JPH11197876A - Hardened surface member, its manufacture and deposited metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hardened surface member that excels both in wear resistance and impact resistance by using a tough material like steel as a base material and forming a hardened surface layer, which has a high hardness and crack resistance, in the area where abrasion resistance is required. SOLUTION: The member is such that a hardened layer is formed on the surface of the base material, and that the hardened surface layer is constituted of deposited metal consisting of, by weight, 0.2-0.9% C, 0.6-1.9% Si, 0.6-1.6% Mn, 2.5-7.5% Cr, 0.1<=W<1.5%, 0.1<=V<1.5%, 1.0-8.0% Mo, and 0.2<B<=0.8%, with the balance Fe and inevitable impurities. As a result, a hardened surface member can be obtained that is provided with an excellent toughness and wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface hardened member, a method of manufacturing the same, and a weld metal forming a surface hardened portion.
More specifically, it is excellent in wear resistance and toughness, and is required to have heavy impact and wear resistance, such as a mantle liner and a cone cable liner of a cone crusher that crushes rock, and a jaw plate of a jaw crusher. And a surface hardened member having excellent toughness and wear resistance.

[0002]

2. Description of the Related Art As a conventional wear-resistant member such as a crusher or a crusher, a high-M material having both wear resistance and toughness has been used.
n Cast steel is widely used. This is because the high Mn cast steel has a matrix of austenite and excellent toughness, and the vicinity of the worn surface becomes extremely hard due to work hardening due to deformation twinning due to impact and plastic deformation or stacking faults. That is, the high Mn cast steel has excellent characteristics as a wear-resistant member subjected to impact such as a crusher liner, which has a hard surface and excellent toughness inside. However, the high Mn cast steel does not increase surface hardness because work hardening does not occur when the impact received is small,
Satisfactory wear resistance cannot be obtained.

Conversely, when the impact received during crushing is large,
Although work hardening occurs sufficiently, the surface hardness does not increase enough to withstand abrasion, and there is still a problem that abrasion remarkably progresses.

In such a case, a material having a high initial hardness (hardness before work hardening) such as a martensitic cast steel or high Cr cast iron is used. That is, it can be said that high Cr cast iron is excellent from the viewpoint of the life and cost of the wear member. However, high Cr cast iron generally has poor toughness, and when applied to members that require abrasion resistance and heavy impact such as cone crusher mantle liners and corn cave liners that crush rocks, brittle fracture occurs during use. In some cases, the crushing machine body may not be used, and the crushing machine body may be damaged. It is considered that such brittle fracture is mainly caused by insufficient toughness of the high Cr cast iron.

[0005] High-Cr cast iron has been disclosed in Japanese Patent Application Laid-Open Nos. 57-5844 and 57-89453,
No. 115343, Japanese Patent Publication No. 4-56102,
Various improvements have been studied as disclosed in, for example, US Pat. No. 240403, but most of them improve the wear resistance by maximizing the hardness and improve the toughness of the high Cr cast iron. At present, no studies have been conducted to improve the brittle fracture.

As described above, in order to solve the problems pointed out in high Mn cast steel and high Cr cast iron and to achieve both high wear resistance and high toughness, a tough material such as steel is used as a base material. The surface hardening method of forming a high-hardness metal material only on the surface layer portion where is required is useful.

As typical surface hardening methods, there are a fusion welding method, a cast-in method, a casting overlay method, and the like, but the following problems are pointed out respectively.

First, in the fusion welding method (hardfacing welding method),
Martensitic and high Cr iron-based materials are typical examples of overlay welding materials that exhibit abrasion resistance. In the case of martensitic overlay welding materials, high hardness carbides are contained in the deposited metal. As a result, the wear resistance is inferior to that of a high Cr iron-based material, and a satisfactory wear life cannot be obtained. In addition, since the high Cr-based overlay welding material contains a carbide having a higher hardness than the martensite-based overlay welding material, it exhibits excellent wear resistance particularly against severe earth and sand wear, but on the other hand, Since the elongation and toughness of the deposited metal are reduced in exchange for the improvement of the wear resistance, a problem arises that the deposited metal is easily cracked.

