KR100411671B1 - Weld crack-resistant and wear-resistant chrome steel overlay welding alloys - Google Patents

Abstract

The present invention is used for the surface overlay alloy of various industrial rolls, etc., and relates to an overlay welding alloy steel having excellent crack resistance and wear resistance in an environment where abrasion and corrosion occurs, C: 0.5 ~ 1.5 in weight% %, Mn: 0.1 ~ 2%, Si: 0.1 ~ 2%, Cr: 5 ~ 13%, Ti: 1 ~ 5%, Nb: 0.5 ~ 5%, other W, V, Mo 3% or less each, Fe And a chromium steel overlay welding alloy composed of other unavoidable impurities and excellent in crack resistance and wear resistance satisfying the following formula (1).

-0.5 <Cf <0.1 ------- Equation (1)

(Where Cf = C (wt%)-Ti (wt%) ÷ 3.99-W (wt%) ÷ 15.31-Nb (wt%) ÷ 7.74-V (wt%) ÷ 4.24)

According to the present invention, it is excellent in wear resistance and excellent in crack cracking resistance, and is excellent in workability during overlay welding construction, and when used as an overlay welding material for various rolls, the life extension effect is greater than that of commercial materials.

Description

Weld crack-resistant and wear-resistant chrome steel overlay welding alloys

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to alloy steel for overlay welding having excellent weld crack resistance and abrasion resistance, and is particularly suitable for preventing weld crack generation of the overlay layer when designing surface overlay alloy components of various rolls used for transferring steel materials. The present invention relates to an alloy steel for overlay welding, in which a carbon content is added to reduce wear cracking sensitivity while providing excellent abrasion resistance. Conventionally, the generation of weld cracks in an overlay layer is largely dependent on the amount of dissolved carbon in the matrix structure. By appropriately adjusting the amount and carbon content of various carbide forming elements, the dissolved carbon content in the matrix structure changes, and thus the weld cracking susceptibility changes. At this time, when carbon of more than the appropriate carbon content is added, cracking during welding is easy and welding workability is deteriorated. If the carbon content is not enough, hardness value of the overlay layer is lowered and wear resistance is also worsened. You won't be able to run out. Therefore, when designing the components of the conventional overlay alloy, it was similar to the component system of the commercial alloy, and the level of addition of some special elements as needed, the addition of a large amount of carbide forming elements was limited. However, if the standard for the proper amount of carbon is established, it overcomes this limitation and adjusts the amount of carbon in accordance with the amount of carbide forming element to reduce the crack susceptibility of the overlay alloy, thereby preventing the occurrence of welding crack and overlay weld alloy having excellent wear resistance. Can be prepared.

In addition, in order to increase the wear resistance of various rolls and to prolong the service life, overlay welding is performed on the surface of the roll. At this time, an alloy having an overlay welding alloy needs to have excellent wear resistance compared to the base material. The element will be added. Recently, in order to further increase wear resistance, carbide forming elements are gradually added in a large amount. Accordingly, the carbon content also increases. At this time, many criteria are unavoidable in order to design a new alloy system because a standard for determining an appropriate amount of carbon is not established. The addition of an appropriate amount of carbon has a large effect on the performance of the overlay alloy, if the carbon content is excessive, there is a problem that the increase in the amount of carbon dissolved in the matrix structure causing cracking during welding.

In general, the overlay alloy has a higher carbon content than a general welded structure steel, and thus requires high temperature preheating to prevent cracking during welding. The preheatable temperature is limited depending on the roll size and the capacity of the auxiliary facilities. It is ready. In order to prevent cracking at normal preheating temperatures (300 ~ 400 ℃), the cracking susceptibility of overlay alloys should not be too high and the carbon content of the matrix should be below a certain level. Next, when the carbon content is too small, the amount of solid solution in the matrix is too small, so that the hardness value of the matrix is reduced, thereby losing the original function of the overlay alloy layer of securing wear resistance. That is, when the amount of solid solution carbon in the matrix structure is too small, the temper resistance is poor at the time of post-weld heat treatment for stress removal, the hardness value is severely reduced, and the wear resistance is remarkably lowered.

