JPH01271045A - Production of lead free cutting steel by continuous casting method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the production of lead free-cutting steel having a core with an increased Pb content by a continuous casting method (hereinafter referred to as continuous casting).

[Conventional technology]

Conventionally, methods for adding Pb to molten steel include adding it in a ladle, adding it to the molten steel injection flow from the ladle to the tundish, and adding it to the mold as described in JP-A-57-168755. There is a method of directly adding molten steel to molded molten steel while electromagnetically stirring it.

However, lead free-cutting steel manufactured by these methods is
There is little variation in lead content, and lead particles are evenly distributed.

For this reason, lead particles are evenly contained in the surface layer of slabs manufactured by the continuous casting method. When this slab is rolled into a billet, the surface area ratio of surface defects caused by lead is high, and the billet needs to be cleaned before being sent to the next process.゛As other prior art related to the present invention, Japanese Patent Application Laid-open No. 142053/1983 filed by the applicant discloses a method for producing free-cutting steel with a high StM content in the core by adding S to the core using a wire. has been done.

Furthermore, Japanese Patent Application No. 61-252898 discloses a method of adding metal using a nozzle below an electromagnetic braking device installed near the lower end of the mold to obtain slabs with different compositions in the rim layer and core layer. There is.

[Problems to be Solved by the Invention] However, in the production of lead free-cutting steel by the conventional method as disclosed in JP-A-57-168755, lead is present in the surface layer of the slab, so it is difficult to roll it into billets. This has a major disadvantage in that the area ratio of surface flaws to be treated is large.

What is shown in JP-A-62-142053 is related to the production of pseudo-rimmed sulfur free-cutting steel, which is different from the production of lead free-cutting steel.

Furthermore, the technology shown in Japanese Patent Application No. 61-252898 is
Powdered metal is added using a nozzle, and there is no mention of manufacturing lead free-cutting steel.

[Means to solve the problem]

The present invention was made in view of the above-mentioned situation, and is a method of adding Pb acid component wire to the unsolidified molten steel after the upper end of the mold where a solidified shell is generated during continuous casting, and adding it to the unsolidified molten steel at the center of the slab. Free-cutting steel containing a large amount of Pb acid component is obtained. At that time, an electromagnetic braking device is provided near the bottom end of the mold, and a Pb component wire is added below it, and an electromagnetic stirring device is provided near the bottom end of the mold, and the Pb component wire is added to the stirred molten steel. It is something to do.

The present invention will be explained in detail below.

The first invention has C: 0.60% by weight or less, Mn: 0.30 to 1.3
0% by weight, P: 0.080% by weight or less, S: 0
．． Contains 400% by weight or less of ingredients, superheating degree 5-50℃
of molten steel is injected into the mold 4 shown in Fig. 1, and an electromagnetic braking device 8 is installed after the lower end of the mold in the slab where a partially solidified shell is generated, to suppress the molten steel in the slab and prevent the molten steel from forming in the slab. It prevents the mixing of unsolidified molten steel, and after the sedation region, 0.5 to 2. , Omm
Lead free-cutting by a casting method characterized by continuous casting of lead free-cutting steel having a core of 0.03 to 0.40 wt % Pb with Pb added by thick iron-coated Pb and Pb compound-filled wire 1 It is a method of manufacturing steel.

With this manufacturing method, the partially solidified shell becomes a rim layer that does not contain Pb, so even if it is rolled into a billet, it will not contain Pb.
No surface flaws caused by b occur. This method is also effective in increasing the lead content in the center of the slab.

In FIG. 1, 2 is a solidified shell, 3 is an unsolidified molten steel, 5 is an immersion nozzle, and 7 is a core solidified portion.

In the second invention, as shown in FIG. 2, an electromagnetic stirring device 6 is provided near the lower end of the mold 4, the unsolidified molten steel 3 is rotated horizontally, and a Pb acid component is added to the stirred molten steel using a wire. This invention allows Pb to be uniformly distributed. This method is effective for distributing Pb as uniformly as possible inside the slab except for the solidified shell 2.

[For production]

FIG. 3 shows the distribution of Pb in a 160 m square billet manufactured by the method of the present invention. It can be seen that only the core part contains a high concentration of Pb, but the shell N (rim layer) does not contain Pb.

Next, the reason why the composition range of molten steel is limited in this invention will be explained.