In a method of casting or overlaying a high Cr cast iron on a substrate made of a tough material typified by steel, since the two materials generally have different coefficients of thermal expansion, residual stress is generated when the two materials are joined. However, as described above, the high Cr cast iron not only has poor toughness but also shows almost no elongation. Therefore, when the residual stress increases, cracks are easily generated in the high Cr cast iron.

[0010] When cracks occur in the surface hardened portion as described above, the cracks develop due to the stress received during operation of the crusher or the crusher parts, causing the hardened metal to separate and significantly reduce wear resistance. Become. Furthermore, the crack tip may become the starting point of fatigue cracking of the surface-hardened base material. If the base material undergoes fatigue failure, it cannot be used as a wear-resistant member nor damage the machine body. It is easy to be done. Therefore, particularly for a cone crusher or the like that is subjected to a heavy impact, it is required to improve the crack resistance of the surface hardened material.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to use a tough material such as steel as a base material and to obtain abrasion resistance. A hardened surface layer having high hardness and excellent crack resistance is formed only on the part to be hardened, and a hardened surface member excellent in both abrasion resistance and impact resistance and a method for producing the same are provided, and the hardened surface portion is formed. The purpose of the present invention is to clarify the constituent overlay welding metal.

[0012]

The surface-hardened member according to the present invention, which can solve the above-mentioned problems, is a member having a hardened layer formed on the surface of a substrate, wherein the surface hardened layer is C: 0. 0.2 to 0.9% Si: 0.6 to 1.9% Mn: 0.6 to 1.6% Cr: 2.5 to 7.5% W: 0.1% or more and less than 1.5% V : Not less than 0.1% and less than 1.5% Mo: 1.0-8.0% B: more than 0.2% and not more than 0.8%, with the balance being composed of a deposited metal comprising Fe and unavoidable impurities Where there is a gist.
In the surface hardened member of the present invention, it is particularly preferable that the amount of Mo in the deposited metal is more than 4.0% and 8.0% or less.

Further, the weld metal according to the present invention is a weld metal welded by overlay welding, characterized in that the weld metal satisfies the requirements of the above component composition.
Further, the manufacturing method according to the present invention has a gist in that a weld metal layer satisfying the above-mentioned composition is formed by overlay welding at a site requiring abrasion resistance in a substrate made of a tough material such as steel.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have paid attention to a method for improving the performance as a wear-resistant member by forming a hardened layer on the surface of a base material as described above. Research has been conducted on various surface hardening materials in order to impart cracking resistance. In particular, factors that affect the hardness and crack resistance of the surface-hardened weld metal have been repeatedly studied from the viewpoint of the chemical composition of the weld metal. As a result, it has been found that the formation of carbides is effective in improving the hardness of the deposited metal, but extremely deteriorates the crack resistance.

However, if the generation of carbides is controlled in order to increase the crack resistance, the hardness of the deposited metal decreases, and satisfactory wear resistance cannot be obtained. Therefore, as a result of repeated investigations to find a weld metal component that can improve the hardness of the weld metal and also improve the crack resistance, the C content in the weld metal was found.
If the respective contents of r, W, V, Mo, and B, particularly the contents of Mo and B, are appropriately controlled and the deposited metal structure is made to be a composite structure composed of martensite and boride of steel, the hardness of the deposited metal can be improved. It has been found that a surface-hardened member having remarkably superior wear resistance as compared with the conventional material can be obtained, as well as the weld metal structure being refined and the crack resistance improved. Hereinafter, the reason for determining the component composition of the deposited metal in the present invention will be described in detail.

