JPH0726148B2 - Method for manufacturing welded structural steel with high vibration damping capacity - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a welded structural steel suitable for use as a member of a welded structure, and particularly to a tensile steel having a high vibration damping ability capable of suppressing vibration and noise. The present invention intends to propose a method for advantageously manufacturing welded structural steel having a strength of 41 kgf / mm ² or more.

In recent years, particularly vibrations caused by the movement of heavy vehicles such as railway bridges and road bridges for automobiles, vibrations generated in facilities such as factories and workshops located near the residential area, or mechanical structures The noise that accompanies the noise is considered to be a social problem.

As a countermeasure for this, various methods such as using a sound absorbing material, a sound insulating material, or a vibration insulating material, and increasing the rigidity of the structure to avoid resonance are taken, but in practice, Vibration, which is a noise source, is complicated, and it is generally difficult to eliminate its cause.

Therefore, a so-called material damping method, which is a method for imparting a vibration damping characteristic, that is, a vibration damping property to the material itself as a structural member, to drastically improve the vibration and noise of the structure, has attracted attention.

The damping performance of an alloy here is generally determined by its internal friction (Q ^-1 ).
Often expressed in size. This is an index of the amount of energy lost per strain amplitude cycle, Q ^-1
The alloy having a larger value has a higher rate of converting vibration energy into heat energy inside the alloy, and has a higher vibration damping effect.

(Prior Art) Several proposals have already been made for the steel material to which the above-mentioned vibration damping property is imparted.

For example, Japanese Examined Patent Publication (Kokoku) 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 cannot be used as a structural member because of its low strength and poor toughness.

Further, JP-A-52-144317 discloses a vibration-proof steel in which 3 to 40 wt% (hereinafter referred to simply as%) Cr and Ti and Al are further added, and JP-A-57-181360 discloses a vibration-proof steel. A damping thick steel sheet containing -9% Al and Japanese Patent Publication No. 57-22981 disclose a damping steel containing 4-7% Cr and 3-5% Al, respectively. .

However, all of the steel materials have problems in weldability, need to improve toughness, and have insufficient vibration damping,
There is a problem that the alloy component is added in a large amount and is expensive.

In addition to the above, Japanese Patent Application Laid-Open No. 53-1621 proposes 18-8 stainless steel which is provided with vibration damping characteristics by grain boundary oxidation, but has a problem in weldability and is not suitable for mass production. There was a problem.

(Problems to be solved by the invention) High tensile strength that has high vibration damping property, has the weldability required as a steel material for welded structure, and has excellent toughness, is relatively inexpensive, and has excellent vibration damping characteristics. It is an object of the present invention to propose a manufacturing method capable of stably mass-producing a welded structural steel of 41 kgf / mm ² or more on an industrial scale.

(Means for Solving the Problem) In the steel of ferromagnetic material, strain (magnetostriction) is generated in the crystal lattice in response to the uniform magnetic spins. It is divided.

When an external force (vibration) is applied to such steel, the magnetic domain wall moves due to the interaction with the magnetostriction. Then, an eddy current is generated so as to cancel the movement of the domain wall, that is, the change in the magnetization, which occurs inside the ferromagnetic body, and the eddy current causes strain through magnetostriction. Since the phase of this strain is delayed with respect to the external force, a vibration damping characteristic appears due to so-called magneto-dynamic hysteresis type internal friction. Regarding this, for example, it is known that pure iron is relatively excellent in vibration damping property.

However, pure iron is low in strength and cannot be applied as a structural member, and it is hard to say that its vibration damping performance is sufficient.

Therefore, the inventors of the present invention can manufacture an industrially mass-produced steel material having strength and toughness as a steel material for welded structure and also having a vibration damping capacity higher than that of pure iron and having stable characteristics. As a result of various studies of the method, hot rolling under appropriate conditions and performing a predetermined intermediate heat treatment,
We have found that it is essential to achieve the above objectives.

That is, the present invention, C: 0.02% or less, Si: 0.02% or less, M
n: 0.08% or less, Cu: 0.05 to 1.50%, Al: 1.0 to 7.0% and N:
A steel material containing 0.0080% or less and the balance Fe and unavoidable impurities is heated to 1000 to 1300 ° C, and then hot-rolled to a rolling finish temperature of 650 to 900 ° C, followed by a cooling rate of 0.1 ° C / Cool to room temperature above s for 800-1300
Of the steel for welded structure with high vibration damping capability, characterized by performing an intermediate heat treatment of cooling at a cooling rate of 1.0 ° C / s or less after heating and holding at ℃, and then performing a final heat treatment of holding at 450 to 700 ° C. Manufacturing method (first invention) and C: 0.02% or less, Si: 0.02% or less, Mn: 0.08% or less, Ni: 0.0
5 to 1.50%, Cu: 0.05 to 1.50%, Al: 1.0 to 7.0% and N: 0.0
A steel material containing 080% or less and the balance consisting of Fe and unavoidable impurities is heated to 1000 to 1300 ° C, respectively, and then hot-rolled to a rolling finish temperature of 650 to 900 ° C, followed by a cooling rate of 0.1 ° C. Cools to room temperature above / s and then 800
For welded structures with high vibration damping capability, characterized by performing an intermediate heat treatment of cooling at a cooling rate of 1.0 ° C / s or less after holding at ~ 1300 ° C, and then performing a final heat treatment at 450 to 700 ° C It is a manufacturing method (2nd invention) of steel.

