US3869319A

US3869319A - Wear resistant deposited steel

Info

Publication number: US3869319A
Application number: US324645A
Authority: US
Inventors: Joo Ishihara; Hiromi Kagohara; Masaichi Nagai; Yasushi Ohuchi
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1972-01-19
Filing date: 1973-01-18
Publication date: 1975-03-04
Anticipated expiration: 1992-03-04
Also published as: JPS4876720A; JPS5032055B2

Abstract

Hard and wear resistant deposited steel including martensite base and vanadium-carbide dispersed therein with the amount of vanadium of 32 to 40 percent in weight. A method for producing the hard and wear resistant steel, said method comprising steps of compression forming powder materials into a welding rod, melting the rod in a non-oxidizing atmosphere by means of a heat produced by an electric arc discharge, and heat treating the solidified substance thus obtained. The invention further provides a novel use of the steel thus produced.

Description

limited States Patent [191 lshihara et a1.

[ 1 Mar. 4, 1975 WEAR RESISTANT DEPOSITED STEEL Inventors:

Assignee:

Filed:

Appl. No.

J00 lshihara; l-liromi Kagohara; Masaichi Nagai, all of Hitachi; Yasushi Ohuchi, Katsuta, all of Japan Hitachi, Ltd., Tokyo, Japan Jan. 18, 1973 Foreign Application Priority Data Jan. 19, 1972 US. Cl 148/315, 29/196, 29/196.1, 29/198, 75/123 J, 75/128 D, 148/34, 29/191.4, 219/145 Int. Cl... C22c 39/50, B32b 15/04, B32b 15/18 Field of Search 29/196, 196.1, 198, 191.4, 29/191.2, 196.2, 196.3, 196.4, 196.5, 196.6; 219/145,146,147;l48/31.5,34, 127,143, 142; 75/122, 134 V, 126 E, 128 V, 123 J,

References Cited UNITED STATES PATENTS Japan 47-6970 Siever 219/146 1,942,364 1/1934 Rood 219/146 2,016,585 10/1935 Busore et a1. 219/146 2,219,462 10/1940 Wissler 219/145 3,514,272 5/1970 Cook 29/196 X FOREIGN PATENTS OR APPLlCATlONS 529,190 8/1956 Canada 75/134 V Primary E.\-aminerCharles N. Lovell Attorney, Agent, or Firnz-Craig & Antonelli [57] ABSTRACT 6 Claims, 6 Drawing Figures PATENIEDHAR 4|s75 SHEET 1 OF 5 FIG. lb

PATENTEU 4|975 3,869.319

sum 3 o 5 HARMESS F/G. 4 Na 8 TEMPERATURE OF OUENCH/NG (6) The present invention relates to a novel steel composition which has-an excellent wear resistant property and which can be easily formed into a desired shape. The present invention also relates to a method for producing such a novel steel.

Hithertofore, a wear resistant high speed tool steel including 1.2 weight percent of vanadium, 19 weight percent of tungsten and 5.5 weight percent of cobalt has been known as SKH3 steel in Japanese Industrial Standard (.IIS) which corresponds to T4 in AISI standard. However, since this steel includes an increased amount of tungsten and cobalt, it is not so cheap. Further, the steel is insufficient in wear resistant property.

In order to provide an improved wear resistant property, there has been proposed to provide a steel including 12 weight percent of vanadium, 1 weight percent of chromium, 1 weight percentof molybdenum and 3.25 weight percent of carbon. However, this steel includes an increased amount of vanadium-carbide produced therein, so that it has inferior melting, casting and forging properties. Thus, the steel of this type has not been widely used in industry.

From the view point of wear resistant property, the most superior known material is an alloy produced through a sintering technique from powder of tungstencarbide. However, since this alloy is a sintered material, it cannot be formed into a complicated shape. Further, it is difficult to provide a uniform particle size of tungsten-carbide particles and the surfaces of the particles are undesirably subjected to oxydization. Moreover, tungsten is very expensive. Thus, the sintered alloy of this type has only a limited use.

