JPS63266042A - Steel for nonmagnetic mold suitable for cvd treatment - Google Patents

Abstract

PURPOSE:To produce the titled steel by incorporating specific ratios of C, Si and Mn into Fe. CONSTITUTION:The steel contg., by weight, 0.3-1.5% C, 0.1-1.0% Si, 12.0-35.0% Mn and the balance consisting of Fe with inevitable impurities is prepd. to obtain the nonmagnetic steel having excellent characteristics which is usable as a mold for molding of a ferrite magnetic and plastic magnet. A mold is formed by said nonmagnetic steel and the surface thereof is applied to a CVD treatment and aging treatment after that, by which the nonmagnetic mold having high strength and excellent wear resistance can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to non-magnetic steel used in molds for molding ferrite magnets and plastic magnets.

(Prior Art) For example, when molding a ferrite magnet, a magnetic field is applied to magnetize the material, but it is essential that the material of the mold be non-magnetic to prevent disturbance of the magnetic field.

Furthermore, in order to improve wear resistance, the mold surface is subjected to nitriding treatment before use, but the wear resistance is insufficient. On the other hand, it is possible to improve wear resistance by fitting cemented carbide onto the surface of the mold, but this has the drawback of increasing mold manufacturing costs.

The inventors have focused on the fact that in order to inexpensively produce a mold with excellent wear resistance, it is advantageous to use a nonmagnetic material whose surface has a coating with excellent wear resistance.

In particular, it is ideal for molds for magnet molding to have a carbide film with a thickness of 3 μm or more, but non-magnetic steel is a suitable material for forming the carbide film by CVD treatment. I can't find it.

Also, the tensile strength of non-magnetic materials is at most 60 to 80 kg/mm.
2, therefore, if a mold made of this material is applied to molding with enemy shots that have a large mold clamping force, permanent deformation will occur. In order to avoid this deformation, measures such as increasing the wall thickness of the mold are taken, but this increases the size of the mold itself and reduces workability. Therefore, materials for non-magnetic molds are also required to have high strength.

On the other hand, JP-A-52-111891 discloses surface hardening treatment of chromium-molybdenum steel and steel for machine structural use, but does not mention application to non-magnetic materials.

Therefore, it is an object of the present invention to provide a non-magnetic steel that has properties suitable for forming a coating with excellent wear resistance on its surface by CVD treatment and strength necessary for molds.

(Means for solving the problem) This invention has the following features: C: 0.3 to 1.5 wt% (hereinafter simply referred to as %)
, Si: 0.1~1.0% and Mn: 12.0~
W4 for non-magnetic molds suitable for CVD processing, containing 35.0% and the balance consisting of Fe and inevitable impurities (first invention)
, Cr: 1.0 to 9.0% and Al
: Non-magnetic mold steel containing one or two of 0.5-1.5% (second invention), V: 0.5-2.0% and Nb in addition to the first invention:
Non-magnetic mold steel containing one or two of 0.5 to 2.0% (third invention), further added to the first invention, S: o, o3 to 0.3%, Pb:
0.03-0.3% and Bi: 0.03-0.3
% (fourth invention), the second invention further contains V; 0.5 to 2.0%
and Nb: Non-magnetic mold steel containing one or two of 0.5 to 2.0% (fifth invention), S: 0.03 to 0.3% in the second invention, Pb;
0.03-0.3% and Bi: 0.03-0.3%
Non-magnetic mold steel containing one or more of the following:
6th invention), S: 0.03 to 0.3% in addition to the 3rd invention
, Pb: 0.03-0.3% and Bi: 0.0
Non-magnetic mold steel containing one or more of 3 to 0.3% (seventh invention); : S
: 0.03~0.3%, Pb: 0.03~0.3
% and Bi: non-magnetic mold steel (eighth invention) containing one or more of 0.03 to 0.3%.

(Function) Next, the reason for limiting the chemical components in this invention will be explained.

C: O, 3-1.5% C is an essential element for coating carbides by CVD processing, but if it is less than 0.3%, the thickness of the carbide produced by CVD processing will be thin, and 1. Even if the carbon content exceeds 5%, the effect will be saturated and the machinability will be significantly reduced, so the content of C is set to be 0.3% or more and 1.5% or less.

Si: 0.1-1.0% St is an essential element for deoxidizing steel, and 0.1% or more is necessary, but if it exceeds 1.0%, the toughness will deteriorate, so if it is 0.1% or more, the toughness will deteriorate. The content was set to be 1% or more and 1.0% or less.

