JP2970309B2 - Method for producing wear-resistant steel with excellent weldability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a wear-resistant steel material, and more particularly to a pneumatic transportation system such as refuse transportation, a slurry-like material such as an ore-slurry calcareous slurry, and a hard-wearing hard material. An object of the present invention is to provide a preferable manufacturing method for a wear-resistant steel pipe, a steel plate, and other steel materials used, particularly, a steel material excellent in weldability and workability.

[0002]

2. Description of the Related Art In a system in which fluid is transported using air or liquid, wear is great, and it is essential that members used in such a system have wear resistance. The wear resistance is improved by increasing the surface hardness of the steel. For this reason, a conventional wear-resistant steel plate is often manufactured by quenching a steel containing a large amount of alloying elements such as C.

As a method of producing a wear-resistant steel by rolling and quenching using a steel having a relatively low carbon equivalent instead of increasing the amount of alloying elements such as C as described above, Japanese Patent Publication No.
6-14127, JP-A-57-89426 and JP-A-61-61.
-76615 and the like are disclosed. Further, there has been developed a steel sheet which increases the surface hardness only by using a composite steel sheet, secures workability and weldability of the steel in a soft interior, and secures abrasion resistance in a hardened portion of a surface layer (Japanese Patent Laid-Open No. Hei 3 (1991)). 22723
3).

Further, with respect to steel pipes, steel pipes in which only the inner surface of the steel pipe is hardened to improve the wear resistance have been developed (Japanese Patent Application Laid-Open Nos. 57-194213 and 01-01532).
3). Also, a method for producing a wear-resistant steel pipe using austenitic or duplex stainless steel excellent in weldability and workability (Japanese Patent Laid-Open No. 51-13361) and a method for producing a wear-resistant clad steel pipe (Japanese Patent Laid-Open No. 63-290616) Are also disclosed.

[0005]

The conventional wear-resistant steel having a high surface hardness by containing a large amount of C or the like as described above is inferior in workability due to its high hardness, and inevitably requires a carbon equivalent. And the weldability is inferior.

The steel manufactured by the quenching process such as the above-mentioned Japanese Patent Publication No. 56-14127 still has poor workability, and the hardened layer is thin in the case of the composite steel plate and the steel manufactured by the internal quenching process. In an environment where the layer is reduced by abrasion, there is a problem that the layer cannot be used for a long time. Further, stainless steel pipes and clad steel pipes have problems such as being expensive. In addition, it manufactures wear-resistant steel plates used for UOE steel pipes and ERW steel pipes that are manufactured by processing and welding after steel plate manufacturing, that is, steel materials that have excellent weldability and workability and have excellent wear resistance. The method has not yet been disclosed.

[0007]

SUMMARY OF THE INVENTION The present invention has been studied to solve the above-mentioned problems in the prior art, and has improved the workability as well as the workability by making the steel component system and heat treatment conditions specific. It has succeeded in appropriately producing an excellent wear-resistant steel plate, and is as follows.

(1) In wt%, C: 0.05 to 0.2
0%, Si: 0.88 to 2.00%, Mn: 0.50
A steel containing 2.50%, the balance being Fe and unavoidable impurities was heated at a temperature of 1000 to 1200 ° C. and a rolling end temperature of 650 to 8
00 after hot rolling at ° C., weldability, characterized by cooling to 500 ° C. or less at 5 ° C. / sec or more cooling rate
Manufacturing method for excellent wear-resistant steel.

(2) In wt%, C: 0.05 to 0.2
0%, Si: 0.88 to 2.00%, Mn: 0.50
2.50%, and Cu: 0.05-1.00%, Ni:
0.05-2.00%, Cr: 0.05-1.0%, M
o: 0.05-0.5%, Nb: 0.005-0.10
%, V: 0.005 to 0.10%, Ti: 0.005 to
0.5%, B: A steel containing any one or more of 3 to 20 ppm and the balance consisting of Fe and unavoidable impurities was heated to a temperature of 1000 to 1200.
° C, after hot rolling at a rolling end temperature of 650 to 800 ° C,
A method for producing a wear-resistant steel material excellent in weldability , characterized by cooling to a temperature of 500 ° C. or less at a cooling rate of 5 ° C./sec or more.

