JPS63441A - Cold pulling-off re-sulfurizing and re-phosphorizing cuttingrod steel having adjusted mechanical property and cutting property - 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 The present invention provides a free-cutting resulfurized
and rephosphorized cold-drawn steel bars, more particularly having controlled chemical properties and whose yield strength is not only due to controlled chemical composition but also due to hot rolling. This relates to a steel bar that is determined by the subsequent dimensions of the bar and the amount of reduction used in drawing the bar.

The main object of the present invention is to provide cold-drawn free-cutting steel bars,
The object of the present invention is to provide a steel bar whose mechanical properties, in particular its yield strength, are determined on the basis of its chemical composition, its dimensions, cross section and applied reduction.

Another object of the present invention is to provide a means for adapting the yield strength of a cold-drawn steel bar to desired processing when optimizing the ratio of constituent components in the chemical composition according to the dimensions of the steel bar. An object of the present invention is to provide a free-cutting cold-drawn steel bar in which the amount of carbon is reduced by adjusting the amount of niobium.

Another object of the present invention is to provide a cold-drawn free-cutting steel bar,
The objective is to provide a cold-drawn free-cutting steel bar in which the properties necessary to improve machinability are optimized by the chemical composition and the physical shape of the bar.

Yet another object of the present invention is to provide re-sulfurization and re-soaking with superior machinability provided by optimizing the relationship between steel chemistry, steelmaking conditions, cold drawing conditions, and cutting conditions. An object of the present invention is to provide a phosphorized free-cutting steel bar.

Another object of the invention is carbon steel, manganese steel, re-sulfurized and re-phosphorized steel, micro-alloy steel (MICR).

The object of the present invention is to provide a cold-drawn free-cutting steel bar production method that is applied to allied 5teel) and high-strength steel, and utilizes the chemical properties of the steel bar, the bar dimensions, and the steel bar manufacturing method.

Still another object of the present invention is to provide a cold drawing material in which the amounts and ratios of manganese, sulfur and niobium (Columbium), and the deformation amount and deformed shape during cold drawing are adjusted so as to give optimum machinability. The purpose is to provide free-cutting steel bars that can be drawn.

Other objects of the invention will become apparent from the following specification and claims.

It is known that certain elements such as sulfur, lead, bismuth, tellurium and selenium are useful in improving the machinability of steel. Machinability is a complex and not well understood property. The influence of alloy composition, from the behavior of alloys when they are cut with cutting tools in operations such as single point turning, forming, drilling, reaming, poling, shaving, and thread cutting.
Another problem is that the plastic deformation and cutting mechanics of metal workpieces cannot be easily controlled. There is also a gap in current knowledge of material behavior between test results obtained from normal unsteady state tensile experiments and results obtained from cutting force data derived from cutting during production processes.

By modifying the chemical composition and optimizing the size, shape, distribution, and chemical composition of inclusions, we can increase the brittleness of chips and increase the lubricity at the tool/chip interface to improve free cutting. Attempts have been made by metallurgists for a long time to improve the machinability of steel bars.

Additionally, it is desirable to prevent the formation of abrasive particles and microstructures within the steel bar. For example, bismuth and tellurium (U.S. Pat. No. 4,230,939
), lead, bismuth, and tellurium and/or sulfur (U.S. Pat. No. 4,244,737), tellurium and sulfur (U.S. Pat. No. 4,279,646). Change is being done. However, such products do not completely satisfy the need for improving the machinability of free-cutting steel bars. In order to improve machinability, special efforts have traditionally been made on the chemical composition, rather than optimizing the reduction or dimensional shrinkage rate during cold working, the dimensions and cross-section of the steel bar. Ta.

The present invention is particularly directed to improving machinability by combining the optimum ratio of chemical components, particularly manganese, sulfur and niobium, the amount of cold work and the optimum dimensions and cross section of the steel bar. . Therefore, in the present invention, the chemical composition, rolling reduction, dimensions, and cross section of the steel bar are adjusted to be particularly suitable for cutting.

