JPH02153035A - Ni-base alloy for hot working tool - Google Patents

Abstract

PURPOSE:To manufacture the title Ni-base alloy having excellent strength and toughness by incorporating specific ratios of C, N, Si, Mn, Al, Mo, W, P and S into Ni. CONSTITUTION:An Ni-base alloy contg., by weight, 0.001 to 0.1% C+N, <=3% Si, 0.01 to 2% Mn, <=3% Al, <=40% Mo, <15% W and >=15% Mo+W, contg., as impurities, <=0.02% P and <=0.01% S and the balance Ni with inevitable impurities is prepd. In this way, the Ni-base alloy having less wear, errosion and cracking even if used at a high temp., having excellent strength, toughness, etc., and having high m.p. which is formed into a stock of a hot working tool having prolonged service life can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to hot tools used at high temperatures, such as piercing plugs and forging metals used in the production of seamless steel pipes.

The present invention relates to an NL-based alloy for hot work tools that has excellent strength and toughness and is suitable for molds and the like.

(Prior art) Tools used for hot working metals (hot working tools), such as drilling plugs and forging dies for hot working high temperature solid billets into seamless steel pipes, include - Generally, the following characteristics are considered necessary.

Namely, ■ high temperature strength, ■ ductility at high temperature, ■ toughness at room temperature,
(2) heat cracking resistance and (2) high temperature oxidation resistance. Among these, (2) heat cracking resistance is closely correlated with (2) ductility at high temperatures and (2) toughness at room temperature.

Various high-temperature materials have traditionally been used for hot tools that require such properties.
Fe-based alloys containing R and 3% by weight or less of Mo and W, or Ni-based alloys such as Inconel 718 (trade name) are used. Although these high-temperature materials exhibit excellent properties up to 1000°C, they have the drawback that their high-temperature strength rapidly decreases at temperatures above 1000'C. Therefore, when high-grade materials such as stainless steel and Ni-based alloys are hot-worked using tools made of these materials, there is a problem in that the tool life is extremely shortened.

For example, in pipe manufacturing and forging, if the workpiece is carbon steel or low-alloy steel, the Fe-based alloys described above are sufficient, but stainless steel or Ni-based alloys have extremely high deformation resistance and harsh processing conditions. In the case of alloys, tools made of Fe-based alloys have poor high-temperature strength at temperatures above 1000'C, and therefore have an extremely short life. In particular, in the case of the perforated plug used when manufacturing seamless steel pipes using the Mannesmann perforation method, not only does the surface temperature reach over 1200'C due to friction with the high-temperature workpiece, but also the machining time for one process is 1 to 100°C. Since the time is 30 seconds or more, which is longer than forging, which is about 20 seconds, severe wear and erosion occur.

For this reason, tools with higher strength are required for processing workpiece materials such as stainless steel and Ni-based alloys.

On the other hand, various ceramics such as aluminum oxide and aluminum nitride are used as materials that have excellent strength even at high temperatures.
Mo or Plo alloy, e.g. Mo-0.2%C
A Mo alloy called TZM having a chemical composition of -1.0% Ti-0.09% Zr is known. All of these materials have sufficient high-temperature strength, but the former ceramic has poor high-temperature ductility and easily cracks during tool manufacturing. Although the latter Mo and -G alloys have sufficient high-temperature ductility, they lack toughness at room temperature, and as a result, not only are they prone to cracking when hot working is started with a tool placed at room temperature, but Mo also has poor acid resistance. Mo has poor oxidation properties and vaporizes when oxidized, resulting in significant depletion.Also, Mo has a strong affinity with oxygen, so it cannot be melted using normal vacuum melting methods. Because it must be manufactured using special melting methods,
The cost will be high.

(Problems to be Solved by the Invention) An object of the present invention is to provide a material that is strong enough to be used as a material for hot-working tools with a long life, with little wear, erosion, and cracking even when used at high temperatures.
The object of the present invention is to provide a Ni-based alloy with excellent toughness and a high melting point.

In particular, the present invention provides a
The purpose of the present invention is to provide a Ni-based alloy suitable for use as a tool material for machining workpieces such as stainless steel and Ni-based alloys, which are processed at temperatures of 00° C. or higher and have significantly high deformation resistance at high temperatures.

(Means for Solving the Problems) The present inventor made perforated plugs from various conventionally known high-temperature materials and actually used them to manufacture seamless steel pipes. It was extremely short. The reason for this is thought to be mainly due to the following points.

(At temperatures above 111200°C, there is insufficient deformation resistance and wear is significant. (2) The plug surface may exceed 1350°C in some cases, but most existing materials have a melting point of 1350°C.
(3) The temperature at which ductility becomes 0% even if melting does not occur (hereinafter referred to as zero ductility temperature) is low. (4) Alloys containing 15% or more of Cr form an oxide film on the surface and have good oxidation resistance, but the chromium oxide formed on the plug surface has a thickness of less than 20μ11. As the plug becomes thin and dense, heat transfer from the workpiece to the plug increases, raising the temperature of the plug surface, and this oxide film has no lubricating effect.