Therefore, the inventors performed efforts to develope a material which is comparable in the wear resistant property to said sintered hard alloy and which is easy to form but less expensive to manufacture. The inventors paid their attention to the fact that vanadium carbide (hereinafter designated at VC) has a hardness of Viskerse 2,800 which is comparable to the hardness of tungsten-carbide which is Viskerse 2,700 to 2,800, while the cost per unit weight of VC is about one-fifth of that of tungsten-carbide, and that VC is about onethird in specific weight as compared with tungsten carbide so that the use of VC is very economical when it is used with the same amount as tungsten carbide is used.

Therefore, the inventors investigated various types of steels including VC and found that, as the amount of VC dispersed in ferrite base increases, the size of educed VC increases and there is produced a well developed dendrite structure having an elongated stem and a plurality of branches with 20 to 30 weight percent of VC content. Such a dendrite structure often causes a stress concentration and breakage propagates therefrom. With the VC content exceeding 30 percent, adjacent VC components interfers with each other pre venting the formation of an elongated dendrite structure, and VC appears in a particulated phase dispersed in the base. Such a steel including an increased amount of VC has an increased hardness and an excellent wear resistant property, and can be produced with a lower cost. Therefore, the steel of this type will provide a practical advantage if it can be industrially produced. The present invention provides a novel steel composition having an increased amount of VC, and a method for producing such a steel.

SUMMARY OF THE INVENTION The present invention has an object to provide a novel metal composition having an excellent wear resistant property which is comparable to that of sintered tungsten-carbide alloy steel.

Another object of the present invention is to provide a method for producing a highly wear resistant iron based metal including 32 to 40 weight percent of vanadium and 6.7 to 8.6 weight percent of carbon.

A further object of the present invention is to provide a tool and a slidable part which has a less expensively formed wear resistant deposit-welded portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la and b are microscopic photographs for showing the effect of vanadium-carbide in metal structure, in which FIG. 1a shows a structure having less educed vanadium-carbide and FIG. lb shows a structure having an increased amount of vanadiumcarbide;

FIG. 2 is a diagram showing the relationship between quenching temperature and hardness with various nickel contents;

FIG. 3 is a diagram showing the relationship between quenching temperature and hardness with various manganese contents;

FIG. 4 is a diagram showing the relationship between quenching temperature and hardness with various carbon contents; and,

FIG. 5 is a diagram showing the relationship between quenching temperature and hardness with various chromium contents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a steel composition having a superior wear resistant property, and provides a deposited steel and a method for manufacturing the same by melting and thereafter solidifying the materials which is then heat treated to form vanadium carbide phase uniformly educed in the martensite matrix.

According to the present invention, there is provided a deposited steel composition including 32 to 40 percent of vanadium, 2 to 4 percent of nickel, and 0.5 to 3 percent of manganese, the balance being steel and impurities with carbon content 0.3 to 0.6 percent higher than one-fifth of the weight of vanadium, said steel being characterized by having an alloy structure including vanadium-carbide educed in a matrix mainly comprising martensite. In accordance with the present invention, the composition of the steel is so adjusted that it can well be heat treated even if the formation of vanadium-carbide is increased, so as to provide a structure having a superior wear resistant property.

Throughout the specification, the term *deposited steel or metal composition is used to mean a material deposited on a substrate in such a manner that it does not receive any adverse effect such as dillution from the substrate.

According to the present invention, the amount of vanadium content is 32 to 40 weight percent. With vanadium exceeding 40 weight percent, satisfactory heat treatment cannot be performed even if the amounts of other components are sufficiently adjusted, so that the steel cannot attain sufficient hardness. Further, when vanadium contents exceeds 40 weight percent, a uniform deposited metal structure cannot be obtained even if TIG welding is employed by using a nonexpendible tungsten electrode. With vanadium content less than 32 weight percent, the educed vanadiumcarbide is developed into an extended dendrite structure. In this area, stress concentration is produced and cracks are developed therefrom.

FIG. la shows in a microscopic photograph a deposited metal including 27.5 percent of vanadium, 50 percent of chromium, 0.5 percent of manganese, 0.7 percent of silicon, 6.2 percent of carbon and the balance iron. From FIG. '10, it will be notedthat the metalstructure has a well developed dendrite structure including an elongated stem portion and branches extending perpendicularly therefrom. FIG. lb shows in a microscopic photograph an example of the deposited metal in accordance with the present invention, which includes 37.2 percent of vanadium, 2.8 percent of chromium, 0.5 percent of manganese, 0.6 percent of nickel and 7.84 percent of carbon. As noted in FIG. lb, the educed vanadium-carbide is relatively round and uniformly dispersed. It should be noted that, with vanadium content of 32 to 40 weight percent, a stable and uniform wear resistant property is provided in the metal and thus it is possible to provide a satisfactory deposited metal.

