JPS5820714B2 - Manufacturing method of wear-resistant bolts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a wear-resistant bolt having high wear resistance.

For example, raw material transport net members installed in sintering plants of steel mills and used to transport raw material ore, etc., are generally made of wear-resistant cast steel, as they are subject to severe wear due to the passage of raw materials. .

To attach the net member for raw material conveyance as mentioned above, it is necessary to use bolts made of a material with excellent wear resistance.If bolts with low wear resistance are used, the net member itself may not wear out. Due to the wear and tear of bolts, installation often requires repair or replacement of equipment, which requires a great deal of time and effort, and requires temporary suspension of production at the factory for said repair and replacement work. Many problems arose, including a decline in production efficiency.

However, there is currently no suitable method for manufacturing bolts with high wear resistance as described above industrially and economically. Although a bolt with high abrasion resistance can be obtained, it is difficult to thread the screw to form a thread on the bolt shaft, and the cost is high, making it impractical.Also, the bolt shaft is made of carbon steel, The upper part of the carbon steel bolt shaft is cast in wear-resistant cast steel such as high chromium-containing cast iron to form the bolt head, but this requires a mold for each bolt, making mass production difficult. There were problems such as difficulty and high cost, making it difficult to manufacture economically.

From the above-mentioned viewpoint, the present invention includes a bolt head made of a wear-resistant material and a bolt shaft made of a threadable material.
This provides an economical method for manufacturing wear-resistant bolts that have high adhesive strength, do not cause thermal cracking, and can provide high tightening stress, using wear-resistant materials such as high chromium cast iron. A bolt shaft mounting hole of a predetermined depth is drilled in advance at the bolt shaft pressure welding point on the lower surface of the bolt head, and an upset portion that is generated during pressure welding is provided at the deep part of the bolt shaft mounting hole. A crimping space is provided, and four square parts each having a length of one side that is approximately the same as the diameter of the bolt shaft are provided on the surface of the space that the bolt shaft comes into contact with; To install the bolt shaft of the bolt head, fit a square plate made of the same material as the bolt shaft, and insert the bolt shaft made of a material that can be threaded into the hole, and then insert the bolt shaft of the bolt head into the hole. The feature is that friction welding is carried out in a state of contact with the square plate, and the upset part is press-fitted to the inner surface of the space.

Next, the present invention will be explained with reference to examples and drawings.

In the method of this invention, as described above, a bolt head made of a wear-resistant material such as high chromium cast iron is joined to a bolt shaft made of a threadable material such as carbon steel by friction welding. However, high chromium cast iron has low thermal shock resistance and is prone to thermal cracking during joining.

Therefore, in order to obtain appropriate bonding conditions that do not cause thermal cracking,
Various bonding tests were conducted using test materials having the chemical composition shown in Table 1 below.

First, the lower surface 1a' of a high chromium cast iron bolt head 1' with a diameter of 50 m and a height of 25 m, as shown in a cross-sectional view in Fig. 1 and a plan view in Fig. 2, is attached to the lower surface 1a' of a high chromium cast iron bolt head 1' with a diameter of 18 m and a height of 80 m. The upper surface 2a' of the carbon steel bolt shaft 2' was friction welded in a flat state.

In friction welding, as shown in the schematic process diagram in FIG. After inserting the bolt shaft portion 2' into the (a) of the same figure, clamp the rotating and stationary sides together (see Figure 1), rotate the fixed base 8 at a predetermined number of rotations, and move the movable base 9 to the fixed base 8 side. (C)
, the bolt head 1' and the bolt shaft 2' are brought into contact with each other for a predetermined period of time under a frictional pressure P1 to generate frictional heat (FIG. 2).

Then, the rotation of the fixed base 8 is abruptly stopped, and the upset pressure P2 is increased.
Press the bolt shaft part 1 against the bolt head 1' with (E) in the same figure.
After the above-mentioned absetting process is completed, open the bolt head 1' clamp of the fixed base 8, move the movable base 9 backward, release the clamp of the movable base 9, and take out the pressure contact part (refer to the same figure). This was done by

During the test, the friction pressure P1 was kept constant at 5-8 kV/mA, and the upset pressure P2 was kept at 9-6 k'i/mr.
M, 13.5h/πJ, and 25.0kq/-.

Table 2 shows the test results according to the above method, in which the upset portion 3' was bonded with a diameter of 26.2 to 27.8 mm and a height of 7.0 to 11.0 mm.

However, the adhesive strength was as low as 5.4 kq/111j to 15.6/rttit, and the adhesive strength was also small. did.

Therefore, in the method of the present invention, the pressure contact portion of the bolt head 1 is shaped as shown in the sectional view in FIG. 4 and in the plan view in FIG. 5.

That is, in the drawing, 1 is a bolt head made of high chromium cast iron;
2 is a bolt shaft made of carbon steel, and the chemical composition of each is as shown in Table 1 above, and the dimensions of the bolt head 1 and bolt shaft 2 are also as shown in FIGS. 1 and 2 above. It is similar to that shown in the figure.

The bolt head 1 according to this embodiment is provided with a hole 4 for mounting the bolt shaft into which the upper part of the bolt shaft 2 can be inserted into the center of its lower surface. A hollow space 5 is provided which has a shape having approximately the same dimensions as the diameter and height of the upset portion formed at the upper end portion of the bolt shaft portion 2 by friction welding.

