JPH034012A - Wear resistant bolt and its manufacture - Google Patents

Abstract

PURPOSE:To improve durability by providing a fixing bolt for a wear resistant liner with a head portion formed integrally compounding an accumulated-bonded layer of cemented carbide alloy pieces with a white cast iron layer for backing. CONSTITUTION:When the melt 2 of white cast iron element is poured on pieces of cemented carbide alloy 1 which is accumulated and placed on the bottom face of a lower casting mold, the melt 2 is penetrated and filtrated into gaps among the pieces and solidated to closely bond the pieces together and strongly support the back thereof. Additionally, the tip 4 of a steel bolt 3 protruded from an upper casting mold is casted over and integrally welded to form the head portion. It is thus possible to form a fitted bolt of excellence in wear resistance and prevent the falling of a liner with a bolt of wear resistance equivalent to that of the liner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mounting bolt necessary for attaching a wear-resistant member in an apparatus, such as a liner lining a raw material input chute in a crusher.

[Prior art] The chute liner as exemplified above is made of wear-resistant material,
For example, it is made of 25% Cr cast iron to ensure that it can be used for as long as possible even under severe usage conditions.

Incidentally, in order to attach members such as a liner to the main body, bolts and nuts are generally used, and since materials with high wear resistance generally have poor weldability, there is little room for application.

However, in this type of installation, the bolts are noticeably less wear-resistant than the liner, so wear accelerates intensively from here, and even if a wear-resistant liner is used, its service life may be shortened. is often short and does not meet expectations.

In order to improve this problem, techniques have been developed to strengthen the bolt heads that are exposed to wear surfaces.

For example, bolts are manufactured from alloy steel such as SN0M material, and only the head part is induction hardened to improve hardness, or only the head part is hardened with a wear-resistant material (such as stellite), or Only the parts are covered with wear-resistant material (e.g. 25%
There are some that are cast-ins of Cr cast iron), and are actually used in various types of equipment.

[Problems to be Solved by the Invention] The wear-resistant bolts illustrated above have longer service periods than the conventional bolts that have been used before.
Although it seems that the initial objective has been achieved to some extent, it is still difficult to say that the wear resistance of the attached liner itself has been infinitely improved due to constantly advancing technology. I can't say it anymore.

It is clearly difficult to achieve the required wear resistance with induction hardened alloy steel, and there is a risk that hardfacing will cause thermal stress due to domestic welding after installation, resulting in welding work performed on site after installation. There are times when this is difficult.

The cast-in manufacturing method for the head, such as high Cr cast iron, also has a high C liner.
When materials were replaced with materials that had a much higher wear resistance than cast iron, the inconsistency between the two began to become noticeable.
This will create new challenges.

In order to solve the above-mentioned new problems, the present invention has the following features:
The purpose is to provide a new wear-resistant bolt that is several steps superior to the conventional mounting bolts 1 to 1.

[Means for Solving the Problems] The wear-resistant bolt according to the present invention has a head made of an integral composite layer of cumulatively bonded pieces of sintered carbide alloy and a white cast iron layer supporting the back of the layer. This solved the above problem.

In addition, the manufacturing method for this wear-resistant bolt is to stack small pieces of sintered carbide alloy on the bottom of a lower mold that forms the bolt head, and place IIII iron bolts vertically in the lower mold. The molten metal and the bolt tip and the molten metal and the sintered carbide alloy cumulative layer are each integrally embedded by embedding the bolt and protruding its tip into the hollow part of the lower mold, and casting the molten metal of white cast iron component together with both molds. Welding J- is proposed.

[Function] Sintered carbide alloy strips accumulate to a certain thickness, and moreover, they are tightly bonded to phase n, facing wear, and are integrally supported from behind by white cast iron. Therefore, the strips will not be peeled off by the passing material that scrapes the surface, and will continue to exhibit their inherent super wear resistance without regret, extending their useful life! On the other hand, as for the method of manufacturing such a wear-resistant bolt, it is said that white powder is deposited on the bottom of the lower mold on top of the sintered carbide alloy strips. Of cast iron components? When the 8 lakes are cast,
The molten metal infiltrates the gaps between the pieces and then solidifies, tightly joining the pieces together and firmly supporting the back of the pieces. Furthermore, since the tips of the steel bolts protruding from the upper mold are cast, they are also welded together, and in the end, the steel bolts, white cast iron, and sintered carbide alloy layer are combined into one.
Excellent wear-resistant bolts can be produced relatively empirically.