C: 0.2 to 0.9% C is a main element that forms a solid solution in a matrix mainly composed of Fe and turns the steel into martensite. The C content in the deposited metal is less than 0.2%. In this case, the amount of solid solution in Fe tends to be insufficient, and the hardness of the matrix becomes insufficient. Even if high hardness boride is generated around the matrix as described later, the hardness of the entire deposited metal cannot be sufficiently increased. On the other hand, when the C content exceeds 0.9%, a part of the deposited metal matrix does not become martensite but remains as austenite. Because austenite has low hardness, it not only lowers the hardness of the entire weld metal, but also has a coefficient of thermal expansion that is significantly different from that of martensite or boride. It will be easier. In consideration of the profit and loss of C interests, the lower limit of the more preferable C amount is 0.25%, and the more preferable upper limit is 0.8%.
It is.

Si: 0.6 to 1.9% Si acts as a deoxidizing component and contributes to cleaning of the deposited metal. In order to effectively exhibit such an effect, the content should be 0.6% or more, more preferably 0.7% or more. However, if it is too much, the toughness of Fe decreases due to an increase in the amount of Si dissolved in the matrix. Therefore, it should be suppressed to 1.9% or less, more preferably 1.7% or less, since the adverse effect on cracking resistance appears.

Mn: 0.6 to 1.6% An element having a deoxidizing effect similar to Si and contributing to the cleaning of the deposited metal, and 0.6% or more for effectively exhibiting its effect. , More preferably 0.7% or more. However, if it is too much, austenite tends to be formed in the deposited metal and adversely affects hardness and crack resistance. More preferably 1.4
%.

Cr: 2.5 to 7.5% Cr is an important element that combines with B to form borides and contributes to increasing the hardness of the deposited metal. It should be contained at least 2.5%, more preferably at least 3.0%. On the other hand, if the Cr content is too large, high temperature cracking is likely to occur when the deposited metal solidifies, so it must be suppressed to 7.5% or less, more preferably 6.9% or less.

W: 0.1% or more and less than 1.5% W also combines with B to form a boride, thereby contributing to an increase in the hardness of the deposited metal, and also provides elongation to the deposited metal to suppress shrinkage cracking and to withstand resistance. It also has the effect of increasing cracking. In order to exert such effects effectively, 0.1% or more, more preferably 0.2%
%, More preferably 0.4% or more. However, if the content is too large, the crack resistance tends to be rather deteriorated. Therefore, 1.5% or less, more preferably 1.% or more. It must be kept at 45% or less, more preferably at 1.3% or less.

V: 0.1% or more and less than 1.5% V also combines with B to form a boride, thereby contributing to increase the hardness of the deposited metal, and also to prevent hot cracking when the deposited metal solidifies. Works effectively. Such an effect can be effectively exhibited by containing 0.1% or more, more preferably 0.2% or more, and still more preferably 0.3% or more. It should be kept below 1.5%, more preferably below 1.4%, even more preferably below 1.2%, most preferably below 1.0%.

Mo: 1.0-8.0% Mo also forms a boride by combining with B, and is a main element contributing to the increase in hardness of the deposited metal, and also contributes to the formation of the boride. Mo also exerts the effect of forming a solid solution in the Fe matrix to enhance the quenchability. In order to effectively exhibit these effects, the content must be 1.0% or more. The more preferable Mo content is 2.0% or more, further preferably 3.0% or more, and most preferably more than 4.0%. However, if it is too large, the toughness of the deposited metal is reduced and the crack resistance is reduced. Since the tendency to inhibit appears, it must be suppressed to 8.0% or less, more preferably 7.0% or less.

B: more than 0.2% and 0.8% or less B is an element indispensable for boride formation,
If the content is not more than 0.2%, a sufficient amount of boride will not be formed in the deposited metal, not only a satisfactory hardness will not be obtained, but also the metal structure will be coarse and sufficient crack resistance will be obtained. Is also difficult to obtain. However, if the content is too large, it causes grain boundary embrittlement and lowers the toughness of the deposited metal, which adversely affects the cracking resistance. Therefore, 0.8% or less, more preferably 0.7% or less. , More preferably 0.6% or less.

The constituent elements constituting the deposited metal in the present invention are as described above, and the balance is substantially Fe, and other elements such as P, S, N, O or other elements are mixed. However, they are also acceptable as long as they are inevitable impurity amounts.