The cold-drawn free-cutting re-sulfurized and re-phosphorized steel bar of the present invention is
Carbon up to 0.08% by weight: 0.6% to 1.4% by weight
% by weight of manganese; up to 0.1% by weight of silicon; at least 0.3% by weight of phosphorus; 0.25% by weight to 0.5% by weight;
50% by weight sulfur; 0.01% to 0.10% niobium; up to 0.1% vanadium; total amount of nickel, chromium, molybdenum and copper up to 0.15% by weight, balance iron. The chemistry consists of fl composition. The ratio of manganese, sulfur and niobium is particularly important in obtaining steel bars with appropriate chemical properties and predicting the yield strength of such bars. Therefore, the ratio of (wt% manganese)/(wt% sulfur) is between 1.6 and 4.
0, and the ratio of [(wt% manganese) - 1,62X (wt% sulfur)]/(wt% niobium) is 2 to 50.
It is.

The yield strength of a steel bar, and therefore its machinability, is determined by the raw material, dimensions and reduction. The raw materials are hot rolled coils, hot rolled bars up to about 5 cm (2 inches) in diameter, and hot rolled bars at least about 5 cm (2 inches) in diameter, taking into account the types of products obtained from the rolling mill. It can be a hot rolled bar. The raw material, hot rolled to specific dimensions and cut to the appropriate length, is then cold drawn.

The reduction or dimensional shrinkage rate during cold drawing is also important in determining the yield strength of the final product, the steel bar.

Cold drawing and cutting are carried out taking into account the role of various chemical elements in the chemical composition of the steel bar and the influence of these elements on the machinability and behavior of the steel bar. In order to keep the work hardening and strain hardening of steel bars to a low level, a low carbon content is an essential condition.

The low carbon content reduces the strength of the steel and ensures that the total amount of residual elements such as nickel, chromium, molybdenum and copper does not exceed 0.15% by weight. By combining this, a product with relatively low ductility of chips generated at the tool-workpiece interface and high brittleness can be obtained. If the remaining elements increase above the specified amount and carbon decreases below the specified amount, this will be detrimental to the free-cutting product, increasing the ductility and decreasing the brittleness of the chips. Furthermore, increasing the carbon content above 0.08 wt.w.w. increases the abrasive particles, increases the possibility of increasing fracture stress, and increases the surface hardness, especially of hexagonal cold drawn steel bars.

The identified manganese content of 0.6 wt-% to 1.4 wt-0% manganese is important for the formation of manganese sulfide (MnS)-based inclusions that affect tool life. . Manganese promotes the hardenability and increases the strength of cold drawn steel bars.

The actual manganese specification in a particular bar will depend on the diameter of the hot rolled bar, the required mechanical properties of the bar and the cutting method prescribed. The manganese content increases as the steel bar size increases and as the target value of yield strength increases.

Silicon up to 0.1% by weight The amount of silicon should be limited to 0.1% by weight since as the silicon content increases the amount of abrasive silicate in the final product increases substantially.

0.25% to 0.50% by weight of hexasulfur is Mn
It is also necessary for the formation of S inclusions, and for this reason the sulfur content should be at least 0.25% by weight. The specific specification of sulfur for a particular bar will depend on the bar dimensions and manganese content.

The lowest sulfur content applies when hot rolled coil is used as the raw material, but the highest sulfur content applies for large diameter cold drawn steel bars with high yield strengths up to approximately 5600 kg/aa (approximately 80 ksi). sulfur content is required.

Since excess sulfur increases hot brittleness and reduces ductility, the upper limit for the amount of sulfur in the products of this invention is 0.5% by weight.

At least 0.03% phosphorus by weight Phosphorus is necessary to improve the smoothness of the finished surface.

However, phosphorus increases work hardening and increases the hardness of chips produced during cutting. Therefore, in high-strength cold-drawn steel bars, the amount of phosphorus (usually 0.09% by weight) customarily added to these types of bars for high-speed cutting operations is
up to).

0.01wt 9% to 0.10% niobium In the steel bar of the present invention, niobium is essential in order to increase the strength, adjust the mechanical properties by adjusting the wall thickness of the steel bar, and reduce the toughness of chips. is an element.