C: The reason for setting it below 0.60% by weight (weight% is hereinafter referred to as %) is because if the C content in the steel exceeds 0.60%, the cutting force increases and the desired machinability cannot be obtained. It's for a reason.

Mn: 0.30 to 1.30% means that Mn is 0.30% to 1.30%.
At less than 30%, hot rolling cracks occur due to a decrease in hot strength due to FeS. On the other hand, if it exceeds 1.30%, workability deteriorates.

P: 0.080% or less, P is 0.080
%, cold forging workability deteriorates and surface cracks occur during processing.

S: 0.400% or less, S is 0.400
This is because if it exceeds %, workability and ductility will be significantly reduced. When PbS is added to the core with a wire, the S of the mother molten steel is reduced to account for this increase in S, and the S of the core is reduced to 0.4.
Set it below 00%.

In addition, setting the Pb of the core to 0.03 to 0.40% means that Pb
When b is less than 0.03%, machinability decreases. On the other hand, 0.4
This is because even if it exceeds 0%, it is meaningless in terms of material properties.

Next, the reason why the degree of superheating of the molten steel for Tandaitsu is set at 5 to 50℃ is that if the temperature is lower than 5℃, the nozzle will become clogged and casting will be impossible, and if the temperature is higher than 50℃, columnar crystals will develop in the slab. This is because if the temperature is too high, center segregation will become significant.

The thickness of the iron coating material of the wire is 0.5 to 2. The reason for choosing Om is that with these types of steel, only the wire between this thickness is completely melted after the bottom end of the mold. The higher the melting point of the steel, the faster the wire will melt. It is necessary to select a wire having a thickness such that it will completely melt when the desired shell thickness is reached after the lower end of the mold.

The reason why Pb and Pb compounds were added after the bottom of the mold was
This is to make the shell corresponding to the rim layer thicker than a certain level. This prevents the shell containing Pb from being exposed during rolling, so that surface defects on the billet due to Pb do not occur.

Also, if Pb or Pb compounds are added before the bottom end of the mold, the shell will become thinner and the core will be exposed during rolling, resulting in less Pb.
(b) causes surface flaws on the billet, which must be cleaned. At the same time, molten steel is discharged from the immersion nozzle 5 of the tandate, and as this creates a turbulent flow within the mold, the added Pb and Pb compounds are engulfed into Pb? This is because a shell with a high R degree is generated and the lead free-cutting steel that is the object of the present invention cannot be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to manufacture lead free-cutting steel that has few surface defects on the billet (and allows the core part of the slab to contain a high concentration of Pb, which is advantageous in terms of cost). can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of the method of the present invention according to claim (1), and FIG. 2 is an explanatory diagram of the method of the present invention according to claim (2). FIG. 3 is a graph showing analysis values of Pb in the shell (rim layer) and core in the billet cross section according to the present invention. 1... Additive wire, 2... Solidified shell, 3...
Unsolidified molten steel, 4... Mold, 5... Immersion nozzle, 6...
... Electromagnetic stirring device, 7 ... Core coagulation section, 8 ... Electromagnetic braking device. Figure 1 Figure 2

Claims (2)

[Claims] (1) Contains components of C: 0.60% by weight or less Mn: 0.30 to 1.30% by weight P: 0.080% by weight or less S: 0.400% by weight or less, superheating degree 5 to 50°C An electromagnetic braking device is installed near the bottom end of the mold where a partially solidified shell is produced, and an electromagnetic braking device is installed near the bottom end of the mold where a partially solidified shell is formed.
Pb was added using a 2.0 mm thick iron-coated Pb, Pb compound filled wire, Pb: 0.03 to 0.40% by weight
A method for producing lead free-cutting steel by a continuous casting method, characterized by continuously casting lead free-cutting steel having a core of . (2) Contains components of C: 0.60% by weight or less Mn: 0.30 to 1.30% by weight P: 0.080% by weight or less S: 0.400% by weight or less, superheating degree 5 to 50°C An electromagnetic stirring device is installed near the bottom end of the mold where a partially solidified shell is produced, and an iron-coated Pb with a thickness of 0.5 to 2.0 mm is poured into the unsolidified molten steel stirred by the device. , Pb was added using a Pb compound-filled wire, Pb: 0.03 to 0.
A method for producing lead free-cutting steel by a continuous casting method, which comprises continuously casting lead free-cutting steel having a core of 40% by weight.