Next, the reason why by specifying the above component composition, it is possible to obtain a weld metal having high hardness and improved crack resistance is obtained.

First, B has the property of easily segregating at the matrix grain boundaries and forming borides by combining with Cr, Mo, W, V and the like. Borides generated by the reaction with these elements are formed in a network along the matrix grain boundaries, exhibiting the characteristic of suppressing the grain growth of the matrix and refining the crystal grains, and improving the toughness of the deposited metal. Increase to improve crack resistance. Moreover, the generated boride has a high hardness and contributes to an increase in the hardness of the deposited metal.

On the other hand, it has been confirmed that Cr, Mo, W and V also easily react with C. However, when B is present in the system, most of them become borides, so that the amount of carbides generated in the deposited metal is increased. Is extremely small. As a result, most of C contained in the deposited metal forms a solid solution in the Fe matrix, which contributes to the formation of Fe into martensite. In general, it is known that the hardness of martensite increases as the amount of C dissolved in Fe increases, and most of the C in the deposited metal is dissolved in the matrix without being used for forming carbides. Then, the hardness of the martensite matrix also increases, and the entire deposited metal becomes harder.

The effect of making the formation of carbides difficult is not limited to increasing the hardness of martensite. That is, since carbides are extremely brittle, the formation of carbides reduces the toughness of the deposited metal and adversely affects the cracking resistance. However, as described above, the content of B, Cr, Mo, W, V, etc. is reduced. In the adjusted component system, it is considered that the amount of carbide inside the deposited metal is extremely small, and this also has a favorable effect on the improvement of crack resistance.

As described above, the effect of adding B is not only to increase the hardness of the deposited metal due to the formation of borides and increase the matrix hardness, but also to reduce the size of crystal grains and suppress the cracking of the deposited metal by suppressing the formation of brittle carbides. It also contributes to the improvement of the weldability, and together with these effects, it has a remarkable effect on increasing the hardness of the deposited metal and improving the crack resistance.

As described above, it is important to make the matrix martensite in order to increase the hardness of the deposited metal. In order to stably transform the matrix into martensite, it is effective to improve the hardenability of the deposited metal, and Mo has a significant effect on the improvement of the hardenability. In addition, Mo generates boride as described above and contributes to the improvement of the hardness of the deposited metal.
Is positioned as a very important element. In order to improve the quenching property of Mo and effectively exhibit the combined effect of boride formation, the Mo content in the deposited metal should be 1.0% or more, more preferably 2.0% or more, as described above. Should be 3.0% or more, and most preferably more than 4.0%. If the Mo content is less than 1.0%, most of the Mo is consumed as boride and solid solution in the matrix. Therefore, the effect of enhancing the hardenability of the deposited metal is not effectively exerted, and the matrix hardness is reduced, and the hardness of the deposited metal is reduced. The effect of Mo saturates at about 4-5%, and 8.0%
If the content exceeds the above range, the toughness of the deposited metal decreases and satisfactory crack resistance cannot be secured.

In the surface hardened layer of the present invention, a trace amount of a slag forming agent, or a carbonate or a fluoride, etc., is added in conjunction with the use of a build-up welding method as described later when forming a deposited metal layer. An arc stabilizer, a gas generating agent, and the like may be mixed in, but a small amount of components derived therefrom is allowed as long as the amount of unavoidable impurities.

The method of forming the surface hardened layer made of the deposited metal satisfying the above-mentioned component composition is not particularly limited. In short, as long as the chemical composition of the site requiring surface hardening can be made within the above-mentioned component composition range.
Although any method such as a fusion welding method, a cast-in method, a casting overlay method can be employed, particularly preferred is a fusion welding method, and more specifically, a carbon dioxide gas arc welding method, and a method of using Ar or the like as a shielding gas. Gas arc welding method mixed with active gas (MIG welding, MAG welding, TIG welding, etc.), submerged arc welding method, covered arc welding method,
Non-limiting examples include powder plasma welding, self-shielded arc welding, gas welding represented by the use of oxygen-acetylene flame, and electroslag welding.