Mn: 12.0-35.0% Mn is an essential element to make steel non-magnetic, and 1
Although it is necessary to contain 2.0% or more, the effect does not change even if the content exceeds 35.0%, and the machinability deteriorates, so the content is set to 35.0% or less.

Cr: 1.0-9% and Al: 0.5-1.5
In the case of molds that require higher surface pressure in order to increase the strength of the coating produced by CVD treatment, Cr and/or A
Using steel containing 1 is advantageous in extending the life of the mold.

Furthermore, the harder the base material is, the longer the life of the mold will be if a film is formed by CVD treatment. Nitriding is a method of increasing the surface hardness of a base material, and Cr and AI can improve the nitriding properties of metal materials.

Cr and AI exhibit the above-mentioned effects, and their contents are as follows.

Cr must be contained in an amount of 1.0% or more in order to satisfy the strength of the produced film or the hardness during nitriding, and even if it is contained in more than 9%, its effect will not be saturated. However, on the contrary, hot workability deteriorates and rolling becomes difficult.
．． It was set to be 0% or more and 9% or less.

In order to satisfy the strength of the produced film or the hardness during nitriding treatment, it is necessary to contain AI in an amount of 0.5% or more, and even if it is contained in more than 1.5%, the effect will be saturated. However, since it rather causes deterioration of hot workability, it is set to 0.5% or more and 1.5% or less.

Nb: 0.5-2.0% and V: 0.5-2.0
It is an essential component to increase the strength by aging treatment after CVD treatment, but it has no effect if it is less than 0.5%.
Even if the content exceeds 2.0%, the effect is saturated. Therefore, the content was set to 0.5% or more and 2.0% or less, respectively.

s: o, o3~0.3%, Pb: 0.03~0.3
% and Bi: 0.03 to 0.3%.S, PB, and Bi exhibit similar effects to improve machinability, and both elements are used to improve machinability. is 0.
It is necessary to contain 0.03% or more, and since it is difficult to contain more than 0.3% in steel manufacturing, each
% or more and 0.3% or less.

The base material of the above materials is refined in a converter, sometimes RH degassed or melted in an electric furnace, refined by LRF, and then converted into slabs, billets, blooms, or ingots by continuous casting or ingot making. It is manufactured into thick plates, flat steel, and steel bars by rolling (including blooming) or forging. Then heated to 600″C without heat treatment or with heat treatment.
1100"C) product.Furthermore, the surface is polished and the C)
By applying the VD treatment, a nonmagnetic material with excellent wear resistance can be provided. Note that the CVD treatment uses TiC
l4: 1-10 vo1%, CH4: 0.5-10
vo1%, 11□: In the remaining furnace atmosphere, the furnace temperature is 90
It is appropriate to apply the treatment under conditions of 0 to 1100° C. and a holding time of 1 to 10 hours.

Further, by performing an aging treatment after the CVD treatment, a nonmagnetic material with high strength and excellent wear resistance can be provided.

(Example) 50 kg ingots having each composition shown in Table 1 were melted by vacuum melting, heated, hot rolled to a thickness of 25 nm and 3 m, and then subjected to solution treatment at 930° C. for 20 minutes.

The obtained hot-rolled plate has a thickness of 20 mm and a width and length of 20 nm each.
+ m test piece was taken, and this test piece was heated at 1000°C for 4
CVD treatment for hours (atmosphere TiC1: 5 vo1%
, CH4: 5νof%, H: remainder) were applied.

In order to evaluate the CVD processing characteristics, the thickness of the film was measured using a microscope, and the surface of the film was measured using a Vickers hardness meter.
Indentations were made under various loads (5 kg, 10 kg, 30 kg), and the strength of the membrane was measured based on the presence or absence of cracks. The measurement results are also listed in Table 1.

In addition, sample No. 2 shown in Table 1. 6.12+ 13.
14+19.20.2L 22.29.30.31.3
For 2.33.35 and 37, a test piece with a thickness of 20 mm, width of 20 mm, and length of 150 mm was cut out from a hot-rolled plate that had been solution-treated at 930°C. A tensile test piece with a parallel part length of 30 mm and a parallel part diameter of 6 mm was taken from a test piece that had been heat treated at °C for 4 hours and then aged at 650 °C for 5 hours, and was subjected to a tensile test. did. As the results are shown in FIG. 1, the invention steel according to the 3.5.7 and 8 inventions is
It can be seen that the tensile strength before the aging treatment is approximately 60 to 90 kgf/mm2, but the tensile strength after the aging treatment is increased.

