KR20120133745A - Producing method for non quenched and tempered steel product - Google Patents

Abstract

PURPOSE: A method for manufacturing microalloyed steel products is provided to improve the strength of the microalloyed steel products through refining and work hardening due to quenching and warm coining. CONSTITUTION: A method for manufacturing microalloyed steel products comprises the steps of: heating steel to 1150-1250°C, hot-forming the steel to obtain a volume ratio of 120% or less, quenching the steel to 650-700°C at a cooling rate of 10°C/s or greater, and warm-coining the steel at a temperature of 600°C or higher. [Reference numerals] (AA) Development process; (BB) Hot forging; (CC) Buster(Volume ratio: 140% ↓); (DD) Blocker(Volume ratio: 130% ↓); (EE) Finisher(Volume ratio: 120% ↓);(FF) Rapid cooling(nitrogen gas)(-680°C, 10°C/sec ↑); (GG) Warm coining(600-680°C, Volume ratio: 100%); (HH) Warm keeping furnace(600°C, 20 minutes &uarr); (II) Shot blast

Description

Manufacturing Method of Non-Steel Steel Products {PRODUCING METHOD FOR NON QUENCHED AND TEMPERED STEEL PRODUCT}

The present invention relates to a method for producing a non-coated steel product which can improve the strength of the non-coated steel product and significantly shorten the manufacturing process.

As a method of improving the strength of a product including a connecting rod composed of a non-coarse steel composition which is not subjected to temper heat treatment, an increase in strength has been sought mainly by the addition of an alloying component and by the refinement of the structure by controlled cooling after forging.

However, in the former case, the addition of alloying components leads to an increase in the price of materials, which limits the addition of elements of increasing strength. there was.

As can be seen in Figure 1, the conventional connecting rod forging, when the deformation is completed in the hot state, after performing the shot blast in the cold state (coining) in the coining (coining) process to correct the bending and large / small end dimensions, generated during coining After the residual stress was removed by heat treatment separately, descaling and shot surface were smoothed by shot blasting. However, a double shot blast process and residual stress relief heat treatment process were added, resulting in a price increase. In addition, the strength increase by the process was insignificant in effect.

In the conventional case, the forming process by forging is a process of adding a rolled material to the upper and lower molds of a product shape to apply a pressure to the press to form the shape. As shown in FIG. When press 3 times, Buster-Blocker-Finisher process is used. When the final product volume is 100%, 120 ~ 130% in Buster process, 110 ~ in Blocker process. 120%, the finisher process was to have a final volume ratio of 100%. For reference, the buster process is to compress the material significantly to remove scale and maintain proper forging ratio. The blocker process smoothes the finisher process by bringing the busted material closer to the finisher shape. The volume ratio for each stage is determined through simulation such as molding analysis in the mold design stage.

The shot blasting process is a process of removing scale and black skin by spraying fine particles of metal or nonmetal called shot or grit on the surface of the product, and cold coining is performed to cool the product after forging, as shown in FIG. It is a process to control the bending correction and the large end and the small end thickness by placing it on the coining mold and pressing it at a constant pressure. This is to improve bending parts such as connecting rods rather than forming a new shape.

The matters described as the background art are only for the purpose of improving the understanding of the background of the present invention, and should not be taken as acknowledging that they correspond to the related art already known to those skilled in the art.

The present invention has been proposed to solve this problem, and the strength is increased by the microstructure of the rapid cooling and the work hardening by warm coining, and the productivity and cost reduction by the continuous stress relief process and the shot blast process deletion It is an object of the present invention to provide a method for manufacturing non-coated steel products.

According to the present invention, there is provided a method of manufacturing a non-coated steel product according to the present invention, which comprises: a hot forging step of heating a steel material at 1150 to 1250 ° C. until the volume ratio is 120% or less; A quenching step of rapidly cooling the material processed in the hot forging step to 650 to 700 ° C. at a cooling rate of 10 ° C./s or more; And a warm coining step performed at a temperature of 600 ° C. or higher.

Alternatively, the hot forging step of heating the steel to 1150 ~ 1250 ℃ until the volume ratio of 120% or less; A quenching step of quenching the material processed in the hot forging step; And a warming step of processing until the volume ratio reaches 100 to 120% by coining the upper, lower, left, and right sides of the material at a temperature of 600 to 680 ° C.