Carbon is combined with vanadium to form vanadium-carbide so as to provide a superior wear resistant property to the steel. The vanadium carbide is formed by approximately weight parts of vanadium and approximately 1 weight part of carbon. In order to obtain a martensite structure, it is required that 0.3 to 0.6

weight percent of carbon is included in the structure in the form of a solid solution. If the carbon content is less than the value referred to above, a ferrite structure is produced during quenching. On the other hand, an austenite structure is produced when the carbon content is greater than the value. Therefore, in the metal structure of the present invention, the carbon content must be 0.3 to 0.6 weight percent higher than one-fifth of the weight of vanadium content.

Nickel is required to provide a quenchable characteristics to the metal. A satisfactory quenchable property can be provided by 2 to 4 weight percent of nickel. With nickel content less than the value, the hardness of the metal is widely varied in response to the change in quenching rate. With nickel content exceeding 4 weight percent the amount of austenite structure is correspondingly increased resulting in a reduced hardness.

Manganese is required in order to prevent any blow hole or other structural defect in the deposited steel and improve quenching property. With manganese content lower than 0.5 weight percent, it cannot provide a sufficient de-oxydization power. With manganese content exceeding 3 weight percent, the amount of austenite structure increases resulting in reduction in wear resistant property.

The deposited steel in accordance with the present invention is constituted by the aforementioned components but it may advantageously include chromium to improve the wear resistant property of the steel as well as quenching property of the matrix. However, the amount of chromium which contributes to the quench ing property is limited because, with chromium content exceeding 3 weight percent, it is impossible to obtain a perfect martensite structure but there is produced a ferrite structure in the matrix resulting in a remarkable reduction in the quenching property.

Phosphor, sulphur and silicon existing in the deposited steel composition must be as small as possible. Further, aluminum and calcium must also be as small as possible because they have adverse effects on the weldability of the steel. The maximum allowable content of aluminum and calcium is 0.1 weight percent for each element.

The wear resistant steel in accordance with the present invention includes an increased amount of vanadium-carbide having a melting point of 2,8 10C, so that 'it'cannot be molten by a conventional means such as a high frequency melting technique. Further, it cannot be formed by sintering as in the case of tungsten-carbide because it is very difficult to reduce the surface of VC. In view of these facts, the inventors accomplished a method in which particulated materials are instantaneously molten by subjecting them to an electric arc discharge in a non-oxydizing atmosphere to provide a steel of a desired composition.

According to the method in accordance with the present invention, particulated materials uniformly mixed in such amounts that can provide a composition referred to above are compression formed with an addition of binder or filled in an iron pipe to form a welding rod. When a phenollic resin is used as the binder, the carbon content in the materials must previously be reduced because the carbon content in the resin is dissolved by the welding heat and allowed to enter the molten metal when the rod is molten as explained below. It has been found that, when a deposited metal is formed from a welding rod including 3 percent of phenol resin as binder, 40 to percent of carbon in the resin is retained in the metal. It should of course be noted that the rate of carbon retained in the metal depends on the welding condition as well as the ratio among other elements, so that it is necessary to perform experiments to find out the rate of carbon retained in the metal.

When powder materials are put into a metal pipe, the composition of the pipe must be taken into account in determining the mixing ratio of the powder materials because the components in the metal pipe are retained in the deposited metal. If the wall of the metal pipe is too thick, the components of the pipe may not, when molten, be completely mixed with the molten materials which have previously put into the pipe in powder form. producing a deposited metal of a non-uniform structure. Therefore, it is required that the wall thickness of the pipe must be less than 0.3 mm.

The density of the welding rod made by the powder materials must be as high as possible. With a lower density, the powder materials may be splashed or fallen away during welding operation. Further, the amount of alloy structure in the deposited metal may be reduced producing a brittle vanadium-carbide in the form of an eutectic mixture. Thus, the powder filling rate of the welding rod must exceed 60 percent.

