JPS59145763A - Alloy tool steel - Google Patents

Abstract

PURPOSE:To obtain an alloy tool steel having high performance, superior wear resistance, shock resistance and hardenability by adding specified amounts of C, Si, Mn, Cr, Mo and V to Fe. CONSTITUTION:The composition of an alloy tool steel is composed of, by weight, 1.3-2% C, <1% Si, <1% Mn, 9-13% Cr, 1.5-3% Mo, 0.5-2% V and the balance Fe with inevitable impurities. 0.8-3.5% Co may be added so as to increase the temper hardness further. The alloy tool steel is provided with superior characteristics by the composite effect of the added alloying elements and the balance among the components.

Description

Detailed Description of the Invention The present invention provides a high-performance alloy tool steel that has a high hardness of Rockwell hardness HRC64 or higher by applying appropriate heat treatment and has excellent wear resistance, impact resistance, and hardenability. It is related to.

Conventionally, roll materials using cold die steel have poor abrasion resistance, so they tend to develop defects such as roughness, scratches, and dents in a short period of time, and the rolls may need to be replaced frequently. It has poor accident resistance. Furthermore, high-speed steel rolls are expensive, prone to cracking, and have poor grindability.

In other words, in the cold rolling industry, when cold rolling stainless steel sheets, silicon steel sheets, copper alloys, etc., the roll materials used for these are cold die steel, semi-finished steel, etc., depending on the type of roll and the purpose. - Chair steel and high speed steel are selectively used.

However, cold rolling rolls not only roll the above-mentioned metal steel into a plate shape, but also improve the grindability of the roll itself.
Quality characteristics such as specularity, abrasion resistance, spalling and rack peeling have a great influence on the quality and cost of rolled materials.

For example, surface defects that tend to occur on the roll surface, such as scratches, cracks, dents, peeling, rough skin, and spalling phenomena, are printed directly onto the product during rolling, which can significantly impair the product's award. be.

In addition, good grindability of the roll is required from the viewpoint of shortening work time and improving efficiency in regrinding the roll, and improving wear resistance to extend the life of the roll and shorten the time lost for replacing the roll. , there is a strong need to improve efficiency.

As described above, the demand for these rolls has become even stronger, and in order to reduce the roll unit cost and improve work efficiency, there is a strong need to develop roll materials that further improve the performance of conventional cold rolling rolls. It is requested.

The present invention was made in response to the above-mentioned demands, and aims to improve not only wear resistance and grinding resistance that are essential for roll performance, but also accident resistance against spalling (cracking, peeling, etc.). We provide alloy tool steels, and in order to solve the defects that tend to occur in rolling rolls of these alloy tool steels, we aim to have a chemical composition that is intermediate between die steel and high-speed steel. It is an alloy tool steel that has a heat treatment hardness of f (RC64 or higher) and has excellent wear resistance, fatigue resistance, spalling resistance, impact resistance, etc. due to the optimum composition balance, and is also expensive. Since the addition of alloying elements is relatively small, it is effective not only for cold roll materials, but also for other uses that take advantage of its excellent properties, such as cold-opening mold materials and thread rolling dies. .

Hereinafter, the reasons for limiting the respective components and content ranges of the alloy tool steel according to the present invention will be explained in detail.

First, in the present invention, the following properties are required for the alloy tool steel applied to the cold roll material.

■ Must be capable of high-temperature tempering at the quenching temperature of a tool steel pot. ■ Must have a tempering hardness of HRC62 or higher. ■ Must have excellent impact toughness, wear resistance, and accident resistance. ■ Must have good grindability. ■ As a result of extensive research and experimentation, the following alloy tool steel was developed as having characteristics that go beyond being economical.

[13 Weight ratio: C: 1.3-2.0%, Si: 1.0
・Ti or less, Mn: 1.0% or less, Cr: 9.0
0~l 3.00chi, Mo: 1.5~3.0%, V
': 0.5 to 2.1, the balance being Fe and impurities. Alloy tool steel.