And, the hot forging step of heating the steel to 1150 ~ 1250 ℃ until the volume ratio of 120% or less; A quenching step of rapidly cooling the material processed in the hot forging step to 650 to 700 ° C. at a cooling rate of 10 ° C./s or more; And a warming step of processing until the volume ratio reaches 100 to 120% by coining the upper, lower, left, and right sides of the material at a temperature of 600 to 680 ° C.

On the other hand, in the hot forging step, the steel material is processed to a volume ratio of 140% or less in the buster stage, to a volume ratio of 130% or less in the blocker stage, and 120% in the finisher stage. It can be made to process to the following.

In addition, the warm coining step, the warming and conveying step of removing the residual stress by transferring the coined (coining) material in the furnace (furnace) is maintained at a warm temperature of 550 ~ 650 ℃; have.

In addition, the warm maintenance transfer step may further include a shot blasting step of removing the scale of the transferred material.

Specifically, the material may be a vehicle connecting rod.

According to the manufacturing method of the non-coated steel product having the structure as described above, the strength is increased by the microstructure of the structure by rapid cooling at 10 ° C / sec or more and the work hardening by warm coining at the time of cooling after forging according to the present invention, continuous It can bring about productivity and cost reduction by eliminating the stress reduction process and the shot blast process.

1 is a view showing a manufacturing method of a conventional connecting rod.
Figure 2 is a view showing the shape of the material produced according to the conventional hot forging.
3 is a view showing a conventional cold coining operation.
4 is a view showing a manufacturing method of a connecting rod according to an embodiment of the present invention.
5 is a view showing the warm coining equipment used in the method of manufacturing the non-coated steel product shown in FIG.

Hereinafter, with reference to the accompanying drawings looks at with respect to the manufacturing method of non-coated steel products according to a preferred embodiment of the present invention.

4 is a view showing a method of manufacturing a non-coated steel product according to an embodiment of the present invention, the method of manufacturing such a non-coated steel product is processed until the steel is heated to 1150 ~ 1250 ℃ until the volume ratio of 120% or less Hot forging step; A quenching step of rapidly cooling the material processed in the hot forging step to 650 to 700 ° C. at a cooling rate of 10 ° C./s or more; And a warm coining step made at a temperature of 600 ° C. or higher.

In another aspect, a method of manufacturing a non-coated steel product includes a hot forging step of heating the steel to 1150 to 1250 ° C. until the volume ratio is 120% or less; A quenching step of quenching the material processed in the hot forging step; And a warming step of processing until the volume ratio reaches 100 to 120% by coining the upper, lower, left, and right sides of the material at a temperature of 600 to 680 ° C.

In another aspect, a method of manufacturing a non-coated steel product includes a hot forging step of heating the steel to 1150 to 1250 ° C. until the volume ratio is 120% or less; A quenching step of rapidly cooling the material processed in the hot forging step to 650 to 700 ° C. at a cooling rate of 10 ° C./s or more; And a warming step of processing until the volume ratio is 100 to 120% by coining the upper / lower / left / right sides of the material at a temperature of 600 to 680 ° C .;

That is, the manufacturing method of the non-coarsened steel product of this invention consists largely of hot forging, rapid cooling, and warm coining. Specific examples include a connecting rod which is a component of a vehicle, which is because a cold coiling operation for catching a bent portion may be omitted according to the present invention in the case of the connecting rod, since the saving effect is large.

The composition of non-coarse steel for this is as follows. C: 0.30 to 0.60 wt%, Si: 0.50 to 2.0 wt%, Mn: 0.80 to 1.40 wt%, P: 0.005 to 0.10 wt%, S: 0.05 to 0.10 wt%, Al: more than 0 0.050 wt% or less, Cr : Greater than 0 and 0.40 wt% or less, V: 0.05 to 0.35 wt%, Ti: greater than 0 and 0.15 wt or less, Nb: greater than 0 and 0.05 wt% or less, Zr: 0.010 to 0.080 wt% and N: greater than 0 and 0.030 wt% or less, And the remainder is characterized by having a composition containing iron (Fe) and impurities.

In the manufacturing method for strength improvement, after hot forging to the volume ratio of 120% or less, the forging material is blown with high pressure nitrogen gas until the temperature of the forging material becomes 680 ℃ directly below the transformation point of A1. It is possible to delete the conventional short blast process by increasing the strength and the scale (in the existing process of FIG. 1, if there is a scale during cold coining, the scale may be rolled into the material during coining and become a defect. Was a necessary process).

