JPH028011B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing a sugar mill roll used in a sugar plant. [Prior art] For example, as shown in FIG.
A plurality of mills 10 each consisting of a combination of three rolls 10a, 10b, and 10c are arranged, and a raw material supply means 11
The raw material 12 such as sugar cane is supplied to the mill 10, and the sugar juice 12a is squeezed out by the mill 10. A conveyance means 13 is disposed between the plurality of mills 10, and the sugar cane 12a is squeezed out multiple times. Conventional sugar mill rolls are manufactured by assembling a cylindrical roller 22 onto a forged steel shaft 21 by shrink fitting, for example, as shown in FIG. 7, and the roller 22 is usually made of high C, high Si gray cast iron. was. [Problems to be Solved by the Invention] The above-mentioned conventional roller for a sugar mill using the gray cast iron roller 22 has a low hardness of about 200 Hv, and as a result, wear and damage are extremely severe, and the roller 22 is made of gray cast iron. It is said that the wear and tear will decrease by 90 to 100 mmφ in diameter in three years. Furthermore, since it is made of cast iron, it has poor toughness and sometimes falls off from the groove 22a shown in FIG. Due to these circumstances, doubling the lifespan has been desired for a long time. Further, conventional rolls required shrink fitting, which was disadvantageous in terms of cost. The present invention overcomes the above-mentioned drawbacks of the conventional forged steel, which has small wear damage, greatly improves the roll unit consumption, eliminates roll breakage, greatly extends the lifespan, and is cost-effective. The object of the present invention is to provide a method for producing a roll for a sugar mill. [Means for Solving the Problems] The means of the present invention for solving the above problems is as follows: in weight percentage, C: 0.70 to 1.35%, Si: 1.5% or less,
Mn: 1.5% or less, Ni: less than 1.0%, Cr: 0.7 to 3.0
%, Mo: 0.2 to 0.5%, with the balance consisting of Fe and accompanying impurities, which is formed into a roll shape by hot working, and then directly heated to a temperature lower than Ac ₁ point and tempered. This is a method for manufacturing a forged steel sugar mill roll. [Function] In order to improve the wear resistance, there is an idea of increasing the hardness of cast iron, but since the toughness will deteriorate over time, the present invention has fundamentally changed the material composition. Also, to reduce internal defects, it is made of forged steel instead of cast metal. In this case, if the steel is made of ordinary forged steel, that is, heat treatment for grain size regulation is applied, the toughness will be excessively improved, so the as-forged state is only tempered at a temperature of Ac ₁ or less. Next, the reasons for limiting the components in the present invention will be explained. Regarding the C content, wear tests of steels with the composition shown in Table 1 show that if it is less than 0.7%, it is superior to gray cast iron materials, but the effect is not sufficient.
Since this is clear from the test results shown in the figure, 0.7% was set as the lower limit (however, the hardness was adjusted to the Witzkers hardness Hv280 level). Furthermore, the influence of the amount of C on the hot working conditions was investigated using the steel types shown in Table 2, and the results are summarized in FIG. Regarding steel types L, M, and P steel, a burning phenomenon in which granular fracture surfaces are observed on the fracture surface appears in the ultra-high temperature tensile test, and the LMP line indicates the burning start line.

【table】

[Table] On the other hand, for I, K, and R, no granular fracture surfaces are observed, but the value of area of area during the tensile test has decreased considerably, and a so-called overheating phenomenon has appeared, and the IKR line is overheated. This is the starting line. H, J, N, O, and Q all have aperture values of 100% or more, indicating normal heating ranges. The point is that if the C content exceeds 1.35%, the forging hot working temperature will drop below 1100°C, making industrial casting operations extremely difficult, so the upper limit of the C content is set at 1.35%. Although Si is added for deoxidation, excessive addition causes deterioration of mechanical properties, so its content was set to a range of 1.5% or less. Mn is added for deoxidation, to prevent the damage of S as MnS nonmetallic inclusions, and to improve hardenability, but if the content exceeds 1.5%, it increases the susceptibility to tempering embrittlement and reduces toughness. Therefore, it was limited to a range of 1.5% or less. Ni solidly dissolves in the matrix to increase strength and improve toughness at the same time. It also improves hardenability, but if it is contained in an amount of 1.0% or more, the hardness obtained will decrease due to an increase in retained austenite γ _R , so the content is limited to less than 1.0%. The amount of Cr is an element that partially dissolves in the matrix to improve hardenability, and at the same time forms carbides to improve wear resistance. According to the abrasion resistance test results, the content is
It is clear from the results shown in FIG. 3 using the steel types T to Z in Table 3 that the wear resistance is significantly improved when the content is 0.7% or more, so 0.7% was set as the lower limit. On the other hand, in this case, it is clear that exceeding 3.0% is no longer effective in reducing the amount of wear, so the upper limit of the Cr content was set at 3.0%. Mo is partially dissolved in the matrix to improve hardenability, increase resistance to temper softening, and is also effective in improving toughness.

