JPH0480320A - Production of steel for welded structure having high vibration damping capacity - Google Patents

Abstract

PURPOSE:To stably mass-produce a steel for welded structure excellent in toughness and vibration damping capacity by limiting respective contents of Si and Mn in a steel and adding proper amounts of Cu and Al. CONSTITUTION:A steel stock having a composition consisting of, by weight, <=0.02% C, <=0.02% Si, <=0.08% Mn, 0.05-1.50% Cu, 1.0-7.0% Al, <=0.0080% N, and the balance Fe with inevitable impurities is heated to 1,000-1,300 deg.C and hot-rolled at 650-900 deg.C rolling finishing temp., followed by cooling down to room temp. at >=0.1 deg.C/s cooling rate. Subsequently, the resulting plate is heated and held to and at 800-1,300 deg.C and cooled at <=1.0 deg.C/s cooling rate to undergo intermediate heat treatment and held at 450-700 deg.C to undergo the final heat treatment. If necessary, 0.05-1.50% Ni is incorporated into the above steel composition. This steel product can be used as substitutes for conventional steel products in all parts of machine structure and can reduce the vibration and noise of the structure with certainty.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to welded structural steel suitable for use as members of welded structures, and particularly to tensile structural steel having high vibration damping ability capable of suppressing vibration and noise. This paper attempts to propose a method for advantageously producing welded structural steel having a strength of 41 kgf/mm2 or more.

In recent years, vibrations occurring in facilities or mechanical structures such as factories and workshops located close to residential areas, including intense vibrations caused by the movement of heavy passing vehicles such as railway bridges and road bridges for automobiles, have been increasing. There is a significant tendency for the accompanying noise to be considered a social problem.

As countermeasures for this, various methods have been taken such as using sound absorbing materials, sound insulating materials, vibration insulating materials, and increasing the rigidity of the structure to avoid resonance. Vibration as a source of noise is complex, and it is generally difficult to eliminate its causes.

Therefore, the so-called material damping method is attracting attention, which is a method that attempts to drastically improve the vibration and noise of a structure by imparting vibration damping properties to the material itself as a structural member.

Here, the damping performance of an alloy is generally determined by its internal friction (Q-'
) is often expressed by the size of This is an index of the amount of energy lost per cycle of strain amplitude, and Q
An alloy with a large value of -' has a large proportion of converting vibrational energy into thermal energy within the alloy, and has a high vibration damping effect.

(Prior Art) Several proposals have already been made regarding steel materials provided with the above-mentioned vibration damping properties.

For example, Japanese Patent Publication No. 60-26813 proposes a method for producing a vibration-proof steel material having a low yield point and coarse grains.

However, this steel material has low strength and poor toughness, so it cannot be used as a structural member.

Furthermore, in Japanese Patent Application Laid-open No. 52-144317, 3 to 40-
Anti-vibration steel with tχ (hereinafter simply expressed as %) Cr further added with Ti and AI is disclosed in JP-A-57-181360, and a thick anti-vibration steel plate containing 1.5 to 9% AI is disclosed.
And, in Japanese Patent Publication No. 57-22981, 4 to 7% C
Steel materials having vibration damping properties having a vibration damping property of 3 to 5% are disclosed.

However, all steel materials have problems with weldability, require improvement in toughness, and lack sufficient vibration damping properties.
The problem remains that a large amount of alloying components are added and it is expensive.

The above-mentioned JP-A-53-1621 proposes 18-8 stainless steel that has been given vibration damping properties through grain boundary oxidation, but it has problems with weldability and is not suitable for mass production. There was a problem.

(Problem to be solved by the invention) A relatively inexpensive material with high vibration damping properties, weldability required as a welded structural steel material, excellent resistance, and tensile strength with excellent vibration damping properties. It is an object of the present invention to propose a manufacturing method that can stably mass-produce welded structural steel of 41 kgf/nym'' or more on an industrial scale.

(Means for solving the problem) Now, in ferromagnetic steel, distortion (f61 strain) occurs in the crystal lattice in response to the alignment of magnetic spins, and mainly due to this effect, the internal It is divided into magnetic domains.