(II) c:i, a~2.0% by weight, Si:X, O
% or less, Mn: 1.0% or less, Cr: 9.00-1
3.00chi, Mo: 1.5-3.0%, V: 0
．． 5-2.0%, C.

:0.8 to 3.5%, the balance being Fe and impurities.

Here, the content range of the alloy tool steel mentioned above is as follows.

C: Among all alloying elements, it is an element that has a large influence on the properties of steel.If C is properly contained, a portion of it will dissolve into the geology, form a martensitic structure, and strengthen the matrix. Retains hardness and strength. Also, most of the remaining C
CrlMo, V, etc., which are carbide-forming elements, and Fe are added to form a complex carbide, which has the effect of increasing hardness and wear resistance. Here, when the amount of C increases by 2.0 degrees, the amount of C and the amount of double carbide in the matrix also increase, and the hardness improves, but the brittleness increases. Therefore, the internal strength is insufficient, and mechanical wear such as chipping and spalling occurs significantly. In addition, hot working is also somewhat difficult and the incidence of cracking increases.

On the other hand, if the C amount is less than 1.3, the amount of C dissolved in the matrix will also be small, resulting in poor hardenability and insufficient heat treatment hardness.

Therefore, not only is the wear resistance insufficient, but mechanical wear is also significantly accelerated. For the reasons mentioned above, it is preferable to limit the C content of the alloy tool steel according to the present invention to 1.3 to 2.0.

Si: Like Mn, it has a deoxidizing effect, and all -v in steel.
) Lix trap solid solution increases tempering resistance and contributes to improvement of wear resistance. However, if it is added in excess, it becomes brittle.
Since it inhibits forgeability and causes deterioration of toughness, it is usually set at 1.0% or less, which is almost similar to that of alloy tool steel.

Mn: Used as a deoxidizing agent, but when added in excess, it stabilizes austenite, expands its area, and increases the amount of retained austenite, leading to a decrease in hardening hardness, making it almost similar to ordinary alloy tool steel. Limited to 1 or 0 attacks or less.

Cr: Exists in a distributed manner in both the matrix and the carbide, and tends to dissolve in solid solution in the matrix as the quenching temperature increases.Therefore, Cr in the matrix increases solid solution in the carbide. It has a great effect of increasing the quenching depth, which gives steel its self-hardening properties. Furthermore, MO, V, and multiple carbides are present, and the presence of a large amount of these carbides increases hardness and wear resistance.

However, in steel types with a large amount of C, such as the alloy tool steel according to the present invention, if the amount of Cr is less than 9%, high hardness cannot be obtained in high temperature tempering, and wear resistance deteriorates. When the amount of Cr becomes 13 or more,
As a result of a predetermined heat treatment, the self-hardening property is reduced and the hardness level is significantly lowered, and as a result, there is a natural limit. Therefore, for the reasons mentioned above, the Cr content of the alloy tool steel according to the present invention is 9.0-1
When limited to 3.0%, it combines with C and Fe in MOz steel to form hard and fine double carbides, so it has strong self-hardening properties.
Increases hardenability and provides wear resistance. Further, it has a higher effect than Cr on temper softening resistance and precipitation hardening, and furthermore, it has an extremely large effect on mechanical properties, especially the toughness of steel. However, if there is a large amount of undissolved carbide after heat treatment, it is effective for wear resistance, but the impact toughness decreases.
It is important to adjust the carbide-forming elements so that hardness is achieved during tempering.

Therefore, if MOI is less than 5%, the specified hardness cannot be obtained and the addition has no effect, and if it is more than 3,0-, there is a large amount of undissolved carbides, but the contribution to wear resistance is small. Considering the economic aspect as well, it is preferable that the amount of MO in the alloy tool steel according to the present invention is limited to 1.5% to 3.0%.