In order to produce a deposited metal from the welding rod including a substantial amount of VC. it is necessary to employ a welding process in which energy of higher density is available. Further, it is necessary to avoid to hold the materials under a high temperature for an extended period in order to prevent the dendrite structure from being developed. Since the vanadium is highly affinitive to oxygen, it is also desirable to perform the process in a non-oxydizing atmosphere. For example, TIG welding which is performed under an inactive atmosphere using a non-expendible tungsten electrode is particularly suitable for the present invention. The inactive gas atmosphere may not be used when a flux such as sodium carbonate, calcium fluoride or liquid glass is coated on the outer surface of the metal pipe or mixed in the powder materials forming the welding rod.

There is no particular limitation on the nature of the substrate on which the molten metal is deposited from the welding rod. In fact, most of iron based material can be used as the substrate of the deposited metal in accordance with the present invention.

The metal prepared in accordance with the present invention has been deposited on a substrate made of a mild steel and the deposited metal is cut and ground to provide a section which is to be tested by an electron probe micro analyzer. Although there may be slight differences in accordance with the change in the welding condition, it has been found that, in the region from the boundary between the deposited metal and the substrate to a position in the deposited metal 0.5 to 1.0 mm apart from the boundary, there is a dillution effect of the substrate, but any effect of the substrate is eliminated in the area apart from the boundary by 1.5 mm or more and a satisfactory structure of the deposited metal is obtained.

In order to increase the hardness of the deposited metal, it may be subjected to a heat treatment as required. The hardness may depend on the metal components and the heat treatment temperature, but it is preferable in the steel composition of the present invention to perform the heat treatment under 950C to 1,100C.

The deposited metal in accordance with the present invention may be machined by an arc discharge or electrolytic machining process and. when a precise machining is required, it may be machined by using a diamond tool.

The steel in accordance with the present invention has an excellent hardness and wear resistant property and can readily be adapted to provide a desired shape by means of depositing. Further, it has a strong adherence to the substrate and is less expensive to manufacture. Therefore, it can be applied to anywhere in which a conventional sintered tungsten-carbide is used. For example, the steel in accordance with the present invention may be used in tools, heavily loaded bearings and cam mechanisms, control rod driving means for a nuclear reactor, and blade tips for a bull-dozer.

It is also possible to deposit the steel prepared in accordance with the present invention on a tough core steel to form a coating of a uniform thickness. This method may be convenient to provide rolls which may be used in a compound roll arrangement in a rolling mill. Such a big roll cannot be provided by a sintered tungsten-carbide because it lacks toughness and is expensive. Even if it is possible to provide a hollow cylindrical sintered body, it cannot be combined with a roll core with a sufficient strength to provide a compound roll.

The present invention will now be described with reference to specific examples.

EXAMPLE 1 A pipe having an inner diameter of 3 mm was prepared from a mild steel plate of 0.2 mm thick. Ironvanadium alloy, graphite, manganese, silicon and chromium, each in the form ofa powder finer than 50 mesh, had been mixed with an appropriate proportion and drawn through a die into a rod having an outer diameter of 2.5 mm to form a welding rod of powder filling rate of 85 percent. The welding rod was then used to perform an argon-arc welding with an electric current level of 140 A. The molten metal was deposited on a substrate made of a steel material JIS-SKDI (AlSI-D3) to form a layer of 10 mm thick. The composition of the deposited steel is shown in Table 1. The samples 1 through 3 have been prepared in order to know the effect of nickel content on the quenching property of the deposited steel. The samples 4 and 5 have been prepared to know the effect of manganese content, the samples 6 to 9 to know the effect of the carbon content, and the samples 9 to 11 to know the effect of chromium.

Table 1 Composition of Deposited Steel (weight 71) FIG. 2 shows the relationship between the heat treat ment temperature and the hardness, the results being obtained from the samples 1 through 3. It was found that the samples 1 and 2 had higher hardness as compared with the sample 3 and did not show any remarkable change in properties in accordance with the change in tempering temperature. The sample 3 is inferior in hardness to the samples 1 and 2 and, moreover,

showed a remarkable decrease in hardness in response to the increase in tempering temperature. This is considered as being caused by an increased austenite in the matrix due to the increase in nickel content. Further, the relationship between the quenching rate and hardness has been investigated with respect to the samples 1 and 2, and found that there is no remarkable change in the sample 2 which includes more nickel but the hardness of the sample 1 remarkably decreases with the quenching rate lower than l,000C/min.