Niobium specifications vary depending on yield strength and bar dimensions. Niobium promotes core hardenability of large diameter cold drawn steel bars and increases work hardenability. Niobium-containing steel bars can be cold drawn at low reductions to minimize surface reinforcement and substantially strengthen the core. However, when the content is higher than the specified amount, the effect of niobium increases the strength too much and thus reduces the life of the tool.

Vanadium Up to 0.1% by weight Vanadium improves the mechanical properties of steel bars, especially large diameter cold drawn steel bars, from the surface through the core. If the vanadium content exceeds the specified amount, the machining characteristics of the steel bar will deteriorate.

The residual elements of up to 0.15% by weight of nickel, chromium, molybdenum and copper increase strength and ductility, and promote the formation of fine grains, all of which contribute to the cutting of steel bars. Said elements are generally detrimental to machinability, as they degrade properties. Therefore, the residual elements must be kept within a specified range.

The ratio of (weight% of manganese)/(weight% of sulfur) is 1.6
4.0, and this ratio defines the amount of manganese and the amount of FeS inclusions in the solid solution.

The relationship between manganese, sulfur and niobium was defined as [(wt% manganese) - 1,62x (wt% sulfur)]/(wt% niobium), which strengthens the product. This is to define the relative contribution of manganese and niobium at the time. Manganese is a changing kine of austenite decomposition.
tics of austenite decompo
niobium reduces grain size and promotes precipitation hardening. Depending on the dimensions of the hot-rolled product, the amount of reduction in reduction to the cold-drawn product, and the required tensile strength of the bar for its final use, the specification of the ratios described above will vary.

Machinability is improved by adding one or more of the following elements in addition to the elements listed above.

0.03% to 0.35% lead by weight; 0.005
0.05% to 0.25% bismuth; 0.03% to 0.15% lead; 0.05% lead; 0.05% by weight lead;
Bismuth from 0.15% by weight; 0.006% to 0.012% nitrogen; 0.
0.05% to 0.25% by weight bismuth and 0.0% to 0.25% by weight bismuth
05% to 0.05% by weight tellurium.

Zircon maximizes machinability by promoting the formation of spherical MS inclusions, while nitrogen promotes chip brittleness that facilitates drilling operations.

The table below shows the amounts of manganese, sulfur and niobium in hot rolled raw materials, i.e. hot rolled coils, hot rolled steel bars up to about 5mm (2 inches) in diameter, or at least about 5mm in diameter.
Table 9, which explains the relationship of Jll (2 inch) to hot rolled steel bars, shows the yield strength for specific products obtained by specific combinations of elements.

Approximately 4200kg/crl (60ksi) or approximately 5
As applicable to hot rolled coils that are to be processed into cold drawn steel bars with yield strengths in the range of 60 Q kg/crJ (80 ks i), Table 1 lists the yield strengths and values of manganese, niobium, The relationship for each weight percent of sulfur as well as the ratio of these three elements is shown. Table 2 shows manganese, sulfur, and niobium specifications for hot rolled steel bars up to about 5 cm (2 inches) and the effect of cross-sectional shrinkage of the bar during cold drawing on yield strength. Table 3 has a diameter of at least approximately 5 cm (2 inches)
This table shows the same contents as Table 2 for hot rolled steel bars.

≦ 4 ≦ ≦Specific examples of products made in accordance with the present invention are listed below.

Oba ■ Upper carbon Up to 0.06% by weight Manganese 0.6% to 1.5% by weight Silicon
Hot rolled coil steel containing up to 0.1% by weight phosphorus 0.03% to 0.06% by weight sulfur 0.25% to 0.40% by weight niobium 0.01% to 0.07% by weight. The total amount of nickel, chromium, molybdenum and copper is up to 0.15% by weight, the balance being iron.

[(manganese weight %) - 1,62X (sulfur weight %)] /
The ratio of (% by weight) is between 2.0 and 22.5;
The ratio of % manganese (wt%)/(wt% sulfur) is between 2.0 and 3.5. The weight percent sulfur is further determined by multiplying the desired yield strength (ksi) by (0,0042-0.0054).