The type of the base material (base material) on which the deposited metal layer constituting the surface hardened layer is formed is a material having strength and toughness capable of withstanding stress during use as a support layer for the surface hardened layer. If so, the type is not particularly limited, but steel materials such as mild steel and low alloy steel are most practically used in consideration of strength characteristics, adhesion to the deposited metal layer, cost, and the like.

As described above, the surface-hardened member of the present invention and the deposited metal constituting the surface-hardened layer have high hardness and excellent crack resistance, and can be used even when applied to a part that is subjected to heavy impact. Since it exhibits excellent toughness and wear resistance, it can be widely applied to crushers and crushers, specifically, cone crushers, jaw crushers, roller mills, impact crushers, and the like. In fields other than crushing and crushing, for example, raw material transport parts of ironworks, various handling parts provided in raw material storage facilities such as iron ore, various wear-resistant parts such as rolling rolls, and construction machine parts such as power shovels. Can be widely used for mining machinery parts used for mining, mining, coal and the like.

[0035]

EXAMPLES Next, examples of the present invention will be described. However, the present invention is not limited by the following examples, and the present invention should be practiced with appropriate modifications within a range that can be adapted to the gist of the preceding and the following. Of course, these are also possible, and all of them are included in the technical scope of the present invention.

Example 1 A mild steel base material (thickness 50 mm × width 150 mm × length 200)
Using a flux-cored wire whose composition was adjusted so that the composition of the deposited metal was as shown in Table 1, hardfacing welding was carried out on the surface of (mm) as shown in FIG. Thus, a deposited metal layer was formed. The flux-cored wire uses mild steel as a hoop material, a flux filling rate: 15 to 38%, and a wire diameter (diameter): 1.2 to 1.6.
mm, and the composition of the metal component charged in accordance with the hoop composition was adjusted to adjust the composition of the deposited metal.
The build-up welding conditions were as follows. (Welding conditions) Welding current: 280 A, welding speed: 40 cm / min, welding voltage: 34 V, wire protrusion length: 25 mm, preheating, interpass temperature: 200 to 250 ° C. Weld metal thickness: 10 mm (three layers), Shielding gas:
CO ₂ 100%

The hardness of the deposited metal (Vickers hardness at a load of 30 kgf) and the state of cracking (color check of the surface of the deposited metal) were examined for each of the overlay welding materials obtained, and the results shown in Table 1 were obtained. .

Further, the same welding conditions as described above were employed, and a wear resistance evaluation test apparatus schematically shown in FIG. 2 [in the figure, 3 is an upper mold substrate (mild steel), 4 is a lower mold substrate (mild steel), 5 Is a hardfacing welded metal layer, 6 is a crushed stone, 7 is an upper material chute, 8 is a lower material chute, 9 is a load detector (load cell), 10
Denotes an actuator, and 11 denotes a tempered glass.] In the working surface of the upper mold base 3 and the lower mold base 4 in
A test material having each of the hardfacing weld metal layers 5 whose components were adjusted as shown in Table 1 was mounted, and chart rock was continuously charged from the upper raw material chute and crushed under the following conditions, before and after the test. Of the test material was measured, and the abrasion resistance was examined by weight reduction (total value of four test materials). Since the weight loss of the test material is expected to be affected by the weight (input amount) of the rock subjected to crushing, the specific wear amount (weight loss of the test material / weight of the crushed rock) was evaluated. . The results are collectively shown in Table 1. (Crushing conditions) Crushing raw material: Chert rock, input size 2-5 mm, outlet size: 2.5 ± 1 mm Frequency during crushing: 6 Hz Average crushing load: 5 kN Number of repetitions: about 8,000 times

[0039]

[Table 1]

From Table 1, the following can be considered. N
o. Nos. 11 to 18 are examples satisfying all the requirements of the present invention. Each of the deposited metals has a Vickers hardness of more than 800, and no cracks are recognized on both the surface and the inside of the deposited metal. However, the hardness of the deposited metal is slightly affected by the amount of Mo added, and even within the range specified in the present invention, the hardness tends to increase as the amount of Mo increases. However, the tendency is almost saturated when the Mo amount exceeds 4%.