When external force (vibration) is applied to such steel, the magnetic domain walls move due to interaction with magnetostriction. Then, an eddy current is generated to cancel out the movement of the magnetic domain wall, that is, the change in magnetization, which occurs inside the ferromagnetic material, and this eddy current causes distortion through magnetostriction. Since the phase of this strain lags behind the external force, vibration damping characteristics are achieved by so-called magneto-mechanical hysteresis type internal friction. Regarding this, for example, it is known that pure iron has relatively excellent vibration damping properties.

However, pure iron has low strength and not only cannot be used as a structural member, but also has insufficient vibration damping performance.

Therefore, the inventors developed a steel material that has the strength and toughness of a welded structural steel material, and also has a higher vibration damping ability than pure iron, which can be industrially mass-produced and has stable characteristics. After examining various methods, we found that hot rolling can be carried out under appropriate conditions and a prescribed intermediate heat treatment can be carried out.
We have obtained knowledge that is essential to achieving the above objectives.

That is, in this invention, C: 0.02% or less, Si: 0.
0.02% or less, Mn: 0.08% or less, Cu: 0
．． 05 to 1.50%, ^1: 1.0 to 7.0%, and N: 0.0080% or less, with the balance consisting of Fe and inevitable impurities.
After heating to 800 to 1,300 degrees Celsius, hot rolling is carried out at a rolling finishing temperature of 650 to 900 degrees Celsius, followed by cooling to room temperature at a cooling rate of 0.1 degrees C/s or more, and then heating and holding at 800 to 1,300 degrees Celsius. A method for producing copper for welded structures having high vibration damping ability, characterized by performing an intermediate heat treatment of cooling at a cooling rate of 1.0 °C/s or less, and then a final heat treatment of maintaining the temperature at 450 to 700 °C (No. 1 invention) and C: 0.02% or less, Si: 0.02% or less, M
n: 0.08% or less, Ni: 0.05 to 1.5
0%, Cu: 0.05-1.50%, Al: 1.0
~7.0% and N: 0.0080% or less,
The steel material, the remainder of which is Fe and unavoidable impurities, is heated to 1000 to 1300"C, then hot rolled to a finishing temperature of 650 to 900C, followed by cooling at a cooling rate of 0.1C/s or higher. Cool to room temperature, then heat and maintain at 800-1300°C, cooling rate 1.0°C/
After performing an intermediate heat treatment of cooling at a temperature of 450 to 70
A method for producing copper for welded structures having a high vibration damping ability, which comprises performing a final heat treatment to maintain the temperature at 0°C (second invention)
It is.

(Function) First, the reason for limiting the component composition range in this invention will be explained.

C is contained as a reinforcing component in ordinary steels, but in the steel of the present invention, since the reinforcing effect of Cu precipitation is utilized, the amount as a reinforcing component is not necessary.

Rather, if the C content exceeds 0.02%, the vibration damping properties will deteriorate, so it is limited to 0.02% or less.

When Si is contained in an amount exceeding 0.02%, vibration damping properties are deteriorated, so the upper limit is set at 0.02%.

Since Mn has a negative effect on toughness when reinforcing by adding Cu, the lower the content, the better.The upper limit of the content is 0.08%, so it was limited to 0.08% or less.

Cu is a component that strengthens steel by precipitating as fine ε-Cu during aging treatment. By adding Cu to steel with a reduced Mn content, it can increase strength without impairing vibration damping properties. It is possible to achieve both toughness and toughness. Therefore, although Cu is an essential component in this invention, if the Cu content is less than 0.05%, the effect will be poor;
If the content exceeds 50%, hot cracking may occur, so the content is set in the range of 0.05 to 1.50%.

AI improves vibration damping properties by reducing Mn to 0.08% or less and including it in steel that has a composition of almost pure iron, but if the content is less than 1.0%, the effect is low. Without,
On the other hand, if the Al content exceeds 7.0%, the toughness of the weld zone deteriorates, so the AI content was set in the range of 1.0 to 7.0%.

A lower N content is preferable from the viewpoint of the toughness of the base metal and welded part, and the allowable upper limit is 0.0080%.

In the second invention, the steel of this invention further contains 0.05 to 1.50% Ni in addition to the above components.