Similarly, sample No. 2 shown in Table 1. 6. 8. 9.
10゜iL 19.20.2L 22.23.For 25 and 26, a test piece with a thickness and width of 20 mm and a length of 150 mm was taken from the hot rolled sheet after solution treatment at 930°C, and this test piece was nitrided. The results of the treatment and measurement of surface hardness are shown in FIG. The figure shows that the invented steel has excellent nitriding properties.

Therefore, the sample Nα3,6°16 shown in Table 1
, 1? , 18.23.24.25.26.28.31
．． In order to evaluate the machinability of No. 33 and No. 37, a cutting test was conducted under the conditions shown in Table 2.

Machinability was evaluated by drilling holes to a certain depth in a 23 mm thick test piece using a drill, and determining the number of holes that could be drilled before it became impossible to drill with one drill. . As shown in FIG. 3, the results show that the machinability of the steels according to the inventions 5.6.7 and 8 is excellent.

Table 2 (Effects of the invention) According to this invention, the carbide layer is reduced to 3 μm by CVD treatment.
When formed to a thickness of m or more, it is possible to provide a non-magnetic steel that has properties optimal for the base material, and therefore it is possible to achieve high strength and improved wear resistance of the coating.

Furthermore, by performing an aging treatment after the C VD treatment, it is possible to increase the strength of the base material itself, thereby realizing the production of a non-magnetic mold that does not cause permanent deformation even if the mold clamping force is increased.

Furthermore, hardening by nitriding, which is important as a pretreatment for CVD processing, can be fully expected, and machinability, which is important when manufacturing molds, can also be improved.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between tensile strength and (Nb + V) amount, Fig. 2 is a graph showing the relationship between nitriding hardness and Cr1l, and Fig. 3 is a graph showing the machinability of each steel material. . Figure 1: Nb+V (wD;'') Figure 3: 5 amount (rwt;g)

Claims (1)

[Claims] 1. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, the balance being Fe and inevitable impurities. CVD consisting of
Non-magnetic mold steel suitable for processing. 2. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further contains Cr: 1.0 to 9.0 wt% and Al. :
Containing one or two of 0.5 to 1.5 wt%,
A non-magnetic mold steel suitable for CVD treatment, consisting of the remainder Fe and unavoidable impurities. 3. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further contains V: 0.5 to 2.0 wt% and Nb. :0
．． A non-magnetic mold steel suitable for CVD treatment, containing one or two of 5 to 2.0 wt%, with the balance being Fe and unavoidable impurities. 4. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further includes S: 0.03 to 0.3 wt%, Pb :0
．． 03~0.3wt% and Bi:0.003~0.3w
Non-magnetic mold steel suitable for CVD treatment, containing one or more of t% and the balance being Fe and unavoidable impurities. 5. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further contains Cr: 1.0 to 9.0 wt% and Al. :
One or two of 0.5 to 1.5 wt% and V: 0.
5 to 2.0 wt% and one or two of Nb: 0.5 to 2.0 wt%, and the balance is Fe and inevitable impurities, and is suitable for a CVD process. 6. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further contains Cr: 1.0 to 9.0 wt% and Al. :
One or two of 0.5 to 1.5 wt% and S: 0.
03 to 0.3 wt%, Pb: 0.03 to 0.3 wt%, and Bi: 0.03 to 0.3 wt%, and the remainder consists of Fe and inevitable impurities. Non-magnetic mold steel suitable for CVD processing. 7. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further contains V: 0.5 to 2.0 wt% and Nb. :0
．． One or two of 5 to 2.0 wt% and S: 0.0
CV containing one or more of 3 to 0.3 wt%, pb: 0.03 to 0.3 wt%, and Bi: 0.03 to 0.3 wt%, with the balance consisting of Fe and inevitable impurities.
Non-magnetic mold steel suitable for D treatment. 8. Contains C: 0.3 to 1.5 wt%, Si: 0.1 to 1.0 wt%, and Mn: 12.0 to 35.0 wt%, and further contains Cr: 1.0 to 9.0 wt% and Al. :
One or two of 0.5 to 1.5 wt% and V: 0.
5 to 2.0 wt% and one or two of Nb: 0.5 to 2.0 wt% and S: 0.03 to 0.3 wt%, Pb
:0.03~0.3wt% and Bi:0.03~0.3
wt%, and the balance is Fe.
and non-magnetic mold steel suitable for CVD treatment, which contains unavoidable impurities.