■: M) Although Cr, MO, 1, and υ are distributed in the carbide in the IJ lux, they are difficult to solidly dissolve in the matrix and are mainly contained in the carbide. This V has a large affinity with C, and most of the V acts together with C to form carbides, and M
O1W forms a V-based carbide that is harder and more stable than the first W material. Incidentally, the carbide forming ability of (2) is said to be the second highest after Ti and Nb, and the v-shape is inevitably severely limited by the amount of C. Further, V partially dissolved in the matrix functions to increase tempering hardness and tempering softening resistance. This V-based carbide is resistant to heat and significantly improves wear resistance.
Furthermore, it is a strong carbide that also has the effect of suppressing the coarsening of crystal grains. Therefore, in a steel type with a high C content such as the alloy tool steel according to the present invention, if Fiv is less than 0.5 inches, the expected effect cannot be obtained, and the effect of addition is weak.
If the content exceeds 2.0%, the grindability will be significantly impaired and the hot workability will also deteriorate. For the reasons mentioned above, the V content of the alloy tool steel according to the present invention is 0.5 to 2.
．． It is preferable to limit it to 0.

Co: has good affinity with PE, but rarely forms carbides; it forms a solid solution only in the matrix, strengthens martensite, increases resistance to tempering softening, and does not contain CO. I'm comparing it.

Next, Table 1 shows the experimental chemical composition of the steel according to the present invention and comparative steel commonly used in the past, and Table 2 shows the heat treatment conditions, hardness, and mechanical properties.

The following margins <Table 1> (Note A: First alloy tool steel of the present invention B: Second alloy tool steel of the present invention F: High speed steel <Table 2> Here, measurement of transverse rupture strength A bending test piece of 10 ψ x 110 m was prepared, and the distance between the supporting points was 80111!, and it was determined using an Amsler universal testing machine with a single point load of the punch tip @ 5R.The Charpy impact value was 10'' at I O$X 55ynw,
A test piece with a notch having a depth of 2 mm was used.

As is clear from Table 2, the transverse rupture strength and impact value of the steel of the present invention are clearly higher than those of the comparative steel, indicating that it has excellent performance in terms of toughness. .

In addition, Fig. 1 shows the continuous tempering hardness curve of the inventive steel, and Fig. 2 shows a comparison of wear resistance using a Nishihara type abrasion tester. is the hardness required for cold rolling rolls, and the HR that was the development target.
Using a hardness of C62 or higher that has been tempered to RC61,
Alloy tool steel 5KD with heat treatment hardness HRC60 as mating material
II was used.

The test conditions were a rotational speed of 80 Or, p, B degree of 01, load stress of 170 kll/1rFrrX, and normal lubricating oil was used for lubrication.

As explained above in detail, the wear resistance of the alloy tool steel according to the present invention is slightly inferior to that of the conventional high-speed steel of comparison steel F, but it is slightly inferior to that of the conventional high-speed steel of comparative steel F.

D, E) are much better.

In addition, as mentioned above, the excellent characteristics of the alloy tool steel of the present invention are obtained by the combined effect of the alloying elements added and the component 74 lance, and it also has wear resistance and impact resistance, and has excellent fatigue resistance. This alloy tool steel has extremely good performance in terms of durability and accident resistance.

Furthermore, the second alloy steel according to the present invention has C
Since it has 0.8 to 3.5 inches of O added to it, it has been confirmed that the tempering hardness is greater than that of the first alloy steel, and therefore the wear resistance is further improved. play.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the continuous tempering hardness of the alloy tool steel according to the present invention, and FIG. 2 is a comparison diagram of the wear resistance measured by a Nishihara type wear tester.

Claims (1)

[Claims] (11 weight ratio C: 1.3 to 2.0%, si: i, o%
Below, Mn: 1.0% or less, Cr: 9.00~
13.00%, MO: 1.5-3.0%, V: 0.5
-2.0%, balance p'e and impurities. (2) C: 1.3-2.0%, Si: 1.0% by weight
Below, Mn: 1.0% or less, Cr: 9.00-13
．． 00%, Mo: 1.5~3.0ch, V: 0.5~
2.0%, Co: 0.8 to 3.5%, the balance being Fe and impurities.