of the single layer of the steel decreased, reaching a maximum of 245 kgJmm. at 0.1 pm. and from that point on gradually decreasing as the thickness of the single layer of the steel decreased. On the other hand, its percentage of elongation increased as the thickness of the single layer of the steel decreased reaching a maximum of 9.4 percent at 0.01 pm. but thereafter decreased sharply as the thickness of the single layer of the steel decreased.

With respect to the samples tempered at 200 C., the tensile strength was seen to increase as the thickness of the single layer of the steel decreased, to reach a maximum at 0.1 am. but thereafter to decrease gradually. The maximum tensile strength in this case in 226 kg./mm. The percentage of elongation is 6 to 7 percent when the thickness of the single layer of the steel is 10 pm, but it is seen to increase as the thickness of the single layer of the steel decreases, to reach a maximum of 9 percent at 0.1 pm. and from that point on to decline with the decrease of the thickness of the single layer of the steel. The sample tempered at 250 C. shows brittle fracture when the thickness of the single layer of the steel is 100 ,um. and ductile fracture when it is 10 pm. It will thus be understood that its tensile strength increases as the thickness of the single layer of the steel decreases with the maximum of approximately 200 kg./mm.

The percentage of elongation also increases with the decrease of the thickness of the single layer of the steel, reaching the maximum of approximately 10 percent. The samples tempered at 400 C. or higher temperatures show ductile fracture at atensile strength of approximately 140 kg./mm. irrespective. of the thickness of the single layer of the steel and their elongation percentage is about 12 percent when the thickness of the single layer of the steel is 0.01 pm. but is seen to decrease as the thickness of the single layer of the steel decreases.

FIG. 4 shows the results of the similar tests conducted on samples composed of the carbon steel plates and the nickel plates at the ratio of to 5. As can be seen from the Figure, all the samples tempered at 100 C. showed unstable fracture, but their maximum tensile strength was as high as 220 kg./mm. The sample tempered at C. showed ductile fracture at 0.1 pm. or less depending upon the variation of the thickness of the single layer of the steel. And the tensile strength is about 210 kg./mm. for those which incurred ductile fracture and the percentage of elongation is 5.8 percent and 7.5 percent when the thickness of the single layer of the steel is 0.1 pm. and 0.01 pm. respectively. The samples tempered at 200 C. exhibited brittle fracture both with respect to one with the thickness of the single layer of the steel of 10 pm. and another with the thickness of 1 pm.

The samples having the thickness of the single layer of the steel of 0.1 pm. and 0.01 am. showed ductile fracture. Their tensile strength are 193 kg./mm. and 188 kg./mm. and percentage of elongation were 6 percent and 10 percent respectively. The samples tempered at 250 C. show brittle fracture when the thickness of the single layer of the steel is 100 am. but they indicate ductile fracture when such thickness is 10 pm. or less. When the thickness of the single layer of the steel is 10 ,u.m., the tensile strength is 197 kgJmm? and the percentage of elongation is 5.8 percent. All the samples tempered at 300 C. show ductile fracture with its maximum tensile strength of 195 kg./mm. The percentage of elongation is approximately 5 percent, which gradually increases as the thickness of the single layer of the steel decreases. The maximum tensile strength of the samples tempered at 400 C. is 150 kg./mm. and the tensile strength decreases as the thickness of the single layer of the steel decreases.

FIG. 5 reveals the results of the similar tests conducted on the samples consisting of 100 parts of the carbon steel plates and 2.5 parts of the nickel plates combined and pressed together. The samples tempered at 250 C. or lower temperature showed brittle fracture irrespective of their thickness of the single layer of the steel and therefore were not shown in the FIGURE. The tensile strengths of the samples tempered at 300 C. were in the neighborhood of 200 kg./mm. and did not so widely vary depending upon the different thickness of the single layer of the steel except when the thickness of the single layer of the steel was 100 pm. The maximum tensile strength is 215 lag/mm. and the elongation percentage is 6.3 percent when the thickness of the single layer of the steel is 0.1 pm. From the results as shown above, we found that the samples consisting of 100 parts of the carbon plates and 20 parts of the nickel plates had tensile strengths of more than kg.lmm. and percentages of elongation of more than 5 percent without showing any unstable fracture when they were tempered at 200 C. and 250 C. and the thickness of the single layer of the steel was approximately 10am. The samples consisting of the steel plates and the nickel plates in a ratio of 100 to 10 and having a thickness of the single layer of the steel of from 10 to 0.001 um. had tensile strengths of 180 kgJmm. or more and the elongation percentage of 5 percent or more when they were tempered at a temperature range of 150 C. to 250 C. and the thickness of the single layer of the steel was up to 0.01 pm. The samples consisting of the steel plates and the nickel plates at the ratio of 100 to 5 showed a tensile strength of 180 kg./mm. or more and the elongation percentage of 5 percent or more when they had the thickness of the single layer of the steel of 0.1 pm. to 0.01 pm. and were tempered at a temperature range of 150 C. to 200 C. and when they had a thickness of the single layer of the steel of 10 to 1 pm. and were tempered at 250C. Among the samples composed of the steel plates and the nickel plates at the ratio of 100 to 2.5, those having the thickness of the single layer of the steel of l to 0.01 am. and tempered at 300 C. and those having the thickness of the single layer of the steel of l pm. and tempered at 350 C. showed the tensile strength of 180 kgJmm. or more and the elongation percentage of 5 percent or more. The results above described indicate that the kinds of multilayer steel which are suitable for the arrest of unstable fracture are those composed of steel plates and nickel plates in a ratio of 100 to 2.5-20 with the thickness of a single layer of steel of to 0.01 pm.