FIG. 3 shows the effect of tempering temperature on the hardness of the deposited steel as measured in the samples 4 and 5. As seen in the drawing, as the manganese content increases, the amount of austenite structure in the matrix increases resulting in a decrease in hardness.

FIG. 4 shows the change in hardness in response to the change in tempering temperature as measured in the samples 6 through 9. The samples having higher carbon contents show greater hardness with the same tempering temperature. The reason why the sample 6 is inferior in hardness to the other samples is that in this sample the carbon content existing in the form of solid solution is so small that the ferrite structure still exists. It should be noted that each of the samples 7 through 9 which has carbon content of 0.3 to 0.6 weight percent higher than one-fifth of vanadium content has a greater hardness. 1

FIG. 5 shows the change in hardness in response to tempering temperature as measured in the samples 9 through 1 l. The chromium content generally improves heat treating and quenching property. However, in the alloy steel composition of the present invention, the effective amount of chromium is relatively limited. According to the inventors experiments, it has been found that the chromium content up to 3 weight percent does not decrease the hardness, however, the sample 11 having 5 weight percent of chromium is found to have a lower hardness.

EXAMPLE 2 EXAMPLE 3 A welding rod including 7.95 weight percent of carbon, 37.8 weight percent of vanadium, 3.0 weight percent of nickel, 1.0 weight percent of manganese, 0.8 weight percent of silicon and the balance iron was prepared from the same metal powders by the same process as in the Example 1. The welding rod was then molten by an argon-arc welding process in the argon gas atmosphere and the molten metal was deposited on a rotor core punching die substrate. The current level was 140 to 150 A and the thickness of the deposited layer was mm. Then the deposited metal was heated to 1,000C in a cylindrical furnace filled by argon gas For the purpose-of comparison, a rotor core punching die was prepared from a dies steel JlS-SKDl (AlSl- D3) and used to punch a silicon steel plate of 0.5 mm thick. It has been found that the burr height was 0.10 mm after 70,000 times of punching operations and the die was already worn beyond the allowable limit.

When a punching die made of a sintered tungstencarbide was used, the burr height was 0.02 mm after 70,000 times and even after 500,000 times of punching operations.

Thus, it has been found that the steel in accordance with the present invention is comparable to the sintered tungsten-carbide.

EXAMPLE 4 Ferro-vanadium, ferro-silicon, ferro-manganese, ferro-molybdenum, ferro-chromium, graphite, and powdered iron are prepared in the form of powder finer than 100 mesh and thoroughly mixed with the existence of phenol resin. The powder materials are then formed into a plate of 2 mm thick under a pressure of 6 ton/cm and thereafter cured by heating the plate in an electric furnace of 180C for 5 minutes. The cured plate is then closely fitted to a substrate of a mild steel and molten and deposited on the substrate by applying an electric discharge are in an argon atmosphere. The deposited metal layer was 5.5 mm thick. The deposited metal was then annealed at a temperature of 800C for 5 hours and cooled in furnace, thereafter it was quenched at 1,000C and tempered at 200C. The deposited metal layer is then machined by means of an electrolytic machining and a diamond tool to form a metal layer which is 5.0 mm thick and has a surface area of 254 mm The chemical components and the hardness of the deposited metal are shown in Table 2. The sample 12 is an alloy steel having vanadium-carbide content less than that of the steel in accordance with the present invention. The samples 13 and 14 are made in accordance with the present invention.

for a certain period and thereafter taken out of the furnace to be quenched in water. The hardness of the deposited steel was H 1,100. The deposited steel was then annealed to a hardness of H, 980 and machined by means of an electric discharge machining and grinding operation to form a punching die.

The punching die thus formed was used to punch a silicon steel plate of 0.5 mm thick. The amount of wear of a punching die as well as those of other dies are usually represented by the height of a burr which-appears in the punched section of a workpiece and the die is usually considered as being unusable when the height of the burr exceeds 0.05 mm. The height of the burr in the silicon steel punched by the aforementioned punching die was 0.01 mm even after 70,000 times of punching operations. Further, it has been found that the burr height did not show any remarkable increase even after 500,000 times of punching operations.

