JPS608298B2 - Forged steel quenching roll for cold rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forged steel quench roll for cold rolling, and more particularly to a hoe steel quench roll suitable for use as a work roll of a Sendzimer rolling mill.

The properties required of cold rolling rolls are generally high hardness and excellent wear resistance and rutting resistance. Work rolls for Sendzimer rolling mills are required to have excellent thermal shock resistance and gloss. Traditionally, Sendzimer mill work rolls have been made of high speed tool steel containing chromium (Cr), molybdenum (Mo), tungsten (W), vanadium (V) and cobalt (Co).

The composition generally used for the work roll is 1.3 to 1.6% carbon (C) and 4 to 6% Cr by weight.
, Mo 4-6%, W 4-6%, V 3.5-6%,
Co is 3.5 to 6%, poppy, elemental (Si) and manganese (Mn) are each 0.6% or less, and the balance is iron (Fe) and impurities. A structure consisting of tempered martensite, retained austenite, and carbide is obtained by heat treatment of quenching and tempering. This work roll has extremely high hardness, exceeding HRc64 on the Rockwell hardness and Hs8 on the Shore hardness, and has a fine structure that does not contain dendrites.
Excellent gloss. Therefore, in cold rolling a stainless steel plate, an extremely glossy steel plate can be obtained. In addition, this work roll has high toughness, that is, bending strength, and is also resistant to thermal shock, so the rolled plate wraps around the work roll during rolling, and the surface of the work roll is heated to 700 to 800°C by frictional heat. Even if an accident occurs, it has the effect of making it difficult for cracks to form and propagate. The excellent toughness and thermal shock resistance are largely due to the inclusion of Co. This is thought to be because the base was strengthened by the addition of Co.
However, since the work roll contains Co, which is produced in small quantities and is difficult to obtain, it has the disadvantage that it is not possible to immediately respond to customer orders. The object of the present invention is to provide a cold roll that has higher hardness and wear resistance than conventional high-speed tool steel rolls containing Co, and has the same or better plowability, even without containing Co, which is difficult to obtain. To provide a roll for inter-rolling.

In the present invention, C is 1.3 to 1. Contains turtle weight%, Cr and Mo
and high speed tool steel containing W and V but not containing Co,
It contains 1.3 to 2.5% by weight of Si, and is forged and tempered to give it a Z structure consisting of competitively tempered martensite, retained austenite, and carbide.

The roll of the present invention has higher hardness and less wear than the conventional Co-containing high-speed tool steel roll.

Also, the ballability is the same or even better. Thermal shock resistance is also superior to that of conventional Z rolls because the amount of Si is within a suitable range. Therefore, it is suitable as a cold rolling roll, and is particularly suitable as a work roll for a Sendzimer rolling mill. of the present invention. A preferred composition of the CI. 3-1.
6%, Mno. 6% or less, Cr4-6%, Mo4-6%
, W42-6%, V3.5-6% and Sil. 3-2.
It consists of 1%. C is required to increase wear resistance and hardness, but if it is less than 1.3%, the hardening effect will not be sufficient and high hardness will not be obtained. It becomes inferior to high speed tool steel rolls.

When the content is more than 1.6%, the material becomes brittle, making forging difficult and prone to quench cracking.

Cr, Mo, W, and V all combine with C to form carbide and improve wear resistance.

Furthermore, Cr, Mo, and W partially form a solid solution in the matrix during quenching, thereby increasing the wear resistance of the matrix. When the amounts of Cr, Mo and W are all less than 4%, and when the amount of V is less than 3.5%, the wear resistance is not significantly improved, and when any of them are more than 6%, The toughness deteriorates and cracks tend to form on the roll surface during quenching or rolling. Mn is a deoxidizing agent and can be contained in an amount normally contained in general high-speed tool steel.

In the case of the fourth invention of the present invention, there is no problem if it is 0.6% or less. Sj
The amount is 1.3 to 2.5%, and by setting it within this range, the hardness, abrasion resistance, and thermal shock resistance can be improved compared to conventional Co-containing rolls. A particularly preferable amount of Si is 1.3 to 2.1%, and within this range, hardness,
It is superior to the conventional Co-containing high-speed tool steel roll in terms of wear resistance, toughness, and thermal shock resistance. The remainder of the roll of the present invention other than the above-mentioned components is F
e and impurities such as phosphorus (P), sulfur (S), and copper (Cu) that are mixed in during melting and manufacturing.

The amounts of these impurities are normally regulated for general high-speed tool steel, namely P and S are each 0.03% or less, Cu
should be kept below 0.25%. Cu is 0.25
%, cracks tend to occur when forging ingots. The roll of the present invention is produced by forging the above-mentioned steel,
Made by hardening and tempering.

By quenching and reheating, a structure consisting of tempered martensite, residual austenite, and carbide is obtained. It would be better if the residual austenite could be reduced. In addition, the bride temperature is approximately 500-58
When it is within the range of 0oo, secondary hardening may occur due to tempering, and the hardness may increase. This is an effect of increasing the amount of Si. The manufacturing process for the roll is the same as the general manufacturing process for rolling rolls.