Ni can suppress the tendency of hot cracking resulting from the addition of Cu without impairing vibration damping properties. The amount of Ni is 0.
If it is less than 0.5%, the effect is poor, while 1.50%
Ni
The content was in the range of 0.05 to 1.50%.

In addition to the above components, in this invention, impurity components include P,
S is allowed up to 0.01% and 0.005%, respectively.

P deteriorates the damping properties as its content increases, but it is permissible up to 0.01%, so the upper limit is set at 0.01%.

Like P, S is a component unfavorable for damping properties, and when its content exceeds 0.005%, damping properties are particularly deteriorated. Therefore, the upper limit of the S content is o, oos%.

Next, the reasons for limiting the rolling conditions and heat treatment conditions will be explained below.

The main parts of the manufacturing method of this invention are as follows: (1) Select hot rolling/cooling conditions under which no Cu precipitation occurs at the end of hot rolling and sufficient rolling strain is accumulated in the steel material; (2) ) In the next intermediate heat treatment, conditions are selected to reduce the subsequent cooling strain as much as possible by aiming to regularize and coarsen the crystal grains and to make the solid solution components into a homogeneous solid solution.

Note that the accumulation of rolling strain due to the hot rolling and cooling described above has the effect of promoting grain growth during this intermediate heat treatment. The cooling end temperature after this intermediate heat treatment may be any temperature from the next heat treatment temperature (450 to 700°C) to room temperature.

(3) The final heat treatment is a treatment to promote Cu precipitation, and is carried out for the purpose of ensuring strength.

From this, each treatment condition was limited as follows.

The heating temperature of the steel material prior to hot rolling was set at 1,000 to 1,300° C. in order to enable hot rolling and to coarsen crystal grains and homogeneously form a solid solution component. If the heating temperature is less than 1000℃, mixing of crystal grains will occur, which is one of the causes of variations in the damping performance of the final product, and 13
If the temperature exceeds 00°C, the oxidation of the copper surface will be significant and it is also economically disadvantageous.

The finishing temperature of the hot rolling was set in a range of 650 to 900° C. in order to suppress Cu precipitation and accumulate rolling strain. When finishing at a low temperature of less than 650° C., Cu precipitation occurs and a mixed grain structure tends to occur, which becomes a factor in destabilizing vibration damping properties. Furthermore, low-temperature finishing is not preferred because it increases the time required for rolling and increases manufacturing costs.

When the finishing temperature of square rolling exceeds 900° C., rolling strain is insufficiently accumulated in the rolled material, and it is difficult to efficiently achieve grain growth and coarsening in the subsequent intermediate heat treatment.

Cooling subsequent to hot rolling is aimed at suppressing Cu precipitation and freezing rolling strain, and requires a cooling rate of 0.1° C./s or more. Note that the upper limit of the cooling rate is not particularly limited in this invention. The industrially practicable range is 6.
It is about 0°C/s or less.

The temperature of the intermediate heat treatment is 800 to 1300° C. for the purpose of regulating and coarsening the crystal grains and completely removing rolling strain.

In addition, when containing less than 1 to 2% of AI, the upper limit is preferably 900 to 950°C, which results in a single phase of ferrite. 1~
In steel containing less than 2% AI, ferrite → austenite transformation occurs at 950 to 1000°C, resulting in a fine-grained structure and a decrease in damping performance.

In addition, when it contains 2% or more of ^1, it becomes a single phase of ferrite, and the higher the treatment temperature, the better the vibration damping property will be improved. ℃. Furthermore, if the intermediate heat treatment temperature is less than 800° C., it is difficult to completely remove rolling strain, and crystal grain coarsening is not sufficient, resulting in deterioration of vibration damping properties. The heating holding time is not particularly limited as it varies depending on the heat treatment temperature and the thickness of the target steel, but it is preferably held for 1 hour or more.

Cooling after the intermediate heat treatment is performed at a cooling rate of 1.0° C. or higher to prevent distortion from being introduced due to uneven cooling at each location. The cooling end temperature is not particularly limited, but any temperature from the subsequent final heat treatment temperature range (450 to 700°C) to room temperature is desirable.

