JPH01294821A - Manufacture of grinding rod - Google Patents

Abstract

PURPOSE:To obtain the title rod provided with wear resistance and toughness and having excellent durability by subjecting a rolled stock of a high carbon- chrome steel to water hardening under specific conditions and executing low temp. tempering thereto. CONSTITUTION:A rolled stock of a high carbon-chrome steel contg., by weight, 0.5-1.50% C, <0.8% Si, <1.0% Mn and 0.90-1.60% Cr is subjected to water hardening under the conditions of 220-380m<3> cooling water content per unit surface area of the rolled stock and 2-4 min cooling time and is thereafter subjected to low temp. tempering. In this way, the quench hardening in the water hardening is suppressed to deepen the hardening depth on the surface and the hardening in the core part is reduced to maintain its toughness, by which the grinding rod provided with wear resistance and toughness and having excellent durability can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a grinding medium for use in a grinder, and particularly relates to an improvement in the method for manufacturing a grinding rod.

[Prior Art] In a cylindrical crusher, such as a rod mill, a rod-shaped crushing rod is used as the crushing medium.

Rod mills are suitable for pulverizing large amounts of relatively coarse grains, and as the rod mill rotates, the pulverizing rods move inside the rod mill like a hot cloth, and the crushed material sandwiched between the pulverizing rods is A violent impact action is applied between the raw material and the raw material to break it, and the crushed product is obtained by sequentially progressing the crushing process. As a result of the above-mentioned crushing, the crushing rods will wear out, and especially in crushing using a rod mill with a large diameter, the movement of the crushing rods will become even more active, and the impact will also increase, leading to the progression of wear and damage. Since the occurrence of cracking increases significantly and the grinding capacity decreases, conventionally, heat-treated rolled materials such as high carbon steel, which has wear resistance and toughness, have been used as grinding rods.

In addition, steel quenching methods that provide high quenched surface hardness have been proposed (for example, Japanese Patent Laid-Open No. 81-4
(See Publication No. 8514).

[Problems to be Solved by the Invention] However, when using high carbon steel in the above manufacturing method of the crushing rod, the hardenability increases as the carbon content increases, and the surface of the crushing rod is hardened by rapid cooling hardening. However, the quench hardening depth is shallow and the surface hardening layer exhibits wear resistance, but if the rod mill is operated for a long time and the wear progresses beyond the surface hardening layer, the quench hardening will be low in the 6 parts. However, there was a problem in that wear progressed rapidly and sufficient wear resistance could not be exhibited, and the crushing rod could not exhibit comprehensive wear resistance. In particular, when producing grinding rods with large diameters, the mass effect during rapid cooling and hardening results in incomplete hardening, making it impossible to obtain sufficient wear resistance. In addition, when using high carbon chromium steel as a manufacturing method for crushing rods, high carbon chromium steel has high hardenability, so the quench hardening depth becomes deep, and hardening occurs in the 6th part, so crushing Although the wear resistance is improved compared to high carbon steel under the action of steel, the impact value and other toughness are low, so the severe impact action of the crushing rod can cause damage such as breakage, resulting in poor durability. There was a problem with being inferior in gender.

The present invention solves these conventional problems,
The object of the present invention is to provide a method for manufacturing a grinding rod that uses high carbon chromium steel, has wear resistance and toughness, and has excellent durability.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides CO35 to 1.5
0% by weight, Si<0.8% by weight, Mn<1.0
weight%.

A rolled material of high carbon chromium steel having a composition of 0.90 to 1.60% by weight of Cr is 220 to 3% per unit surface area of the rolled material.
It is characterized by being rapidly cooled and hardened by water quenching under a cooling water amount of 80 rrr3 and a cooling time of 2 to 4 minutes, followed by low temperature tempering.

[Function] The present invention has the following effects due to the above configuration. In other words, when manufacturing the crushing rod using high carbon chromium steel, rapid hardening during water quenching can be suppressed by adjusting the amount of cooling water and the cooling time. It is possible to reduce hardening in the parts and maintain toughness, thereby producing a highly durable crushing rod with wear resistance and toughness.