[0010]

In the present invention, the composition of steel is limited as described above. The reasons for limiting the steel composition of the present invention will be described first as follows.

C: 0.05 to 0.20 wt% When the steel of the present invention is heated to a temperature range of Ac ₁ to Ac ₃ and then cooled, a two-phase structure of ferrite or bainite and martensite is obtained as the microstructure of the steel. . This two-phase structure shows excellent wear resistance performance. C is an important element in order to make the steel structure such a two-phase structure and to obtain excellent wear resistance. When the amount is less than 0.05%, the effect is small. 05%. If the amount exceeds 0.02%, the weldability deteriorates, so the upper limit of the amount is set to 0.20%.

Si: 0.88 to 2.00 wt% When the amount of Si is reduced, a pearlite structure is formed, the amount of martensite and retained austenite is reduced, and good wear resistance cannot be obtained. Therefore, the lower limit of the addition amount is 0.88 %
And to ensure adequate wear resistance. Further, an excessive addition causes a reduction in hot ductility of the steel sheet and a deterioration in weldability, so the upper limit is made 2.00%.

Mn: 0.50 to 2.50 wt% Mn is effective in increasing the amount of martensite, but is effective in increasing the amount of martensite.
If it is less than 50%, the effect is small, and if it exceeds 2.50%, the weldability deteriorates. Therefore, the lower limit of the addition amount is set to 0.50% and the upper limit is set to 2.50%.

The above are the essential components of the present invention. The addition amount of the selected element in the present invention and the reason for limiting it are as follows. That is, Cu, Ni, Cr, Mo, and Nb may be added in the following ranges in order to increase the amount of martensite and improve the wear resistance and corrosion resistance of ferrite or bainite. That is, the lower limit of the addition amount is the minimum amount required to exhibit the above effects, and the upper limit thereof is the upper limit value at which the effects are exhibited without deteriorating the weldability. Cu: 0.05 to 1.00 wt% Ni: 0.05 to 2.00 wt% Cr: 0.05 to 0.50 wt% Mo: 0.05 to 0.5 wt% Nb: 0.005 to 0.10 wt%

In the present invention, V, Ti, and B may be added in the following ranges in order to increase the hardness of the ferrite portion after the heat treatment and obtain more excellent wear resistance. The lower limit of the addition is the lowest value that is effective in increasing the hardness, and the upper limit is the lowest value that does not deteriorate the weldability and workability. V: 0.005 to 0.10 wt% Ti: 0.005 to 0.10 wt% B: 3 to 20 ppm

[0016] The method of the present invention is then, as described above
A heating temperature of 1000 to 1200 ° C. The steel consisting of chemical composition
After heating , hot rolling is performed at a rolling end temperature of 650 to 800 ° C., and then cooling is performed at a cooling rate of 5 ° C./sec or more to 500 ° C. or less. The reasons for limitation in this case are as follows.

Slab heating temperature: 1000 to 1200 ° C. If the slab heating temperature exceeds 1200 ° C., a large amount of scale is generated during heating, which causes surface scratches on the steel sheet. Therefore, the upper limit of the heating temperature is 1200 ° C. If the heating temperature is 1000 ° C. or lower, the lowering of the heating temperature is set to 1000 ° C., because this lowers the rolling efficiency and causes unevenness of the material.

The rolling end temperature: the upper limit of the finish rolling temperature since 650 to 800 ° C. rolling end temperature is above 800 ° C. When the final structure crystal grain size becomes large good abrasion performance can not be obtained and 800 ° C.. If the rolling end temperature is 650 ° C. or lower, the rolling efficiency is reduced, so the lower limit of the rolling end temperature is 650 ° C.

Cooling rate: 5 ° C./sec or more The reason why the cooling rate is set to 5 ° C./sec or more is that when cooling is performed at a higher cooling rate, a part of austenite at the start of cooling is transformed into martensite. If the cooling rate is lower than 2, a two-phase structure of ferrite and martensite cannot be obtained stably. Therefore, the lower limit of the cooling rate is set to 5 ° C./sec. There is no particular upper limit for the cooling rate.

