JPS6256555A - Alloy tool steel excellent in wear resistance, corrosion resistance and toughness - Google Patents

Abstract

PURPOSE:To develop and alloy tool steel combining high hardness and wear resistance with corrosion resistance and toughness by adding Cu and Co in combination and by increasing V content in a conventional alloy tool steel. CONSTITUTION:As alloy tool steel, an alloy steel having a composition containing, by weight, 0.8-1.25% C, <0.8% Si, <0.8% Mn, 6.0-10.0% Cr, 0.5-3.0% Mo, 0.5-4.0% V, 0.1-4.0% Co and <2% Cu or further containing <2.5% Ni is used. In the above alloy tool steel, acid resistance is improved by the combined addition of Cr and Co and, if necessary, by the addition of Ni, toughness is improved by reducing the amounts of C and Cr as compared with conventional alloy tool steels to refine primary carbides and wear resistance is also improved by increasing V content to increase the proportion of VC carbides.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to alloy tool steel, and more specifically (higher hardness,
This invention relates to an alloy tool steel suitable for applications that require wear resistance, corrosion resistance, and high toughness at the same time.

It has excellent wear resistance, corrosion resistance, and toughness, making it ideal for applications such as screw backflow prevention valves in plastic injection molding machines, molds, and cutlery and rolls used in food production such as tomato ketchup and sports drinks, and other corrosive environments. It is an alloy tool steel.

<Conventional technology> Screws, check valves, etc. of plastic injection molding machines require materials with excellent wear resistance, but with the advancement and diversification of plastic materials in recent years, materials with even higher wear resistance have been required. Along with this, corrosion resistance has also come to be required.

Specifically, injection molding of plastic materials such as epoxy resin, polyacetal resin, ABS resin, and polycarbonate-1-fluororesin is performed under extremely high temperature conditions, so thermal decomposition of some raw materials can be avoided. Some people take it for granted that a certain amount of corrosive gas will be generated.

In particular, if a halogen-containing compound is added to make it flame retardant (7), a large amount of corrosive gas will be generated.After that, tools such as screws will be constantly exposed to a corrosive environment, and these tools will have a high level of corrosion resistance is required. However,
The pressure applied during molding is quite high, and the inorganic fillers that are often added to improve strength are extremely hard, so tools such as screws are required to have a high level of wear resistance. Ru.

Conventionally, for this type of corrosion and wear resistance, high C-high Cr j
JIS 5US440C, high C-high Cr M
o V steel JT'S SK11 or Al5I D5 with Go added to it is used,
It was not sufficient for corrosive wear in various gas atmospheres generated from plastics.

The components of these gases are H2S, Ce, HCI, No2°HF, No, etc., and it is thought that steel for this type of use must have corrosion resistance against various oxidizing and reducing acids. Furthermore, these conventional steels lacked toughness2, resulting in accidents such as screw breakage.

Furthermore, rolls and cutlery used in corrosive environments must have corrosion resistance and high hardness against these acids.

In addition to wear resistance, toughness is also required, and as with the screws of injection molding machines, the conventional steels mentioned above are insufficient.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and its purpose is to improve #4 wear resistance, corrosion resistance, and toughness that can be sufficiently adapted to the severe usage conditions as described above. The aim is to provide an excellent alloy tool steel.

Means for Solving the Problems> In order to solve the above problems, the alloy tool steel of the first invention has the following weight ratios: C: 0.8 to 1.25% Si: 0.8% or less Mn: 0.8% or less Cr: 6.0-10.0% Mo: 0.5-3.0% V: 0.5-4.0% Co: 1. O ~ 4.0% CI]: 2% or less, with the remainder consisting of Fe and impurities, and the alloy tool steel of the second invention is such that N: 2% or less is added to the above components. be.

Compared to conventional alloy tool steel, the alloy tool steel of the present invention has ■C
The acid resistance is improved by the addition of u, Co and, if necessary, Ni, and compared to conventional alloy tool steel, C,
Improved toughness by reducing the amount of Cr and refining the primary carbides, ■ Improved wear resistance by increasing the ratio of VC carbides by increasing the amount of V compared to conventional alloy tool steels. It is something.

Its characteristics and strengths are that after quenching, it forms a martensite group J1 with sufficient hardness through tempering treatment, and by dispersing an appropriate amount of hard undissolved carbide, it achieves a high balance between wear resistance and toughness. Moreover, C ur Cr r G OrN i , M solidly dissolved in the base
It also has excellent corrosion resistance due to o.

