JPS61143567A - Manufacture of high temperature spring - Google Patents

Abstract

PURPOSE:To maintain a fixed spring strength for a long time in high temp., by applying a process for controlling the majority of metal sructure to equi-axis crystals by soln. heat treating Ni alloy composed of prescribed ratios of C, Mn, Cr, Al, Ti, Nb, Fe, Mo. CONSTITUTION:Ni base ppt. hardened alloy comnposed of, by weight, <=0.1% C, <=1% Si, <=1% Mn, 10-25% Cr, 0.1-1% Al, 0.-2% Ti, 1.5-6% Nb, 2-25% Fe, 2-10% Mo, and the balance Ni is refined. Wire rod, etc. of the alloy is soln. heat treated, to convert the majority of metal structure to equi-axis crystals. This is formed to a prescribed shape to improve spring strength higher than a desired strength. next, it is heated under stress load and stabilizing treated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to springs used for long periods of time at high temperatures in various machines and equipment.

[Technical background of the invention and its problems] High-temperature springs are used in various machines and equipment such as steam turbines, gas turbines, and other internal combustion engines. High-temperature springs that have been used conventionally have zero carbon. IJ or less, silicon 1.0% or less1. Manganese 1.0% or less, chromium 10-20%, aluminum 0.3-1.0%, titanium 2.0-3.0%, niobium 0.5-1.5%, iron 5-1096. remaining nickelyo F
) A wire, bar, or plate material of a precipitated Ni-based precipitation-strengthened alloy is formed into a predetermined groove shape and then subjected to an aging treatment. However, when this conventional spring metal is used at high temperatures, the strength of the spring rapidly decreases over time due to raxation, and there is a drawback that a constant spring strength cannot be maintained at all times. Another drawback is that the spring strength is low in response to the recent increase in temperature and miniaturization of various jaw machines due to improvements in thermal efficiency.

[Purpose of the invention]

The present invention has been made in view of such conventional circumstances, and
An object of the present invention is to provide a method for manufacturing a high-temperature spring that has a higher spring strength than conventional high-temperature springs, has less deformation and lowering of spring strength due to gluing during use, and has excellent strength relaxation resistance.

[Summary of the invention]

The present invention relates to a wire rod of a Ni-based precipitation-strengthened alloy that is a spring material,
There are two steps: solution treatment of bar or plate material to make the majority of its metallographic structure equiaxed, a step of forming it into a shape that has a spring strength greater than the required strength, and a stress-load heating process to obtain the required spring strength. It is characterized by comprising a stabilization process that imparts spring strength, shape, and excellent raxization resistance.

This is a method for producing high-strength, high-temperature springs with high resistance to cracking, and the spring material is carbon 0.1% or less, silicon 1.0% or less, manganese 1.0% or less, and chromium 10-10% by weight.
25%, aluminum 0.1-1.0%, titanium 0.1
~2. , O%, niobium 1.5-6.0%, iron 2-25%
, 2.0 to 10.0% molybdenum and the balance nickel, and is a high-strength, raxation-resistant high-temperature spring that is characterized by having undergone the above-mentioned processes.

Here, the reason for the limitation of the present invention will be explained. First of all, the reason why most of the metal structure is made equiaxed by solution treatment is that if most of the structure is processed by hot forging, hot rolling, hot wire drawing, etc., it is not possible to obtain rakishing properties. It's for a reason. Note that the solution treatment temperature' is 980°C or higher,
Desirably, the temperature is 1.0000C or higher, and some cold working may be added thereafter. Next, the reason why the spring is formed into a shape that has a spring strength higher than the required strength is that it is essential to achieve the required spring strength and shape through stabilization treatment, and it is necessary to mold the spring into the desired shape from the beginning. This is because, in this case, the predetermined spring strength and shape cannot be obtained due to deformation caused by the stabilization process.