As can be seen from the above, the carbon content of the overlay alloy should be added in consideration of the content of the various carbide forming elements contained in the steel can be seen that the overlay layer is an important variable that can play the original role. Accordingly, the present invention is to solve the above problems, an object of the present invention is to set the content and carbon content of various carbide-forming elements in the chromium alloy steel in order to establish a standard for the appropriate carbon content in setting the component system of the overlay alloy By investigating the occurrence of weld cracks and adding the theoretical basis for this, it is possible to provide an alloy with excellent wear resistance while suppressing the occurrence of cracks during welding of the overlay alloy.

Hereinafter, the present invention will be described in more detail.

In the present invention, the weight% C: 0.5-1.5%, Mn: 0.1-2%, Si: 0.1-2%, Cr: 5-13%, Ti: 1-5%, Nb: 0.5-5%, W: 3% or less, V: 3% or less, Mo: 3% or less, and is composed of the remaining Fe and other unavoidable impurities, and is configured to satisfy the following Equation (1), and is composed of Ti and Nb with low cracking sensitivity during overlay welding. The uniform distribution of the composite carbide provides an alloy material for overlay welding having excellent wear resistance.

-0.5 <Cf <0.1 -------------------------------------------- ---(One)

(Where Cf = C (wt%)-Ti (wt%) ÷ 3.99-W (wt%) ÷ 15.31-Nb (wt%) ÷ 7.74-V (wt%) ÷ 4.24, hereinafter denoted as Cf)

Next, in the present invention, the addition range of carbide forming elements and the method of determining the appropriate carbon content will be described.

C is an iron strengthening element and generally increases hardness. In the present invention, C combines with Ti, Nb, W, V and the like to form carbides of high hardness, and the rest is dissolved in the matrix structure surrounding these carbides. At this time, if the amount of C employed in the matrix structure is too high without binding to the carbide forming elements Ti, Nb, W, V, etc. added to the alloy, the toughness of the material is insufficient and the crack susceptibility is high. If less, the wear resistance is lowered, and thus the original function of the overlay alloy cannot be achieved. Therefore, a standard called Cf was introduced to predict the amount of carbon employed in the matrix except for the carbon bonded to Ti, W, Nb, V and the like. That is, since the total carbon content added to the alloy minus the carbon content combined with the carbide forming element is the carbon value dissolved in the matrix, the alloy element content is the chemical equivalent ratio between each alloy element and carbon (3.99 for Ti). The value obtained by dividing by) and subtracting this value from the total carbon content is the basis for the amount of carbon employed in the matrix. Of course, not all carbide forming elements combine with carbon, so the Cf value may not be consistent with the amount of solid carbon, but it is the basis for predicting the actual value. Experimental results show that Cf value and crack initiation of various alloys show that cracks occur during overlay welding when the Cf value is 0.1 or more, and wear resistance of the overlay weld layer decreases when the Cf value is -0.5 or less. Therefore, Cf value is -0.5 or more and 0.1 or less is preferable.

Cr is an essential element in the alloy of the present invention. In general, since various rolls are used in an atmosphere in which corrosion occurs along with abrasion, the overlay alloy of the rolls must have corrosion resistance, that is, corrosion resistance, and for this, Cr must be added. However, when the amount of Cr added is more than 13%, the corrosion resistance is excessive, so that it is attached to the hot rolled coil material passing through the roll, so that a sticking phenomenon occurs, rather it promotes abrasion, which is required when adding 5% or less. It does not have corrosion resistance, so the appropriate amount of Cr is about 5 ~ 13%.

Ti and Nb are also essential elements in the alloy of the present invention. The role of these alloying elements is to combine with carbon to form a high hardness composite carbide serves to improve the wear resistance. In particular, since the hardness of Ti carbide is higher than that of other carbides, it is expected to contribute the most to the wear resistance. The more these carbide forming elements, the higher the wear resistance but the lower the toughness. Therefore, if the addition amount of Ti and Nb is too high, there is a high possibility of cracking, so the appropriate addition amount is preferably about 0.5 to 5%, respectively. If 0.5% or less, the effect of improving the wear resistance is lost, and at 5% or more, the weldability is greatly reduced.

W, Mo, and V form some of the carbides in the alloy of the present invention and others have a solid solution in the matrix to make them resistant to tempering at high temperatures. In consideration of economy, addition of 3% or less is preferable, respectively.