For Kusaku The reasons for determining the alloy components in the present invention will be described below.

C; 0.8 to 1.25 wt, % C is an element that generally plays a fundamental role in greatly determining various properties of tool alloy steel. In the case of the steel of the present invention, Cr, Mo,
It is an element that forms a composite carbide with V and contributes to wear resistance, and also forms a solid solution in the matrix to obtain high hardness. The amount of C is determined based on the balance between hardness, wear resistance, corrosion resistance, and toughness, but the lower limit is hardness sufficient for Me11 wear engineering steel, Fr.
It was set to 0.8% to obtain 4M abrasion resistance. If Cff1 is too large, giant carbides are generated, leading to a decrease in toughness, and a large amount of Cr and Mo in the matrix is consumed, leading to deterioration of corrosion resistance. Therefore, the upper limit was set at 1.25%.

Si: 0.8 wt% or less Si is added as a deoxidizing agent in the steel manufacturing process. If it is too large, the machinability and grindability will deteriorate, so the upper limit should be set at 0.8.
%.

Mn: 0.8 wt% or less.

Mn is also added as a deoxidizing agent. If it is too large, a large amount of retained austenite will be formed, causing a decrease in hardness, so the upper limit is set to 0.8%.

Cr: 6,0 to 10, Ow t% As mentioned above, Cr is dissolved in the matrix to increase corrosion resistance, and in combination with C and other elements, forms a composite carbide and contributes to wear resistance. Its content is determined in combination with the amount of C, but if it is less than 6%, corrosion resistance, wear resistance, and hardenability are insufficient, so the lower limit is set to 6%. Moreover, if it exceeds 10%, giant carbides will appear and cause toughness deterioration, so the upper limit is set at 10%.

Mo: 0.5 to 3.0 wt% Moi After quenching, like Cr, it exists in both the matrix and the carbide, providing wear resistance and corrosion resistance, and increasing resistance to temper softening. If it is less than 0.5%, it will be difficult to obtain the result of B.
Moreover, if it exceeds 3%, MGC-type giant carbides will increase and toughness will be impaired, so the content is limited to 0.5 to 3.0%.

V: 0.5 to 4.0 wt% (2) forms a highly hard MC type carbide, which basically increases wear resistance and at the same time provides resistance to temper softening. If this effect is less than 0.5%, f'44 <, and the lower limit is 0.5%, but if it exceeds 4%, giant carbides will be produced excessively, resulting in poor toughness, hot workability, and cold machining. Since it deteriorates properties, the upper limit is set at 4.0%.

Co: 1.0-4. Owt% CO forms a solid solution in the matrix, providing resistance to tempering softening and at the same time significantly increasing corrosion resistance. Please greatly reduce the corrosion resistance caused by hydrochloric acid by adding it simultaneously with C11. The above effect requires a content of 1.0% or more, but 4.0%
The effect reaches saturation at this point, and adding too much will degrade toughness and hot workability, so the upper limit is set at 4.0%. Therefore, 1.5 to 3.5% is preferred.

Cu: 2wt% or less Cu is dissolved in solid solution in the base like Co and improves corrosion resistance. In particular, it significantly improves hydrochloric acid corrosion resistance, but 2.0%
If it exceeds 2.0%, hot workability will deteriorate, so set the upper limit to 2.0%.
shall be. Therefore, 0.5 to 1.5% is preferred.

Ni: 2.5 wt% or less Ni is added as necessary, and similarly to Go and CIJ, it is dissolved in the matrix to strengthen the passive film and improve corrosion resistance. If the amount is too high, a large amount of residual austenite (retained after quenching) will be generated, causing a decrease in hardness, so the second limit should be set to 2.5.
%.

In addition to the above composition, Ae used as a deoxidizer, il added for the purpose of refining crystal grains, and 7) Ti are added.

Nb, Zr, REM, and N@ do not significantly affect the properties of the steel of the present invention up to a range of 0.3%.

<Example> Table 1 shows the composition of the steel used in the test. N in the table.

Steels 1 to No. 4 are inventive steels, and comparative steels No. 5 to No. 7 are prototype materials tested during development for the invention and are superior to conventional steels, so they are listed for reference. No, 8~N
010 is conventional steel No. 8 is JIS 5KDII,
No. 9 is AIS ID 5, No. 10 is JIS 5US440G. Steels with these compositions were tempered under heat treatment conditions not shown in Table 2 and subjected to 114 corrosion tests against various corrosive acids.