Based on these findings, the inventor investigated what specific conditions should be met for a tool material for machining workpieces that have high deformation resistance at high temperatures, and found the following. I came to a conclusion.

That is, ■ has high deformation resistance of 15 Kgf/ma+'' at 1250'C or more, ■ excellent ductility with a reduction of 30% or more at 1250°C, and ■ has a melting point of 1350'C or more.
The zero ductility temperature is 1250°C or higher, and (2) it is capable of forming an oxide film with heat insulation and lubricating effects.

As long as the tool material satisfies at least these conditions, excellent durability can be obtained even when processing workpieces that have high deformation resistance at high temperatures.

The present inventor has attempted to select a hot tool material from this perspective, but none of the existing alloys has been found that satisfies all of the above conditions.In particular, Fe-based alloys have poor high-temperature strength and melting point. It has been found that there is no material that satisfies both requirements at the same time, and that it must be at least a Ni-based alloy.

It has also become clear that, as alloying elements added to Ni-based alloys, it is necessary to suppress the content of components that lower the melting point of the alloy.

Here, the gist of the present invention is a Ni alloy for hot tools having the following composition. Note that all "%" regarding alloy components are "% by weight".

rC+N 0.001~O, 1%, Si 3% or less, M
n is 0.01 to 2% or less, 80 is 3% or less, gate O is 40
% or less, W is less than 15%, Mo+W is 15% or more, P as impurities is 0.02% or less, S is 0.01% or less, the balance is Ni and unavoidable impurities.
Base Alloy 1 The above alloy of the present invention further contains the following elements of the first group,
or/and may contain one or more of the elements of the second group.

Group 1 elements: Cr of 10% or less, preferably 2% or more and 1O% or less.

20% or less, preferably 2% or more and 20% or less of Fe, 1
0% or less, preferably 2% or more and 10% or less of Co, secondary
Group elements: Y, Mg, La, Ce, Z in a total amount of 0.05% or less, preferably o,oos% or more and 0.05% or less
One or more types from r and Ca.

In addition, in the above-mentioned alloy of the present invention, the total amount of C and N is 0.
001-0.05%, Si at Oat% or less, Al at 0.001-0.05%.
25% or less, Mo 15 to 40%, P as an impurity 0.01% or less, S o, oos% or less, and Y,
If the total amount of one or more of Mg, La, Ce, Zr and Ca is 0.01% or less, the melting point and 1 ductility temperature will become higher. Such alloys are particularly suitable as materials for hot-working tools used under harsh conditions.

The characteristics of the alloy of the present invention are that the types and contents of the elements constituting the alloy are appropriately selected, and in particular, Cr, which is added in large amounts as an essential component in conventional hot tools, is Since it greatly lowers the melting point of the alloy, its content is suppressed, and the impurities P and S, which also lower the melting point, are reduced. On the other hand, MO (!: W) content is significantly reduced, which has a remarkable effect of increasing deformation resistance at high temperatures. The major feature is that it contains a specific amount of one kind of Cr.Reducing the content of Cr not only increases the melting point of the alloy, but also forms an oxide film with a thickness of 20 μm or more on the alloy surface. Tools made of such alloys have extremely excellent performance for hot working because they have a large heat insulating effect and also have a lubricating effect.

(Function) Hereinafter, the reason for limiting the chemical composition of the Ni-based alloy for hot working tools of the present invention as described above will be explained together with its function and effect.

C and N: Both C and N are solid solution strengthening elements and have the effect of increasing deformation resistance at high temperatures. To achieve this effect,
It is necessary to contain 0.001% or more of C1N. However, on the other hand, C and N are elements that increase (lower) the melting point of the alloy and also lower the 1 ductility temperature.
If the ductility temperature is low, which is not 0°C or higher, cracking is likely to occur at high temperatures. This ductility temperature becomes higher as the content of C and N decreases. 1 ductility temperature 1300
“To achieve C or higher, C+N should be 0.05% or lower.

Si: SL has a deoxidizing effect and forms an oxide at high temperatures to improve the lubricity and heat insulation properties of the tool surface. However, as the content increases, the melting point and paper temperature decrease, so it is best to keep it below 3%.If it exceeds 3%, the melting point will be less than 1350"C.
For tools used in environments above °C, it is better to keep the Si content below 0.1%.
If the temperature is below, the paper temperature will be 1300°C or higher, 125°C.
The aperture at 0°C is 30% or more. The lower limit of the content is desirably about 0.01% at which the above-mentioned effects appear.