[Example] The crushing rod contains 0.88% by weight of C and 0.4% of Si.
4% by weight, Mn 0.53% by weight, P 0.014
Weight%, So, 012% by weight, Cr 1.35% by weight
A rolled steel bar with a diameter of 90+U+ high carbon chromium steel having a composition of 0.5 kg/cm2 of cooling water has a cooling water amount of 700 to 1200 J/win and a cooling time of 2! l
It is ejected at 1 inch for 30 seconds, and the crushing rod is rapidly cooled and hardened by water quenching. The cooling zone length of the cooler is 1
．． 6 m, and the moving speed of the crushing rod is 0.5 m/m
in, and the amount of cooling water is the unit surface area of the crushing rod m2
This corresponded to 220 to 380 m' per area. Thus, by adjusting the cooling rate during water quenching, hardening of 6 parts is suppressed. Next, it was put into a heating furnace, heated to 210°C, taken out of the furnace, and then low-temperature tempered by air cooling.

The quench hardening characteristics of the crushing rod manufactured through the above process are shown by curve 1 in FIG. In other words, the quench hardening depth is increasing, and the hardening is lower in the 6th part compared to the surface.For comparison, curve 2 in Figure 1
The dotted line shows the quench hardening characteristics of a conventional grinding rod made of high carbon steel. That is, the quench hardening depth is extremely small, and the hardening in the 6th part is low.

Curve 3 in FIG. 1 shows the quench hardening characteristics of a grinding rod made of conventional high carbon chromium steel by a chain line. In other words, it was found that the hardness was almost the same from the surface to the 6th part, and the core hardness was as high as HRC48, indicating that the toughness was not sufficient.

Next, the mechanical properties of the obtained crushing rod were measured, and the results are shown below.

As is clear from the above results, the surface layer of the crushing rod is hardened to a sufficient depth, and part 6 has reduced hardening and has sufficient toughness in terms of elongation, reduction of area, and impact value. It is indicated. Further, the microscopic structure in the cross section of the obtained crushed rod exhibited martensite and bainite structures in the surface layer part, and a fine pearlite structure in the 6th part.

FIG. 2 shows a wear diagram of the obtained crushing rod. For comparison, curve 2 shows the wear status of a grinding rod made of conventional high carbon steel. The crushing rod is used in a rod mill to crush hard sandstone, and the initial diameter shows a wear condition that decreases with long-term use, until reaching the service limit of 40 mm. It turns out that the durability period is about 4 times longer. Since the crushing rod has sufficient toughness even near the usage limit of 40 mm, the crushing rod can be used with high durability without being damaged.

As described above, according to the above example, by using high carbon chromium steel with good hardenability and adjusting the cooling rate during water quenching, hardening of the 6 parts is suppressed. Therefore, it is possible to manufacture crushing rods with a thick quench hardening depth, high wear resistance, and high toughness.
Its durability as well as the economy of the grinding operation can be significantly improved.

[Effects of the Invention] As is clear from the above examples, the present invention uses high carbon chromium steel, and hardening in the 6th part is suppressed compared to the surface layer, resulting in a thicker quench hardening depth and richer wear resistance. Since it is possible to manufacture a crushing rod with high toughness and high toughness, its durability and the economical efficiency of the crushing operation can be significantly improved.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the quench hardening characteristics of the crushing rod according to the manufacturing method of the crushing rod in one embodiment of the present invention, and Figure 2 is a wear diagram of the same, both of which are shown in comparison with the conventional technology. . Figure 1 Distance from center (mm) Grinding rod diameter mm

Claims (1)

[Claims] C0.5-1.50wt%, Si<0.8wt%, Mn
A rolled material of high carbon chromium steel having a composition of <1.0% by weight and 0.90 to 1.60% by weight of Cr is processed using a cooling water amount of 220 to 380 m^3 per unit surface area of the rolled material and a cooling time of 2 to 4 minutes. A manufacturing method for crushing rods characterized by rapidly cooling and hardening by water quenching under conditions, followed by low-temperature tempering.