That is, it can be manufactured through the steps of ingot annealing treatment, forging, annealing treatment, processing, quenching and resetting treatment, and processing. After forging and final processing,
We perform magnetic flaw detection, dye inspection, and dimensional inspection. Examples Samples having the chemical compositions shown in Table 1 were melted in a high-frequency melting furnace, forged, and then processed into various test pieces by being annealed with bran.

After that, it is hardened and tempered, hardness tested,
Abrasion tests, bending tests and thermal shock tests were conducted. Second
The test results are shown in the table. In addition, Akatsuki annealing processing is 88000
The quenching is done by holding for 5 hours at 1200℃.
The process was carried out by repeating three times the process of holding at a temperature of 520 qo for 1 hour, cooling with oil, holding at a temperature of 520 qo for 1 hour, and then cooling in air. The present invention is No. 4 to 7. The hardness test in Table 2 was measured using a Rockwell hardness meter using a test piece at an elevation angle of 15.

Conventional Co-containing high-speed tool steel test piece No. 1 is HRc
66 (Shore hardness HS approximately 92), and test piece No. 66 of the present invention. It is clear that samples 4 to 7 are slightly harder than this.
The wear test was performed at a rotation speed of 60 m.p.m. p. m. Rotating diameter 2
The test was carried out by placing emery vapor on a turntable with 0 skin ◇, pressing a circular section of a test piece of 18 ribs and 15 heights onto it under a load of 800 mm, and causing it to wear between 2 minutes and 2 minutes. Wear resistance was evaluated based on the difference in weight before and after.

Those with a Si content of 1.3% or more are conventional Co-containing high-speed tool steel test piece No. It is clear that the wear resistance is superior to that of No. 1. In the bending test, a prismatic specimen of willow with vertical and horizontal dimensions of 4 sides and 5 sides and a length of 55 mm was placed on fulcrums spaced 4 times apart, and a load was applied to one point in the center. The test was carried out by bending and breaking, and the load and deflection at the time of breakage were measured. The specimen according to the present invention is a secondary Co-containing high-speed tool steel test piece No. More than 1. It has a large amount of damage, and the breaking load is about the same or No. was found to be greater than 1. The thermal shock test was conducted by intermittently high-frequency induction heating a test piece with a diameter of 2 views and a length of 5 views at a frequency of 450 KHz to generate heat cracks in the test piece. The test piece was heated to 700° C. for 8 seconds, immediately cooled with water, and subjected to this thermal shock repeatedly until cracking occurred. A platinum-platinum rhodium thermocouple was welded to the surface of the test piece, and the temperature of the surface of the test piece was constantly measured. Thermal shock resistance was evaluated by the number of thermal shocks until cracking occurred.
The test piece of the present invention containing 1.3% or more of Si is different from the conventional No.
．． It was revealed that the thermal shock resistance was superior to that of No. 1. The figure is a graphical representation of the test results shown in Table 2.

The amount of Si is plotted on the horizontal axis, and various characteristics are plotted on the vertical axis. From this, the influence of the amount of Si can be grasped. In the figure, Sio.
The properties recorded on the 5% line are for Co-containing high-speed tool steel specimen no. 1. The hardness is determined when the amount of Si is 2.
It increases as the amount of Si increases up to 1%, and after that it tends to decrease. No. Hardnesses higher than 1 have been obtained at Sil% or higher. The abrasion resistance also shows the same tendency as in the case of the above-mentioned hardness, and the amount of wear decreases up to Sj 2.1%, but increases when it exceeds that. No. in Sil%. If the same amount of wear as No. 1 is obtained and it is greater than No. It will be less than 1. The breaking load and the amount of deflection in bending tests are closely related to each other. No matter how large the breaking load is, if the amount of deflection is small, it cannot be said that the bending strength is large, and therefore it cannot be said that the warpability is excellent. From the figure, the amount of Si is 1~
If it is 2.5%, it is No. Almost the same work efficiency as 1 can be obtained,
In particular, if it is 1.3 to 2.1%, it is No. It is clear that better ballability than No. 1 can be obtained. Thermal shock resistance is also Si
When 1%, No. 1 and is equivalent to Sil. No. 3% or more. Better than 1.

As is clear from the above examples, according to the present invention, it is possible to obtain a roll that has higher hardness and dust resistance than the conventional Co-containing high-speed tool steel roll, and has equivalent plowability. can. In particular, when the Si content is 1.3 to 2.1%, the roll can be made superior to Co-containing high-speed tool steel rolls in terms of toughness and thermal shock resistance. Therefore, the present invention is most suitable as a cold rolling roll, particularly as a work roll for a Sendzimer rolling mill.

[Brief explanation of the drawing]

The figure shows various properties required for cold rolling rolls and Si
It is a graph showing the relationship with quantity.

Claims (1)

[Claims] 1% by weight: carbon 1.3-1.6%, manganese 0.6%
Below, chromium 4-6%, molybdenum 4-6%, tungsten 4-6%, vanadium 3.5-6%, silicon 1.3
~2.5%, the balance being iron, for cold rolling, characterized by being integrally constructed of forged steel that has been forged, quenched and tempered to have a structure consisting of tempered martensite, retained austenite and carbides. Forged steel hardened roll.