Ale: Mn has the effect of fixing P, which will be described later, and increasing the temperature of the paper, and must be contained in an amount of 0.01% or more to fully obtain this effect. However, if its content exceeds 2%, the melting point will drop significantly.

^J2: Like Si, Ae also has a deoxidizing effect, forms oxides at high temperatures, and has the effect of improving the lubricity and heat insulation properties of the tool surface. In order to obtain such an effect, it is desirable to contain 0.01% or more. But A! Because it lowers the melting point and paper temperature, its content is set to 3% or less.

130 required for tools used in environments above 1200°C
Paper temperature above 0°C and 30°C at 1250°C
% or more, the Al content is preferably 0.25% or less.

MO: Mo is a high melting point metal like W, and when added to a Ni-based alloy, it has the effect of increasing deformation resistance at high temperatures.

However, even if it is added excessively, its effect will be saturated and it will become difficult to ensure a high melting point of the alloy and a high reduction of area at high temperatures. Especially when W is not added, if Mo exceeds 40%, the melting point will be lower than 1350°C, 1250°C.
The aperture at C or higher is less than 30%.

Figure 1 shows the results of investigating the relationship between the Mo content and the melting point in those without and with W added, and Figures 2 and 3 show the same deformation at < 1250°C. This figure shows the results of changes in resistance and changes in aperture.

In the figure, those marked with O are W-free, and those marked with 1 are marked with 1.
It contains 0% W.

From Figures 1 and 3, it can be seen that when Mo content exceeds 40%, the melting point decreases to below 1350"C and the reduction of area rapidly decreases to 30% at 1250°C. It can be seen that the deformation resistance increases with the increase in Mo content from Fig. 2.
%, it can be seen that the effect is saturated.

Therefore, in the present invention, when W is not added, Mo is preferably contained in a range of 15% or more to 40%.

The deformation resistance and aperture shown in FIGS. 2 and 3 are as follows: A test piece of 10 m+mφ was prepared, and strain rate (e): 1. The evaluation was made by measuring the drawing strength and compressive strength when tensile and pressure l1iI tests were carried out under the conditions of O/sec.

W: Like Mo, W has the effect of increasing deformation resistance, so
In the present invention, W is added to complement 10. However, since W is expensive, its content is set to less than 15%.

Even if W is less than 15%, it can be supplemented with Mo to increase the melting point, drawing resistance, and deformation resistance.

In the present invention, as mentioned above, Mo and W are each 40
% or less and less than 15%, but the total amount must be 15% or more.

This is because even in a region where Mo is less than 15%, as long as the total amount with W is 15% or more, the desired melting point, reduction of area, and deformation resistance can be ensured even in alloys within this range.

P and S: Since P and S as impurities both lower the paper temperature, it is desirable that their content be small. If the respective contents are 0.02% or less for P and 0.01% or less for S, the paper temperature can be set to 1250°C or higher. Furthermore, if the content is reduced, the stratus ductility temperature can be increased. Specifically, if P is 0.01% or less and S is 0,00% or less, the stratus ductility temperature can be increased to 1300%. °C or higher.

In addition to the above-mentioned elements, the Ni-based alloy for hot work tools of the present invention consists essentially of Ni. However, in order to further improve its properties, in addition to the above elements, one or more of the following Cr, Fe and CO and/or Y
, Mg, La, , Ce, Zr, and Ca.

The effects of these elements are as follows.

Cr, Fe, and Co: One or more of these elements are added to the Ni-based alloy and have the effect of forming an oxide film having both heat insulation and lubricity on the tool surface. However, for Cr, the content is 1
If it exceeds 0%, not only will the melting point of the alloy drop significantly, but the oxide film formed will be as thin as 20μ or less, and the heat insulation and lubrication effects will drop significantly. For Fe, if it exceeds 20%, it is impossible to ensure a melting point of 1350° C. or higher, and for CO, if it exceeds 10%, oxidation is suppressed, so the oxide film becomes thinner and becomes expensive.

Note that the desirable lower limit of these elements is Cr.

2% for each of Fe and Co.

Y, Mg, La, Ce, Zr and Ca: These elements enter the oxide film formed at high temperatures and make the oxide film denser, preventing cracking and peeling during machining and reducing tool wear. It has the effect of preventing such things. Furthermore, all of these elements are strong deoxidizing agents, and have the effect of improving the toughness of the alloy at room temperature and increasing the permeability temperature.

If you expect such an effect, the total content should be 0゜00
It is desirable to add 0.05% or more, but if the total content of one or more of them exceeds 0.05%, on the contrary, the permeability temperature becomes low.

The present invention will be further explained below with reference to Examples.

(Example) An alloy having the chemical composition shown in Table 1 was melted in a vacuum induction melting furnace, and a rough mold material was produced by hot forging.
After solution heat treatment for 1 to 10 hours at a temperature of 200 to 1250°C, a perforated plug with a diameter of 50 m was fabricated by machining.