Stabilization treatment by stress-load heating is an essential process to ensure that the spring has the required strength, proper shape, and excellent rachisage resistance. This is due to the large changes in spring and spring shape, making it impossible to obtain a high-temperature spring that exhibits stable spring strength over a long period of time.

Note that this stress negative stabilization treatment is preferably performed after the aging treatment, but it may also be performed concurrently with the aging treatment.

Next, the reason for limiting the chemical composition of the spring material is that it can be processed into wire rods, bars, plates, etc., and that it can be easily formed into the desired spring shape. Depends on what you get.

The reason for limiting each component of the chemical composition will be described below.

Carbon is the next necessary element that dissolves in the alloy and improves its strength, and is preferably added in an amount of about 0.02 to 0.06%, but if it is added in a large amount, carbides will precipitate at grain boundaries, resulting in poor intergranular corrosion resistance. Since it impairs toughness, the content should be 0.1% or less.

Silicon is added as a deoxidizing agent during melting, and is preferably contained in a range of about 0.1 to 0.6 silicon, but since adding too much silicon impairs toughness and processability, the silicon content should be 1.0 or less.

Manganese is added as a deoxidizing and desulfurizing agent during melting, and is preferably contained in an amount of about 0.1 to 0.5%. However, even if a large amount is added, the effect will be small, so it should be kept at 171.0 inches or less.

Chromium is an element that improves the strength, oxidation resistance, and corrosion resistance of the alloy, and is preferably in the range of 10 to 25 inches, particularly 15 to 20 degrees. If it is less than 100%, the effect of addition is small;
If it exceeds %t, the processability will be impaired, so it is specified within the above range.

Molybdenum has the effect of improving the strength of the alloy as well as its corrosion resistance, and must be added in an amount of at least 2.0 h. However, if a large amount of addition exceeding 10% is added, processing is required.
It needs to be lower than this because it causes deterioration.

Aluminum is an element that forms an intermetallic compound with nickel, precipitates in the alloy, and improves the strength of the alloy. In this case, if it is less than 0.1%, the effect will be small, and if it is added in a large amount exceeding 10%, the processability will deteriorate, so 0.1 to 1%.
The range of 0 inches is good, and the range of 0.2 to 0.7 inches is particularly desirable.

Titanium, like aluminum, is an element that improves the strength of the alloy, and is added in an amount of 0.1% or more, preferably 0.2% or more.

However, adding a large amount causes poor workability, although there is a balance between aluminum and niobium, so it was set at 2.0%.

Iron is an element that improves the hot forgeability of the alloy. In this case, adding less than 2% will have little effect, and
Addition of more than 5% leads to poor corrosion resistance, so the amount was kept below this.

Niobium, like aluminum and titanium, is an effective element that forms compounds with nickel to improve the wear resistance and strength of alloys. In this case, if it is less than 1.5%, the effect will not be sufficiently obtained, and if it exceeds 6.0%, workability will be impaired like aluminum or titanium, so this range was set.

[Embodiments of the invention]

Example 1 Using a high frequency induction melting furnace, C: 0.31%, 8i:
0.23%, MM: 0.20%, Cr: 18
．． 4%, F'e: 17.5%, Ti2O, 77%.

At: o, 43 yen, Nb: 5.4%, Mo:
Alloy Inborator is made up of 3.6% Ni and the balance is Ni.

Next, this ingot is subjected to hot forging and wire drawing processing.
．． 4 Mi'J wire rod was used.

A part of the wire obtained in this way was cut out, heated at 1020°C for 30 minutes, rapidly cooled, and then cold drawn.1.
It was made of 2mm wire.

Subsequently, a coil spring with a center diameter of 11 mm, a free length of 21.5 mm, an effective number of turns of 4.5 turns, and a total number of turns of 6.5 turns was formed from this wire, and after being exposed to light, it was aged at 718°C for 8 hours and at 621°C for 8 hours. Processed. Further, this coil spring was compressed to a coil length of 12 mm, and then subjected to stabilization treatment at 700° C. for 2.5 hours, and then subjected to a test. In addition, as a result of observing the metal structure of this coil spring, it was found to be an equiaxed crystal with twin crystals.