Cooling stop temperature: 500 ° C. or less The reason why the cooling stop temperature is set to 500 ° C. or less is that if cooling is stopped at a temperature higher than this, martensitic transformation does not proceed sufficiently and a proper two-phase structure cannot be obtained. Therefore, the upper limit of the cooling stop temperature is set to 500 ° C. The lower limit of the cooling stop temperature is not particularly limited.

In the case of manufacturing the target member according to the present invention, the manufacturing method is not particularly limited.

[0022]

EXAMPLES Specific examples according to the present invention will be described. First, the composition of the steel of the present invention and the comparative steel used by the present inventors are as shown in Table 1 below.

[0023]

[Table 1]

Each of the steels in Table 1 described above has a Ceq value of about 0.45 or less, and its weldability is equivalent to that generally used as structural steel.

[0025] While the steel as described above are steel, it der as antiwear performance for specific production conditions and products obtained thereby are shown in the following Table 2 according to the invention in that case, For the evaluation of abrasion resistance, water and silica sand were used.
Specimen Rotation Wear Test Specimen Wear in Mixed Environment
The measurement was performed by measuring the attrition loss. The wear resistance in the table is SS
Value obtained by dividing the weight loss of the 400 specimen by the weight loss of the test material
The larger the value, the better the wear resistance.
The outline of the test machine is as shown in FIG.
Attach the test piece 1 at an interval of 150 mm from the rotating shaft 2
The test piece 1 has a width of 10 m.
m and a length of 60 mm.

[0026]

[Table 2]

That is, according to the results in Table 2 , when the steel according to the present invention was treated under the conditions of the present invention, the steel pipe was SS4
Abrasion resistance 1.5 times or more as compared with 00 is obtained. Even when using steel chemical composition according to the present invention, a high B-2 of rolling end temperature, not after rolling accelerated cooling the steel plate B-
3. B-4 with improper accelerated cooling conditions did not have a wear resistance of 1.5 or more. In addition, steel plates N-1 , O-1 ,
Unless steel having the component composition according to the present invention is used as in Q-1 , good wear resistance cannot be obtained even when the accelerated rolling in the present invention is performed. Further, even when the steel is not of the composition according to the present invention as in P-1 and the rolling accelerated cooling conditions are not the conditions of the present invention, good wear resistance is not obtained.

[0028]

According to the present invention as described above, a specific low-alloy steel is subjected to a specific and appropriate heat treatment so that a stable two-phase set of ferrite and martensite is obtained.
It is an invention which has good abrasion resistance by obtaining a woven fabric and can obtain various steel products having good workability and weldability, and is industrially highly effective.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a tester used for evaluating wear characteristics in the present invention.

[Explanation of symbols]

 1 Test piece 2 Rotation axis

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/58 C22C 38/58 (56) References JP-A-57-89426 (JP, A) JP-A-1-234520 (JP) JP-A-62-274027 (JP, A) JP-A-6-220534 (JP, A) JP-A-6-158163 (JP, A) Patent 2699785 (JP, B2) (58) Int.Cl. ⁶ , DB name) C21D 8/00-8/10 C21D 9/08

Claims (2)

(57) [Claims] (1) C: 0.05 to 0.20% in wt%;
Si: 0.88 to 2.00%, Mn: 0.50 to 2.5
0%, the balance consisting of Fe and unavoidable impurities was heated at a temperature of 1000 to 1200 ° C. and a rolling end temperature of 650.
800 After hot rolling at ° C., welding, characterized in that cooling to 500 ° C. or less at 5 ° C. / sec or more cooling rate
Method for producing wear-resistant steel with excellent heat resistance. 2. C: 0.05 to 0.20% in wt%;
Si: 0.88 to 2.00%, Mn: 0.50 to 2.5
0%, Cu: 0.05-1.00%, Ni: 0.05-2.0
0%, Cr: 0.05 to 1.0%, Mo: 0.05 to
0.5%, Nb: 0.005 to 0.10%, V: 0.0
05 to 0.10%, Ti: 0.005 to 0.5%, B:
A steel containing any one or more of 3 to 20 ppm and the balance consisting of Fe and unavoidable impurities was heated at a heating temperature of 10%.
After hot rolling at 00 to 1200 ° C and a rolling end temperature of 650 to 800 ° C , 500 ° C at a cooling rate of 5 ° C / sec or more.
A method for producing a wear-resistant steel material excellent in weldability , characterized by cooling to the following.