Mn and Si serve to remove dissolved oxygen in molten steel during solidification in the alloy of the present invention, and Mn hardly deoxidizes when added below 0.1% and lowers the hardness of the material when added above 2%. As the resistance to abrasion is impaired, an appropriate amount of addition is preferably 0.1 to 2.0% .Since 0.1% or less is added, the deoxidation function is weak, and when it is added more than 2%, it causes brittleness of the material and induces a pearlite phase that inhibits abrasion resistance. Therefore, the appropriate amount of addition is preferably 0.1 to 2.0%. Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

An alloy having an alloy component system as shown in Table 1 below was prepared by overlay welding. At this time, the alloying of the present invention by overlay welding, in consideration of the dilution rate at the time of welding, the metal powder is mixed to prepare the flux cored wire so that the weld metal is an alloy component of the present invention, generating an arc between the wire and the base material It was prepared by melting the welding rod by arc heat and welding it to the base metal surface.

Table 2 shows the tendency of welding crack generation and low stress scratch abrasion tester (Dry Sand Rubber Wheel Abrasive Test: ASTM Standard G65-85) during overlay welding construction for the present invention and the comparative material: load: 20 kg, rotation speed: 300 rpm, Test time: The result was tested under the same conditions of 30 minutes.

As shown in Table 2, in the case of Comparative Material 1, although a large amount of carbide-forming elements were added, the amount of solid carbon in the matrix was small, and thus the wear resistance was poor.In contrast, in the case of Comparative Materials 3 and 4, the amount of carbon added was greater than that of carbide added. The amount of dissolved carbon in the matrix was excessive, and as a result, cracks occurred during welding.

In the case of the inventive material, the carbon addition amount coincided chemically with the addition amount of the carbide forming element, so that the weld crack did not occur with excellent wear resistance. When designing the components of the wear-resistant overlay alloy steel as described above, if the Cf value is -0.5 or more and less than 0.1, the overlay weld alloy with high wear resistance by adding a large amount of carbides with low weld cracking sensitivity is good. It can be seen that can be prepared.

division Component ratio (wt%) Cf C Si Mn Cr Ni Mo W Ti Nb V Comparative Material 1 0.76 1.15 1.74 8.05 2.85 2.28 1.98 1.88 1.63 0.55 -1.78 Invention 1 0.81 1.37 1.95 7.30 3.12 2.32 - 2.38 0.92 0.98 -0.14 Conventional Materials 1 0.66 0.58 1.69 5.34 1.24 0.05 0.03 0.01 4.20 0.82 -0.08 Invention 2 1.04 0.97 1.45 6.99 0.1 2.24 1.82 1.32 3.32 0.77 -0.02 Conventional material 2 0.48 0.45 2.01 3.07 0.09 2.89 - 0.027 2.22 0.81 0.00 Conventional Materials 3 0.17 0.45 1.96 3.36 2.77 2.09 - - - 0.51 0.05 Invention 3 0.81 1.05 1.50 6.89 2.69 2.07 1.89 1.62 0.82 0.51 0.06 Comparative Material 2 0.35 1.30 2.92 4.96 1.54 0.91 - 0.39 0.77 0.36 0.07 Comparative Material 3 0.98 1.14 1.63 6.50 2.59 1.98 1.76 1.76 1.01 0.53 0.17 Comparative Material 4 0.76 1.20 1.95 9.33 3.41 2.44 0.01 0.52 0.99 1.20 0.22

division Crack occurrence during welding Wear loss (g) Invention 1 X 0.5 Invention Material 2 X 0.9 Invention 3 X 0.8 Conventional material 1 X 2.7 Conventional material 2 X 2.1 Conventional Materials 3 X 12.7 Comparative material 1 X 2.6 Comparative material 2 X 4.5 Comparative material 3 O - Comparative material 4 O -

As described above, the present invention is used in abrasion and corrosion environment because the addition of a large amount of carbide forming element, by adding a carbon content suitable for the addition amount, suppresses the generation of welding cracks, good welding workability, excellent wear resistance When used as an overlay welding material of various rolls, the life extension effect is greater than in the prior art.

Claims (1)

By weight% C: 0.5-1.5%, Mn: 0.1-2%, Si: 0.1-2%, Cr: 5-13%, Ti: 1-5%, Nb: 0.5-5%, W: 3% or less , V: 3% or less, Mo: 3% or less, the remaining Fe and other unavoidable impurities, alloy steel for overlay welding excellent weld resistance cracking resistance and wear resistance characterized by satisfying the following equation. -0.5 <Cf <0.1 (Where Cf = C (wt%)-Ti (wt%) ÷ 3.99-W (wt%) ÷ 15.31-Nb (wt%) ÷ 7.74-V (wt%) ÷ 4.24)