Senbune Yoshu Carbon 0. Manganese up to OS wt% 0.7 wt% to 1.30 wt% Silicon Phosphorus up to 0.1 wt% 0.03 wt% to 0.09 wt% Sulfur 0.28 wt% to 0.50 wt% Niobium 0. Hot rolled steel bars up to about 5 cm (2 inches) in diameter containing up to 0.1 wt% vanadium.

The total amount of nickel, chromium, molybdenum and the like is up to 0.15% by weight, the balance being iron.

[(manganese weight %) - 1,62X (sulfur weight %)] /
The ratio of (wt% manganese)/(wt% sulfur) is between 4 and 51, and the ratio (wt% manganese)/(wt% sulfur) is between 2.2 and 3.2. The weight percent sulfur is determined by multiplying the desired yield strength (ksi) by (0,0045-0.0058).

Jitsai I Tsuhashi Carbon Manganese up to 0.08% by weight Silicon 0.8% to 1.4% by weight
up to 0.1% by weight IJ 7 0.03% to 0.9% by weight Sulfur 0.3% to 0.5% by weight Niobium
A hot rolled steel bar having a diameter of at least about 5 cm (2 inches) containing from 0.02% to 0.10% by weight up to 0.1% vanadium.

The total amount of nickel, chromium, molybdenum and copper is 0.
Up to 15 weight, the balance being iron.

[(manganese weight %) - 1,62X (sulfur weight %)] /
The ratio of (wt% niobium) is 5 to 25, and the ratio of (wt% manganese)/(wt% sulfur) is 2.0 to 3.5.
It is. The weight percent of sulfur is further determined by the desired yield strength (k
si) by (0,0045 to 0.0063).

The weight percentages of manganese, sulfur and niobium increase as the desired yield strength of the product increases.

The contribution of niobium to the strengthening of steel bars also increases as the yield strength target of the product increases.

Excellent machinability in high-speed drilling and forming is due to the yield strength of approximately 4200 kg/cIIl (60ks
i) or about 4550 kg/an! (65ksi)
This is achieved by using cold drawn steel bars. Improving the processed surface will result in a yield strength of approximately 4550 kg.
/ci (65ksi) or about 4900 kg/cA
(70 ksi) cold drawn steel bar.

An important feature of the present invention is that steel bars with various machining specifications, various machining performances, and various machining compatibility can be used.
The present invention allows one to choose from the range of mechanical and chemical property combinations disclosed herein. The shrinkage rate during cold drawing also substantially affects yield strength. Yield strength is the shrinkage rate in cold drawing, bar 24
It is directly related to the type of hot-rolled material used to make it, as well as the manganese, niobium, and sulfur content.

Although preferred embodiments of the invention have been described, it should be appreciated that many improvements, modifications, and substitutions may be made thereto.

Claims (1)