The final heat treatment is carried out for the purpose of increasing the strength by precipitation of ε-Cu, but since the precipitation effect is not sufficient below 450°C and above 7αO'C, the temperature was set in the range of 450 to 700°C. Note that this holding time is not particularly limited because it varies depending on the heat treatment temperature and the thickness of the target steel, similarly to the intermediate heat treatment, but it is preferably held for about 1 hour.

The material of this invention can be made into a thick steel plate by conventional melting, casting and rolling. In addition to thick steel plates, thin steel plates,
It can also be used for shaped steel, steel bars, wire rods, etc.

(Example) Steels having various component compositions shown in Table 1 were melted and cast according to conventional methods.

These masterpieces were subjected to hot rolling, intermediate heat treatment and final heat treatment under various conditions. The thickness of the steel plate was 25 mm, and the cooling rate was varied by adjusting the concentration of the refrigerant and using a heat insulating material.

Mechanical properties and damping properties (Q-
') was investigated. Mechanical properties were measured by taking a test piece from the center of the plate thickness, and damping properties by taking a 1.5 m thick strip-shaped test piece from the center of the plate thickness.

Excellent rolling conditions, heat treatment conditions and obtained mechanical properties,
The attenuation characteristics are summarized in Table 2.

In Table 1, steels A-C are steels having the composition of the present invention, and steels D-F are comparative steels having compositions outside the composition range of the present invention. In the classification in Table 2, examples conforming to the present invention are indicated by an O mark, and comparative examples are indicated by an X mark.

As is clear from Table 2, all of the conforming examples satisfy the mechanical properties required for welded structural steel plates, and the internal friction Q-' is significantly improved compared to the comparative example.

Q ratio can be significantly improved only when the chemical composition of the steel is within the range of this invention and the manufacturing conditions are compatible with this invention.

Next, the toughness of the welded part was measured, and the obtained results are shown in Table 3. Welding was performed by submerged arc welding with a heat input of 10 kJ/mm, and the test was conducted by making a notch in the joint bond.

Table 3 From Table 3, it can be seen that the conforming example has a weld absorption energy that can be used for welded structures.

(Effects of the Invention) The steel manufactured by the manufacturing method of the present invention has sufficient strength, toughness, and weldability comparable to conventional structural materials, has high vibration damping ability, and is easy to manufacture industrially. production is possible. This copper material can replace conventional steel materials in all parts of mechanical structures, and can reliably reduce vibration and noise in structures, making it extremely useful industrially.

Claims (1)

[Claims] 1. C: 0.02wt% or less, Si: 0.02wt% or less, Mn: 0.08wt% or less, Cu: 0.05-1.50wt%, Al: 1.0-7 A steel material containing 0.0wt% or less and N: 0.0080wt% or less, with the remainder consisting of Fe and unavoidable impurities, is heated to 1000 to 1300°C, and then rolled to a finishing temperature of 65°C.
Hot rolling is carried out at 0 to 900°C, followed by cooling to room temperature at a cooling rate of 0.1°C/s or more, then heated and held at 800 to 1300°C, and then at a cooling rate of 1.
A method for manufacturing welded structural steel having high vibration damping ability, which comprises performing an intermediate heat treatment of cooling at 0° C./s or less, and then performing a final heat treatment of maintaining the steel at 450 to 700° C. 2, C: 0.02 wt% or less, Si: 0.02 wt% or less, Mn: 0.08 wt% or less, Ni: 0.05 to 1.50 wt%, Cu: 0.05 to 1.50 wt%, Al: A steel material containing 1.0 to 7.0 wt% and 0.0080 wt% or less of N, with the remainder consisting of Fe and unavoidable impurities is heated to 1000 to 1300°C, and then rolled to a finishing temperature of 65°C.
Hot rolling is carried out at 0 to 900°C, followed by cooling to room temperature at a cooling rate of 0.1°C/s or more, then heated and held at 800 to 1300°C, and then at a cooling rate of 1.
A method for manufacturing welded structural steel having high vibration damping ability, which comprises performing an intermediate heat treatment of cooling at 0° C./s or less, and then performing a final heat treatment of maintaining the steel at 450 to 700° C.