On the other hand, no. Nos. 1 to 10 are comparative examples lacking any of the requirements specified in the present invention, and have a problem in either hardness or crack resistance as described below.

No. 1: Since B is not contained in the deposited metal, the hardness is low and low-temperature cracking has occurred. No. 2: High Cr content caused high temperature cracking, and insufficient Si content caused many blow holes inside the deposited metal.

No. 3: Since the amount of C is insufficient and the amount of Mn is too large, the hardness of the deposited metal is low. In addition, cracks are observed in the deposited metal because the Mn content is too large. No. 4: High temperature cracking occurs in the deposited metal because V is not contained, and low temperature cracking occurs due to too much Mo content.

No. 5: The hardness of the deposited metal was low because the C content was too large. Moreover, since the contents of C and B are too large, low-temperature cracking occurs in the deposited metal. No. 6: The hardness of the deposited metal is low due to insufficient Cr content.

No. 7: Since the Si content is too large, the crack resistance is reduced and low-temperature cracking is caused. Further, since the amount of Mn is insufficient, many blow holes are observed inside the deposited metal. No. 8: Since W is not contained, hardness is low and low-temperature cracking has occurred.

No. 9: The Mo content is insufficient, so that the hardness of the deposited metal is low, and the V content is too large, whereby the crack resistance is reduced and low-temperature cracking is caused. No. 10: Since the W content is too large, the crack resistance is reduced, and the weld metal is cracked.

No. Nos. 11 to 18 (Example) and
Comparing 1 to 10 (Comparative Examples) as a whole, it can be seen that the specific wear amount is much better for the former and has excellent wear resistance. That is, in the comparative example in which even one of the above-mentioned prescribed requirements defined in the present invention is not present, the surface hardness of the deposited metal is low, or defects such as cracks and blow holes occur in the surface or inside of the deposited metal layer. The specific abrasion amount is increased due to chipping and peeling from the surface. The hardness and wear resistance of the deposited metal are dependent on the Mo content, and the higher the Mo content, the higher the hardness and the better the wear resistance. However, it can be confirmed that the tendency is almost saturated when the Mo content is about 4%.

Example 2 Manufacture of a cone crusher corn cave and mantle as schematically shown in FIG. 3 [12 is a mantle (base material), 13
Indicates a corn cave (base material), 14 indicates a build-up deposited metal,
15 shows a raw material rock (chart) for the crushing test], by using the same welding conditions as in the first embodiment on the respective working surfaces of the mantle 12 and the cone cave 13,
A hardfacing deposited metal satisfying the chemical components specified in the present invention was formed. Accordingly, the composition of the deposited metal is the same as shown in Table 1 above. The hardfacing layer was formed with a thickness of 50 mm on the portion of the cone cave and mantle where abrasion resistance was required (on the side of the crushing chamber). The prepared mantle and corn cave were applied to an actual cone crusher, and a rock crushing test was performed under the following conditions, and the results shown in Table 1 were obtained. [Crushing conditions] Rock raw material: chert rock, input size: 170-200
mm, outlet size: 20-25mm, frequency: 7Hz,
The service life was defined as follows. If the crushing condition is good and there is no problem such as cracks in the deposited metal or the base material, the number of days until the deposited deposited metal (thickness 50 mm) disappears, When a problem such as a crack occurred in the base material, the number of days that the member could be operated as a wear-resistant member was set.

In Table 1, No. Nos. 11 to 18 (Example) and Comparing 1 to 10 (Comparative Examples) as a whole, it can be seen that the life as the liner material is much better for the former, and that it has excellent wear resistance. That is, in the comparative example in which even one of the requirements specified in the present invention is missing, the surface hardness of the deposited metal is low, or defects such as cracks or blow holes occur in the surface layer or inside of the deposited metal layer, and the In some cases, chipping or peeling occurs, and furthermore, the substrate is broken by fatigue, and the life is short.