Further, on the surface of the hollow space 5 that the bolt shaft portion 2 comes into contact with, there is a 1
A square recess 6 having a side length the same as the diameter of the bolt shaft 2 and a predetermined depth is formed, and the square recess 6 includes:
A square anti-rotation plate 7 made of the same carbon steel as the bolt shaft portion 2 is fitted therein.

Insert the upper part 2a of the carbon steel bolt shaft 2 into the shaft mounting hole 4 of the high chromium cast iron bolt head 1 having the shape described above, and insert the upper end surface into the corner of the back surface of the cavity 5. Friction welding was performed in a state in which the plate 7 was in contact with the plate 7 by the same process as that described with reference to FIG. 3 above.

For the test, first, the friction pressure P1 was set to 5.8 kg, similar to the pressure welding in the flat state shown in Figures 1 and 2 above.
/yna is constant, and the upset pressure P2 is 9.6/mix, 13.5 Ay/m, and 25.0 phantom/m.
Friction welding was performed by changing it to "it".

As a result, as shown in the cross-sectional view in FIG. 6, the upper end surface of the bolt shaft 2 is joined to the bolt head 1 in the cavity 5 formed in the hole 4, and friction welded. The upset portion 3 that has been hollowed out as a result fills the void 5 without any gaps, and the upset portion 3 allows the upper end surface of the bolt shaft portion 2 to meet the inner circumferential surface 5a of the void 5 and the void 5. It was integrally joined to the surface of the square plate 7 which was fitted into the square recess 6 formed in the square plate 7.

Table 3 shows the above pressure welding results, and although it was possible to obtain a higher adhesive force than the above-mentioned plane pressure welding, thermal cracking was observed in the bolt head 1 depending on the test conditions.

Therefore, we conducted further research and increased the upset pressure P2 to 25. O
Ay/mlj was assumed to be constant and the friction pressure P1 was conversely reduced from 3°8hAnit to 1.9h1. As a result, as shown in Table 4, the thermal cracking of the bolt head 1 was did not occur at all, and the adhesion force and friction pressure P was 3.8 Jcg.
/ma, 41.3 k'1Ana 53.8
@/11171, an extremely high value was obtained.

From the various test results mentioned above, the thermal cracking of the bolt head 1 that occurs during pressure welding is strongly influenced by the friction pressure P1, and when the friction pressure P1 is high, the bolt head is likely to crack, and the It was also found that the frictional pressure P1 is more influenced by the force than the upset pressure P2 or the welding time.

That is, when attaching the bolt shaft to the bolt head 1, a hole 4 and a cavity 5 are formed, and the upset part 3 is frictionally welded so as to fill the cavity 5 without any gap, and the friction pressure in this case is I chose a low value of about 3. s icy/m7jl, it was possible to press the bolt head 1 without any thermal cracking.

In addition, the adhesive force required for wear-resistant bolts is generally determined by the formula for the appropriate tightening stress (σθ) for the bolt, σθ = 0.6.
From σγ (yield stress of bolt leg),
If σγ of carbon steel (S45C) is 38mm7i, σθ
-i23 #Ala, and 23/- is required, whereas the bolts pressure-welded by the method of this invention have an adhesive strength of 413 kg/m11 to 58.3 kg as described above.
/md, it was possible to obtain a high adhesive strength far exceeding the above-mentioned appropriate adhesive strength.

Further, a square plate 7 made of carbon steel for preventing rotation is fitted into the square recess 6 of the adhesive surface of the bolt head 1 to the bolt shaft 2, and the upset portion 3 produced by friction welding is fixed to the rotation prevention surface. Since the bolt is pressed against the square plate 7, the bolt head will not rotate idly when the bolt is used, and high tightening stress can be obtained.

As explained above, according to the method of the present invention, the head part is made of a wear-resistant material and the shaft part is made of a threadable material, and the adhesive force between the head part and the shaft part is strong. Excellent effects are brought about, such as making it possible to economically and industrially manufacture wear-resistant bolts that do not undergo thermal cracking.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a wear-resistant bolt in which the head and shaft are friction welded in a flat state, Fig. 2 is a plan view of the same, Fig. 3 is a schematic process diagram of friction welding, and Fig. 4 is the method of the invention. FIG. 5 is a plan view of the head and shaft portion of a wear-resistant bolt that is friction-welded by the method of the present invention, and FIG. 6 is a cross-sectional view of the wear-resistant bolt that is friction-welded by the method of the present invention. In the drawings, 1.1'...bolt head, 2,2'...
...Bolt shaft, 3゜3/...Upset part, 4...
Bolt shaft mounting hole, 5...vacancy, 6...recess, 7
... Square plate for preventing rotation, 8... Fixed stand, 9... Moving stand.

Claims (1)

[Scope of Claims] 1. In manufacturing a wear-resistant bolt by joining a bolt head made of a wear-resistant material such as high chromium cast iron and a bolt shaft made of a threadable material by friction welding, A bolt shaft mounting hole of a predetermined depth is drilled in advance at the location where the bolt shaft is pressure welded on the lower surface of the bolt head made of an abrasive material. A space is provided for crimping the upset portion that occurs in the space, and a square recess with one side having approximately the same length as the diameter of the bolt shaft is provided on the surface of the space that the bolt shaft comes into contact with. A square plate made of the same material as the bolt shaft is fitted into the square recess, and the bolt shaft made of the threadable material is inserted into the hole to attach the bolt head. A method of manufacturing a wear-resistant bolt, characterized in that the tip surface is brought into contact with the square plate by friction welding, and the upset portion is crimped onto the inner surface of the cavity.