Comparative Example 1 The above 1.2 mm wire has a center diameter of 11 mm and a free length of 20 mm.
Mi! J % A coil spring having an effective number of turns of 4.5 and a number of turns of the base of 6.5 was molded, and then subjected to aging treatment at 718° C. for 8 hours and at 621° C. for 8 hours, and subjected to a strain test.

Comparative Example 2 Cut out a part of the above-mentioned 1 and 4 mm IJ wire, and
After heating at 4°C for 1 hour and quenching, draw the wire in the cold to form 1
．． It was made of 2mm wire.

Next, after forming a coil with a center diameter of 11 mm, a free length of 21.5 mm, an effective number of turns of 4.5 turns, and a total number of turns of 6.5 turns, heat treatment was performed at 718°C for 8 hours and at 621°C for 8 hours. Furthermore, this coil spring was compressed to a coil length of 12 mm and heated to 600℃.

It was subjected to a stabilization treatment for 1.5 hours and then subjected to a strain test.

Note that the metal structure of this coil spring did not appear to be equiaxed.

Comparative Example 3 Conventional high temperature spring material C: 0.06%, Si20,
13%.

MM: 0.62%, Cr: 15.4%lFe
Near, 2%, Ti: 2.5%, At: 0.8
An alloy consisting of 3% Nb, 0.82% Nb, and the balance Ni was melted in a high frequency induction melting furnace.

The wire was then hot-forged and wire-drawn to form a 1.4 mm wire rod, which was then heated at 1093°C for 30 minutes and rapidly cooled. Subsequently, this wire was cold-drawn into a 1.2 mm wire, and the coil was made into a wire with a center diameter of 11 mm and a free length of 20 mm.

The coil spring was formed into a coil spring having an effective number of turns of 4.5 turns and a total number of turns of 6.5 turns, and was subjected to an aging treatment at 650° C. for 5 hours and subjected to a test.

The test was carried out at 60°C and 70°C with the compression coil springs of Example 1 and Comparative Examples 1 to 3 compressed and fixed to 12 mm.
The spring was placed in a furnace at 0°C, heated for a predetermined period of time, then taken out to room temperature, and after removing the load, the free length of the spring and the load required to compress the spring length to 12 mm were measured. Note that the metal structure of this spring was an equiaxed crystal. The test results are shown in Figures 1 and 2.

As is clear from the figure, the high-strength, high-temperature spring of the present invention is more durable than the spring of the comparative example, even when used at high temperatures and under stress for a long time.

It can be seen that the coil length and spring strength hardly change, and the spring has excellent resistance to rachising and is industrially useful because it can always maintain a constant spring strength for a long time.

[Brief explanation of drawings]

FIGS. 1 and 2 show the high-strength, high-temperature raking spring according to the present invention and the spring of the comparative example, which are loaded and compressed to a spring length of 12 mm. What is the free spring length and spring length when the load is removed after heating the spring? FIG. 3 is a characteristic diagram showing measurement results necessary for compression to 12 mm. Figure 1 P=T(fagt+zD)・rff'T; Figure 2

Claims (1)

[Scope of Claims] 1. Process of solution-treating a wire, rod or plate material of Ni-based precipitation-strengthened alloy, which is a spring material, to make the majority of its metallographic structure equiaxed, and to obtain the required spring strength. A method for producing a high-temperature spring, comprising a step of forming the spring into a shape that has a higher strength, and a step of stabilizing the spring by stress-load heating. 2. The spring material contains less than 0.1% carbon by weight,
Silicon 1.0% or less, manganese 1.0% or less, chromium 10
~25%, aluminum 0.1-1.0%, titanium 0.
1-2.0%, niobium 1.5-6.0%, iron 2-25%
, 2.0 to 10.0% molybdenum, and the balance nickel.