Abrasion tests and Charpy impact tests were conducted. The results are shown in FIGS. 1 to 6.

(The following is a margin) Table 2, Figure 1 shows the corrosion weight loss against hydrochloric acid for each test No. 1 to) lo, 1.0. No. 1 to No. of the steel of the present invention
, No. 4 showed particularly excellent corrosion resistance, with a weight loss of less than 100 g compared to the comparison steel and the conventional steel teeth No. 5 to No. 10. .

FIG. 2 shows the corrosion reduction f& with respect to nitric acid for each test No. 1 to No. 10. No. 1 to No. 4 of the steel of the present invention
is even better than 5US440G, which is N010, which has the smallest weight loss among the conventional steels No. 8 to 1.0.

FIG. 3 shows the corrosion loss of each test steel No. 1 to No. 10 against sulfuric acid. Steels of the present invention No. 1 to No. 4 are almost equivalent to No. 1 O S tJ 3440 G, which has the smallest weight loss among the comparative steels and conventional steels No. s to No. 10.

FIG. 4 shows the corrosion weight loss of each test steel No. 1 to No. 10 against hydrofluoric acid. No. 1 to No. of the steel of the present invention,
4 has the smallest weight loss among the conventional steel Nos. 8 to 10, and is even better than No. 10, 5US440C.

Figure 5 shows inventive steel No. 1 to No. 4 and conventional steel No.
o, No. 8 to No., No. 10, Okoshi type abrasion test results are not shown.

lJo of the steel of the present invention, 1 to No, 4 is conventional 3fq N
Compared to Al5I D5 of No. 9, which has the best abrasion resistance among No. 8 to No. 10 j), it has the same or higher wear resistance at each friction speed.

FIG. 6 shows the Charpy impact test results for each test steel (Jo, No. 1 to No. 10). The steel of the present invention is conventional steel No. 8
It has superior toughness compared to No. 10.

Table 3 shows the results of practical tests in which steels of the present invention No. 1, No. 1, No. 2, and conventionally used steels such as SACM645 nitriding steel and 5KDII were used as screws for plastic injection molding machines. It is clear that the steels of the present invention No. 2, No. i.No. 2, and No. 2 have very superior properties compared to conventionally used steel types.

(Left below) <Effects of the Invention> As explained in detail above, the alloy tool steel of the present invention is made of Cu.
-Co, in addition to combined addition of N1 if necessary, C and C
Due to the balance of r, it has corrosion resistance higher than that of conventional tool steel, and due to the balance of C, Cr, Mo, and V and the effect of adding CO, it achieves both wear resistance and toughness to a high degree.

[Brief explanation of the drawing]

Figure 1 is a graph showing the corrosion loss of each test steel in response to boiling hydrochloric acid (2%), Figure 2 is a graph showing the corrosion loss of each test steel in response to boiling nitric acid (2%), and Figure 3 is a graph showing the corrosion loss of each test steel in response to boiling nitric acid (2%). A graph showing the corrosion loss against boiling sulfuric acid (2%), Figure 4 is a graph showing the corrosion loss against 40°C hydrofluoric acid (1%) of each test steel, and Figure 5 is the present invention steel No. 1 to No. 4. FIG. 6 is a graph showing the results of the Charpy impact test of each test steel. Patent applicant Nippon Koshuha Steel Co., Ltd. Agent Patent attorney Hide Akira Fuji' ” ” Hemi Fuji \ ~ COz+6 1 & scream Hemi fox 5th excitement, 2 3, friction 4J (
a)

Claims (2)

[Claims] (1) Weight ratio: C: 0.8-1.25% Si: 0.8% or less Mn: 0.8% or less Cr: 6.0-10.0% Mo: 0.5-3.0% An alloy with excellent wear resistance, corrosion resistance, and toughness, characterized by containing V: 0.5 to 4.0% Co: 1.0 to 4.0% Cu: 2% or less, with the balance consisting of Fe and impurities. tool steel. (2) Weight ratio: C: 0.8-1.25% Si: 0.8% or less Mn: 0.8% or less Ni: 2.5% or less Cr: 6.0-10.0% Mo: 0 .5 to 3.0% V: 0.5 to 4.0% Co: 1.0 to 4.0% Cu: 2% or less, with the balance consisting of Fe and impurities, Alloy tool steel with excellent corrosion resistance and toughness.