In addition, when directly below the A1 transformation point, the upper / lower / left / right directions are all-coined at a volume ratio of 120% or less to remove flashes generated during dimensional refinement and trimming, so that milling of the side part is required during machining. The process can be omitted. 5 shows such warm coining equipment, which compresses the material in all directions of the upper, lower, left, and right sides of the material and processes the material close to 100% at a volume ratio of 120%. This is different from the coining operation (refer to FIG. 3), which conventionally presses only up and down, such as the bending of a bent portion, to perform a relatively simple calibration. It can be understood as a concept that simultaneously executes an aspect.

In addition, it is possible to further increase the strength due to the work hardening effect by plastic deformation during warm coining. After warm coining, the residual stress is removed by maintaining the temperature at 600 ℃ for 20 minutes in a belt conveyor furnace that can be heated, thereby transferring and reinforcing the material. Therefore, cost reduction is possible through the conventional omission of the residual stress removal heat treatment (SRA) work by cold coining.

Existing processes have low productivity due to discontinuous hot forging and cooling after cold cooling, shot blasting, and SRA processes in separate facilities, but the process of the present invention is continuously maintained after warming and warming. High productivity can be achieved through the role of reinforcement. The present invention implements a unique effect of improving the strength by the rapid cooling process, warm coining, eliminating the process and improving the quality through the continuous heat retention section.

Specifically, according to the present invention, in the hot forging step, the steel material is processed to a volume ratio of 140% or less in the buster stage, to a volume ratio of 130% or less in the blocker stage, and to a finisher In the step, it can be processed up to 120% by volume. In other words, in the finisher stage, processing is performed at 120% instead of 100%, and the remaining 20% is held by compression during warming in the future to eliminate shot blasting and cold coining. . Further, the effect of the increase in strength can be obtained by plastic deformation during warm coining.

On the other hand, the warm coining step, the warming conveying step of removing the residual stress by transferring the coined (coining) material in the furnace (furnace) is maintained at a warm temperature of 550 ~ 650 ℃; And residual stress must be removed at the same time. In addition, the warm maintenance transfer step, the short blast step of removing the scale of the transferred material; to further include to smooth the material finally. That is, in the present invention, unlike the prior art, only one shot blasting operation may be finally performed.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

Claims (7)

A hot forging step of heating the steel to 1150 to 1250 ° C. until the volume ratio is 120% or less;
A quenching step of rapidly cooling the material processed in the hot forging step to 650 to 700 ° C. at a cooling rate of 10 ° C./s or more; And
The method of manufacturing a non-coated steel product comprising a; warming (coining) step made at a temperature of 600 ℃ or more. A hot forging step of heating the steel to 1150 to 1250 ° C. until the volume ratio is 120% or less;
A quenching step of quenching the material processed in the hot forging step; And
Manufacturing a non-coated steel product comprising a; warming (coining) step of processing until the volume ratio of 100 ~ 120% by coining the top / bottom / left / right sides of the material at a temperature of 600 ~ 680 ℃ Way. A hot forging step of heating the steel to 1150 to 1250 ° C. until the volume ratio is 120% or less;
A quenching step of rapidly cooling the material processed in the hot forging step to 650 to 700 ° C. at a cooling rate of 10 ° C./s or more; And
Manufacturing a non-coated steel product comprising a; warming (coining) step of processing until the volume ratio of 100 ~ 120% by coining the top / bottom / left / right sides of the material at a temperature of 600 ~ 680 ℃ Way. 4. The method according to any one of claims 1 to 3,
In the hot forging step, the steel material is processed to a volume ratio of 140% or less in the buster stage, to a volume ratio of 130% or less in the blocker stage, and to a volume ratio of 120% or less in the finisher stage. A method for producing a non-alloyed steel product, characterized in that it is processed. 4. The method according to any one of claims 1 to 3,
The warm coining step may further include a warm maintenance transport step of removing the remaining stress by transferring the coined material in a furnace in which warm temperature of 550 to 650 ° C. is maintained. Method of making non-coated steel products. The method according to claim 5,
The warm maintenance transfer step, the shot blasting step of removing the scale of the conveyed material; manufacturing method of non-coated steel products further comprising. 4. The method according to any one of claims 1 to 3,
The material is a manufacturing method of non-coated steel product, characterized in that the vehicle connecting rod.

Images