EXAMPLE 2 The percentage of pure copper to the carbon steel when the former is employed as unstable fracture arresting material may be varied as in the case of the nickel plate. In the preferred embodiment, we used the samples composed of the carbon steel plates and the pure copper plates in a ratio for a mean value of thickness of 100 to 10 and conducted on such samples tests similar to those described in example I. The results of the tests are shown in FIG. 6.

All the samples tempered at 150 C. showed brittle fracture irrespective of the thickness of the single layer of the steel and the maximum tensile strength is 292 kg./mm. Among the samples tempered at 200 (1., those having the thicknesses of the single layer of the steel of 100 pm. and 10 pm. showed brittle fracture, and those having less thickness of the single layer of the steel showed ductile fracture with the maximum tensile strength of 258 kg./mm. when the thickness of the single layer of the steel was 1 pm. In the samples having steel with lower thicknesses for the single layer of the steel, the tensile strength decreased as the thickness of the single layer of the steel decreased and was 215 kg./mm. at 0.01 am. with the percentage of elongation of approximately 5 percent. The samples tempered at 250 C. showed the similar trend as the samples tempered at 200 C. However, a tensile strength reached the maximum of 240 kg./mm. in the sample with the thickness of the single layer of the steel of 1 pm. In the samples having less thickness of the single layer of the steel, the tensile strength decreased as the thickness of the single layer of the steel decreased but in any case did not become less that 200 kg./mm. The elongation percentage was 5 percent or higher when the thickness of the single layer of the steel was 1 am. or less. In the samples tempered at 300 C., the tensile strength gradually decreased with the decrease of the thickness of the single layer of the steel and was 175 kg./mm. at 1.0 pm. The elongation percentage was 5 percent or higher at 1 am. or less. In the samples tempered at 400 C., the tensile strength remained rather fixed around 150 kg./mm. re gardless of the thickness of the single layer of the steel, and the elongation percentage was seen to decrease as the thickness of the single layer of the steel was reduced. The elongation percentage was 10.5 percent at 100 um. and was found to be reduced to as low as 6 percent at 0.01 pm.

The above indicated results are suggestive that to obtain a percentage of elongation of 5 percent or higher at the tensile strength of 180 kg./mm. it is desirable that the thickness of the single layer of the steel be in the range of 10 um. to 0.01 run.

EXAMPLE 3 The composition ratio of the monel metal, which is a typical nickel-copper alloy, to the steel when the former is used as an unstable fracture arresting material may be varied as in the case of the nickel plates. In this example, we used the samples consisting of the steel plates and the monel metal plates in a ratio for a mean value of thickness of 100 to 10, which were pressed together in multilayers at a high temperature, and carried out on such samples tests similar to those employed in the foregoing examples. The results are shown in FIG. 7. Among the samples tempered at 150 C., those having the single layer of the steel of 10 pm. or more suffered from unstable fracture and those having thickness for the single layer of the steel of 1pm. or less showed ductile fracture. The tensile strength of the sample with the thickness for a single layer of the steel of 1pm. was 250 kg./mm. with the percentage of elongation of 6 to 7 percent. Among the samples tempered at 200 C., those having the thickness of the single layer of the steel of p.m. surrendered to brittle fracture and those having such thickness of 10 pm. showed ductile fracture. The tensile strength remained approximately 235 kg./mm. up to l pm. but was seen to decrease when the thickness became less than the said value. The percentage of elongation was approximately 5 percent in the samples whose thickness of the single layer of the steel was 10 um. and approximately 8 percent in the samples with such thickness of 1 pm. The percentage of elongation was seen to decrease as the thickness of the single layer of the steel was further reduced. Among the samples tempered at 250 C., those with the thickness of the single layer of the steel of 100 am. surrendered to brittle fracture. The tensile strength remained almost unchanged up to 10 to 0.1 nm. and was 220 kgJmm. at 1 pm. The elongation percentage increased. with the decrease of the thickness of the single layer of the steel and reached about 5 percent at 10 pm. In the samples tempered at 300 C., the tensile strength was in the neighborhood of 200 kg./mm. irrespective of the thickness of the single layer of the steel and the elongation percentage was roughly 5 to 7 percent. Those results suggest that when monel metal is used as an unstable fracture arresting material, it is desirable that the thickness of the single layer of the steel be in the range of 10 run. to 0.01 pm. in order to produce multilayer steel having a tensile strength of 180 kg./mm. or more and an elongation percentage of 5 percent or higher.