Thedeposited steel having the surface area of 254 mm is pushed under a uniform load of 800 gr onto an abrasive surface which is rotating at a speed of 720 r.p.m. and the amount of wear was measured after an hours operation. For the purpose of comparison, J IS- SKDl (AlSI-D3), SKH3 (AlSl-T4) and a sintered tungsten-carbide were tested under the same condition to measure the amount of wear.

The amount of wear of the samples 13 and 14 was two times as much as that of the tungsten-carbide but about one-fifth of that of the sample 12. Further, the amount of wear of the samples 13 and 14 was less than one-twentieth of that of SKDI or SKH3. Thus, the alloy steel of the present invention can be satisfactorily used in the place of the tungsten-carbide.

Although the invention has thus been shown and described with reference to specific examples, it should be noted that the invention is in no way limited to the details of the described examples and the scope of the invention is limited only by the appended claims.

We claim:

1. Wear resistant structure comprising a metal substrate and a layer of steel deposited thereon, said steel consisting essentially of, in weight percent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel, and 0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadium content, and the rities accompanying therewith, said steel having vanadium-carbide structure educed in a matrix mainly comprising martensite.

3. Wear resistant structure in accordance with claim 1, in which said impurities include aluminum and calcium, each being less than 0.1 weight percent.

4. Wear resistant structure in accordance with claim 2, in which said impurities include aluminium and calcium, each being less than 0.1 weight percent.

5. Wear resistant structure comprising a metal sub strate and a steel layer deposited thereon with a thickness more than 1.5 mm, said deposited steel layer having a portion free from the effect of said substrate, said portion consisting essentially of, in weight percent, 32 to 40 percent of vanadium, 2 to 4 percent of'nickel, 0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadium content, chromium less than 3 percent, and the balance iron and impurities accompanying therewith, said portion further having vanadium-carbide structure educed in a matrix mainly comprising martensite, said substrate having a tenacity higher than that of the deposited steel.

6. A welding rod for producing a wear resistant deposited steel consisting essentially of, in weight percent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel, 0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadium c0ntent, and the balance iron and impurities accompanying therewith, said welding rod comprising an iron based metal pipe having a wall thickness less than 0.3 mm, said vanadium, nickel, manganese, carbon and iron being filled in powder form in said pipe with a filling rate at least percent.

Claims

1. WEAR RESISTANT STRUCTURE COMPRISING A METAL SUBSTRATE AND A LAYER OF STEEL DEPOSITED THEREON, SAID SHEET CONSISTING ESSENTIALLY OF, IN WEIGHT PERCENT, 32 TO 40 PERCENT OF VANADIUM, 2 TO 4 PERCENT OF NICKEL, AND 0.5 TO 3 PERCENT OF MANGANESE, CARBON OF 0.3 TO 0.6 PERCENT HIGHER THAN ONE-FIFTH OF THE VANADIUM CONTENT, AND THE BALANCE BEING IRON AND IMPURITIES ACCOMPANYING THEREWITH, SAID STEEL HAVING VANADIUM-CARBIDE STRUCTURE EDUCED IN A MATRIX MAINLY COMPRISING MARTENSITE.

2. Wear resistant structure comprising a metal substrate and a layer of steel deposited thereon, said steel including, in weight percent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel, and 0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadium content, and chromium less than 0.3 percent, and the balance being iron and impurities accompanying therewith, said steel having vanadium-carbide structure educed in a matrix mainly comprising martensite.

5. Wear resistant structure comprising a metal substrate and a steel layer deposited thereon with a thickness more than 1.5 mm, said deposited steel layer having a portion free from the effect of said substrate, said portion consisting essentially of, in weight percent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel, 0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadium content, chromium less than 3 percent, and the balance iron and impurities accompanying therewith, said portion further having vanadium-carbide structure educed in a matrix mainly comprising martensite, said substrate having a tenacity higher than that of the deposited steel.

6. A welding rod for producing a wear resistant deposited steel consisting essentially of, in weight percent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel, 0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadium content, and the balance iron and impurities accompanying therewith, said welding rod comprising an iron based metal pipe having a wall thickness less than 0.3 mm, said vanadium, nickel, manganese, carbon and iron being filled in powder form in said pipe with a filling rate at least 60 percent.