[Example] An example considered to be the most desirable of the wear-resistant bolt and its manufacturing method will be shown.

The most preferable range for the components of the white cast iron to be mixed is that the amount of C is between 2.5% and 4.0%, and the ratio of Cr/'C is within the range of 1 to 12.

When the ratio is less than 1, the formation of composite carbides is slightly lost, the matrix hardness is low, and graphite crystallization occurs. Moreover, when this ratio exceeds 12, C is used for carbide formation.
When carbon is insufficient, C is taken away from the sintered carbide alloy, forming a brittle phase at the interface between the two.

In addition, in order for the white cast iron molten metal to completely penetrate into the narrow gaps formed between the sintered carbide alloy particles, the pouring temperature must be at least 50° below the freezing point of the white cast iron with respect to the particle layer thickness Tcm.
It needs to be equal to or higher than T'C.

In addition, in order to avoid excessive sintered carbide alloy into white cast iron), the pouring temperature is 180 (1,
It must be in the range 75+T>'C.

Regarding the properties of the particles, if the particle size is too small, the spacing between the sintered carbide alloys becomes small, and even if the casting humidity is increased, the white cast iron will not penetrate sufficiently between the particles. Moreover, if the temperature is raised too much, the amount of melt a of the sintered carbide alloy into the white cast iron increases significantly.

If the particle size is too coarse, not only will the volume fraction of the sintered carbide alloy decrease, but also the mean free path cut by the abrasive particles of the interparticle white cast iron base material will increase, resulting in deterioration of wear resistance. Therefore, 70% of the total particles are 2mm to 15mm.
The above configuration is optimal.

On the other hand, it is desirable to carve a concave groove so that it is difficult to handle the wI bolt, which is to be cast.

FIG. 1 is a cross-sectional view illustrating the most typical embodiment;
The back of the sintered carbide alloy layer 1 is supported by a white cast iron part 2, and a bolt 3 is cast into this white cast iron part, but at this time, the groove 4 for the stopper is said to further strengthen the engagement between the two. It also exhibits unique effects.

Effects of the Invention] Since the present invention has the configuration and operation described above, when applied to an actual device, the service life is greatly extended. This effect will be illustrated by the trial results of Examples. The configuration is unified to that shown in FIG. 1, and the comparative example also uses conventional products of exactly the same shape side by side under the same conditions.

Comparative Example 1 is an SNCM bolt whose head is induction hardened, and Comparative Example 2 is a bolt made of 25% Cr cast iron.

In the present embodiment, layers of approximately 10 mm thick are cumulatively bonded using a sintered body of tungsten carbide and cobalt. 2.9
%C-31%(Cr+W+V)-1,5(Ni 10Mo) is a composite material with white cast iron as a base material. The parts used are the mounting bolts of iron ore input hopper liners in steel plants, and the number of days of use is shown in Table 1.

Table 1

[Brief explanation of drawings]

FIG. 1 is a front sectional view of the embodiment of the present application.

Claims (2)

[Claims] (1) A wear-resistant bolt characterized by having a head made up of an integrally composite layer of cumulatively bonded pieces of sintered carbide alloy and a white cast iron layer supporting the rear of the layer. (2) Sintered carbide alloy strips are accumulated and placed on the bottom of the lower mold that forms the bolt head, and a steel bolt is buried vertically in the upper mold and its tip is inserted into the lower mold. A method for producing a wear-resistant bolt that protrudes into a hollow part, aligns both molds, and pours a molten metal of white cast iron component, and integrally welds the molten metal to the bolt tip and the molten metal to a sintered carbide alloy cumulative layer.