(Operation) The reason for limiting the component composition range in the present invention will be described first.

C is contained as a strengthening component in ordinary steel, but in the steel of the present invention, since the strengthening action by precipitation of Cu is utilized, the amount as a strengthening component is not necessary. Rather, the C content is
If it exceeds 0.02%, the vibration damping property deteriorates, so it was limited to 0.02% or less.

If Si is contained in excess of 0.02%, the vibration damping property deteriorates, so 0.02% was made the upper limit.

Mn adversely affects toughness when strengthened by addition of Cu, so the lower the content, the better. The upper limit of the content is 0.08%, so Mn was limited to 0.08% or less.

Cu is precipitated as fine ε-Cu by aging treatment,
It is a component that strengthens steel, and is used for steel with a reduced Mn content.
By including Cu, it is possible to achieve both strength and toughness without impairing the vibration damping property. Therefore, although it is an essential component in the present invention, its effect is poor if the Cu content is less than 0.05%, while if it exceeds 1.50%, it may cause hot cracking, so 0.05-1.50.
The range is%.

Al reduces the Mn to 0.08% or less, and improves vibration damping characteristics by including it in steel with a composition of almost pure iron, but if the content is less than 1.0%, it has no effect, while 7.0% If the content of Al exceeds 1.0, the toughness of the welded part deteriorates, so the Al content was made 1.0 to 7.0%.

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

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

Ni can suppress the tendency of hot cracking resulting from the addition of Cu without impairing the vibration damping property. If the Ni content is less than 0.05%, the effect is poor, while if it exceeds 1.50%, the disadvantage of being uneconomical occurs.
The range was 1.50%.

In addition to the above components, in the present invention, P as an impurity component,
S can be allowed up to 0.01% and 0.005%, respectively.

P deteriorates the vibration damping property as its content increases, but up to 0.01% is acceptable, so the upper limit is made 0.01%.

S, like P, is a component that is not preferable for damping properties, and if its content exceeds 0.005%, the damping properties are particularly deteriorated. Therefore, the upper limit of the S content is 0.005%.

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

The main part of the manufacturing method of the present invention is: (1) selecting hot rolling / cooling conditions in which Cu precipitation does not occur at the end of hot rolling and sufficient rolling strain is accumulated in a steel material; ) In the next intermediate heat treatment, the conditions are selected so that the crystal grains are sized and coarsened or the solid solution components are homogeneously dissolved, and the cooling strain thereafter is reduced as much as possible. The accumulation of rolling strain due to the hot rolling and cooling has the effect of promoting grain growth during this intermediate heat treatment. The cooling end temperature after this intermediate heat treatment is the heat treatment temperature to be performed next (450 to 700 ° C).
To any temperature from room temperature to room temperature.

(3) The final heat treatment is a treatment for promoting Cu precipitation and is performed for the purpose of ensuring strength.

From this, each processing condition was limited as follows.

The heating temperature of the steel material prior to hot rolling was set to a temperature at which hot rolling was possible, and 1000 to 1300 ° C. in order to coarsen the crystal grains and homogenize the solid solution components. Heating temperature is 1000 ℃
If the temperature is less than 1, it will be one of the causes of the variation of the vibration damping performance of the final product due to the mixing of crystal grains, and if it exceeds 1300 ° C, the oxidation of the steel surface will be remarkable and it will be economically disadvantageous.

The rolling finishing temperature of hot rolling suppresses the precipitation of Cu,
The temperature was set to 650 to 900 ° C in order to accumulate rolling strain. 65
If the low temperature finish is less than 0 ° C., precipitation of Cu occurs and a mixed grain structure is likely to be formed, which becomes a factor of destabilizing the vibration damping property. In addition, low-temperature finishing is not preferable because it takes longer time for rolling and increases manufacturing cost. On the other hand, when the rolling finishing temperature exceeds 900 ° C, the accumulation of rolling strain in the material to be rolled is insufficient, and it is difficult to efficiently achieve grain growth and coarsening in the subsequent intermediate heat treatment.

Cooling subsequent to hot rolling requires a cooling rate of 0.1 ° C / s or higher for the purpose of suppressing Cu precipitation and freezing of rolling strain.
The upper limit of the cooling rate is not particularly limited in this invention. The industrially feasible range is about 60 ° C / s or less.