For comparison, a mantle or cone cave made of high Mn cast steel or high Cr cast iron usually used as a liner material [see FIG. 4, where 16 is a mantle, 17 is a cone cave, and 18 is a crush test The raw material rock (chart) is shown], and a martensitic, high carbon steel conventionally used as a hardfacing welding material
Using a mantle or a corn cave in which an iron (carbide) -based overlay layer (thickness: 50 mm) was formed on a mild steel base material, a rock crushing test was performed by applying the same method to an actual cone crusher in the same manner as described above. Table 2
Were obtained.

Regarding the life of the cast product (high Mn cast steel or high Cr cast iron), when the crushing condition is good and no problem such as cracking of the liner material occurs, about 2 /
The number of days until 3 (thickness: about 50 mm) disappeared, and when the crushing condition was poor and a problem such as cracking occurred in the liner material, the number of days that the liner material could be operated was determined.

[0052]

[Table 2]

As is clear from Table 2, in the case of the conventional hardfacing type, at least one of the hardness and the crack resistance of the deposited metal is insufficient, and the deposited metal may be chipped or dropped. Has an insufficient hardness, and has an extremely short life as compared with the embodiment shown in Table 1. In addition, casting materials also have cracks due to insufficient life and insufficient toughness due to insufficient hardness.

[0054]

The present invention is configured as described above, and particularly as a constituent material of the surface hardened layer, C, B, Cr, Mo,
By forming a specified weld metal layer such as W, V, etc., surface hardening that is high in hardness and excellent in toughness and exhibits excellent wear resistance even when exposed to crushing and pulverizing conditions subject to heavy impact A member can be provided.

[Brief description of the drawings]

FIG. 1 is a sketch showing a hardfacing weld metal forming material used in an experiment.

FIG. 2 is a schematic sectional explanatory view showing a rock crushing test method for evaluating the wear resistance of a hardfacing welded metal layer.

FIG. 3 is an operation schematic diagram (build-up type) during a crushing test using a cone crusher.

FIG. 4 is an operation schematic diagram (casting mold) during a crushing test using a cone crusher.

[Explanation of symbols]

 Reference Signs List 1 base material (base material) 2 weld metal 3 upper die base material (mild steel) 4 lower die base material (mild steel) 5 hardfacing deposited metal layer 6 crushed stone 7 upper raw material chute 8 lower raw material chute 9 load detector ( Load cell) 10 Actuator 11 Tempered glass 12 Mantle (base material) 13 Cone cave (base material) 14 Hardfacing deposited metal 15 Raw material stone (chart) 16 Mantle (cast product) 17 Corn cave (cast product) 18 Raw material stone (chart)

Claims (5)

[Claims] 1. A member having a hardened layer formed on the surface of a base material, wherein the hardened surface layer comprises: C: 0.2 to 0.9% (meaning mass%, the same applies hereinafter) Si: 0.6 To 1.9% Mn: 0.6 to 1.6% Cr: 2.5 to 7.5% W: 0.1% or more and less than 1.5% V: 0.1% or more and less than 1.5% Mo : 1.0 to 8.0% B: more than 0.2% to 0.8% or less, the balance being constituted by a deposited metal comprising Fe and unavoidable impurities. 2. The surface hardened member according to claim 1, wherein the amount of Mo in the deposited metal is more than 4.0% and not more than 8.0%. 3. A weld metal welded by overlay welding, wherein the weld metal is: C: 0.2 to 0.9% Si: 0.6 to 1.9% Mn: 0.6 to 1.6 % Cr: 2.5 to 7.5% W: 0.1% to less than 1.5% V: 0.1% to less than 1.5% Mo: 1.0 to 8.0% B: 0.2 %, With the balance being Fe and unavoidable impurities. 4. The amount of Mo in the deposited metal is more than 4.0% 8.0.
% Of the deposited metal according to claim 3. 5. A method for producing a surface-hardened member, comprising forming the welded metal layer according to claim 1 on a surface of a base material by overlay welding.