As for comparative alloys T and U, after melting, the as-cast alloys were machined into perforated plugs. The conventional materials are all commercially available materials, the symbol X is a low-alloy cast material, and the symbol Y is alloy 718. The former is used to make a perforated plug as it is (as cast), and the latter is forged into a round bar. A perforated plug was fabricated by machining.

When making the perforated plug, a test piece was taken from each alloy,
The melting point, intrinsic temperature, deformation resistance, reduction of area and toughness were investigated. The results are shown in Table 2.

On the other hand, 8011II diameter x 300s - length (7) SO3
304 (deformation resistance: 10 g/thickness at 1200'C was used as the workpiece material, and after heating it to 1200°C, it was made into a seamless steel pipe of 80mm diameter x 7m11 wall thickness using the above-mentioned perforation plug. The number of perforations until it became impossible to perforate was determined.The results are also shown in Table 2.

Note that the melting point was evaluated using the liquidus line. In addition, the normal temperature can be determined by measuring the lowest temperature at which the reduction of area becomes 0% in a tensile test, and the deformation resistance and reduction of area at even higher temperatures can be determined by making a test piece of 10-Fφ and using a Grieple test machine. in,
The toughness can be determined by measuring the drawing strength and compressive strength at 1250°C during tensile and compression tests under the condition of strain rate (ε): 1.0/see.
Charpy impact test piece (2+++II
Each was evaluated by making a U-notch (U-notch) and measuring the absorbed energy at 20'C.

(Hereinafter, blank space) As is clear from Table 2, the Ni-based alloys of the present invention (symbols A-Q) all have a melting point of 1350°C or higher, a melting point of 1250°C or higher,
The normal temperature is more than 1250'C, the reduction is more than 30% and the deformation resistance is more than 15Kgf/mm'', and even 5
Since the toughness is more than Kg-m, when a perforated plug made from these materials was used, even austenitic stainless steel with high deformation resistance could be perforated four times or more.

On the other hand, the comparative alloys (symbols R-W) and conventional alloys (symbols X, Y) have low melting points, low deformation resistance, and permeability temperatures of 1250'C or less. Due to these poor characteristics, cracks occurred during one drilling, and drilling could no longer be continued. Or, it was so worn that it could not be used for the next drilling.

(Effects of the invention) As explained above, the Ni-based alloy of the present invention has a high melting point,
In addition, it has excellent deformation resistance at high temperatures, ductility, and toughness at room temperature, so tools made of this alloy have little melting damage and wear, and have a long life.

For this reason, the Ni-based alloy of the present invention is particularly suitable as a material for hot tools that are processed at high temperatures and that process stainless steel and Ni-based alloys that have high deformation resistance at high temperatures.

[Brief explanation of the drawing]

Figures 1 to 3 show the relationship between Mo content, melting point, deformation resistance at 1250°C, and reduction of area at the same temperature in Ni-based alloys when no W is added and when 10% W is added. This is a graph showing the results of investigating.

Claims (4)

[Claims] (1) C+N 0.001-0.1% by weight, Si
is 3% or less, Mn is 0.01 to 2%, Al is 3% or less,
Mo is 40% or less, W is less than 15%, and Mo+W is 15% or more, P as an impurity is 0.02% or less, S
0.01% or less, the balance being Ni and unavoidable impurities. (2) In weight%, C+N is 0.001-0.1%, Si
is 3% or less, Mn is 0.01 to 2%, Al is 3% or less,
Mo is 40% or less, W is less than 15%, and Mo+W is 15% or more, and further contains one or more of 10% or less Cr, 20% or less Fe, and 10% or less Co, and contains impurities. A Ni-based alloy for hot working tools, containing 0.02% or less of P, 0.01% or less of S, and the balance being Ni and unavoidable impurities. (3) In weight%, C+N is 0.001-0.1%, Si
is 3% or less, Mn is 0.01 to 2%, Al is 3% or less,
Mo is 40% or less, W is less than 15%, and Mo+W is 15% or more, and Y and Mg have a total amount of 0.05% or less
, containing one or more of La, Ce, Zr and Ca, P as an impurity is 0.02% or less, S is 0.01% or less,
A Ni-based alloy for hot tools, the balance being Ni and unavoidable impurities. (4) C+N is 0.001 to 0.1% by weight, Si
is 3% or less, Mn is 0.01 to 2%, Al is 3% or less,
Mo is 40% or less, W is less than 15%, and Mo+W is 15% or more, and furthermore, one or more of 10% or less Cr, 20% or less Fe, and 10% or less Co, and a total amount of 0.0
5 or less of Y, Mg, La, Ce, Zr, and Ca, P as impurities is 0.02% or less, S is 0.01% or less, and the balance is Ni and inevitable impurities. Ni-based alloy for tools.