[Table] In the case of rolls for sugar mills, there are problems with chipping and breakage from the crests and troughs of the roll grooves, so
Requires greater toughness than traditional gray cast iron rolls. However, if the toughness is improved too much, damage to other parts of the plant is caused instead of preventing damage from the roll part. Therefore, in consideration of the low level of toughness of steel rolling rolls, the upper limit of the impact value was set at 1.5 Kgf·m/cm ² in a 2 mm V-notch impact test, which was used to determine the Mo content range. The results of the toughness test using the steel types A ₁ to _{E 1} in Table 4 are shown in FIG. 4. As a result, in order to have higher toughness than current cast iron rolls and to satisfy a value lower than 1.5Kgf・m/ ^cm2 , the amount of Mo should be 0.2 to 0.5% by weight under the conditions of coarse grains that do not become austenitized after forging. Something has become clear.

〔Example〕

Next, embodiments of the present invention will be described. Fifth
Using a steel ingot having the composition of the present invention material shown in the table, a roll 1 as shown in FIG. 5 was formed by hot forging. On the other hand, for comparison, a roll 1 shown in FIG. 5 was cast using gray cast iron. In this case, both the body portion 2 and the shaft portions 3, 3 are integrally formed of the same material.

〔Effect of the invention〕

As explained above, the present invention provides a roll for a sugar mill that can significantly improve the roll consumption rate by forming a steel ingot with a predetermined composition into a roll shape by hot forging and subjecting the formed roll to a predetermined heat treatment. can do. In addition, since the rolls produced by the present invention are not subjected to any austenitizing treatment to refine the grains after forging, they have coarse grains, resulting in moderate roughness and wear, which deteriorates the sugar cane biting performance of conventional cast iron rolls. is inherited as is. Moreover, the rolls produced by the method of the present invention do not have excessive toughness but have appropriate toughness, so there is no roll breakage and the lifespan is extended, and there is no damage to other parts of the plant. also improves machinability. In addition, according to the present invention, the first-generation new roll does not require shrink-fitting and is advantageous in terms of cost. After the small diameter roll is discarded, it is used as an arbor after being machined to a predetermined size, and this arbor is made of forged steel of the same material. Just shrink fit the sleeve.

[Brief explanation of drawings]

Figure 1 is a diagram showing the effect of C content on wear amount using the steel types shown in Table 1, and Figure 2 is a diagram showing hot deformation (high temperature tensile test) using the steel types shown in Table 2. Figure 3 is a diagram examining the effect of Cr content on wear amount using the steel types shown in Table 3. Figure 4 is a diagram examining the effect of Cr content on wear amount A diagram showing the effect of Mo content on toughness (Sharp energy value) using the steel types shown in the table, Figure 5 is a side view of an example of a roll manufactured according to the present invention, Figure 6 is a sugar mill FIG. 7 is a longitudinal sectional view showing the structure of a conventional assembled roll for a sugar mill. FIG. 8 is a diagram showing the wear resistance of Examples and Comparative Examples. 1...roll, 2...body, 3...shaft.

Claims (1)

[Claims] 1 In weight percent, C: 0.70-1.35%, Si:
1.5% or less, Mn: 1.5% or less, Ni: less than 1.0%,
Contains Cr: 0.7~3.0%, Mo: 0.2~0.5%, the balance is
A method for manufacturing a forged steel sugar mill roll, which comprises forming a steel ingot made of Fe and accompanying impurities into a roll shape by hot working, and then directly heating and tempering the steel ingot at a temperature lower than Ac ₁ point.