The temperature of the intermediate heat treatment is 800 to 1300 ° C. for the purpose of grain size regulation and coarsening or complete removal of rolling strain. A
When the content of l is less than 1 to 2%, the upper limit is preferably 900 to 950 ° C, which is a ferrite single phase. Steel containing Al of less than 1 to less than 2% undergoes ferrite → austenite transformation at 950 to 1000 ° C., resulting in a fine-grained structure, and vibration damping performance deteriorates. In addition, when 2% or more of Al is contained, the higher the processing temperature is, the more it becomes a ferrite single phase, and the higher the processing temperature is, the better the vibration damping property is. However, the upper limit is 1300 ° C from the surface properties after processing and industrial economical efficiency. And Further, if the intermediate heat treatment temperature is less than 800 ° C, it is difficult to completely remove the rolling strain, and the crystal grain coarsening is not sufficient, so that the vibration damping property deteriorates. The heating and holding time is not particularly limited because it depends 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./s or less in order to prevent introduction of strain due to uneven cooling at each position. The cooling end temperature is not particularly limited, but an arbitrary 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 due to the precipitation of ε-Cu, but the precipitation effect is not sufficient at temperatures below 450 ° C and above 700 ° C, so the range was set to 450 to 700 ° C. The holding time is not particularly limited because it depends on the heat treatment temperature and the thickness of the target steel as in the intermediate heat treatment,
It is preferable to hold it for about 1 hour.

The material of the present invention can be made into a thick steel plate by ordinary melting, casting and rolling. In addition to thick steel plates, thin steel plates,
It can also be used for shaped steel, steel bars, wires and the like.

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

Each of these steels was subjected to hot rolling, intermediate heat treatment and final heat treatment under various conditions. The steel plate thickness was 25 mm, and the cooling rate was variously changed by adjusting the concentration of the refrigerant and using a heat insulating material.

The mechanical properties and damping properties (Q ^-1 ) of each of the obtained steel sheets were examined. For the mechanical properties, a test piece was sampled from the central part of the plate thickness, and for the damping property, a strip-shaped sample piece having a thickness of 1.5 mm was sampled from the central part of the plate thickness and measured.

Rolling conditions of each steel, heat treatment conditions and the obtained mechanical properties,
The damping characteristics are summarized in Table 2.

In Table 1, Steels A to C are steels having the composition of the present invention, and Steels D to F are comparative steels having compositions outside the range of the composition of the present invention. The categories in Table 2 are those in which the applicable examples of the present invention are marked with a circle and the comparative examples are marked with a cross.

As is clear from Table 2, all of the conforming examples satisfied the mechanical properties required for the steel plate for welded structure, and the internal friction Q ^-1 was remarkably improved as compared with the comparative example.

Only when the composition of the steel is within the scope of the present invention and the manufacturing conditions are adapted to the present invention, Q ^-1 is remarkably improved.

Next, the toughness of the welded portion 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 notching the joint bond.

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

(Effects of the Invention) The steel material manufactured by the manufacturing method of the present invention has sufficient strength, toughness and weldability comparable to those of conventional structural materials, has a high vibration damping capability, and is industrially easy. Can be manufactured. The steel material of the present invention can replace the conventional steel material in any place of the machine structure, and can surely reduce the vibration and noise of the structure, which is extremely useful industrially.

Claims (2)

[Claims] 1. C: 0.02 wt% or less, Si: 0.02 wt% or less, Mn: 0.08 wt% or less, Cu: 0.05 to 1.50 wt%, Al: 1.0 to 7.0 wt% and N: 0.0080 wt% or less However, the balance is a steel material consisting of Fe and unavoidable impurities, heated to 1000 to 1300 ° C, then hot-rolled to a rolling finish temperature of 650 to 900 ° C, and then cooled to room temperature at a cooling rate of 0.1 ° C / s or more. High vibration damping characterized by performing cooling, then heating and holding at 800-1300 ° C, intermediate heat treatment for cooling at a cooling rate of 1.0 ° C / s or less, and final heat treatment at 450-700 ° C. Of manufacturing welded structural steel having high performance. 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: 1.0 to 7.0 wt% and A steel material containing N: 0.0080 wt% or less and the balance Fe and unavoidable impurities is heated to 1000 to 1300 ° C, and then hot-rolled to a rolling finish temperature of 650 to 900 ° C, followed by a cooling rate. After cooling to room temperature at 0.1 ℃ / s or more, then heat and hold at 800 to 1300 ℃, then perform intermediate heat treatment to cool at a cooling rate of 1.0 ℃ / s or less, then perform final heat treatment at 450 to 700 ℃ A method for manufacturing steel for welded structures having a high vibration damping ability, which is characterized by the above.