As will be understood from the foregoing descriptions, the optimum thickness of the single layer of the steel is in the range of approximately 10 to 0.01 pm. when such steel as can retain its maximum strength without surrendering to unstable fracture is produced from quenched and tempered steel by placing plates of nonferrous metals or their allows and steel plates on top of another so as to form multiple layers of such plates and pressing them together. Also the examples described above indicate that the optimum ratio for the means value of thickness between the steel and the unstable fracture arresting materials is 100 to 2.5-20, as can be seen in the case of the nickel plates. However, such recommended unstable fracture arresting materials as copper, nickel and their alloys are generally more expensive than steel and therefore it is not desirable to use a large quantity of any of such materials because it will increase the price of the finished product. The most economical ratio for the mean value of thicknesses between the steel plates and the plates of such unstable fracture arresting metals and their alloys is 100 to 2.5-l5 for the purpose of obtaining the steel of the present invention whicliis free from unstable fracture and which has a tensile strength of 180 kg./mm. or more and a percentage of elongation of 5 percent or higher.

As other unstable fracture arresting materials than those discussed above, pure iron and low-carbon steel may be taken into consideration. However, these materials are not suitable as unstable fracture arresting materials of this invention, because the carbon in the carbon steel which is the main component of the steel of this invention may easily diffuse into such materials during the process of combining and pressing together the carbon steel plates and the plates of such materials at a high temperature.

What is claimed is:

l. A multilayer ductile ultra-high-strength steel comprising a plurality of integrally joined layers wherein each single layer is formed of an integrally joined quenched and tempered steel and nonferrous metal or nonferrous alloy plate whose modulus of elasticity is not higher than that of the quenched and tempered steel and whose percentage of elongation and rate of reduction of area are greater than those of the quenched and tempered steel and further having such characteristics as the extremely low diffusion of iron and carbon which are the principal components of the steel phenomenon with the quenched and tempered steel, wherein the ratio between the quenched and tempered steel and the nonferrous metal or nonferrous alloy in said multilayer steel and the wetting amounts to from 100 to 2.5l based on the mean value of the thickness of the plates of such materials and wherein the thickness of each single layer'of steel in the composite of the quenched and tempered steel and nonferrous metal or nonferrous allo'y amounts to from 10 to 0.01 pm, said layers in said multilayer steel providing an alternating sequence of steel and nonferrous metal or nonferrous alloy layers.

2. Method of manufacturing a multilayer ductile ultra-highstrength steel according to claim 1 which comprises the steps of applying a layer of nonferrous metal or nonferrous alloy on top of a layer of steel, pressing said combined layer together to form a single layer having a ratio of thickness of steel to nonferrous metal or nonferrous alloy of 100 to 2.5- thereafter applying said single layers one over the other to form a multilayer body having alternating steel and nonferrous metal or nonferrous alloy layers and pressing said multilayer body so that the thickness of said single layer of steel and nonferrous metal or nonferrous alloy formed from said pressing will amount to from 10 to 0.01 pm. and then quenching and tempering said multilayer body wherein said quenching and tempering are carried out by heating said multilayer body to a temperature higher than the recrystallization temperatures of said layers and nonferrous metal or nonferrous alloy layers having modulus of elasticity not higher than that of the quenched and tempered steel and a percentage of elongation and rate of reduction of area greater than that of said quenched and tempered steel and having such characteristics as an extremely low diffusion of iron and carbon which are the principal components of steel and the wetting phenomenon with the quenched and tempered steel.

3. A multilayer ductile ultra-high-strength steel according to claim 1 wherein said nonferrous metal or nonferrous alloy is a member selected from the group consisting of nickel, copper and alloys thereof.

4. A multilayer ductile ultra-high-strength steel according to claim 1 wherein said quenched and tempered steel comprises a high-carbon steel containing 0.85 percent of carbon.

Claims

2. Method of manufacturing a multilayer ductile ultra-high-strength steel according to claim 1 which comprises the steps of applying a layer of nonferrous metal or nonferrous alloy on top of a layer of steel, pressing said combined layer together to form a single layer having a ratio of thickness of steel to nonferrous metal or nonferrous alloy of 100 to 2.5-15 thereafter applying said single layers one over the other to form a multilayer body having alternating steel and nonferrous metal or nonferrous alloy layers and pressing said multilayer body so that the thickness of said single layer of steel and nonferrous metal or nonferrous alloy formed from said pressing will amount to from 10 to 0.01 Mu m. and then quenching and tempering said multilayer body wherein said quenching and tempering are carried out by heating said multilayer body to a temperature higher than the recrystallization temperatures of said layers and nonferrous metal or nonferrous alloy layers having modulus of elasticity not higher than that of the quenched and tempered steel and a percentage of elongation and rate of reduction of area greater than that of said quenched and tempered steel and having such characteristics as an extremely low diffusion of iron and carbon which are the principal components of steel and the wetting phenomenon with the quenched and tempered steel.
3. A multilayer ductile ultra-high-strength steel according to claim 1 wherein said nonferrous metal or nonferrous alloy is a member selected from the group consisting of nickel, copper and alloys thereof.
4. A multilayer ductile ultra-high-strength steel according to claim 1 wherein said quenched and tempered steel comprises a high-carbon steel containing 0.85 percent of carbon.