JPS6143531A - Screw for injection molding machine of fluorine resin - Google Patents

Abstract

PURPOSE:To obtain a screw for an injection molding machine of fluorine resin which is superior in resistance to corrosion by fluoric acid, strength and resistance to abrasion, by applying the treatment to an Ni group alloy in specific composition after liquifying treatment of the Ni group alloy. CONSTITUTION:After an alloy bar material consisting of 0.05-0.20% C, Si of less than 0.5%, Mn of less than 1.0%, 14.0-22% Cr, 8.0-12.0% Co, 8.0-12.0% Mo, 0.75-1.5% Al, 2.0-3.0% Ti, Fe of less than 5.0%, the remainder of Ni and impurities by wt% has been made into a predetermined shape by processing the same under a state of liquifying treatment, the same is made to separate out and cure at hardness of more than HRC36 by applying age treatment to the same at the temperature of around 760 deg.C. With this construction, a screw for injection molding machine of fluorine resin which is favorable in resistance to corrosion by fluoric acid and is high in strength and resistance to abrasion can be formed.

Description

[Detailed description of the invention] , relating to machine screws.

Plastic injection molding is a process in which plastic material is heated to a high temperature, melted into a fluid state, and then injected into a mold at high speed under high pressure. That is, in an injection molding machine.

In this case, the plastic material is plasticized and melted by the heating by the heating cylinder and the frictional heat generated by the rotation of the screw, and the material is injected by the forward movement of the screw. Properties such as strength, high wear resistance, and good corrosion resistance are required.

Conventionally, screws for plastic injection molding machines have been made of nitrided steel SAOM or hot die steel SKD that has been nitrided.

As the uses of plastics expanded to include fluororesins such as Teflon, it became clear that these steel types lacked corrosion resistance.

, In fluororesin molding, bumps occur during molding.

Because it generates hydrogen, a high degree of corrosion resistance is required.
Hastelloy C, which is a Ni-based heat-resistant alloy, is used as the screw for fluororesin molding.

Hastelloy C has jj%N'1. /7%MO, #%Or
.

An alloy containing g%W%j%Fe, θ3%V.

It has very good corrosion resistance against butic acid (HF), but its hardness is as low as HRO/4t and lacks strength. The disadvantage is that it wears out.

The present invention has been developed in view of these problems.The present invention has been developed for a fluororesin injection molding machine that has almost the same corrosion resistance to acetic acid as Ysteroy C2, and has a hardness that is precipitation hardened to Hn036 or higher. The purpose is to provide a screen for use.

That is, in the present invention, 0θθj to θ2θchi, SiO,
! r% or less, Mn/:θchi or less, Or/lAθ~22%
, Oo&θ~/2θchi, Mo&θ~/yuθchi, An O
, 7j~/, 5% Ti, Zθ~3θchi, Feiθchi or less, the balance Ni and some impurities are processed into a predetermined shape by processing in a solution/annealing state, 76
This is a fluororesin injection molding machine screw with excellent corrosion resistance, which is characterized by being precipitated and hardened to a hardness of 81036 or higher by aging treatment at a temperature of around 0°C.The screw has good corrosion resistance to fluoric acid. , □It has the characteristics of high strength and wear resistance.

Next, the reason for limiting the raw material of the composition for screen according to the present invention will be described. C forms a solid solution in austenite and carbonizes with Or s Mo s T 1 and the like, but if C is less than θθj, the strength is poor.

If it exceeds 920%, the toughness decreases, so a0
5 to θλθchi. 8i is added as a deoxidizing agent,
0! If it exceeds θj%, the toughness decreases, so it is set to θj% or less. Mn is also added as a deoxidizing agent and has the effect of improving hot workability, but if it exceeds 10%, the corrosion resistance decreases, so it was set to below /θ. Or improves corrosion resistance and oxidation resistance, but if it is less than 711%, the effect is small, and if it exceeds u%, the toughness decreases, so /4t, θ
〜、、2Uθ・Chi. 00 has the effect of improving corrosion resistance and heat resistance and promoting precipitation hardening, but is less than θ.

The effect is small, and if it exceeds 72%, the toughness decreases, so it was set as θ~/yuθchi. Mo improves corrosion resistance and increases the strength at room temperature and high temperature, but its effect is less at temperatures less than 2θ.

Since toughness decreases when the value exceeds θ, it is set as θ~/2θ. Al and Ti combine with -Ni to form Ni3(AJ,T
i) creates intermetallic compounds and causes precipitation hardening, but Af! , and if Ti is too small, the aging hardness is too low,
Furthermore, if too much B and Ti are present, the toughness is reduced, so the content of B and Ti is limited to θ7j~/S%, and the content of Ti is limited to 20~3θchi. Although Fe reduces corrosion resistance and strength, 5
It was limited to 0% or less. The remainder consists of Ni and some impurities, but Ni has the effect of improving corrosion resistance and strength.

Hereinafter, the effects of the present invention will be explained using examples.

Table 1 shows the chemical composition of the screw according to the invention and the conventional screw. In the table, symbol A indicates the screw according to the present invention, symbol B indicates the SAOM/screw, and symbol C indicates the component of the Hastelloy C alloy. .

The first photochemical component Table 2 shows the heat treatment and hardness applied to the screw, and the
The results of a corrosion test for an aqueous thifluoric acid (IF) solution are shown.

The screw code A of the present invention was softened by I-IRQ27VC after solution treatment at 7066℃ and air cooling, but due to aging treatment (Table 2), heat treatment hardness and corrosion test results were HFl0.
Precipitation hardening occurred at 39 degrees. On the other hand, the hardness of 7-steroid O with symbol C after solution treatment at /20θ°C is HRO/g.

In the corrosion test, a φ/θXjOrrm specimen was immersed in a 5% HF aqueous solution at 20° C. to measure corrosion loss. The results are shown in Table 2, and it can be seen that the material with the symbol A has excellent corrosion resistance and properties that are almost equivalent to Hastelloy C with the symbol C.

As explained above, the present invention provides C0θS-0, λθchi, S
iθj% or less, Mn/θchi or less, Cr/ku θ~2uθchi, Cog, θ~72θchi, Mo&θ~/, 2. θ section, A
r1.7! ~73%, Ti, Zθ~3θ Chi, Fej
% or less, the balance is Ni and some impurities, and is precipitated hardened before and after IROJ by aging at 7°C after solution treatment, and its corrosion resistance against butic acid is equivalent to Hastelloy C. It is suitable for screws in fluororesin injection molding machines because it has good mechanical properties, strength, and abrasion resistance.

Claims (1)

[Claims] C0.05 to 0.20% by weight, Si 0.5% or less,
Mn 1.0% or less, Cr14.0-22%, Co8.0
~120%, Mo8.0~120%, Al0.75~1
．． A rod of an alloy consisting of 5% Ti, 2.0-3.0% Ti, 5.0% or less Fe, the balance Ni and some impurities is processed into a predetermined shape under solution treatment, and then heated at around 760℃. A screw for a fluororesin injection molding machine with excellent corrosion resistance, characterized by being precipitation-hardened to a hardness of H_RC36 or higher by aging treatment at a high temperature.