[Claims] 1. Carbon (C) up to 0.08% by weight, manganese (Mn) 0.6% to 1.4% by weight, silicon (Si) up to 0.1% by weight, phosphorus at least 0.03% by weight of (P), 0.25% to 0.50% by weight of sulfur (S), and 0.01% to 0.10% by weight of niobium (Cb).
, vanadium (V) up to 0.1% by weight, nickel (Ni), chromium (Cr), molybdenum (Mo
) and copper (Cu) up to 0.15% by weight, the balance is iron (Fe), and the ratio (weight% of manganese)/(weight% of sulfur) is between 1.6 and 4.0. and [(wt% of manganese) - 1.62 x (wt% of sulfur)
]/(wt % of niobium) is from 2 to 50. 2.Additionally 0.03% to 0.35% by weight of lead (Pb)
% by weight of the cold drawn steel bar according to claim 1. 3. The cold drawn steel bar according to claim 1, further containing 0.005% to 0.05% by weight of zircon (Zr). 4. Bismuth (Bi) is further added from 0.05% by weight to 0.
．． The cold drawn steel bar according to claim 1, containing 25% by weight. 5.Additionally 0.03% to 0.15% by weight of lead (Pb)
The cold drawn steel bar according to claim 1, further containing 0.05% to 0.15% by weight of bismuth (Bi). 6. Further nitrogen (N) from 0.006% by weight to 0.0% by weight
The cold drawn steel bar according to claim 1, containing 12% by weight. 7. Bismuth (Bi) is further added from 0.05% by weight to 0.
．． The cold drawn steel bar according to claim 1, further comprising 25% by weight of tellurium (Te) and 0.005% to 0.05% by weight of tellurium (Te). 8. The amount of niobium (Cb) is 0.01% by weight to 0.04% by weight
% by weight and a yield strength of about 4200 kg/cm^2. 9. The amount of niobium (Cb) is 0.02% by weight to 0.06%
% by weight and a yield strength of approximately 4550 kg/cm^2. 10. The amount of niobium (Cb) is 0.02% by weight to 0.0%
7% by weight, yield strength is approximately 4900kg/cm^2
The cold drawn steel bar according to claim 1, characterized in that: 11. The amount of niobium (Cb) is 0.06% by weight to 0.1
% by weight and a yield strength of about 5600 kg/cm^2. 12. Carbon (C) up to 0.06% by weight, Manganese (Mn) 0.6% to 1.15% by weight
, silicon (Si) up to 0.1% by weight, phosphorus (P) from 0.03% to 0.06% by weight, sulfur (S) from 0.25% to 0.40% by weight, niobium (Cb) ) is 0.01% to 0.07% by weight
, nickel (Ni), chromium (Cr), molybdenum (Mo
) and copper (Cu) up to 0.15% by weight, the remainder is iron (Fe), and the ratio (weight% of manganese)/(weight% of sulfur) is 2.0 to 3.5. , [(wt% of manganese) - 1.62 x (wt% of sulfur)
]/(wt% of niobium) is 2 to 50,
and (wt% of sulfur) = (0.0042 to 0.0054) x
A cold drawn resulfurized and rephosphorized free machining steel bar formed from hot rolled coiled copper having a composition of (desired yield strength (ksi)). 13. The cross-sectional shrinkage rate during cold drawing is 15% to 30% of that of the hot rolled bar, and the yield strength is approximately 4200 kg/cm^
2 to about 5,600 kg/cm^2. 14. Made of hot-rolled bar with a cross section of up to about 5 cm, and contains up to 0.08% by weight of carbon (C) and 0.7% to 1.30% by weight of manganese (Mn).
, silicon (Si) up to 0.1% by weight, phosphorus (P) from 0.03% to 0.09% by weight, sulfur (S) from 0.28% to 0.50% by weight, niobium (Cb) ) is 0.02% to 0.08% by weight
, vanadium (V) up to 0.1% by weight, nickel (Ni), chromium (Cr), molybdenum (Mo
) and copper (Cu) up to 0.15% by weight, the remainder being iron (Fe), and the ratio of (weight% of manganese)/(weight% of sulfur) is 2.0 to 3.2. , [(wt% of manganese) - 1.62 x (wt% of sulfur)
]/(wt% of niobium) is 4 to 51, and (wt% of sulfur)=(0.0045 to 0.0058)×
A cold-drawn re-sulfurized and re-phosphorized free-machining steel bar having a composition of (desired yield strength (ksi)). 15. made from a hot-rolled bar with a cross section of at least about 5 cm, and containing up to 0.08% by weight of carbon (C), 0.8% to 1.4% by weight of manganese (Mn), and silicon (Si). up to 0.1% by weight, phosphorus (P) from 0.03% to 0.9% by weight, sulfur (S) from 0.30% to 0.50% by weight, and niobium (Cb) from 0.02% by weight. Weight% to 0.10% by weight
, vanadium (V) up to 0.1% by weight, nickel (Ni), chromium (Cr), molybdenum (Mo
) and copper (Cu) up to 0.15% by weight, the balance being iron (Fe), and the ratio of (weight% of manganese)/(weight% of sulfur) is 2.0 to 3.5. Yes, [(wt% of manganese) - 1.62 x (wt% of sulfur)
]/(wt% of niobium) is 5 to 25, and (wt% of sulfur)=(0.0045 to 0.0063)×
A cold-drawn re-sulfurized and re-phosphorized free-machining steel bar having a composition of (desired yield strength (ksi)).